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Articles 1 - 11 of 11
Full-Text Articles in Physical Sciences and Mathematics
Ab Initio Study Of Formazan And 3-Nitroformazan, G. Buemi, F. Zuccarello, P. Venuvanalingam, M. Ramalingam, Salai Ammal
Ab Initio Study Of Formazan And 3-Nitroformazan, G. Buemi, F. Zuccarello, P. Venuvanalingam, M. Ramalingam, Salai Ammal
Salai C. Ammal
Formazan and 3-nitroformazan have been investigated at abinitio level (MP2/6-31G** and B3LYP/6-31G**) in all their possible conformations, for studying the various possibilities of intramolecular hydrogen bonding formation. The trans-syn-s-cis (TSSC), known also asyellowform, has been found to be the most stable conformer (at least in the gas phase) in both compounds. This particular structure is strongly stabilized by a N–H···N hydrogen bridge, which gives rise to a hexatomic chelate ring, with the possibility of a proton transfer process.This closely resembles that of malondialdehyde, previously studied, in the evolution of the potential energy shape but with a greater barrier height. Various …
Modeling The Noble Metal/Tio2 (110) Interface With Hybrid Dft Functionals: A Periodic Electrostatic Embedded Cluster Model Study, Salai Ammal, Andreas Heyden
Modeling The Noble Metal/Tio2 (110) Interface With Hybrid Dft Functionals: A Periodic Electrostatic Embedded Cluster Model Study, Salai Ammal, Andreas Heyden
Salai C. Ammal
The interaction of Aun and Ptn (n=2,3) clusters with the stoichiometric and partially reduced rutile TiO2 (110) surfaces has been investigated using periodic slab and periodic electrostatic embedded cluster models. Compared to Au clusters, Pt clusters interact strongly with both stoichiometric and reduced TiO2 (110) surfaces and are able to enhance the reducibility of the TiO2 (110) surface, i.e., reduce the oxygen vacancy formation energy. The focus of this study is the effect of Hartree–Fock exchange on the description of the strength of chemical bonds at the interface of Au/Pt clusters and the TiO2 (110) surface. Hartree–Fock exchange helps describing …
Dynamic Path Bifurcation For The Beckmann Reaction: Observation And Implication, H. Yamataka, M. Sato, H. Hasegawa, Salai Ammal
Dynamic Path Bifurcation For The Beckmann Reaction: Observation And Implication, H. Yamataka, M. Sato, H. Hasegawa, Salai Ammal
Salai C. Ammal
The reaction of oximes to amides, known as the Beckmann rearrangement, may undergo fragmentation to form carbocations + nitriles instead of amides when the cations have reasonable stability. The reactions of oxime derivatives of 1-substituted-phenyl-2-propanones and 3-substituted-phenyl-2-butanones in aqueous solvents gave both rearrangement and fragmentation products, the ratio of which was dependent on substituents. Transition state (TS) optimizations and intrinsic reaction coordinate (IRC) calculations for the reaction of 1-phenyl-2-propanone oximes showed that there is a single TS for each substituted compound. The IRC path from the TS either led to a rearrangement product or a fragmentation product depending on the …
Density Functional Theory Calculations Of Molecular Nitrogen On A Ruthenium Cluster, K. Shrivastavaa, Salai Ammal, H. Tsuruya, S. Takami, A. Endou, M. Kubo, K. Teraishi, A. Miyamoto, A. Ozaki
Density Functional Theory Calculations Of Molecular Nitrogen On A Ruthenium Cluster, K. Shrivastavaa, Salai Ammal, H. Tsuruya, S. Takami, A. Endou, M. Kubo, K. Teraishi, A. Miyamoto, A. Ozaki
Salai C. Ammal
No abstract provided.
Ab Initio And Dft Investigations Of Lithium/Hydrogen Bonded Complexes Of Trimethylamine, Dimethyl Ether And Dimethyl Sulfide, Salai Ammal, P. Venuvanalingam
Ab Initio And Dft Investigations Of Lithium/Hydrogen Bonded Complexes Of Trimethylamine, Dimethyl Ether And Dimethyl Sulfide, Salai Ammal, P. Venuvanalingam
Salai C. Ammal
Ab initio and DFT computations have been carried out on LiF and HF complexes of a set of n-donors viz. trimethylamine, dimethyl ether and dimethyl sulfide with a 6-31++G(d,p) basis set. The effect of correlation has been included with MP2, MP4 and DFT calculations. NBO analyses of the wavefunctions have been performed to examine the intermolecular interaction at the orbital level. Calculations reveal that these donors form strong n→σ* complexes and computed binding energies of the (CH3)2O···HF complex agree very well with the experimental binding energies from IR spectroscopy. LiF forms stronger complexes than HF, …
Π-Systems As Lithium/Hydrogen Bond Acceptors: Some Theoretical Observations, Salai Ammal, P. Venuvanalingam
Π-Systems As Lithium/Hydrogen Bond Acceptors: Some Theoretical Observations, Salai Ammal, P. Venuvanalingam
Salai C. Ammal
Ab initio calculations at the Hartree–Fock and correlated levels and density functional theory calculations have been performed with 6-31++G(d,p) and 6-311++G(d,p)basis sets on LiF and HF complexes of benzene, ethylene, and acetylene. Complex binding energies have been corrected for basis set superposition error, and zero point energy corrections have been done on Hartree–Fock binding energies. Computed results indicate that the complexes exist in different conformations and among them those with π-lithium and π-hydrogen bonds are the most stable. π-lithium bonds are stronger than π-hydrogen bonds. The computed binding energies and geometry of HF complexes correlate well with the available experimental …
Electron Donor-Acceptor Complexes Of I2 With Diethyl Ether And Diethyl Sulphide. An Ab Initio Mo Study, Salai Ammal, S. Ananthavel, J. Chandrasekhar, P. Venuvanalingam, M. Hegde
Electron Donor-Acceptor Complexes Of I2 With Diethyl Ether And Diethyl Sulphide. An Ab Initio Mo Study, Salai Ammal, S. Ananthavel, J. Chandrasekhar, P. Venuvanalingam, M. Hegde
Salai C. Ammal
No abstract provided.
Ultraviolet Photoelectron Spectroscopy Of Complexes Of Bromine With N-Donors In The Vapor Phase, S. Ananthavel, Salai Ammal, P. Venuvanalingam, J. Chandrasekhar, M. Hegde
Ultraviolet Photoelectron Spectroscopy Of Complexes Of Bromine With N-Donors In The Vapor Phase, S. Ananthavel, Salai Ammal, P. Venuvanalingam, J. Chandrasekhar, M. Hegde
Salai C. Ammal
No abstract provided.
Spectroscopically Distinct Cobalt(Ii) Sites In Heterodimetallic Forms Of The Aminopeptidase From Aeromonas Proteolytica: Characterization Of Substrate Binding, Brian Bennett, Richard Holz
Spectroscopically Distinct Cobalt(Ii) Sites In Heterodimetallic Forms Of The Aminopeptidase From Aeromonas Proteolytica: Characterization Of Substrate Binding, Brian Bennett, Richard Holz
Richard C. Holz
The Co(II)Zn(II)- and Zn(II)Co(II)-substituted derivatives of the aminopeptidase from Aeromonas proteolytica (AAP) were probed by EPR spectroscopy. EPR spectra of the high-spin S = 3/2 Co(II) ions in [CoZn(AAP)] and [ZnCo(AAP)] indicated that each metal binding site provides a spectroscopically distinct signature. For [CoZn(AAP)], subtraction of EPR spectra recorded at pH 7.5 and 10 revealed that two species were present and that the relative contributions to each of the experimental spectra were pH-dependent. The first EPR species, predominant at lower pH values, was simulated as a relatively featureless axial signal with geff values of 2.20, 3.92, and …
Synthesis, Molecular Structure, And Reactivity Of Dinuclear Copper(Ii) Complexes With Carboxylate-Rich Coordination Environments, Richard Holz, John Bradshaw, Brian Bennett
Synthesis, Molecular Structure, And Reactivity Of Dinuclear Copper(Ii) Complexes With Carboxylate-Rich Coordination Environments, Richard Holz, John Bradshaw, Brian Bennett
Richard C. Holz
The dinucleating ligand N,N‘-(2-hydroxy-5-methyl-1,3-xylylene)bis(N-(carboxymethyl)glycine) (CH3HXTA) has been used to synthesize the dinuclear Cu(II) bis(pyridine) complex Na[Cu2(CH3HXTA)(Py)2]·1.5(1,4-dioxane) (Na(1)): triclinic space group P1̄ (a = 12.550(3) Å, b = 13.413(3) Å, c = 13.540(4) Å, α = 117.12(2)°, β = 104.70 (2)°, and γ = 92.13(2)°). The structure shows two distinct distorted square pyramidal Cu(II) centers with each Cu(II) ion bound by two carboxylate oxygen atoms, one amine nitrogen atom, a phenolate oxygen atom, and one pyridine nitrogen atom. The Cu--Cu separation is 3.531 Å, …
Structural Basis And Distal Effects Of Gag Substrate Coevolution In Drug Resistance To Hiv-1 Protease, Aysegul Ozen, Kuan-Hung Lin, Nese Yilmaz, Celia Schiffer
Structural Basis And Distal Effects Of Gag Substrate Coevolution In Drug Resistance To Hiv-1 Protease, Aysegul Ozen, Kuan-Hung Lin, Nese Yilmaz, Celia Schiffer
Celia A. Schiffer
Drug resistance mutations in response to HIV-1 protease inhibitors are selected not only in the drug target but elsewhere in the viral genome, especially at the protease cleavage sites in the precursor protein Gag. To understand the molecular basis of this protease-substrate coevolution, we solved the crystal structures of drug resistant I50V/A71V HIV-1 protease with p1-p6 substrates bearing coevolved mutations. Analyses of the protease-substrate interactions reveal that compensatory coevolved mutations in the substrate do not restore interactions lost due to protease mutations, but instead establish other interactions that are not restricted to the site of mutation. Mutation of a substrate …