title: Water binding energies of [Pb(amino acid-H)H2O]+ complexes determined by blackbody infrared radiative dissociation.
abstract: The water binding energies (E(0)) of eight deprotonated Pb(2+)-amino acid (Aa) complexes of the form [Pb(Aa-H)H(2)O](+) (Aa = Gly, Ala, Val, Leu, Ile, Phe, Glu, and Lys) were determined using blackbody infrared radiative dissociation (BIRD). A Fourier transform ion cyclotron resonance (FT-ICR) mass spectrometer was used to trap ions generated by electrospray ionization (ESI) in a "zero"-pressure (~10(-10) torr) cell where dissociation can only occur by absorption of thermally generated photons. Since the [Pb(Aa-H)H(2)O](+) complexes have relatively few vibrational degrees of freedom (36-78) and are within the slow-exchange kinetic limit, the master equation was solved to extract meaningful threshold dissociation energies and thermal unimolecular dissociation rate constants (k(uni)). The master equation analysis uses variable reaction coordinate transition state theory (VRC-TST) to minimize the Rice-Ramsperger-Kassel-Marcus (RRKM) dissociation rate constants. The determined water binding energies range from 76.6 to 113.6 kJ mol(-1), and agree well with 0 K dissociation energies calculated using the B3LYP/6-31+G(d,p) and MP2(full)/6-311++G(2d,2p)//B3LYP/6-31+G(d,p) methods. The relative strengths of the binding energies reflect the known structural isomers (A-, B-, C-, and D-type) of these [Pb(Aa-H)H(2)O](+) complexes.
authors.affiliation: Department of Chemistry, Memorial University of Newfoundland, St. John's, Newfoundland and Labrador, Canada, A1B 3X7.
authors.forename: Michael B
authors.initials: MB
authors.lastname: Burt
authors.forename: Sarah G A
authors.initials: SG
authors.lastname: Decker
authors.forename: Travis D
authors.initials: TD
authors.lastname: Fridgen
mesh_terms: D000596:Amino Acids / Q000737:chemistry*; D001665:Binding Sites; D056831:Coordination Complexes / Q000737:chemistry*; D007700:Kinetics; D007854:Lead / Q000737:chemistry*; D021241:Spectrometry, Mass, Electrospray Ionization; D014867:Water / Q000737:chemistry*
chemical_list: D000596:Amino Acids; D056831:Coordination Complexes; D014867:Water; D007854:Lead