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 ([KF 6 + H] + , [F 6 K + H] + , and [F 3 KF 3 + H] + ) formed by matrix‐assisted laser desorption ionization. The critical energy ( E 0 ) and entropy (Δ S ‡ ) 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 Δ S ‡ . On the basis of highly negative Δ S ‡ , presence of intramolecular interaction involving a basic group in the transition structure was proposed. Copyright © 2009 John Wiley & Sons, Ltd.