Craig A. Bayse

Determination of copper binding sites in peptides containing basic residues: a combined experimental and theoretical study

Abstract The energetics of monodentate Cu+ binding to model systems representing amino acid side chains and bidentate Cu+ binding in amino acid residues are investigated using electronic structure methods. Results from these calculations are compared with mass spectral data to determine Cu+ binding sites for gas-phase [M+Cu]+ peptide ions. Calculated monodentate Cu+ binding energies for amino acid models predict a relative Cu+ affinity ordering: arg > his > lys > cys > ser, whereas bidentate Cu+ binding energies give a relative Cu+ affinity ordering of arg > lys > his > gln > asn > glu > asp. Calculated results are in agreement with current and published experimental results.

Pseudo second-order Jahn-Teller effects and symmetry considerations in transition metal polyhydride complexes

Abstract Pseudo second-order Jahn-Teller distortions are proposed to explain why the equatorial hydride ligands in a series of cyclopentadienyl metal polyhydrides (Cp ∗ ReH 6 , Cp ∗ OsH 5 , Cp ∗ IrH 4 ) bend away from the Cp ring at such large angles. Restricted Hartree-Fuck (RHF) geometry optimizations on models of these complexes where the Cp* ring has been replaced by a hydride reproduce these large distortions. Walsh diagrams and Mulliken populations have been used to show that the stability provided by distortion results from maximizing the overlap population between the hydride s orbitals and the metal d orbitals. This study also includes a comparison of previous work on the structures of do MH6 complexes with our work on d 2 MH6 complexes. We found that an occupied d orbital has a significant effect on the geometry of this type of molecule due to the change in hybridization on the metal from sd 5 to spd 4 . Symmetry arguments are demonstrated as a means to predict the low energy geometries of these complexes.