Density functional methods have been applied to investigate the irreversible transamination between glyoxylic acid and pyridoxamine analog and the catalytic mechanism for the critical [1,3] proton transfer step in aspartate aminotransferase (AATase). The results indicate that the catalytic effect of pyridoxal 5'-phosphate (PLP) may be attributed to its ability to stabilize related transition st...

Steady-state bacterial photosynthesis is modelled as cyclic chemical reaction and is examined with respect to overall efficiency, power transfer efficiency, and entropy production. A nonlinear flux-force relationship is assumed. The simplest two-state kinetic model bears complete analogy with the performance of an ideal (zero ohmic resistance of the P-N junction) solar cell. In both cases power...

ATP synthase is a unique rotary machine that uses the transmembrane electrochemical potential difference of proton (Delta(H(+))) to synthesize ATP from ADP and inorganic phosphate. Charge translocation by the enzyme can be most conveniently followed in chromatophores of phototrophic bacteria (vesicles derived from invaginations of the cytoplasmic membrane). Excitation of chromatophores by a sho...

The properties of confined water and diffusive proton-transfer kinetics in the nanoscopic water channels of Nafion fuel cell membranes at various hydration levels are compared to water in a series of well-characterized AOT reverse micelles with known water nanopool sizes using the photoacid pyranine as a molecular probe. The side chains of Nafion are terminated by sulfonate groups with sodium c...

Photosynthesis converts solar energy to chemical energy using chlorophylls (Chls). In a late stage of biosynthesis of Chls, dark-operative protochlorophyllide (Pchlide) oxidoreductase (DPOR), a nitrogenase-like enzyme, reduces the C17 = C18 double bond of Pchlide and drastically changes the spectral properties suitable for photosynthesis forming the parental chlorin ring for Chl a. We previousl...

This paper presents a derivation of rate expressions for nonadiabatic proton-coupled electron transfer ~PCET! reactions in solution. The derivation is based on a multistate continuum theory in which the solvent is described by a dielectric continuum, the solute is represented by a multistate valence bond model, and the transferring proton~s! are treated quantum mechanically. In this formulation...

In the present work, the joint use of the potential energy, the reaction electronic flux profiles and NBO analysis along the intrinsic reaction coordinate within the framework of the reaction force analysis allows us to gain insights into the mechanism of the proton transfer process in amino acids. The reaction was studied in alanine and phenylalanine in the presence of a continuum and with add...

The prospect that protons from water may be transferred to N-heterocyclic molecules due to the presence of an excess electron is studied in hydrated azabenzene cluster anions using anion photoelectron spectroscopy and computational chemistry. In the case of s-triazine (C3H3N3), which has a positive adiabatic electron affinity, proton transfer is not energetically favored nor observed experiment...

A series of pyrene photoacids is used to investigate excited-state proton transfer with time-dependent pump-probe spectroscopy. The deprotonation dynamics of a cationic photoacid, 8-aminopyrene-1,3,6-trisulfonic acid trisodium salt (APTS), shows single exponential dynamics( approximately 30 ps) in water. This is in contrast to what is observed for the neutral photoacids 8-hydroxypyrene-1,3,6-tr...

Quantum cluster and embedded cluster approaches were used to investigate the proton transfer reaction for a series of model clusters of zeolite/(H2O)n ; n = 1, 2, 3, and 4, using the B3LYP/6-31G (d,p) level of theory. For both calculations, without promoted water, the hydrogen-bonded dimer of the zeolite/water system exists as a simple hydrogen-bonded complex, ZOH(H2O)2, and no proton transfer ...