title: Temperature of peptide ions generated by matrix-assisted laser desorption ionization and their dissociation kinetic parameters.
abstract: Product ion yields in postsource decay and photodissociation at 193 and 266 nm were measured for some peptide ions without a basic amino acid residue ([Y(6) + H](+), [F(5) + H](+), and [YPFVEPI + H](+)) generated by matrix-assisted laser desorption ionization (MALDI). Data indicated statistical nature for the dissociation processes. Assuming that peptide ions formed by MALDI are in thermal equilibrium at temperature T and that their dissociation rate constants are specified by the critical energy (E(0)) and entropy (DeltaS(double dagger)), a method based on kinetic analysis was devised to determine these parameters simultaneously. The matrix used was found to affect the effective temperature of peptide ions, 2,5-dihydroxybenzoic acid (400-430 K) < sinapinic acid (440 K) < alpha-cyano-4-hydroxycinnamic acid (460-510 K), in agreement with previous perceptions. E(0) of around 0.6 eV and DeltaS(double dagger) of -24 eu were smaller than previous quantum chemical results for small model peptide ions.
authors.affiliation: Department of Chemistry, Seoul National University, Seoul 151-742, Korea. jhdal@kribb.re.kr
authors.forename: Jeong Hee
authors.initials: JH
authors.lastname: Moon
authors.forename: So Hee
authors.initials: SH
authors.lastname: Yoon
authors.forename: Myung Soo
authors.initials: MS
authors.lastname: Kim
mesh_terms: D007477:Ions / Q000737:chemistry; D007700:Kinetics; D010455:Peptides / Q000737:chemistry*; D019032:Spectrometry, Mass, Matrix-Assisted Laser Desorption-Ionization / Q000379:methods*; D013696:Temperature
chemical_list: D007477:Ions; D010455:Peptides