There is a growing interest in the study of structures and properties of biomolecules in gas phase. Applications of force fields are highly desirable for the computational efficiency of the gas phase study. To help th...There is a growing interest in the study of structures and properties of biomolecules in gas phase. Applications of force fields are highly desirable for the computational efficiency of the gas phase study. To help the selection of force fields, the performances of five repre- sentative force fields for gaseous neutral, protonated, deprotonated and capped amino acids are systematically examined and compared. The tested properties include relative conforma- tional energies, energy differences between cis and trans structures, the number and strength of predicted hydrogen bonds, and the quality of the optimized structures. The results of BHandHLYP/6-311＋＋G（d,p） are used as the references. GROMOS53A6 and ENCADS are found to perform poorly for gaseous biomoleeules, while the performance of AMBER99SB, CHARMM27 and OPLSAA/L are comparable when applicable. Considering the general availability of the force field parameters, CHARMM27 is the most recommended, followed by OPLSAA/L, for the study of biomolecules in gas phase展开更多
The excited-state intramolecular hydrogen abstraction reactions of butanal have been investigated using the CAS-MP2/6-311＋G^＊//CASSCF/6-31G^＊ methods. Calculated results show that the hydrogen transfer induced fluo...The excited-state intramolecular hydrogen abstraction reactions of butanal have been investigated using the CAS-MP2/6-311＋G^＊//CASSCF/6-31G^＊ methods. Calculated results show that the hydrogen transfer induced fluorescence quenching of the n,π^＊-excited state of covalent butanal with three paths： （1） The first path corresponds to direct S0-react reconstitution, which involves the first S1 decay by partial hydrogen atom transfer. （2） The second stepwise mechanism can be viewed as a full hydrogen atom transfer followed by a partial hydrogen atom back transfer, electron transfer （near S1/S0 or S0-TS） and finally a proton transfer to S0-react. （3） On the triplet surface, the surface crossing to the singlet state would be clearly much efficient at the T1/S0 region due to the large SOC value of 8.3 cm^-1. The S0-react decay route from T1/S0 was studied with an intrinsic reaction coordinate （IRC） calculation at the CASSCF level, resulting in the S0-React minimum.展开更多
This work investigates the physico-chemical and mechanical properties of tannins extracted from wood for composite materials manufacturing. Sustainable knowledge (in terms of physico-chemical properties and behaviours...This work investigates the physico-chemical and mechanical properties of tannins extracted from wood for composite materials manufacturing. Sustainable knowledge (in terms of physico-chemical properties and behaviours) of the material is needed to further enhance its applications. The condensed tannins extracted from the Bark of Ficus platyphylla (BFP) and the Bark of Vitellaria paradoxa (BVP) were analyzed using Matrix Assisted Laser Desorption/Ionization Time-Of-Flight (MALDI-TOF), Mass Spectroscopy and Attenuated Total Reflectance Fourier Transform Mid-InfraRed (ATR-FT MIR) spectra in the ranges 1800 cm-1 and 600 cm-1, as well as using CP MAS 13C-NMR. It was found that, these two tannins are procyanidin/prodelphinidin and made up of catechin/epicatechin, gallocatechin/epigallocatechin units, fisetinidin, galloyl and carbohydrates residues. Furthermore, BFP and BVP tannin bonded particleboard densities lie in the range recommended by NF EN 326-1994 standard. The resins also yielded good internal bond strength results of the panels, above relevant international standard specifications minimum requirements for interior-grade panels. The Transmission Electron Microscopy with Energy Dispersive X-ray Spectroscopy Analysis (TEM/ EDXA) are showing the ultrastructure and reveal that most of the resin material appears to be in an amorphous phase mainly composed of carbon/oxygen with small amounts of K, Ca and Mg. These particles have a very irregular morphology.展开更多
文摘There is a growing interest in the study of structures and properties of biomolecules in gas phase. Applications of force fields are highly desirable for the computational efficiency of the gas phase study. To help the selection of force fields, the performances of five repre- sentative force fields for gaseous neutral, protonated, deprotonated and capped amino acids are systematically examined and compared. The tested properties include relative conforma- tional energies, energy differences between cis and trans structures, the number and strength of predicted hydrogen bonds, and the quality of the optimized structures. The results of BHandHLYP/6-311＋＋G（d,p） are used as the references. GROMOS53A6 and ENCADS are found to perform poorly for gaseous biomoleeules, while the performance of AMBER99SB, CHARMM27 and OPLSAA/L are comparable when applicable. Considering the general availability of the force field parameters, CHARMM27 is the most recommended, followed by OPLSAA/L, for the study of biomolecules in gas phase
基金supported by ‘Qinglan’ Talent Engineering Funds and Key Subject of Inorganic Chemistry by Tianshui Normal University
文摘The excited-state intramolecular hydrogen abstraction reactions of butanal have been investigated using the CAS-MP2/6-311＋G^＊//CASSCF/6-31G^＊ methods. Calculated results show that the hydrogen transfer induced fluorescence quenching of the n,π^＊-excited state of covalent butanal with three paths： （1） The first path corresponds to direct S0-react reconstitution, which involves the first S1 decay by partial hydrogen atom transfer. （2） The second stepwise mechanism can be viewed as a full hydrogen atom transfer followed by a partial hydrogen atom back transfer, electron transfer （near S1/S0 or S0-TS） and finally a proton transfer to S0-react. （3） On the triplet surface, the surface crossing to the singlet state would be clearly much efficient at the T1/S0 region due to the large SOC value of 8.3 cm^-1. The S0-react decay route from T1/S0 was studied with an intrinsic reaction coordinate （IRC） calculation at the CASSCF level, resulting in the S0-React minimum.
文摘This work investigates the physico-chemical and mechanical properties of tannins extracted from wood for composite materials manufacturing. Sustainable knowledge (in terms of physico-chemical properties and behaviours) of the material is needed to further enhance its applications. The condensed tannins extracted from the Bark of Ficus platyphylla (BFP) and the Bark of Vitellaria paradoxa (BVP) were analyzed using Matrix Assisted Laser Desorption/Ionization Time-Of-Flight (MALDI-TOF), Mass Spectroscopy and Attenuated Total Reflectance Fourier Transform Mid-InfraRed (ATR-FT MIR) spectra in the ranges 1800 cm-1 and 600 cm-1, as well as using CP MAS 13C-NMR. It was found that, these two tannins are procyanidin/prodelphinidin and made up of catechin/epicatechin, gallocatechin/epigallocatechin units, fisetinidin, galloyl and carbohydrates residues. Furthermore, BFP and BVP tannin bonded particleboard densities lie in the range recommended by NF EN 326-1994 standard. The resins also yielded good internal bond strength results of the panels, above relevant international standard specifications minimum requirements for interior-grade panels. The Transmission Electron Microscopy with Energy Dispersive X-ray Spectroscopy Analysis (TEM/ EDXA) are showing the ultrastructure and reveal that most of the resin material appears to be in an amorphous phase mainly composed of carbon/oxygen with small amounts of K, Ca and Mg. These particles have a very irregular morphology.
