THE EASE OF PEPTIDE DETECTION BY MATRIX-ASSISTED LASER-DESORPTION IONIZATION MASS-SPECTROMETRY - THE EFFECT OF SECONDARY STRUCTURE ON SIGNAL INTENSITY

Several structurally well-characterized model peptides were used to ex amine the relationship between peptide structure and signal intensity in matrix-assisted laser desorption/ionization mass spectrometry (MALD I-MS), It was found that peptides displaying stable alpha-helical and beta-sheet structures show lower signal intensities than the correspon ding analogs having disturbed secondary structures caused by substitut ion of two adjacent amino acids by their D isomers, Since such substit utions do not affect properties other than the secondary structure pro pensity, the differences observed are ascribed to this phenomenon or s ome related effect such as association, The results indicate that the formation of stable secondary structures in peptides may be a possible source of incomplete peptide mass fingerprints resulting from protein digestion and for difficulties in the quantitative evaluation of pept ide mixtures via MALDI-MS. (C) 1998 John Wiley & Sons, Ltd.