FRAGMENTATION OF PROTONATED PEPTIDES - SURFACE-INDUCED DISSOCIATION IN CONJUNCTION WITH A QUANTUM-MECHANICAL APPROACH

This paper describes the results of a systematic investigation designe d to assess the utility of surface-induced dissociation in the structu ral analysis of small peptides (500-1800u). A number of different pept ides, ranging in mass and amino acid sequence, are fragmented by colli sion with a surface in a tandem mass spectrometer and the spectra are compared with data obtained by gas-phase collisional activation. The s urface-induced dissociation spectra provide ample sequence information for the peptides. Side-chain cleavage ions of type w, which are gener ally detected upon kiloelectron volt collisions with gaseous targets b ut not upon electronvolt collisions with gaseous targets, are detected in the ion-surface collision experiments. A theoretical approach base d on MNDO bond order calculations is suggested for the description of peptide fragmentation. This model, supplemented by ab initio calculati ons, serves as a complement to the experimental work described in the paper and explains (i) the easy cleavage of the amide bond, (ii) charg e-remote backbone and side-chain cleavages, and (iii) the influence of intramolecular H-bonding.