Mixed gas chemical ionization mass spectrometry of peptide derivatives

Abstract

In chemical ionization mass spectrometry, the use of a noble reagent gas mixed with a proton transfer reagent gas is known to produce mass spectra which contain both protonated molecules and fragment ions. We have used a mixture of isobutane and argon to improve the mass spectra of peptides which have been derivatized to O-TMS-polyamino alcohols. The molecular weight is deduced from a prominent [M+ H]+ ion; the sequence of amino acids is deduced from the usual A-and Z-series fragment ions. This technique enhances the sequence ions for lysine and glycine-containing peptides, and retains the ability to distinguish C-terminal leucine and isoleucine.

The Journey Is the Reward, a Taoist Proverb: John B. Fenn Award for Distinguished Contribution in Mass Spectrometry Lecture

“…By balancing the ratio of argon and isobutane used for peptide ionization, a large protonated molecule could be produced with substantial EI-like fragmentation. 12 One of the assignments in Professor Anderegg's graduate mass spectrometry class was to present the research findings from a leading mass spectrometry laboratory. I chose the laboratory of Professor Donald Hunt at the University of Virginia (UVA) whose laboratory had been at the forefront of chemical ionization research in the 1970s and who was starting to use mass spectrometry to sequence peptides.…”

“…Isobutane is a gentle chemical ionization reagent that creates protonated molecular ions when peptides are ionized by it. By balancing the ratio of argon and isobutane used for peptide ionization, a large protonated molecule could be produced with substantial EI-like fragmentation …”