1P-30 PDF
A Study of MO Calculation for One-Side Preferential Cleavage at N-Cα bond of Peptide Backbone in Matrix-Assisted Laser Desorption/Ionization In-Source Decay Mass spectrometry
In-source decay(ISD) coupled with MALDI has been recognized as a top-down approach for obtaining amino acid sequence from intact proteins without pre-digestion. The recent research showed that the N-Cα bonds of specific amino acid residues, Gly-Xxx and Xxx-Asp/Asn were more susceptible to MALDI-ISD than other residues. The reactions of N-Cα bond cleavage and one-side preferential cleavage at the N-Cα bond of Gly-Xxx, Xxx-Asp/Asn would be discussed on the basis of ab initio calculations. The result indicates that accessibility of hydrogen-radicals to the backbone carbonyl oxygens of analyte proteins is essential for the preferential cleavage leading to the observation of discontinuous intense ISD fragment ions.