Electrospray fundamentals and non-covalent peptide-lipid interactions as studied by Fourier transform ion cyclotron resonance mass spectrometry.

摘要

A novel electrochemical probe has been designed, built, and used to characterize the distribution in solution potential within the metal capillary and Taylor cone of the electrospray (ES) device. Results show that the measured potential difference increases as the internal probe travels toward the ES capillary exit, with values rising sharply as the base of the Taylor cone is penetrated. Higher conductivity solutions exhibit potentials of higher magnitude at longer distances away from the counter electrode, but these same solutions show lower potentials near the ES capillary exit. Removal of easily oxidizable species from the solution causes the measured potential difference to have nonzero values at distances further within the capillary, and the values measured at all points are raised. The influence of the diameter of the spray tip employed for nano-electrospray mass spectrometry (nano-ES-MS) upon mass spectral charge state distributions was investigated. A detailed comparison of charge state distributions obtained for nanospray capillaries of varying diameters was undertaken while systematically varying experimental parameters such as sample flow rate, analyte concentration, solvent composition, and electrospray current. The general tendency to obtain higher charge states from narrow diameter capillaries was conserved throughout, but tips with smaller orifices were more sensitive to sample flow rate, while tips with larger orifices were more sensitive to analyte concentration and pH of the solution.; Electrospray mass spectrometry (ES-MS) has been employed to study noncovalent associations between lipids and fusion peptides. Detailed binding specificities between selected phospholipids and model fusion peptides were investigated. Strong evidence has been compiled to demonstrate the importance of the initial hydrophobic interaction to the observation of lipid-peptide binding by ES-MS. Initial hydrophobic interactions in solution contributed heavily to the formation of these peptide-lipid complexes, particularly for [peptide+PC] complexes, whereas electrostatic interactions played a larger role for [peptide+PG] complexes. The influence of solution pH and degree of unsaturation of lipids upon the binding strength of [peptide+PC] complexes were also investigated. These experiments help to establish ES-MS as a viable new biotechnology tool capable of providing valuable information regarding the strength of hydrophobically driven, noncovalent interactions.