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Your search keyword '"Fang, Wei‐Hai"' showing total 43 results
Start Over Author "Fang, Wei‐Hai" Publisher wiley
43 results on '"Fang, Wei‐Hai"'

18. Semiempirical prediction of the hyperpolarizabilities for cyanovinyl-substituted donor-acceptor molecules

Author

Zhao Cun‐Yuan, Zhang Yong, Fang Wei-Hai, and You Xiao-Zeng

Subjects
Nonlinear optical, Donor acceptor molecules, Computational chemistry, Chemistry, Molecule, Nonlinear optics, Charge (physics), General Chemistry, Conjugated system, Dihedral angle, Acceptor
Abstract

We present here a systematically theoretical study on the nonlinearities and their structure-property relationship of cyanovinyl-substituted donor-acceptor molecules by virtue of semiempirical PM3/AM1-FF approach. Good consistency between measured and calculated hyperpolarizabilities is obtained. Results show that conformation has a significant effect on hyperpolarizabilities. The torsion angle change between two conjugated parts of the molecular systems can substantially alter the nonlinearities. The total amount of charge transfer difference from donor to acceptor has been introduced to understand the microscopic nature of the nonlinear optical properties for the title molecules. General guidelines may be sought out in the search of molecules with large values of β. Some molecules with large molecular hyperpolarizabilities can be predicted by the optimization for the longer δ-electron systems with both acceptor and donor groups.

Published
2010

42. Mechanism of the O 2 ( 1 Δ g ) generation from the Cl 2 /H 2 O 2 basic aqueous solution explored by the combined ab initio calculation and nonadiabatic dynamics simulation.

Author

Wang YT, Liu XY, and Fang WH

Abstract

In the present work, mechanism of the O 2 ( 1 Δ g ) generation from the reaction of the dissolved Cl 2 with H 2 O 2 in basic aqueous solution has been explored by the combined ab initio calculation and nonadiabatic dynamics simulation, together with different solvent models. Three possible pathways have been determined for the O 2 ( 1 Δ g ) generation, but two of them are sequentially downhill processes until formation of the OOCl - complex with water, which are of high exothermic character. Once the complex is formed, singlet molecular oxygen is easily generated by its decomposition along the singlet-state pathway. However, triplet molecular oxygen of O 2 ( Σ 3 g - ) can be produced with considerable probability through nonadiabatic intersystem crossing in the 1 Δ g / Σ 3 g - intersection region. It has been found that the coupled solvent, heavy-atom, and nonadiabatic effects have an important influence on the quantum yield of the O 2 ( 1 Δ g ) generation. © 2018 Wiley Periodicals, Inc., (© 2018 Wiley Periodicals, Inc.)

Published
2019
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43. Theoretical studies on pyridoxal 5'-phosphate-dependent transamination of alpha-amino acids.

Author

Liao RZ, Ding WJ, Yu JG, Fang WH, and Liu RZ

Subjects
Amination, Aspartate Aminotransferases metabolism, Glutamic Acid metabolism, Protons, Pyridoxal Phosphate, Quantum Theory, Amino Acids metabolism, Models, Theoretical
Abstract

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 states through structural resonance. Additionally, the PLP hydroxyl group and the carboxylic group of the amino acid can shuttle proton, thereby lowering the barrier. The rate-limiting step is the tautomeric conversion of the aldimine to ketimine by [1,3] proton transfer, with a barrier of 36.3 kcal/mol in water solvent. A quantum chemical model consisting 142 atoms was constructed based on the crystal structure of the native AATase complex with the product L-glutamate. The electron-withdrawing stabilization by various residues, involving Arg386, Tyr225, Asp222, Asn194, and peptide backbone, enhances the carbon acidity of 4'-C of PLP and Calpha of amino acid. The calculations support the proposed proton transfer mechanism in which Lys258 acts as a base to shuttle a proton from the 4'-C of PLP to Calpha of amino acid. The first step (proton transfer from 4'-C to lysine) is shown to be the rate-limiting step. Furthermore, we provided an explanation for the reversibility and specificity of the transamination in AATase., ((c) 2008 Wiley Periodicals, Inc.)

Published
2008
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