Electrospray ionization (ESI) has become an important method of ionization for the mass spectrometric analysis of biological samples. The study of non covalent interactions involving proteins and peptides is one such topic that ESI has been applied to. ESI can preserve non covalent complexs formed in native solution through a transition into the gas phase as multiply charged ions, which are required for mass spectrometric measurements.
Nano electrospray ionization is a variation of ESI which produces much smaller primary droplets than standard ESI- in the range of between 100-200 nm instead of several μm. It is therefore unsurprising that the most widely acknowledged advantage of using nano-ESI is a very low sample consumption. Reducing the quantity of analyte, however, does not necessarily result in lower signal intensities, infact intensities are normally either equal or even higher than when using conventional ESI. Other advantages of nano- ESI include a higher tolerance towards salt contamination, fewer analyte suppression effects in mixtures, and mild conditions that allow the detection of non-covalent complexes
The production of Nano ESI needles is rigidly controlled because nano- ESI spectra have been shown to be highly dependent on the properties of the nanospray needle used, small variations in needle aperture size and coating can lead to a lack of reproducibility and differing ion intensities. Despite this, the advantages of nano ESI makes it an ideal method for probing problems of biological and biochemical interest
Fig 1. Side and end view of a dual channelled nano-ESI emitter
In this project FTICR mass spectrometry has been used to study whether new dual channelled nano-ESI emitters would form an electrospray suitable for mass spectrometric measurements and whether mixing would occur between samples loaded down different sides of the dual emitter.