Negative Ion Mass Spectrometry in Peptide Sequencing

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A new method for peptide sequencing will be developed involving negative ion mass spectrometry. Negative chemical ionization mass spectrometry (NCI-MS) can provide the dramatic enhancement in sensitivity necessary to keep pace with the mechanical and engineering improvements in automated protein sequencing. For molecules which are strongly electron-capturing, NCI-MS has been reported to have detection limits in the femtomole to attomole (10-18) range. Because of the selectivity of the ionization process, background noise is diminished, further enhancing signal to noise ratio. The proposed research will involve exploring a variety of electron-capturing phenylisothiocyanate (PITC) derivatives by NCI-MS and demonstrate a highly sensitive detection method for use in protein and peptide sequencing. protein sequencing is important for an understanding of the roles of modified amino acids in protein structure and to provide probes for cloning genes as well as to deliminate the boundaries of DNA segments coding for proteins. This instrument development proposal seeks also to be able to work with far smaller amounts of material than current efforts in microchemistry.