Surface chemical ionization mass spectra of protein amino acids

Abstract

The mass spectra of nineteen protein amino acids have been studied using a new type of time-of-flight mass spectrometer that employs 252Cf fission fragments to ionize the sample molecules. The amino acids investigated include glycine, alanine, serine, proline, valine, threonine, cysteine, leucine, isoleucine, aspartic acid, lysine, glutamic acid, methionine, histidine, phenylalanine, tyrosine, tryptophan, arginine, and cysteine. Positive and negative ion spectra were obtained for each amino acid. The spectra have been interpreted and correlated to molecular structure. Fragmentation mechanisms and been proposed. Samples were prepared using the technique of nebulization and vacuum evaporation. Fast timing techniques and fast electronics were used to generate logic timing signals for an EG&G time digitizer which was interfaced to a 4096-channel analyzer. The new technique which has been developed uses solid samples and ionization occurs without sample volatilization so many compounds which are not amenable to other mass spectrometric methods are now accessible.