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Abstract: The possibility of sulfur-nitrogen (S--N) three-electron bond formation in a one-electron oxidized methionine peptide model was investigated computationally following the detection of such species in pulse radiolysis experiments (C. [...]

A comparative study of the binding affinities of the ligands X:=(CH3)2S, CH3S(super -), Ch3NH2, MeImid, PhO(super -), and CH3CO2(super -) to Cu(II) in the distorted square planar model complexes (NH3)-(H2O)3(sub 3-i)Cu(II)-H2O is conducted. The calculated binding affinities for Cu(II) reveal that CH3S(super -) is an excellent ligand for Cu(II), delta G(super o')= -16.0 to -53.5 kJ mol(super -1).

A systematic study of the binding motifs of Cu(II) and Cu(I) to a methionine model peptide, N-formylmethioninamide is carried out by quantum chemical computations. Based on the results, the participation of Met35 as a low affinity binding site of Cu(II) in Abeta, and its role in the redox chemistry underlying Alzheimer's disease is discussed.

Three electron bonding between sulfide radical cation of dimethyl sulfide and various biologically available oxygen and nitrogen electron pair donors is studied in aqeous solution with a view to quantifying its effect on the reduction potential of dialkyl sulfides and methionine. S triple bond X dissociation enthalpies (BDEs) were determined by single point calculations at the CBS-RAD level, a method designed for quantitative thermochemistry of free radicals.

Photochemical reduction of several 4-picolyl- and N-methy-4-picolinium esters is examined using product analysis, laser flash photolysis, and fluorescence quenching. It is demonstrated that the radical (anions) formed in these reactions readily fragment t yield a carboxylic acid and a 4-pyridylmethyl radical intermediate.

The diastereofacial selectivity of 2-methyl-5-X-adamant-2-yl cations toward methanol is investigated in the gas phase at 750 Torr and in the 40-120 degreeC temperature range and compared with that of I(sub F) (X = F) and I(sub Si) (X = (CH(sub 3))(sub 3)Si) measured previously under similar conditions. Detailed analysis of the energy surface of the I(sub Me) (X = CH(sub 3)) ion reveals that the activation barrier of its syn addition to methanol is significantly lower than that of the anti attack.

Research has been conducted on the camphenyl cation. The structure and dynamics of this cation has been investigated via the experimental and computational approaches, and the results of the solvation-simulation molecular orbital studies for the camphenyl chloride system ionization are reported.

Diastereofacial selectivity in tertiary 2-adamantyl cations was investigated in the gas phase.

The molecular dynamics (MD) simulations using Gromacs are applied to obtain a bilayer consisting of 1-palmitoyl-2-linoleyl-snglycero-3-phosphatidylcholine (PLPC). The MD simulations of the polyunsaturated lipid bilayer provide the structural properties of the system and show that the unsaturation induces disorder and affects the physical properties of the membrane.

The Radical Model of Alzheimer's Disease (AD) is presented in some detail. The model provides a unified picture for the role of the amyloid beta peptide (Abeta), Met35, copper ions, oxygen, beta sheet secondary structure, and the generation of hydrogen peroxide, in mediating oxidative stress in AD. It predicts a role for glycyl radicals as long-lived species which can transport the damage into cell membranes and initiate lipid peroxidation. Previous work has established the thermodynamic and kinetic viability of most of the steps. In the present work, QM/MM and Amber calculations reveal that self assembly of antiparallel beta-sheet which brings Met35 into the required close proximity to a glycine residue is more likely if the residue is Gly29 or Gly33, than any of the other four glycine residues of Abeta.