COPPER-BINDING ABILITIES OF THE TRIPEPTIDE DIGLYCYLHISTIDINE STUDIED BY LASER-INDUCED LIQUID BEAM IONIZATION DESORPTION MASS-SPECTROMETRY IN AQUEOUS-SOLUTION/

Laser-induced liquid beam ionization/desorption (LILBID) mass spectrom etry is capable of desorbing ions directly from a liquid beam into the gas phase by means of an IR laser pulse tuned to an absorption band o f the solvent used. Up to now, it has been restricted to the use of al coholic solutions owing to the limitations of the desorbing IR laser s ystem, This paper presents the first results using an Nd:YAG-optical p arametric oscillator laser system that enables us to study aqueous sol utions. Using this laser system, studies on the Cu(II)-binding abiliti es of the tripeptide diglycylhistidine are presented. Complex formatio n with various concentrations of Cu(II) ions was observed in water at basic pH. The use of buffer solutions did not affect the signal intens ity of the peptide-related peaks. in acidic solutions, the complex par tially dissociates. The free tripeptide and the released Cn(II) can be observed in the mass spectrum. The results obtained with this method were compared with measurements undertaken with electrospray ionizatio n mass spectrometry. (C) 1997 John Whey & Sons, Ltd.