Influence of basic residues on dissociation kinetics and dynamics of singly protonated peptides: time-resolved photodissociation study

Product ion yields in postsource decay and time-resolved photodissociation at 193 and 266 nm were measured for some peptide ions with lysine ([KF₆ + H]⁺, [F₆K + H]⁺, and [F₃KF₃ + H]⁺) formed by matrix-assisted laser desorption ionization. The critical energy (E₀) and entropy (ΔS[double dagger]) were determined by RRKM fitting of the data. The results were similar to those found previously for peptide ions with histidine. To summarize, the presence of a basic residue, histidine or lysine, inside a peptide ion retarded its dissociation by lowering ΔS[double dagger]. On the basis of highly negative ΔS[double dagger], presence of intramolecular interaction involving a basic group in the transition structure was proposed. Copyright © 2009 John Wiley & Sons, Ltd.