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<title>Structure and Functional Relationships in Proteins</title></titleStmt>

<publicationStmt><distributor>BASE and Oxford Text Archive</distributor>


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The recordings and transcriptions used in this study come from the British

Academic Spoken English (BASE) corpus, which was developed at the

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(Warwick) and Paul Thompson (Reading). Corpus development was assisted by

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<item n="speechevent">Lecture</item>

<item n="acaddept">Medicine</item>

<item n="acaddiv">ls</item>

<item n="partlevel">PG</item>

<item n="module">Molecules</item>





<u who="nm0442"><kinesic desc="projector is on showing slide" iterated="n"/> today we're going to <trunc>s</trunc> cover structural and functional relationships in proteins <pause dur="0.5"/><kinesic desc="changes slide" iterated="n"/> and i'm sure as most of you will really all be aware this is going to be <pause dur="0.5"/> # you know we're going to only cover a very small proportion of <pause dur="0.5"/> of # structural and functional relationships in proteins <pause dur="1.2"/> proteins are of course the sort of workhorses the machines of the cells <pause dur="0.3"/> and they perform all of the reactions that are compatible with life including those ones <pause dur="0.4"/> listed there <pause dur="0.9"/> # <pause dur="1.1"/> and of course there are very <pause dur="0.2"/> many relevant medical examples to how <pause dur="0.3"/> the structure <pause dur="0.4"/> and function of a protein <pause dur="0.3"/> is related to <pause dur="0.5"/> the normal physiology <pause dur="0.3"/> is related to a disease whereby <pause dur="0.7"/> a loss of function results in an important medical condition i'm <trunc>think</trunc> thinking of things like <pause dur="0.3"/> cystic fibrosis <pause dur="0.7"/> where the gain of a function <pause dur="0.5"/> is a problem for example a <pause dur="0.3"/> tumour <pause dur="0.5"/> tumour genes <pause dur="0.3"/> things like rasp found in a large proportion of <pause dur="0.3"/> human tumours <pause dur="0.3"/> and even when the normal function <pause dur="0.2"/> of a protein <trunc>be</trunc> could become a a

medical problem <pause dur="0.4"/> i'm thinking there particularly of things like multidrug resistance <pause dur="0.3"/> both in bacteria <pause dur="0.5"/> and again in tumours <pause dur="0.7"/> so <pause dur="0.3"/> with that in mind <pause dur="0.3"/> we will briefly and it will be brief and this is <pause dur="0.2"/> essentially part of i guess your <pause dur="0.3"/> assumed knowledge we'll review the basic <pause dur="0.2"/> aspects of # protein structure <pause dur="0.3"/> and go on to <pause dur="0.3"/> some <pause dur="0.4"/> medically relevant examples <pause dur="1.6"/><kinesic desc="changes slide" iterated="n"/> so the basic <pause dur="0.6"/> # unit of protein structure is of course the peptide bond <pause dur="0.8"/> # <pause dur="0.6"/> a polypeptide <pause dur="0.3"/> # it's a sequence of amino acids <pause dur="0.3"/> that are joined through peptide bonds that represents the <pause dur="0.4"/> the primary structure <pause dur="0.5"/> of that protein <pause dur="0.7"/> the peptide bond is formed through the condensation of a <pause dur="0.2"/> carboxylic <pause dur="0.6"/> acid group from an amino acid <pause dur="0.4"/> and a <pause dur="0.9"/> amine group from an amino acid <pause dur="1.9"/> the # carbonyl oxygen <pause dur="0.6"/> and the nitrogen <pause dur="0.5"/> are electronegative and that effectively means that the peptide bond itself <pause dur="0.3"/> has extensive double-bonded character <pause dur="0.6"/> it's rigid and planar <pause dur="0.5"/> it can't rotate <pause dur="1.5"/> but of course there's free rotation <pause dur="0.5"/> of the bonds on either side <pause dur="0.4"/> of that peptide bond <pause dur="0.6"/> and so the

side chains of the amino acids <pause dur="0.3"/> could in theory <pause dur="0.3"/> form any number of angles in relation to that peptide bond <pause dur="2.4"/> i'm sure as you know in fact <pause dur="0.6"/> # <pause dur="0.2"/> there are relatively few angles <pause dur="0.3"/> that are allowed <pause dur="0.4"/> on either side of that peptide bond <pause dur="1.5"/> and most of the angles are not allowed because they're sterically unfavourable <pause dur="0.3"/> they represent <pause dur="0.6"/> clashes interactions between <pause dur="0.5"/> the # side chains of amino acids <pause dur="0.5"/> or the side chains of amino acids and the and the polypeptide chain <pause dur="1.2"/> and so <pause dur="0.4"/> the confirmations of the bonds <pause dur="0.3"/> on either side of the peptide bond can actually <pause dur="0.3"/> only form <pause dur="0.2"/> relatively few <pause dur="0.4"/> what are generally termed secondary structures <pause dur="2.1"/> the one with the largest scope is the is the beta sheet <pause dur="0.7"/> # i should say that <pause dur="0.2"/> psi and phi are of course the they're the names of the two bonds on either side of the peptide bond you don't really <pause dur="0.2"/> need to know that <pause dur="0.5"/> # <pause dur="0.9"/> but for a beta sheet <pause dur="0.4"/> those psi and phi angles suggest that the only <pause dur="0.3"/> the favourable <pause dur="0.2"/> energetic confirmation <pause dur="0.8"/> # for the side chains of these amino acids <pause dur="0.2"/> would be <pause dur="0.2"/> if

they were essentially opposed <pause dur="0.3"/> on either side <pause dur="0.3"/> of the peptide bond <pause dur="0.6"/> and so they alternate <pause dur="0.5"/> on either side of the peptide bond <pause dur="1.2"/> # beta sheets # the that # opposition of # side chains allows for extensive <pause dur="0.3"/> hydrogen bonding between <pause dur="0.5"/> separate polypeptide chains that are in the beta sheet <pause dur="0.3"/> confirmation <pause dur="0.7"/> and i'm actually not really going to talk much more about beta sheets that's not because i don't think they're important <pause dur="0.4"/> # # or indeed have medically relevant examples it's just there isn't <trunc>s</trunc> time <pause dur="0.4"/> within this lecture to really go into beta sheet structures <pause dur="0.3"/> other than to describe <pause dur="0.7"/> # the Ramachandran conditions <pause dur="1.2"/><kinesic desc="changes slide" iterated="n"/> # <pause dur="0.7"/> obviously there are very <pause dur="0.3"/> pertinent examples indeed the transition between alpha helical structures and beta pleated sheet structures is pathological in various diseases such as Alzheimer's that's that ameloid <pause dur="0.4"/> transition <pause dur="1.8"/> the second set of allowed angles <pause dur="0.5"/> on either side of the peptide bond are essentially <pause dur="0.3"/> # <pause dur="0.6"/> offset by about i think about # a hundred-and-ten

a hundred-and-twenty degrees <pause dur="0.9"/> and the only way you can conceptualize the arrangement of side chains in a polypeptide that are offset like that is if they're essentially rotating and that gives you <pause dur="0.3"/> the <trunc>i</trunc> notion that that would be a helix <pause dur="1.0"/> you can see there there's one small <pause dur="0.4"/> area that's allowed if van der Waals' radii <pause dur="0.2"/> radii are taken to be a little smaller <pause dur="0.3"/> and that's a left-handed helix <pause dur="0.5"/> and we'll talk about that <pause dur="0.9"/> # <pause dur="0.2"/> and generally <pause dur="0.4"/> # most amino acids <pause dur="0.2"/> fall into these Ramachandran rules Ramachandran was of course a <pause dur="0.3"/> Indian mathematician who who who # worked out these rules <pause dur="0.3"/> # for a secondary structure <pause dur="0.5"/> in the # turn of the <trunc>s</trunc> turn of last century now <pause dur="0.9"/> using both mathematical principles and # models of peptides <pause dur="1.0"/> the only amino acid that can be found in <pause dur="0.3"/> virtually any <pause dur="0.5"/> angle confirmation <pause dur="0.5"/> is # is glycine of course and that's because it's secondary <pause dur="0.3"/> # it's # sorry side chains of course hydrogen <pause dur="2.6"/><kinesic desc="changes slide" iterated="n"/> so most proteins contain <pause dur="0.3"/> alpha helix and indeed some <pause dur="0.2"/> are nearly all alpha

helix <pause dur="0.4"/> and <pause dur="0.2"/> things like myoglobin and haemoglobin <pause dur="0.2"/> are predominantly alpha helical <pause dur="0.4"/> indeed the <pause dur="0.3"/> structures the parts of the protein that are not alpha helices <pause dur="0.3"/> in myoglobin and haemoglobin <pause dur="0.4"/> are involved in turning <pause dur="0.8"/> the molecule back on itself <pause dur="0.3"/> to give <pause dur="0.2"/> the very characteristic compacted <pause dur="0.5"/> shapes of those molecules <pause dur="1.7"/><kinesic desc="changes slide" iterated="n"/> so i'm sure that <pause dur="0.8"/> oh <pause dur="0.5"/> if anybody's struggling with their right-handed and left-handed helices that's what that's <pause dur="0.2"/> there for <pause dur="1.6"/><kinesic desc="changes slide" iterated="n"/> so this then is an actual alpha helix <pause dur="2.4"/> we can see that # <pause dur="1.2"/> the side chains are nicely arrayed <pause dur="0.4"/> to the outside of the helix on <kinesic desc="indicates point on slide" iterated="n"/> this side and on <kinesic desc="indicates point on slide" iterated="n"/> this side <pause dur="0.5"/> # that # it being it it being right-handed it pitches essentially from # # from the left towards the right upwards <pause dur="0.5"/> # in this particular helices you can see that there's essentially hydrophobic <pause dur="0.7"/> side chains on <kinesic desc="indicates point on slide" iterated="n"/> this side <pause dur="0.5"/> and <pause dur="0.3"/> # charged side chains on <kinesic desc="indicates point on slide" iterated="n"/> this side and this gives you an idea as to the orientation <pause dur="0.2"/> potentially <pause dur="0.2"/> of that helix in a protein <pause dur="0.3"/> obviously the hydrophobic side would be inward-facing <pause dur="0.5"/>

the hydro<pause dur="0.4"/>philic side <pause dur="0.3"/> would be facing towards the aqueous environment <pause dur="1.3"/> you can see on the top there the <pause dur="0.2"/> how the # <pause dur="1.3"/> the # side chains essentially <pause dur="0.2"/> overlap and the <pause dur="0.4"/> # <pause dur="0.9"/> array themselves such they're approximately four residues apart as they go up <pause dur="0.7"/> the side of the helix <pause dur="1.4"/> so that's as i said there's approximately three-and-a-half amino acids per turn <pause dur="1.7"/> and also you can see that the helices <pause dur="0.3"/> this arrangement of helices <pause dur="0.3"/> allows for hydrogen bonding within the chain <pause dur="1.1"/> so interchain hydrogen bonding and this helps stabilize the structure and it's why helical structures are so <pause dur="0.4"/> <trunc>oft</trunc> alpha helical structure energetically very favourable <pause dur="5.7"/><kinesic desc="changes slide" iterated="n"/> so if we look at the primary <pause dur="0.6"/> so the the the notion that there's periodicity or there appears to be certain periodicity <pause dur="0.2"/> in helices allows you to look at the primary structure <pause dur="0.2"/> and make predictions <pause dur="0.3"/> as to <pause dur="0.3"/> # what the secondary structure is most likely to be <pause dur="0.3"/> there is frequently periodicity <pause dur="0.2"/> in amino acid sequences <pause dur="0.3"/> # and certain amino acids are indeed

preferred in helices <pause dur="0.2"/> yet others are not preferred in helices <pause dur="0.6"/> glycine isn't preferred in helices and proline as you know is a <pause dur="0.5"/> an amino acid that will essentially kink <pause dur="0.4"/> a polypeptide chain that won't be found in <pause dur="0.3"/> helices <pause dur="4.7"/><kinesic desc="changes slide" iterated="n"/> so this then demonstrates with that helices i was just showing you that the <pause dur="0.2"/> indeed the <pause dur="0.4"/> the polar residues <pause dur="0.4"/> # the sorry the non-polar residues are in the centre of the myoglobin molecule <pause dur="0.5"/> and the polar residues are arrayed on the surface <pause dur="0.8"/> aiding the solubility of myoglobin <pause dur="2.4"/> and in now allowing myoglobin and indeed haemoglobin as it's since it's very <trunc>r</trunc> closely related to myoglobin to # <pause dur="1.6"/> be in solution at relatively high concentration <pause dur="3.9"/><kinesic desc="changes slide" iterated="n"/> so this of course is what we are really going to talk about today <pause dur="0.9"/> myoglobin and haemoglobin <pause dur="8.7"/> this then shows the arrangement <pause dur="2.0"/> of the secondary structure <trunc>wi</trunc> in myoglobin which is <trunc>predo</trunc> predominantly alpha helical <pause dur="0.4"/> into the globin fold so that would be its tertiary structure <pause dur="1.6"/> and the tertiary structure <pause dur="0.2"/> is essentially an

arrangement of eight <pause dur="0.5"/> alpha helices <pause dur="0.4"/> in globins <pause dur="0.2"/> # <pause dur="0.3"/> labelled A to H <kinesic desc="indicates point on slide" iterated="n"/> this was A <pause dur="0.5"/> <kinesic desc="indicates point on slide" iterated="n"/> B and C are behind here <kinesic desc="indicates point on slide" iterated="n"/> this is D <pause dur="0.5"/> <kinesic desc="indicates point on slide" iterated="n"/> this is E <pause dur="0.6"/> <kinesic desc="indicates point on slide" iterated="n"/> this is F <pause dur="0.4"/> <kinesic desc="indicates point on slide" iterated="n"/> this is G <pause dur="0.6"/> and <kinesic desc="indicates point on slide" iterated="n"/> this is H <pause dur="2.3"/> you can also see that in myoglobin it has a prosthetic group <pause dur="0.3"/> that's <kinesic desc="indicates point on slide" iterated="n"/> this red molecule here <pause dur="2.2"/> and this prosthetic group <pause dur="0.3"/> is essentially held in position <pause dur="0.4"/> in a myoglobin in a <pause dur="0.3"/> in a <trunc>r</trunc> in a a reasonable cleft or fold that helps protect that prosthetic group from oxidation <pause dur="1.6"/> and <trunc>m</trunc> and the prosthetic group haem <pause dur="0.5"/> of course is held in position <pause dur="0.4"/> by two histidine residues <pause dur="0.9"/> histidine <pause dur="0.7"/> E-seven <pause dur="0.2"/> and histidine F-eight so it's <pause dur="0.4"/> the seventh residue in the <pause dur="1.1"/> # <pause dur="0.4"/> E helix and the eighth residue in the F helix <pause dur="1.7"/> you can see that <pause dur="0.6"/> the F-eight histidine appears to be quite close to the haem group <pause dur="0.8"/> the <pause dur="0.6"/> E <pause dur="0.2"/> histidine appears a little bit further away <pause dur="0.7"/> so the F-<pause dur="0.3"/>eight histidine is called the proximal histidine <pause dur="1.1"/> and the E-seven histidine is called the distal histidine <pause dur="9.5"/><kinesic desc="changes slide" iterated="n"/> so what we are going to talk about today of course is the binding of oxygen to myoglobin and

haemoglobin <pause dur="1.9"/> we'll talk about the functions of myoglobin and haemoglobin <pause dur="0.7"/> # <pause dur="0.2"/> myoglobin acts as essentially as an oxygen store in muscle <pause dur="1.9"/> and it you'll see that its structure is entirely consistent with its function <pause dur="0.6"/> # whereas haemoglobin which is of course oxygen transport for transporting oxygen from the lungs to the tissues <pause dur="0.4"/> we'll talk about the factors affecting oxygen binding <pause dur="2.7"/> transport of carbon dioxide and P-H regulation <pause dur="7.9"/><kinesic desc="changes slide" iterated="n"/> when we consider the binding of oxygen to haemoglobin and indeed myoglobin we'll <pause dur="0.6"/> perhaps worth considering what atmospheric oxygen <pause dur="0.5"/> # the <pause dur="0.2"/> partial pressure <unclear>axle</unclear> <pause dur="0.2"/> atmospheric oxygen is around about a hundred-and-fifty <trunc>m</trunc> millimetres of mercury or twenty <pause dur="0.3"/> sometimes referred to as twenty pascals in other textbooks <pause dur="1.7"/> a significant proportion of that <pause dur="0.5"/> enters into the wet surface of the lungs providing of course those <pause dur="0.6"/> # lung surfaces are wet if they're not for whatever reason <pause dur="0.4"/> then you do not get efficient exchange between the atmospheric

oxygen <pause dur="0.9"/> and the lung mucosa <pause dur="1.4"/> of the oxygen that dissolves into the <pause dur="0.5"/> lung mucosa <pause dur="0.4"/> the majority of that is taken up <pause dur="0.5"/> into the blood <pause dur="0.2"/> through exchange in the lungs <pause dur="4.7"/> oxygen then is # the blood is then circulated oxygenated by this circulated in the tissues <pause dur="0.6"/> and <pause dur="0.4"/> a relatively small proportion <pause dur="0.3"/> perhaps less certainly less than fifty per cent of <pause dur="0.2"/> oxygenated haemoglobin <pause dur="0.3"/> a relatively small proportion of the oxygen it carries is unloaded into the tissues <pause dur="1.6"/> carbon dioxide is picked up from the <trunc>o</trunc> <pause dur="0.3"/> from the active tissues and that's transported back via the blood <pause dur="0.3"/> back to the lungs <pause dur="0.7"/> and then back <pause dur="0.3"/> # in exchange back into the <pause dur="0.8"/> air that we breathe <pause dur="1.5"/> so one of the <pause dur="0.2"/> first factors that's going to affect <pause dur="0.6"/> the <pause dur="0.4"/> binding of oxygen to haemoglobin <pause dur="0.4"/> is the efficient physiology <kinesic desc="indicates point on slide" iterated="n"/> here at <pause dur="0.2"/> at the lung <pause dur="1.3"/> # circulation interface <pause dur="1.4"/> another more subtle perhaps <pause dur="0.2"/> # notion is that it all relies on the fact that atmospheric oxygen is <pause dur="0.7"/> what i said is up there <pause dur="0.6"/> and of course there are certain conditions when it's not for

example altitude <pause dur="1.7"/> and <pause dur="0.4"/> that the lungs are # <pause dur="0.3"/> # <pause dur="0.2"/> functioning efficiently <pause dur="0.2"/> that the circulation is functioning efficiently you can see that of the <pause dur="0.4"/> oxygen that dissolves into the wet surface <pause dur="0.3"/> the majority of it is taken up by the lung <pause dur="0.2"/> by <pause dur="0.2"/> by the blood in the lungs <pause dur="1.2"/> so this is a fairly <pause dur="0.3"/> this is working to almost its maximum efficiency <trunc>n</trunc> <pause dur="0.2"/> at <pause dur="0.2"/> at this point and anything <pause dur="0.3"/> that affects that <pause dur="0.4"/> well it ultimately affects <pause dur="0.4"/> oxygenation of the tissues <pause dur="4.4"/><kinesic desc="changes slide" iterated="n"/> so the rate at which you breathe <pause dur="1.0"/> the so-called ventilation rate and the perfusion of the lungs I-E how much blood is passing through the lungs at any given time <pause dur="0.7"/> # must be matched <pause dur="0.4"/> that's called a ventilation and perfusion match <pause dur="0.9"/> and the ratio must be approximately four litres of breathing per minute and five litres of blood per minute passing through the lungs giving you a ventilation <pause dur="0.4"/> perfusion match of point-eight <pause dur="2.2"/> anything that impears impairs breathing such as a a crushed chest <pause dur="0.9"/> a deflated lung <pause dur="0.9"/> chronic lung disorder <pause dur="0.9"/> # <pause dur="0.3"/> somebody <pause dur="0.3"/> making

the <kinesic desc="puts hand round throat" iterated="n"/> universal choking sign <pause dur="0.7"/> # will affect <pause dur="0.2"/> the amount of oxygen that's <pause dur="0.2"/> that's breathed that they're that they're <pause dur="0.2"/> able to <pause dur="0.4"/> obtain <pause dur="1.3"/> obviously if they have a problem with their blood flow <pause dur="0.7"/> like they're bleeding from <pause dur="0.5"/> a large artery in the leg <pause dur="0.4"/> will ultimately affect <pause dur="0.4"/> their oxygenation of their tissues but under those conditions i suggest you're more focused on the leg issue <pause dur="1.0"/> # at least initially <pause dur="0.2"/> and of course this relates to <pause dur="0.4"/> the A B C of <pause dur="0.2"/> first aid in many respects <pause dur="0.3"/> airway breathing <pause dur="0.2"/> circulation <pause dur="2.6"/> and any <pause dur="0.3"/> mismatch in ventilation or perfusion <pause dur="0.2"/> will ultimately lower <pause dur="0.4"/> the amount <pause dur="0.3"/> of oxygen <pause dur="0.2"/> in the arterial blood <pause dur="1.2"/> so that reveals to you <pause dur="0.2"/> that there's a problem with oxygen <pause dur="0.2"/> oxygenation <gap reason="inaudible" extent="1 sec"/> <pause dur="4.7"/><kinesic desc="changes slide" iterated="n"/> so accepting that <pause dur="0.6"/> the lungs are working properly and there's the right the correct concentration of atmospheric oxygen <pause dur="0.5"/> we can then go back and and think about the binding of oxygen to haemoglobin and and myoglobin <pause dur="1.5"/><kinesic desc="indicates point on slide" iterated="n"/> this is the haem <pause dur="1.1"/> # <pause dur="0.7"/> prosthetic group found in myoglobin and haemoglobin <pause dur="0.6"/> it's made up of the the carbony

bit it's called the protoporphyrin and in the middle there is <pause dur="0.6"/> iron <pause dur="1.1"/> the ferrous iron <pause dur="0.4"/> that's iron two-plus <pause dur="0.9"/> the as i said the hydrophobic fold <pause dur="0.6"/> of myoglobin and haemoglobin protects oxidation of that iron <pause dur="0.4"/> if that iron does become oxygenated # <pause dur="0.2"/> oxidized it can no longer bind oxygen <pause dur="1.4"/> so in that and in that case it's <pause dur="0.2"/> that would be referred to as a met-myoglobin or a met-haemoglobin that's iron <pause dur="0.5"/> in the <pause dur="0.2"/> three-plus oxidation state <pause dur="1.9"/> the iron can make six coordination bonds it makes four <pause dur="0.4"/> with nitrogens <pause dur="0.3"/> that are in the pyrrole group <pause dur="0.9"/> it makes one <pause dur="0.2"/> with the <trunc>pro</trunc> with the nitrogen in the proximal <pause dur="0.7"/> histidine <pause dur="0.6"/> and the last one <pause dur="0.4"/> is for the binding of oxygen as i'll show you <pause dur="0.3"/> and essentially <kinesic desc="indicates point on slide" iterated="n"/> this molecule <pause dur="0.7"/> is planar <pause dur="0.3"/> in isolation <pause dur="5.7"/> so this then <pause dur="0.5"/> # puts the haem then in context of those two histidines <pause dur="2.1"/> # you can see here the proximal <pause dur="0.5"/> # histidine providing the <trunc>s</trunc> the fifth coordination point for the iron <pause dur="0.9"/> and oxygen is able to intercede between the <pause dur="0.5"/> the distal <pause dur="0.5"/> nitrogen in the histidine <pause dur="0.4"/>

and that provides the binding site for oxygen to <pause dur="0.8"/> <trunc>h</trunc> <pause dur="0.2"/> to haemoglobin <pause dur="0.2"/> or indeed myoglobin <pause dur="1.5"/> and in this case <pause dur="0.2"/> in the presence of oxygen you can see that the <pause dur="0.3"/> haem <pause dur="0.6"/> remains planar <pause dur="0.8"/> and and i'll explain why that's important in a little while <pause dur="2.1"/><kinesic desc="changes slide" iterated="n"/> the other thing i want to point out is about # carbon monoxide <pause dur="1.0"/> isolated haem <pause dur="0.5"/> has a very strong affinity for carbon monoxide <pause dur="0.3"/> much more <pause dur="0.4"/> # # much stronger than it does for oxygen <pause dur="0.7"/> but haem <pause dur="0.3"/> in the presence of protein such as myoglobin or haemoglobin <pause dur="0.4"/> there are <trunc>r</trunc> the <pause dur="0.2"/> the differential between the affinities for carbon dioxide <pause dur="0.5"/> and <pause dur="0.6"/> oxygen is reduced such that it goes from twenty-five-thousand times difference in <pause dur="0.3"/> isolated haem <pause dur="0.4"/> to two-hundred times different <pause dur="0.6"/> in the context of the protein so the protein plays an important role <pause dur="0.4"/> in hopefully limiting the effects of carbon dioxide <pause dur="1.1"/><kinesic desc="changes slide" iterated="n"/> the reason <pause dur="0.6"/> that that's important is of course is firstly carbon dioxide is the single most <pause dur="0.3"/> # single <pause dur="0.4"/> biggest <pause dur="0.4"/> metabolic poison <pause dur="1.5"/> it's far more potent and there are far more deaths

from carbon monoxide than there are for any other metabolic poisons that might <pause dur="0.2"/> cyanide for example <pause dur="5.7"/> and carbon monoxide <pause dur="0.7"/> obviously actively competes <pause dur="0.2"/> for oxygen binding sites <pause dur="4.1"/> normally <pause dur="0.3"/> # the # when once carbon monoxide is bound to haemoglobin or <pause dur="0.4"/> to haemoglobin it will be referred to as <trunc>carb</trunc> carboxyhaemoglobin <pause dur="1.7"/> and there is a small percentage of <trunc>carboxyhaem</trunc> haemoglobin in our blood normally <pause dur="1.4"/> in smokers for example that percentage goes up to about fifteen per cent <pause dur="1.5"/> and around thirty per cent it's a medical emergency <pause dur="0.7"/> and around fifty per cent you're probably going to die <pause dur="1.5"/> so carboxyhaemoglobin <pause dur="0.4"/> is a significant <pause dur="0.3"/> problem <pause dur="1.0"/> because it's able to <pause dur="0.2"/> effectively reduce <pause dur="0.3"/> the oxygen <trunc>ca</trunc> carrying capacity <pause dur="0.7"/> of blood <pause dur="6.2"/><kinesic desc="changes slide" iterated="n"/> so now let's just think a little bit about this <pause dur="2.9"/> planar haem molecule <pause dur="10.9"/> this is the proximal histidine <pause dur="0.3"/> here's the planar haem molecule in the presence of oxygen <pause dur="1.7"/> in this form <kinesic desc="indicates point on slide" iterated="n"/><pause dur="0.4"/> haemoglobin or myoglobin would be referred to as relaxed <pause dur="1.7"/> when it becomes deoxygenated <pause dur="0.6"/> the

interaction between this nitrogen and the <pause dur="0.4"/> iron in the haem group is so strong <pause dur="0.4"/> that the haem tends to dome in <pause dur="1.2"/> to that # <pause dur="0.5"/> proximal histidine <pause dur="0.7"/> in this case the <pause dur="0.2"/> and that's deoxygenated form of haemoglobin <unclear>it</unclear> referred to as tense <pause dur="1.5"/> so the binding of oxygen <pause dur="0.4"/> to myoglobin or haemoglobin <pause dur="0.3"/> essentially represents a tense <pause dur="0.4"/> to relaxed transition <pause dur="1.6"/> and that tense to relaxed <pause dur="0.3"/> transition <pause dur="0.4"/> can be transmitted through the molecule <pause dur="0.3"/> because it is a shape change <pause dur="7.2"/><kinesic desc="changes slide" iterated="n"/> so we've talked in general about the binding of oxygen to haem and everything so far i've told you is the case for as it is for <pause dur="0.5"/> myoglobin as it is for haemoglobin <pause dur="1.1"/> but of course haemoglobin is actually <pause dur="0.2"/> a tetramer it has <pause dur="0.2"/> four globins <pause dur="0.2"/> so this is now a quarternary structure <pause dur="1.7"/> the globin fold <pause dur="0.8"/> of all four <pause dur="0.3"/> of the <pause dur="0.5"/> # <pause dur="0.2"/> subunits in haemoglobin is shown <pause dur="1.2"/> and you can see <pause dur="0.5"/> the four haem groups <pause dur="1.3"/> so oxygen is a # sorry so haemoglobin will bind four oxygens <pause dur="0.4"/> as opposed to myoglobin which will only bind one <pause dur="2.0"/> there you can see the

doming in this particular haem group you can see the doming <kinesic desc="indicates point on slide" iterated="n"/> there <pause dur="1.1"/> of the <pause dur="0.4"/> haem <pause dur="0.5"/> group <pause dur="0.7"/> and of the <trunc>i</trunc> the iron being pulled into <pause dur="0.3"/> the proximal histidine <pause dur="3.4"/> adult haemoglobin there are there are three globin genes but there and there are multiple copies <pause dur="0.8"/> in your D-N-A <pause dur="0.3"/> # <pause dur="0.6"/> adult haemoglobin is predominantly so-called alpha-beta <pause dur="0.4"/> haemoglobin <pause dur="0.2"/> you always express a little bit of <trunc>delt</trunc> delta haemoglobin <pause dur="0.6"/> # during the first few months of life <pause dur="0.6"/> you switch <pause dur="0.5"/> from <pause dur="0.2"/> the fetal haemoglobin <pause dur="0.5"/> to these <pause dur="0.2"/> adult forms <pause dur="0.6"/> so obviously fetuses <pause dur="0.2"/> fetal <pause dur="0.3"/> expression is of <pause dur="0.6"/> the H-B-F <pause dur="0.2"/> and an adult's <pause dur="0.3"/> a little bit of H-B-A-two <pause dur="0.4"/> and H-B-A sometimes also referred to as H-B-A-one <pause dur="8.4"/><kinesic desc="changes slide" iterated="n"/> so <pause dur="2.6"/> now we understand a little bit more about the structure of haemoglobin and myoglobin how can we relate that to their functions <pause dur="2.5"/> on the <trunc>r</trunc> on the left-hand side we have the <trunc>s</trunc> degree of saturation oxygen saturation of the proteins and <pause dur="0.5"/> # partial pressure of oxygen <pause dur="0.2"/> along the bottom <pause dur="1.4"/> the green line <pause dur="0.7"/> represents the binding of oxygen <pause dur="0.7"/> to myoglobin <pause dur="1.0"/> and it shows a

simple hyperbolic relationship <pause dur="1.7"/> entirely consistent <pause dur="0.3"/> with a single binding site <pause dur="2.8"/> and its responsiveness to <pause dur="0.3"/> changes in oxygen pressure <pause dur="0.8"/> are consistent with its role as a oxygen storage protein in muscle <pause dur="2.9"/> myoglobin <pause dur="0.2"/> is rapidly saturated over a relatively small <trunc>concentra</trunc> change in concentration <pause dur="0.9"/> and will remain saturated <pause dur="3.0"/> as a tissue a muscle's demand for oxygen increases <pause dur="0.8"/> # <pause dur="0.2"/> some oxygen can then be released <pause dur="0.3"/> from myoglobin <pause dur="0.2"/> in order to support the metabolism <pause dur="0.3"/> in active muscle <pause dur="3.9"/> this is <pause dur="0.8"/> # quite different to the curve that you see for haemoglobin <pause dur="1.7"/> which is sigmoidal <pause dur="0.6"/> in shape <pause dur="0.8"/> consistent with <pause dur="0.6"/> a multiple binding site <pause dur="0.2"/> which we as we know is four <pause dur="4.0"/> <kinesic desc="indicates point on slide" iterated="n"/> this <pause dur="0.5"/> type of <pause dur="0.5"/> # curve <pause dur="0.7"/> <trunc>a</trunc> <pause dur="0.7"/> reflects <pause dur="0.3"/> what's called cooperative <pause dur="0.2"/> or <trunc>politi</trunc> <pause dur="0.2"/> <trunc>positi</trunc> </u><gap reason="break in recording" extent="uncertain"/> <u who="nm0442" trans="pause"> allosteric binding <pause dur="0.9"/> so oxygen <pause dur="0.7"/><kinesic desc="indicates point on slide" iterated="n"/> here <pause dur="0.3"/> acts as an allosteric regulator of the binding of oxygen <pause dur="0.5"/> to haemoglobin <pause dur="1.0"/> the way to conceptualize that is this <pause dur="1.4"/> <kinesic desc="indicates point on slide" iterated="n"/> here at the very <pause dur="1.2"/> over a relatively wide concentration range at # here at the low end <pause dur="0.3"/> of # haemoglobin's

responsiveness to oxygen <pause dur="0.5"/> it's very reluctant <pause dur="0.3"/> to give up <pause dur="0.3"/> its oxygen <pause dur="1.7"/> as oxygen <pause dur="0.5"/> # partial pressure increases <pause dur="0.3"/> there's a rapid increase <pause dur="0.8"/> in <pause dur="0.2"/> haemoglobin's ability to bind oxygen <pause dur="1.5"/> the only way you can <trunc>s</trunc> conceptualize that <pause dur="0.2"/> is if the subunits <pause dur="0.2"/> are cooperating <pause dur="0.2"/> in their binding <pause dur="0.6"/> of oxygen to haemoglobin <pause dur="1.8"/> the probably the better way the best way to think of it is as they release <pause dur="0.3"/> is as haemoglobin release oxygen <pause dur="0.5"/> as it releases oxygen <pause dur="0.2"/> it becomes progressively harder for haemoglobin to release further oxygen <pause dur="3.6"/> and of course <pause dur="0.7"/><kinesic desc="indicates point on slide" iterated="n"/> here <pause dur="0.2"/> fully saturated <pause dur="0.7"/> the haem groups are relaxed <pause dur="0.6"/> and here <pause dur="0.5"/><kinesic desc="indicates point on slide" iterated="n"/> as they're deoxygenated <pause dur="0.8"/> they <pause dur="0.5"/> become tense <pause dur="5.4"/><kinesic desc="changes slide" iterated="n"/> so the binding of oxygen to haemoglobin # exhibits <pause dur="0.4"/> positive allosterism it is cooperative <pause dur="3.0"/> the cooperativity <pause dur="0.3"/> essentially represents communication between the subunits <pause dur="0.9"/> the # <pause dur="0.2"/> quarternary structure i showed you showed that the subunits are in very close <pause dur="0.3"/> proximity <pause dur="0.2"/> and there are interaction faces between <pause dur="0.3"/> all of the four subunits <pause dur="0.7"/> so the binding of oxygen for example <pause dur="0.2"/><kinesic desc="indicates point on slide" iterated="n"/> here

perhaps in the red subunit <pause dur="0.5"/> can be transmitted <pause dur="0.6"/> to <pause dur="0.2"/> the other four subunits <pause dur="0.2"/> so they're in close proximity <pause dur="3.2"/> and that's because there's a <pause dur="0.3"/> change of shape at the haem group and that can be transmitted <pause dur="0.5"/> with a much larger change of shape <pause dur="0.2"/> at the interactional face <pause dur="4.7"/> this # <pause dur="0.6"/> change in terms of <pause dur="0.3"/> oxygenated and relaxed haemoglobin tends to close <pause dur="0.3"/> a pocket <pause dur="0.4"/> that <trunc>form</trunc> that can form in the middle <pause dur="0.2"/> of the four subunits <pause dur="0.7"/> in a deoxygenated form <pause dur="0.5"/> this pocket tends to be <pause dur="0.5"/> a little bit more open <pause dur="0.3"/> and we'll see the relevance of that <pause dur="0.2"/> in a minute <pause dur="7.0"/><kinesic desc="changes slide" iterated="n"/> so oxygen represents a positive allosteric regulator of the binding of oxygen to haemoglobin <pause dur="0.3"/> and there are also some negative allosteric regulators of the binding of oxygen to haemoglobin <pause dur="0.5"/> of course <pause dur="0.5"/> i should remind you of course that myoglobin <pause dur="0.2"/> is a monomer so there is no allosteric regulation <pause dur="0.4"/> of the binding of oxygen to myoglobin <pause dur="2.0"/> this i'm sure you'll recognize is a little bit of glycolysis <pause dur="0.4"/> <unclear>which i</unclear> <pause dur="0.3"/> all medical students are always delighted

to see glycolysis <pause dur="1.5"/><vocal desc="laughter" iterated="y" n="ss" dur="1"/> and # <pause dur="0.2"/> in the erythrocytes there is a small side <pause dur="0.7"/> # reaction <pause dur="0.6"/> that's able to convert one of the intermediates of glycolysis to one-three-bisphosphoglycerate into two-three-bisphosphoglycerate <pause dur="0.8"/> it's discovered by this guy Rapoport and Luebering and it's called the Rapoport-Luebering shunt <pause dur="0.2"/> not as somebody put in their exams last year the Freddie Ljungberg shunt <pause dur="3.7"/> <vocal desc="laughter" iterated="y" n="ss" dur="2"/> two-three-bisphosphoglycerate <pause dur="0.2"/> is electronegative <pause dur="3.0"/><kinesic desc="changes slide" iterated="n"/> and it is at very high concentration in erythrocytes <pause dur="0.7"/> it's approximately equimolar with the concentration of haemoglobin <pause dur="0.3"/> in erythrocytes <pause dur="2.1"/> so you can see <pause dur="1.2"/> glucose as it enters into glycolysis essentially <pause dur="0.5"/> all the intermediates in glycolysis there's very little <pause dur="0.3"/> of those <pause dur="0.6"/> glucose enters into glycolysis in essentially <pause dur="0.3"/> in erythrocytes of course is converted to lactate because they have no citric acid cycle no mitochondria and so on <pause dur="0.9"/> the only other <pause dur="0.3"/> intermediate <pause dur="1.7"/>

is two-three-bisphosphoglycerate <pause dur="0.3"/> formed by the <pause dur="0.7"/> the shunt <pause dur="4.2"/><kinesic desc="changes slide" iterated="n"/> and the role of two-three-bisphosphoglycerate is <trunc>effecti</trunc> is <trunc>e</trunc> to effectively lower the affinity <pause dur="0.6"/> of haemoglobin for oxygen <pause dur="11.6"/> this is a little bit schematic in the absence of <pause dur="0.4"/> # bisphosphoglycerate this this curve actually would shift be shifted quite <pause dur="0.2"/> quite a little way to the left <pause dur="0.3"/> in relation <pause dur="0.4"/> to the normal <pause dur="0.5"/> haemoglobin <pause dur="0.4"/> in erythrocytes <pause dur="3.0"/> so in the absence of # in the absence of two-three-bisphosphoglycerate <pause dur="0.3"/> haemoglobin would be quite reluctant to give up its oxygen at all <pause dur="1.0"/> obviously as this would be a problem <pause dur="0.3"/> for the delivery of oxygen <pause dur="0.3"/> to tissues <pause dur="0.4"/> and <trunc>ov</trunc> and clearly we have adapted <pause dur="0.2"/> to use <trunc>two-three-bo</trunc> bisphosphoglycerate <pause dur="0.3"/> to enable us to moderate <pause dur="0.2"/> the release <pause dur="0.2"/> of oxygen <pause dur="0.5"/> # in the active tissues <pause dur="2.2"/><kinesic desc="changes slide" iterated="n"/> the two-three-bisphosphoglycerate is <pause dur="0.2"/> is <pause dur="0.2"/> is <pause dur="0.9"/> binding site is found in the centre <pause dur="1.4"/> of the <pause dur="0.6"/> haemoglobin <pause dur="0.8"/> # tetramer <pause dur="0.5"/> it's <pause dur="0.2"/> predominantly formed by interactions with <pause dur="0.2"/> some alpha chain interactions and predominantly beta chain <pause dur="0.3"/> interactions <pause dur="0.6"/> # and these

are positive residues electropositive residues like lysine and arginine and histidine <pause dur="2.7"/> two-three-B-P-G combined to the <pause dur="0.6"/> deoxygenated form of haemoglobin helps stabilize <pause dur="0.6"/> # the dexoygenated form <pause dur="0.2"/> and helps release oxygen <pause dur="0.5"/> into the tissues <pause dur="7.8"/><kinesic desc="changes slide" iterated="n"/> a clear demonstration of the importance of two-three-bisphosphoglycerate is the fact that there is no two-three-bisphosphoglycerate binding site in fetal haemoglobin <pause dur="1.2"/> so the gamma chain <pause dur="0.4"/> in # fetal haemoglobin does not have those <trunc>electropos</trunc> positive residues <pause dur="0.2"/> so that binding site isn't present <pause dur="1.5"/> this means that fetal haemoglobin has a higher affinity <pause dur="0.6"/> # for oxygen than does the maternal <pause dur="0.4"/> haemoglobin <pause dur="1.2"/> and that ensures that oxygen will flow from maternal haemoglobin <pause dur="0.2"/> to fetal haemoglobin <pause dur="4.1"/> one can imagine other scenarios where the level of two-three-bisphosphoglycerate <pause dur="0.4"/> would be moderated <pause dur="0.2"/> in order to increase the supply <pause dur="0.4"/> of oxygen <pause dur="0.8"/> to the tissues <pause dur="0.3"/> for example at altitude <pause dur="0.3"/> one of the adaptions to altitude <pause dur="0.2"/> is to increase <pause dur="0.4"/> your levels of

two-three-bisphosphoglycerate <pause dur="0.2"/> and that helps unload <pause dur="0.3"/> oxygen in the tissues <pause dur="0.8"/> chronic lung disease <pause dur="0.3"/> is another case in which you see <pause dur="0.4"/> increases <pause dur="0.2"/> in two-three-bisphosphoglycerate concentration <pause dur="0.4"/> as the body's attempting to compensate <pause dur="0.2"/> for poor oxygenation <pause dur="0.4"/> and to deliver as much oxygen as possibly can <pause dur="0.6"/> to the tissues <pause dur="1.4"/> this has to be a temporary solution and in people with chronic lung disease it <pause dur="0.2"/> it itself <pause dur="0.2"/> perpetuates the problem <pause dur="1.0"/> since <pause dur="0.3"/> they increase their two-three-bisphosphoglycerate and it becomes progressively harder then to reoxygenate your haemoglobin in the lungs <pause dur="1.5"/> does everybody understand the role of two-three-bisphosphoglycerate <pause dur="1.7"/> is there any divers in the room <pause dur="2.0"/> any divers scuba people come on there must be one or two <pause dur="0.2"/> <kinesic desc="indicates member of audience" iterated="n"/> you <pause dur="0.8"/> if i give you the choice <pause dur="0.7"/> imaginary choice <pause dur="0.6"/> two-three-bisphosphoglycerate <pause dur="0.2"/> small white powder <pause dur="1.1"/> or air <pause dur="0.9"/> and you're going diving <pause dur="0.3"/> which are you going to take </u><pause dur="1.7"/> <u who="sf0443" trans="pause">

it's obviously a trick question isn't it </u><u who="nm0442" trans="overlap"> no <pause dur="0.3"/> it's not a trick question <vocal desc="laughter" iterated="y" n="ss" dur="1"/> </u><pause dur="2.7"/> <u who="sf0443" trans="pause"> <gap reason="inaudible" extent="1 sec"/></u><pause dur="0.4"/> <u who="nm0442" trans="pause"> the air <pause dur="0.2"/> you're going to take the air </u><pause dur="0.3"/> <u who="sf0443" trans="pause"> yeah </u><pause dur="0.4"/> <u who="nm0442" trans="pause"> two-three-bisphosphoglycerate is not an oxygen substitute <pause dur="1.3"/> okay <pause dur="0.2"/> one of the favourite answers of medical students <pause dur="1.1"/> think of the diver give him the option <pause dur="0.3"/> of the white powder or the air <pause dur="0.3"/> and see which one he takes <pause dur="0.4"/> nobody takes the two-three-bisphosphoglycerate <pause dur="0.4"/> it is a negative <pause dur="0.3"/> allosteric regulator of the binding <pause dur="0.3"/> of oxygen to haemoglobin <pause dur="0.4"/> it is not <pause dur="0.2"/> an oxygen substitute <pause dur="1.2"/> good <pause dur="4.3"/><kinesic desc="changes slide" iterated="n"/> there are two other negative allosteric regulators of the binding of oxygen to haemoglobin <pause dur="2.6"/> they are hydrogen <pause dur="0.2"/> and carbon dioxide <pause dur="2.0"/> and as you can see here a <trunc>d</trunc> a decrease in P-H <pause dur="0.5"/> effectively reduces <pause dur="0.8"/> the affinity of <pause dur="0.5"/> haemoglobin for oxygen <pause dur="2.4"/> and that <pause dur="0.5"/> helps <pause dur="0.6"/> unload <pause dur="0.2"/> oxygen <pause dur="0.4"/> in active tissue <pause dur="0.5"/> since in

active tissue <pause dur="0.3"/> the concentration of hydrogen <pause dur="0.2"/> and carbon dioxide is high <pause dur="4.1"/> both these molecules do so <pause dur="1.2"/> by interfering <pause dur="0.9"/> with cross-bridging that interaction between <pause dur="0.2"/> haemoglobin subunits <pause dur="0.7"/> carbon dioxide can interfere with cross-bridging <pause dur="0.5"/> firstly because it actually of course can <pause dur="0.7"/> in solution <pause dur="0.2"/> can increase the hydrogen ion concentration <pause dur="0.3"/> as we'll <pause dur="0.2"/> see in a minute <pause dur="0.8"/> and secondly <pause dur="0.4"/> because <trunc>i</trunc> <pause dur="0.4"/> it can bind to haemoglobin <pause dur="0.5"/> it it doesn't bind <pause dur="0.7"/> at <pause dur="0.3"/> the ion <pause dur="1.6"/> so a certain amount of carbon dioxide is transported by haemoglobin <pause dur="0.6"/> but is transported covalently <pause dur="0.5"/> attached to free amine groups <pause dur="2.1"/> so that's called carbaminohaemoglobin <pause dur="1.4"/> and that's different from carboxyhaemoglobin which is carrying carbon monoxide <pause dur="0.8"/> at the ion <pause dur="3.9"/> so carbaminohaemoglobin carrying carbon dioxide obviously <pause dur="0.2"/> interferes with cross-bridging interferes with oxygen binding <pause dur="0.5"/> and hydrogen ions interfere with <pause dur="0.3"/> cross-bridging <pause dur="0.2"/> communication between subunits <pause dur="0.4"/> and can lower the affinity <pause dur="0.5"/> of haemoglobin for oxygen <pause dur="2.7"/> so let's just consider <pause dur="0.6"/> a

little bit the transport of carbon dioxide <pause dur="4.8"/><kinesic desc="changes slide" iterated="n"/> carbon dioxide <pause dur="0.3"/> and water can be combined in the erythrocyte using the <trunc>a</trunc> enzyme carbonic <trunc>anhydrogena</trunc> <pause dur="0.5"/> carbonic anhydrase <pause dur="0.2"/> to produce carbonic acid <pause dur="0.3"/> which rapidly diassociates to form a carbonate ion <pause dur="0.5"/> and hydrogen <pause dur="1.6"/> the majority of carbon dioxide produced in tissues is transported <pause dur="0.6"/> in the form of carbonate <pause dur="1.2"/> once it's made in the erythrocyte it passes out through the erythrocyte in a specific transporter and <pause dur="0.5"/> <trunc>i</trunc> <pause dur="0.2"/> # present in the <pause dur="0.6"/> plasma <pause dur="1.7"/> a relatively small proportion is transported back <pause dur="0.3"/> actually covalently linked to <pause dur="0.4"/> # <pause dur="0.5"/> haemoglobin <gap reason="inaudible" extent="1 sec"/> and <pause dur="0.4"/> interestingly of course the covalent link <pause dur="0.2"/> of carbon dioxide to <pause dur="0.3"/> haemoglobin <pause dur="0.3"/> also <pause dur="0.7"/> lowers <pause dur="0.9"/> D-P-H raises the hydrogen ion concentration <pause dur="4.6"/><kinesic desc="changes slide" iterated="n"/> just to remind you of course <pause dur="0.2"/> carbon dioxide protons all their equivalents are of course the major metabolic end points <pause dur="0.4"/> when i say equivalents i'm thinking about <pause dur="0.8"/> lactate lactate or ketones what have you <pause dur="21.0"/> <event desc="drinks" iterated="n"/> so we come back we <trunc>f</trunc> we return

to the lungs and consider now <pause dur="1.1"/><kinesic desc="changes slide" iterated="n"/> the binding of oxygen to haemoglobin in the lungs <pause dur="0.4"/> here i've represented haemoglobin <pause dur="0.5"/> carrying a proton <pause dur="0.8"/> which is released as oxygen binds <pause dur="0.8"/> this proton <pause dur="1.5"/> can drive the carbonate equilibrium <pause dur="0.5"/> to the left <pause dur="1.1"/> pushing carbonate back to carbonic acid and causing the <pause dur="0.5"/> the <pause dur="0.2"/> evolution of carbon dioxide in the lungs <pause dur="1.4"/> oxygenation of this species is reducing the concentration of this species in the blood <pause dur="0.4"/> and that helps <pause dur="0.8"/> drive this equilibrium <pause dur="0.5"/> to the left <pause dur="0.5"/> to release <pause dur="0.2"/> the bound carbon dioxide <pause dur="0.4"/> that's bound to haemoglobin <pause dur="1.9"/> so then the lungs of course because oxygen concentration is high <pause dur="0.4"/> favours <pause dur="0.5"/> oxygenation <pause dur="0.5"/> of haemoglobin <pause dur="3.8"/><kinesic desc="changes slide" iterated="n"/> so that's shown on the left <pause dur="0.7"/> sort of schematically the erythrocyte <pause dur="0.4"/> the alveolar surface <pause dur="1.3"/> incoming oxygen <pause dur="0.4"/> the shift in the hydrogen ions so-called isohydride shift <pause dur="1.7"/> and the driving of carbon dioxide out of <pause dur="1.0"/> the erythrocytes <pause dur="0.4"/> and <pause dur="0.2"/> into <pause dur="0.4"/> the alveoli <pause dur="0.9"/> and into <pause dur="0.2"/> the air we breathe out <pause dur="0.6"/> and exactly the opposite is true <pause dur="1.6"/> in active tissues in active tissues <pause dur="0.4"/> carbon

dioxide and hydrogen are are <pause dur="0.2"/> concentrations are high <pause dur="0.9"/> they're taken into the erythrocyte <pause dur="0.3"/> converted to the carbonate ion <pause dur="1.0"/> the carbonate ion is transported out by <pause dur="0.3"/> # # <pause dur="0.4"/> a chloride carbonate antiporter it's called band three in erythrocytes you'll learn a bit more about transporters in the next couple of weeks i think <pause dur="1.5"/> there's the isohydride shift <pause dur="0.3"/> that helps to drive <pause dur="0.2"/> oxygen off <pause dur="0.4"/> haemoglobin <pause dur="0.5"/> and drive it into <pause dur="0.6"/> the tissues where it's needed <pause dur="4.1"/><kinesic desc="changes slide" iterated="n"/> obviously all this <pause dur="0.2"/> # <pause dur="0.3"/> movement of hydrogen ions essentially means that <pause dur="0.3"/> the P-H <pause dur="0.6"/> in blood has to be very tightly regulated <pause dur="1.2"/> normal <pause dur="0.4"/> physiological <trunc>pa</trunc> P-H is in a very narrow range <pause dur="1.2"/> and any factors that <pause dur="0.4"/> <trunc>t</trunc> # <pause dur="0.5"/> take the <pause dur="0.3"/> normal physiological P-H outside this range can be <trunc>dager</trunc> dangerous indeed deadly <pause dur="1.4"/> you <trunc>ca</trunc> if you would look up <pause dur="0.2"/> # you can look up things like # acidosis <pause dur="0.3"/> in newborn children or # <pause dur="0.2"/> # premature children <pause dur="0.5"/> and <pause dur="0.3"/> you can see the you'll be able to read about the effects <pause dur="0.2"/> of <trunc>acido</trunc> that acidosis has <pause dur="0.3"/> on both the physiology <pause dur="0.3"/> # the long term <pause dur="0.3"/> development

of children their mental acuity and so on <pause dur="1.3"/> so regulating P-H is very very important <pause dur="2.2"/><kinesic desc="changes slide" iterated="n"/> and of course the main system that does it is the one we've just described it's the bicarbonate buffering system this represents about seventy per cent <pause dur="0.2"/> of the buffering capacity of blood <pause dur="1.4"/> phosphate also can be involved in <pause dur="0.8"/> # buffering and indeed of course the various proteins <pause dur="0.5"/> can do a little bit of buffering <pause dur="2.0"/> but of course this system is open <pause dur="0.3"/> it's open at <kinesic desc="indicates point on slide" iterated="n"/> this end because it's open in the lungs the carbon dioxide <pause dur="0.6"/> the equilibrium's open at <kinesic desc="indicates point on slide" iterated="n"/> that end <pause dur="0.4"/> the # equilibrium's open at the proton end because protons are the major metabolic <pause dur="0.3"/> end points <pause dur="0.2"/> as indeed is carbon dioxide <pause dur="3.0"/><kinesic desc="changes slide" iterated="n"/> so we can relate the control of blood <pause dur="0.5"/> to the way in which we are respiring <pause dur="4.4"/> if we're hyperventilating perhaps panicking about the molecules exam <pause dur="2.5"/> <vocal desc="laughter" iterated="y" n="ss" dur="1"/> then we're breathing deeply and rapidly <pause dur="1.8"/> that will force <pause dur="0.3"/> carbon dioxide out of the lungs <pause dur="0.7"/> draw this equilibrium <pause dur="0.5"/> to the left pulling protons

in <pause dur="0.7"/> and the P-H of the blood will essentially <pause dur="0.6"/> become more alkali <pause dur="3.2"/> so <trunc>in</trunc> <pause dur="1.8"/> yeah <pause dur="0.8"/> so it <pause dur="0.4"/> so hyperventilation is <pause dur="0.3"/> towards the alkali <pause dur="0.8"/> poor <pause dur="0.4"/> ventilation <pause dur="0.3"/> chronic <pause dur="0.3"/> obstructive pulmonary disease <pause dur="0.5"/> is going to keep carbon dioxide deep in the lungs and force the equilibrium <pause dur="0.3"/> to the left <pause dur="0.6"/> and the hydrogen ion concentration will increase <pause dur="1.2"/> so <trunc>hyperventi</trunc> hypoventilation <pause dur="0.4"/> is going to be giving you <pause dur="0.3"/> acidosis <pause dur="0.6"/> and hyperventilation <pause dur="0.5"/> is giving you <pause dur="0.2"/> alkalosis <pause dur="3.9"/><kinesic desc="changes slide" iterated="n"/> this of course <pause dur="1.1"/> the realization here is of course that the <pause dur="0.5"/> the lungs represent a very major control <pause dur="0.2"/> of P-H <pause dur="3.9"/> so here's respiratory alkalosis <pause dur="0.4"/> caused by hyperventilation <pause dur="0.2"/> simple treatment <pause dur="0.3"/> rebreathe or administer carbon dioxide <pause dur="3.4"/> conversely <trunc>re</trunc> respiratory acidosis caused by inadequate breathing <pause dur="0.2"/> unable to <pause dur="0.2"/> exchange the carbon dioxide in the lungs <pause dur="1.4"/> # <pause dur="0.9"/> have to administer more buffering <pause dur="1.1"/> probably I-V <pause dur="4.1"/> so the important point here <pause dur="1.9"/> is that <pause dur="0.9"/> because those equilibria are open <pause dur="0.4"/> at

either end <pause dur="2.3"/> # <pause dur="0.4"/> respiratory <pause dur="0.2"/> changes in P-H <pause dur="0.3"/> are related to metabolic changes in P-H <pause dur="5.7"/><kinesic desc="changes slide" iterated="n"/> so there are various much more common conditions that <pause dur="0.2"/> for example <pause dur="0.5"/> uncontrolled diabetes diarrhoea <pause dur="0.2"/> overdose of aspirin <pause dur="1.6"/> where or indeed <pause dur="0.2"/> prolonged heavy exercise <pause dur="0.3"/> <trunc>hec</trunc> exercise where you become metabolically acidotic you produce a lot of acid equivalents <pause dur="1.9"/> and that interferes <pause dur="0.2"/> with that carbonate buffering system <pause dur="0.8"/> and it overloads it at the right-hand end <pause dur="1.8"/> and so you go into deep <pause dur="0.8"/> rapid breathing you hyperventilate <pause dur="0.5"/> to blow off carbon dioxide <pause dur="0.9"/> what you're trying to do is pull hydrogen ions in <pause dur="0.5"/> from the metabolic <pause dur="0.7"/> acidosis <pause dur="0.7"/> and blow carbon dioxide off <pause dur="0.7"/> so respiratory alkalosis is linked to metabolic acidosis <pause dur="0.7"/> and therefore <pause dur="0.8"/> a <trunc>m</trunc> <pause dur="0.2"/> a respiratory alkalosis <pause dur="0.2"/> although is a condition itself <pause dur="0.2"/> may be caused <pause dur="0.9"/> by metabolic acidosis <pause dur="1.2"/> similarly the opposite is true if you're prolonged vomiting you lose a lot of hydrogen ions from the stomach you become <pause dur="0.6"/> # and you go into metabolic alkalosis <pause dur="0.4"/> then <pause dur="0.2"/> your breathing becomes

shallow and infrequent <pause dur="0.3"/> as the <pause dur="0.5"/> body attempts to compensate for that <pause dur="0.6"/> by holding on to the carbon dioxide forcing the equilibria to the right <pause dur="0.5"/> and increasing the hydrogen ion concentration <pause dur="0.3"/> to combat <pause dur="0.4"/> the alkalosis in the blood <pause dur="2.7"/> okay <pause dur="1.4"/> so we've talked about the transport of oxygen we've talked about the transport of <trunc>car</trunc> <pause dur="0.2"/> carbon dioxide and we've even talked a little bit about respiratory control of P-H <pause dur="0.5"/> i've talked about <pause dur="0.4"/> acidosis and alkalosis <pause dur="0.3"/> in relation to the <pause dur="0.7"/> lung <pause dur="0.4"/> the other major organ which i'm not going to talk about that controls P-H is of course the kidney <pause dur="5.4"/><kinesic desc="changes slide" iterated="n"/> so <pause dur="0.5"/> clinical correlations <pause dur="0.7"/> other clinical correlations perhaps <pause dur="3.1"/> haemoglobin can become glycosylated in blood this is a spontaneous <pause dur="0.2"/> # <pause dur="0.2"/> reaction between haemoglobin and glucose <pause dur="0.5"/> and in <pause dur="0.3"/> uncontrolled diabetes <pause dur="0.3"/> when <pause dur="0.3"/> glucose levels are elevated in blood <pause dur="0.4"/> glycated haemoglobin <pause dur="0.3"/> acts as a measure <pause dur="0.4"/> over the previous <pause dur="0.7"/> three <pause dur="0.3"/> three or four months <pause dur="0.5"/> # <pause dur="0.4"/> acts as a measure <pause dur="0.4"/> of the level of control <pause dur="1.0"/> of diabetes <pause dur="0.3"/> for example if # a diabetic

hasn't been <pause dur="0.3"/> following the insulin regime <pause dur="0.3"/> their glucose concentration will have been fluctuating wildly <pause dur="0.6"/> in their blood <pause dur="0.6"/> and <trunc>gluc</trunc> and the <pause dur="1.2"/> glycosylated haemoglobin acts as a marker for that <pause dur="1.6"/> we've already talked about the role of two-three-bisphosphoglycerate <pause dur="0.2"/> stored blood of course <pause dur="0.4"/> the two-three bisphosphoglycerate rapidly <pause dur="0.3"/> # degrades <pause dur="0.4"/> so it <trunc>nus</trunc> needs to be added to stored blood if it's going to be transfused and we've also talked about the physiological <pause dur="0.7"/> # <pause dur="0.2"/> conditions that may alter the level of two-three-bisphosphoglycerate <pause dur="1.4"/> what we haven't talked about at all <pause dur="0.4"/> are haemoglobinopathies <pause dur="0.5"/> such as sickle cell and the related thalassemias they are relatively rare and there are many of them <pause dur="0.9"/> they all relate to either alterations in the globin structure or indeed <pause dur="0.4"/> # a loss <pause dur="0.4"/> of expression of a globin gene <pause dur="0.3"/> thalassemias <trunc>p</trunc> vary in their <pause dur="0.4"/> # severity from relatively mild <pause dur="0.6"/> to relatively severe <pause dur="0.9"/> # and this would be an area i suggest you have a brief look at if you get the

time <pause dur="2.1"/> right <pause dur="1.7"/> hello oh <pause dur="0.9"/> good <pause dur="0.7"/> well that <pause dur="1.5"/> has <pause dur="0.3"/> taken nearly <pause dur="0.2"/> well just over half the lecture i thought we'd just have a little break now <pause dur="0.7"/> and do something a little bit different </u><gap reason="break in recording" extent="uncertain"/> <u who="sf0444" trans="pause"> <kinesic desc="video plays" iterated="y" dur="3:16"/> <pause dur="9.6"/> so obviously they just brought somebody in unconscious <gap reason="inaudible due to background noise" extent="1 sec"/> </u><pause dur="29.8"/> <u who="sf0444" trans="pause"> and Malucci being a bigot just ask first and then he completely ignores <unclear>what he said</unclear> </u><pause dur="21.9"/> <u who="sf0444" trans="pause"> <gap reason="inaudible due to background noise" extent="1 sec"/> heart attack <gap reason="inaudible due to background noise" extent="1 sec"/> </u><pause dur="23.4"/> <u who="sf0444" trans="pause"> so Malucci's really caught up in the <gap reason="inaudible" extent="1 sec"/> <pause dur="0.3"/> he's <gap reason="inaudible" extent="1 sec"/> <pause dur="0.3"/> <gap reason="inaudible" extent="1 sec"/> </u><pause dur="18.1"/> <u who="sf0444" trans="pause"> and now he's just trying to pressure the doctor into making his decision </u><pause dur="26.4"/> <u who="sf0444" trans="pause"> they've just lost the patient </u><pause dur="23.8"/> <u who="sf0444" trans="pause"> now <gap reason="inaudible" extent="1 sec"/> in the scene </u><pause dur="44.5"/> <u who="sf0444" trans="pause"> and then he's still stuck on the fact that it's drug-related <pause dur="0.2"/> though <pause dur="0.2"/> <gap reason="inaudible" extent="1 sec"/> </u><pause dur="11.5"/> <u who="sf0444" trans="pause"> so they've started giving a clot-buster to somebody who's completely bleeding out so now he has no <gap reason="inaudible" extent="1 sec"/> <pause dur="7.1"/> and he's <unclear>haemorrhaging</unclear> <pause dur="0.6"/> <gap reason="inaudible" extent="1 sec"/> <pause dur="8.7"/> and <kinesic desc="indicates point on screen" iterated="n"/> that's the i'm in big shit look <event desc="stops video" iterated="n"/></u><pause dur="2.1"/> <u who="nm0442" trans="pause">

round of applause for <gap reason="name" extent="1 word"/> there <pause dur="1.1"/> <kinesic desc="applause" iterated="y" n="ss" dur="6"/> well done <pause dur="5.9"/><kinesic desc="changes slide" iterated="n"/> ooh get rid of that <pause dur="4.3"/> okay <pause dur="2.3"/> so the classic differential <pause dur="0.5"/> on M-I <pause dur="0.8"/> is dissection <pause dur="0.9"/> the aorta the aorta splitting <pause dur="0.7"/> and if you misdiagnose your M-I <pause dur="0.5"/> you give a clot-buster and they bleed into the chest because they're dissecting and it was the clot that was holding them together <pause dur="1.6"/> and <pause dur="0.9"/> as # <pause dur="0.3"/> Carter the unstoppable sex machine spotted <pause dur="1.5"/> <vocal desc="laughter" iterated="y" n="ss" dur="2"/> # this guy's a Marfan <pause dur="1.0"/> and a Marfan <pause dur="0.6"/> is # a collagen or it's actually a collagen-related disease <pause dur="0.2"/> he has Marfan's syndrome <pause dur="0.7"/> and Marfan's syndrome <pause dur="0.3"/> is a defect in collagen <pause dur="0.9"/> and frequently <pause dur="0.8"/> # pathologically <pause dur="0.4"/> these people suffer from vascular problems <pause dur="0.3"/> and various other <pause dur="0.3"/> presentations of a a collagen disease <pause dur="0.4"/> so <pause dur="0.4"/> what we're going to talk about now <pause dur="0.5"/> is collagen <pause dur="2.0"/> so in everything i've kind of told you about haemoglobin and about helices <pause dur="0.3"/> when it comes to collagen you

begin to throw all these things out of the window <pause dur="1.9"/> the first thing is that it has # essentially a repeating structure of of essentially three amino acids it's a gly-X-Y as it says there gly-X-Y motif <pause dur="0.4"/> and X and Y are either proline or hydroxyproline lysine or hydroxylysine mainly <pause dur="1.8"/> # <pause dur="0.5"/> it's found in of course <pause dur="0.4"/> tendons cartilage <pause dur="0.5"/> bones on the surface on the articular surface of bones even in the eye <pause dur="1.8"/> # the micrograph there just gives you an idea of the structure of collagen fibres and we see this kite <pause dur="0.2"/> quite characteristic <pause dur="0.4"/> # <pause dur="0.4"/> banded pattern that's seen in obviously only in fibres <pause dur="0.4"/> and then at the end there this cross section you can see how they represent <trunc>bu</trunc> fibres of <pause dur="0.3"/> # bundles of fibres bundled together <pause dur="4.8"/><kinesic desc="changes slide" iterated="n"/> there are <pause dur="0.4"/> it says at least ten there are about <pause dur="0.2"/> thirty <pause dur="0.9"/> different types of collagen <pause dur="1.6"/> some form fibrils <pause dur="1.0"/> some <pause dur="0.2"/> <trunc>s</trunc> form <trunc>mal</trunc> small fibrils called microfibrils <pause dur="0.7"/> some are associated with fibrils and are a little bit fibrillar-like <pause dur="0.5"/> but also have <pause dur="0.4"/> interruptions in their fibrillar

structure <pause dur="0.3"/> and some <pause dur="0.2"/> just form network <pause dur="0.2"/> meshworks <pause dur="1.6"/> so there are fibrillar types <pause dur="0.9"/> microfibrillar types <pause dur="0.3"/> non-fibrillar types and <pause dur="0.3"/> fibrillar associated collagens <pause dur="0.2"/> with interrupted triple helix <pause dur="0.7"/> facit <pause dur="1.2"/> okay <pause dur="0.2"/> for those of you are from Essex that's not <pause dur="0.2"/> <shift feature="voice" new="mimicking Essex accent"/>fuck it <shift feature="voice" new="normal"/><pause dur="5.8"/><vocal desc="laughter" iterated="y" n="ss" dur="5"/> okay <pause dur="0.8"/> and the structure is completely different <pause dur="0.4"/> it's a left-handed helix <pause dur="2.9"/><kinesic desc="changes slide" iterated="n"/> it is a very tight turning helix and it's it's left-handed <pause dur="0.4"/> and tight turning because of the residues in there <pause dur="0.3"/> proline helps <pause dur="0.4"/> # the tight turn <pause dur="0.6"/> as does hydroxyproline <pause dur="1.1"/> glycine has <pause dur="0.2"/> virtually no <pause dur="0.3"/> side chain <pause dur="0.2"/> so that allows <pause dur="0.2"/> the turn to be very tight <pause dur="3.5"/> and a single collagen <pause dur="0.4"/> left-handed helix <pause dur="0.4"/> is wound with two other left-handed helices <pause dur="1.4"/> to form a right-handed helices <pause dur="0.3"/> # a coiled coil <pause dur="0.5"/> and coiled coils of course <pause dur="0.2"/> structurally <pause dur="0.2"/> are very strong <pause dur="1.0"/> that's not to say that <pause dur="0.4"/> # <pause dur="1.3"/> any strong protein structure has to be helices because there are plenty of examples of <pause dur="0.2"/> strong protein structures that are beta sheet <pause dur="0.2"/> and silk fibroid <pause dur="0.2"/> is a very good example of that <pause dur="0.5"/>

but <pause dur="0.2"/> nevertheless coiled coiled <pause dur="0.3"/> type structures <pause dur="0.2"/> are structurally <pause dur="0.5"/> very strong <pause dur="2.0"/><kinesic desc="changes slide" iterated="n"/> so i'm just going to briefly <pause dur="0.5"/> review <pause dur="0.7"/> the biosynthesis and post-translation of collagen and then we're going to go through it in a little more detail in subsequent slides <pause dur="0.2"/> but basically <pause dur="1.7"/> of course the M-R-N-A is translated and it is <pause dur="0.3"/> both translated and secreted <pause dur="0.4"/> into the E-R <pause dur="2.7"/> in the E-R <pause dur="0.6"/> the <pause dur="0.2"/> lysines and prolines become hydroxylated <pause dur="0.9"/> by specific hydroxylases <pause dur="3.9"/> some of the hydroxylated residues will subsequently become <pause dur="0.2"/> glycosylated <pause dur="0.7"/> so there's O-link glycosylation on those hydroxylated residues <pause dur="0.8"/> others will be involved <pause dur="0.4"/> in promoting hydrogen bonding and it <pause dur="0.3"/> the hydroxy residues are involved in hydrogen bonding <pause dur="0.2"/> and also indeed in cross-linking <pause dur="0.2"/> as we'll see further along <pause dur="2.1"/> there's also some end-linked glycosylation <pause dur="1.7"/> of of collagen <pause dur="1.7"/> and the ends of the collagen molecule are <pause dur="0.4"/> disulphide bridged to form a sort of globular structure <pause dur="2.0"/> so there are several post-translational modifications that occur <pause dur="0.3"/> in the

E-R <pause dur="0.8"/> the hydroxylation the glycosylation <pause dur="0.4"/> and the formation of disulphide bonds <pause dur="1.6"/> three <pause dur="1.5"/> collagen helices are then wound together <pause dur="1.0"/> and this winding <pause dur="0.5"/> involves <pause dur="0.5"/> the <pause dur="0.7"/> # <trunc>r</trunc> arraying these <trunc>collage</trunc> these <trunc>s</trunc> sorry globular <pause dur="0.7"/> <trunc>gr</trunc> # <pause dur="1.0"/> modules at the end <pause dur="0.5"/> of the collagen fibre <pause dur="0.5"/> they help bring the three collagen fibres together and promote the winding of three collagen fibres <pause dur="1.7"/> glycosylation <pause dur="0.2"/> in amongst the <pause dur="0.5"/> wound areas helps # interrupt the helices hence <pause dur="0.3"/> interrupted <pause dur="0.4"/> triple helix <pause dur="1.9"/> <trunc>go</trunc> so glycosylation plays an important role in <pause dur="0.3"/> # interrupting the triple helix <pause dur="0.3"/> it also plays a role <pause dur="0.3"/> in maintaining the solubility <pause dur="0.2"/> of collagen <pause dur="0.4"/> so it's a <pause dur="0.4"/> the # carbohydrate molecules help <pause dur="0.3"/> attract the water <pause dur="2.0"/><kinesic desc="indicates point on slide" iterated="n"/> this then is secreted <pause dur="1.6"/> out of the cell and the secretion of such a large molecule is not an insignificant task <pause dur="2.2"/> the globular <pause dur="0.3"/> portions will be removed <pause dur="1.4"/> leaving the mature fibre <pause dur="0.5"/> with a degree of <pause dur="0.3"/> interruption in the triple helix or not <pause dur="0.5"/> and some of the <trunc>re</trunc> residual <pause dur="0.5"/> hydroxyl groups particularly the ones at

the ends <pause dur="0.4"/> of the mature fibre <pause dur="0.3"/> are involved in cross-linking <kinesic desc="indicates point on slide" iterated="n"/> this fibre <pause dur="0.3"/> to another fibre <pause dur="0.4"/> and that cross-linking <pause dur="0.5"/> # <pause dur="0.3"/> is evidenced by the banded pattern <pause dur="0.2"/> that we see <pause dur="0.4"/> in collagen in fibrillar collagens <pause dur="2.2"/><kinesic desc="changes slide" iterated="n"/> so in a little more detail then <pause dur="0.9"/> # this <pause dur="0.2"/> <trunc>exe</trunc> example for proline <pause dur="1.9"/> there are specific <pause dur="0.4"/> # <pause dur="1.9"/> hydroxylases in the # <pause dur="2.0"/> E-R <pause dur="0.7"/> and they're vitamin C requiring <pause dur="3.8"/> the absence of vitamin C <pause dur="0.5"/> # <pause dur="1.3"/> results in improper hydroxylation <pause dur="0.4"/> of <pause dur="0.3"/> proline <pause dur="0.2"/> and lysine <pause dur="1.4"/> and vitamin C deficiency is of course scurvy <pause dur="1.5"/><kinesic desc="changes slide" iterated="n"/> i quite like this little description of scurvy from <pause dur="0.3"/> # Jacques Cartier who # <pause dur="0.3"/> discovered Canada <pause dur="0.3"/> fifteen-hundred like the last <trunc>bi</trunc> bit the best <pause dur="0.3"/> <reading>their mouth became stinking <pause dur="0.4"/> their gums so rotten <pause dur="0.4"/> that all the flesh did fall off even to the roots of the teeth <pause dur="0.2"/> teeth <pause dur="0.2"/> which did also almost all fall out</reading> <pause dur="0.7"/> course in retrospect he didn't know <pause dur="0.2"/> that they were on the Atkins diet <pause dur="2.0"/> <vocal desc="laughter" iterated="y" n="ss" dur="1"/><vocal desc="laughter" iterated="y" n="sl" dur="4"/> <pause dur="2.2"/> so <pause dur="0.3"/> first key point in # collagen biosynthesis <pause dur="0.4"/> you need vitamin C <pause dur="3.6"/><kinesic desc="changes slide" iterated="n"/> the <trunc>sp</trunc> the the

residues <pause dur="0.8"/> glycine hydroxyproline and proline <pause dur="0.2"/> permit the association of the three <trunc>chai</trunc> the three chains together and they can be <pause dur="0.2"/> become intimately <pause dur="0.2"/> interwoven <pause dur="0.5"/><kinesic desc="indicates point on slide" iterated="n"/> here <pause dur="0.6"/> one of the residues <pause dur="0.6"/> # has been mutated <pause dur="0.8"/> in silico in the computer <pause dur="0.3"/> to an alanine <pause dur="0.7"/> and that drives the chain apart in <kinesic desc="indicates point on slide" iterated="n"/> this <pause dur="0.3"/> area <pause dur="0.6"/> so a simple <pause dur="0.5"/> mutation <pause dur="0.4"/> in collagen <pause dur="0.3"/> can drive <pause dur="0.3"/> the chains apart <pause dur="1.2"/> and weaken the overall collagen structure <pause dur="1.7"/> this is of course the basis <pause dur="0.3"/> of osteogenesis imperfecta <pause dur="1.0"/> where there is a mutation <pause dur="0.4"/> of a glycine in <trunc>s</trunc> <pause dur="0.3"/> <trunc>mi</trunc> most of the time it's to a cysteine it occurs in <pause dur="0.3"/> one of the major <trunc>coloni</trunc> <pause dur="0.3"/> collagen types <pause dur="2.2"/><kinesic desc="changes slide" iterated="n"/> there are <trunc>sev</trunc> because there are <pause dur="0.3"/> three <pause dur="0.7"/> three collagen genes there are <pause dur="0.8"/> multiple variations <pause dur="0.3"/> into the presentation of osteogenesis imperfecta <pause dur="2.1"/> normally they of course will have <pause dur="0.2"/> brittle bones as the name suggests osteogenesis is <pause dur="0.4"/> generation of bones imperfecta <pause dur="0.3"/> imperfect <pause dur="0.6"/> it is relatively rare <pause dur="1.7"/> and in certain cases <pause dur="0.2"/> can be absolutely lethal <pause dur="1.6"/><kinesic desc="changes slide" iterated="n"/> give you an idea of what sort of X-ray of what a <trunc>p</trunc> a baby with

osteogenesis imperfecta looks like you can see these <pause dur="0.6"/> multiple fractures here <kinesic desc="indicates point on slide" iterated="n"/><pause dur="1.2"/> the <pause dur="0.2"/> sort of <pause dur="0.9"/> thickening and the <trunc>thinneni</trunc> thinning of the bone these you can't see the ribs very well but the ribs are <trunc>v</trunc> quite characteristically in this sort of <pause dur="0.4"/> # <pause dur="0.8"/> this sort of # <pause dur="0.2"/> appearance on X-ray <pause dur="1.9"/> so it's quite a severe disease <pause dur="0.2"/> it's also some <trunc>s</trunc> <pause dur="0.2"/> frequently collagen <trunc>disor</trunc> disorders can be picked up <pause dur="0.6"/> in the whites of the eye the so-called sclera of the eye they have a <trunc>s</trunc> slightly blue or greyish tinge <pause dur="0.3"/> because of the collagen <pause dur="0.4"/> that's in the # the whites of the eye <pause dur="0.6"/> and in # <pause dur="0.2"/> patients with osteogenesis imperfecta <pause dur="0.5"/> there's less collagen in the eye <pause dur="0.3"/> and a pigment from behind the <trunc>e</trunc> the eye shows through <pause dur="0.3"/> and so they have an apparent blue tinge <pause dur="0.4"/> to the sclera <pause dur="4.6"/><kinesic desc="changes slide" iterated="n"/> the <pause dur="0.2"/> part of the <pause dur="0.2"/> structural integrity of collagen is through hydrogen bonding between those hydroxyprolines <pause dur="0.4"/> # <pause dur="0.2"/> and # <pause dur="0.2"/> glycines and proline residues <pause dur="0.3"/> that gives <pause dur="0.8"/> cross-chain or <pause dur="0.3"/> interchain <pause dur="0.4"/> hydrogen bonding it helps stabilize the <trunc>hae</trunc> helix and <pause dur="0.2"/> contribute

to the mechanical strength <pause dur="0.3"/> that's seen in <pause dur="1.0"/> collagenous <pause dur="0.4"/> # tissues like tendon <pause dur="6.9"/><kinesic desc="changes slide" iterated="n"/> here we can see a little more detail on the the role of this globular domain <pause dur="0.6"/> it helps bring the three chains together allows them to twist together to form the <pause dur="1.2"/> mature <pause dur="0.5"/> tropocollagen and then these are removed <pause dur="0.4"/> in the extracellular space <pause dur="0.7"/> by an enzyme called procollagen peptidase <pause dur="2.7"/><kinesic desc="changes slide" iterated="n"/> a deficiency in procollagen peptidase is characterized by <pause dur="0.3"/> a syndrome called Ehlers syndrome Ehlers Danlos syndrome <pause dur="2.3"/> heard a little bit about this in the genetics lecture because Ehlers' very complex <pause dur="0.2"/> can have complex inheritance <pause dur="0.7"/> it's quite <trunc>char</trunc> characteristic <pause dur="0.3"/> hypermobile <pause dur="0.3"/> joints and very stretchy skin </u><gap reason="break in recording" extent="uncertain"/> <u who="nm0442" trans="pause"> # <pause dur="0.7"/> and <pause dur="0.9"/> like many of these <pause dur="0.3"/> # collagen and collagen-related diseases the prognosis may be shortened <pause dur="0.5"/> because of vascular complications in the heart <pause dur="0.3"/> or in the major vessels <pause dur="8.9"/><kinesic desc="changes slide" iterated="n"/> once the mature collagen <pause dur="0.3"/> fibre has been secreted into the <trunc>extras</trunc> extracellular space it's cross-linked <pause dur="0.2"/> it's cross-linked at the <trunc>en</trunc> <pause dur="0.4"/> at

the ends here <pause dur="1.8"/> free hydroxyls from <trunc>l</trunc> # <pause dur="0.2"/> free hydroxyls <pause dur="0.2"/> free hydroxylysines <pause dur="0.2"/> or indeed lysines <pause dur="0.2"/> are covalently linked <pause dur="0.3"/> across <pause dur="0.8"/> these <pause dur="0.6"/> triple helices <pause dur="3.5"/><kinesic desc="changes slide" iterated="n"/> this gives you an idea actually this is a lysine cross link <pause dur="0.6"/> to form a so-called shift base <pause dur="2.4"/> you don't really <pause dur="0.3"/> you just need to know that that's a covalent link you don't really need to worry about the <trunc>f</trunc> the <pause dur="0.6"/> <trunc>fan</trunc> fascinating structure of a shift base <pause dur="0.5"/> # <pause dur="0.7"/> nevertheless <pause dur="0.6"/> there is another disease associated with the <pause dur="0.6"/> improper cross-linking of collagen and that's called lathyrism <pause dur="2.4"/> inhibition of lysyl oxidase the <trunc>cro</trunc> the collagen cross-linking enzyme <pause dur="1.3"/> by found <pause dur="0.4"/> this compound's found in sweet pea so although sweet pea of course is a <pause dur="0.5"/> very good source of vitamin C <pause dur="0.2"/> it's not necessarily the best cure for scurvy <pause dur="0.4"/> because actually what you do is you inhibit the lysyl oxidase <pause dur="1.2"/><kinesic desc="changes slide" iterated="n"/> okay and again <pause dur="2.2"/> a collagen disease where dislocations of the joints <pause dur="0.2"/> and vascular problems <pause dur="1.7"/> are associated with the disease <pause dur="2.7"/><kinesic desc="changes slide" iterated="n"/> all of those diseases represent loss <pause dur="0.3"/> of function <pause dur="1.7"/>

but gain of function or <pause dur="0.3"/> deposition of collagen <pause dur="0.2"/> can be <trunc>le</trunc> <pause dur="0.2"/> can be equally as dangerous <pause dur="0.6"/> it's referred to medically as fibrosis <pause dur="2.9"/> in <trunc>exa</trunc> for example in a medical student liver <pause dur="0.2"/> being constantly abused by alcohol scarred <pause dur="0.6"/> collagen is busily being deposited in <pause dur="0.2"/> that gentleman up there who's <pause dur="0.2"/><vocal desc="laughter" iterated="y" n="sl" dur="1"/> <pause dur="0.4"/> busy partying every night <pause dur="0.6"/> and # <pause dur="1.9"/> that can result in impaired liver function <pause dur="0.9"/> similarly in the heart fibrosis of the heart tissue is going to result in severe <pause dur="0.5"/> # reduction in the efficiency of the heart in stroke volume and so on <pause dur="1.3"/> and that and that # again <pause dur="1.4"/> serious # complication <pause dur="0.6"/> lung fibrosis is quite interesting and and of course <pause dur="0.7"/> lung fibrosis is going to dramatically reduce the oxygen uptake <pause dur="0.5"/> the oxygen uptake ability of the lungs <pause dur="0.4"/> and lung fibrosis is frequently caused <pause dur="0.6"/> # in <pause dur="0.3"/> it's frequently found in patients in long term stay in hospital <pause dur="1.7"/> and can be induced <pause dur="0.3"/> indeed quite rapidly by certain drug treatments as well so you can <pause dur="0.2"/> you can treat patients with certain drugs and

all of a sudden <pause dur="0.3"/> you induce lung <trunc>fun</trunc> fibrosis and it's a very serious problem <pause dur="1.2"/> so both loss of function and gain of function of collagen <pause dur="0.4"/> are serious <pause dur="0.3"/> medical issues <pause dur="5.3"/><kinesic desc="changes slide" iterated="n"/> in the main we've talked about these fibrillar collagens and the # the # notion that they're <pause dur="0.9"/> they're of course involved in ligaments tendons in the architecture of joints <pause dur="0.5"/> # that they are <pause dur="0.7"/> in in <pause dur="0.2"/> in those cases they're complex molecules they contain fibrillar collagens microfibrils they contain collagens that are <trunc>is</trunc> just <pause dur="0.2"/> there to be associated <pause dur="0.2"/> with the fibril <pause dur="1.4"/> other collagens <pause dur="0.3"/> and <trunc>du</trunc> generally these collagens will be much more heavily glycosylated <pause dur="0.2"/> form branch structures <pause dur="0.5"/> they form <pause dur="0.6"/> meshworks <pause dur="0.2"/> that are involved in the formation of basement membranes which <pause dur="0.2"/> endothelial layers <pause dur="0.4"/> grow on the when on which fibroblast <pause dur="0.6"/> layers will grow <pause dur="2.9"/><kinesic desc="changes slide" iterated="n"/> right well should just say as well of course in in this case the extracellular matrix is not just collagen it's associated with a lot of other proteins proteoglycans <pause dur="0.4"/> # glycoproteins <pause dur="0.3"/> and the

various elastins <pause dur="0.4"/> and <pause dur="1.5"/><kinesic desc="changes slide" iterated="n"/> it's the elastin gene <pause dur="0.5"/> which there's only one <pause dur="0.6"/> # <pause dur="0.2"/> # gene # one elastin gene <pause dur="0.2"/> that's mutated in Marfan <pause dur="2.5"/> it's similar to collagen it has this glycine and proline <pause dur="0.7"/> rich sequence <pause dur="1.0"/> has # <pause dur="0.4"/> more valine in it <pause dur="0.3"/> it's essentially very hydrophobic <pause dur="1.6"/> it <pause dur="0.2"/> it # <pause dur="0.3"/> it's <trunc>le</trunc> much less post-translationally modified than is collagen <pause dur="0.2"/> it has very little secondary <trunc>struc</trunc> recognisable secondary structure perhaps that's consistent with its # more elastic properties <pause dur="0.9"/> it is cross-linked in the same way as collagen is by the lysyl oxidase <pause dur="2.6"/> and it's mutations in that fibrillin gene <pause dur="0.4"/> that make up elastin fibres <pause dur="0.2"/> that are responsible <pause dur="0.4"/> for the Marfan <pause dur="0.5"/> syndrome <pause dur="3.2"/> and quite characteristically the Marfans are tall <pause dur="0.6"/> they have # <pause dur="0.2"/> long limbs <pause dur="0.2"/> arachnodactyly which is spidery long fingers <pause dur="0.6"/> and the thing that # <pause dur="0.4"/> alerted <pause dur="0.4"/> Carter was the <pause dur="0.2"/> <trunc>pec</trunc> pectus excavatum which essentially means a slightly sunken chest <pause dur="5.4"/><kinesic desc="changes slide" iterated="n"/> so <pause dur="1.5"/> in just about an hour we have reviewed protein structure <pause dur="1.1"/> we've talked about the

binding regulation of the binding of oxygen to haemoglobin and myoglobin and we've even <pause dur="0.3"/> watched telly and done the collagen diseases <pause dur="0.4"/> you will notice at the end of your lecture handout <pause dur="0.4"/> that there are a few <trunc>sli</trunc> there are a few slides i've included about # <pause dur="0.3"/> the molecular basis <pause dur="0.6"/> of the contraction of muscle <pause dur="0.5"/> something that we <pause dur="0.2"/> don't have time to cover <pause dur="0.8"/><kinesic desc="changes slide" iterated="n"/> in this series and something i suggest you use your hour <pause dur="0.8"/><kinesic desc="changes slide" iterated="n"/> now <kinesic desc="changes slide" iterated="n"/> to have a little brief look at and familiarize yourself with <pause dur="0.3"/><kinesic desc="changes slide" iterated="n"/> in particular <pause dur="0.8"/> the basic <pause dur="0.4"/> # <pause dur="0.5"/> apparatus that's involved in skeletal <pause dur="1.1"/> smooth and cardiac muscle that regulates the contraction <pause dur="0.6"/> and even a little bit on how to recognize what a skeletal muscle cell looks like <pause dur="0.3"/> compared to a smooth muscle cell <pause dur="0.5"/> compared to a cardiac muscle <pause dur="1.0"/> okay <pause dur="0.9"/> so we're done for the <pause dur="0.3"/> the groups that have got to go i suggest you go if there's anybody who wants to come and ask me something come down when <pause dur="0.3"/> when <pause dur="0.2"/> the first group have <pause dur="0.3"/> got away