Jianhong Liu

RANK-ORDERING THE BINDING AFFINITY FOR FKBP12 AND H1N1 NEURAMINIDASE INHIBITORS IN THE COMBINATION OF A PROTEIN MODEL WITH DENSITY FUNCTIONAL THEORY

The quantum mechanical interaction energies between FKBP12 as well as H1N1 neuraminidase and their inhibitors were directly calculated with an efficient density functional theory by mimicking the whole protein with a protein model composed of the amino acids surrounding the ligands. It was found that the calculated quantum mechanical interaction energies correlate well with the experimental binding free energies with the correlation coefficients of 0.88, 0.86, and the standard deviation of 0.93 and 1.00 kcal/mol, respectively. To compare with force field approach, the binding free energies with the correlation coefficient R = 0.80 and 0.47 were estimated by AutoDock 4.0 programs. It was indicated that the quantum interaction energy shows a better performance in rank-ordering the binding affinity between FKBP12 and H1N1 neuraminidase inhibitors than those of AutoDock 4.0 program. In combination protein model with density functional theory, the estimated quantum interaction energy could be a good predictor or scoring function in structure-based computer-aided drug design. Finally, five new FKBP12 inhibitors were designed based on calculated quantum mechanical interaction energy. In particular, the theoretical Ki value of one compound is as low as 0.05 nM, nearly 8-fold more active than FK506.

SUPPLEMENTING THE PBSA APPROACH WITH QUANTUM MECHANICS TO STUDY THE BINDING BETWEEN CDK2 AND N2-SUBSTITUTED O6-CYCLOHEXYLMETHOXYGUANINE INHIBITORS

Because classical Poisson–Boltzman Surface Area (PBSA) model does not allow re-polarization of charges and does not account for charge transfer when a ligand binds to a protein, we have examined a hybrid approach in which we describe the protein–ligand interface by quantum mechanics and the rest of the system with the classical PBSA model. We found this approach to rank order the binding of five N2-substituted O6-cyclohexylmethoxyguanine inhibitors to CDK2 (cyclin-dependent kinase 2) properly. The calculated binding free energy correlated well with experimental Log(IC50) with a correlation coefficient of 0.94. A regression fit between experimental Log(IC50) and calculated binding free energy yielded a root-mean-square error of 0.48 when Log(IC50) spanned a range over three units. In addition, we observed charge transfer between the ligand and the protein at the interface — an effect not accounted for by the classical PBSA model. We also found that the direct interactions between the protein and the ligands provided the dominant factor to distinguish the binding affinity of the five ligands studied here. This hybrid approach can better prioritize derivatives of lead compounds for synthesis and biological evaluation.

Graphene-like membrane supported MnO2 nanospheres for supercapacitor

Manganese dioxide/graphene composite is receiving intensive attention because of its potential applications in energy storage field. In this paper, a novel MnO2 nanocomposite material for high performance supercapacitor was prepared in situ on graphene-like membrane using liquid-polyacrylonitrile as the carbon source. Successful composite formation was confirmed and textural properties were obtained from XRD, FTIR and Raman spectra studies. Morphological characterizations of the nanocomposite were investigated by FE-SEM and TEM measurements. For capacitive properties tests, cyclic voltammetry, galvanostatic charge/discharge and electrochemical impedance spectroscopy were carried out in a three-electrode system with a working potential window from 0 to 1xa0V. The results show that the membrane has a typical graphene-like layer carbon structure. Moreover, the electrochemical performance reveals that the average capacitance of the composite at the mass fraction of graphene-like membrane of 30xa0% is as high as 302xa0Fxa0g−1 at 1xa0Axa0g−1 in 1xa0molxa0L−1 Na2SO4 electrolyte, which permit excellent performance as electrode materials for supercapacitors.

DENSITY FUNCTIONAL THEORY/TIME-DEPENDENT DENSITY FUNCTIONAL THEORY STUDY ON THE STRUCTURES AND SOLVENT EFFECTS ON THE ELECTRONIC SPECTRA OF Ru(II) POLYPYRIDYL COMPLEXES: [Ru(bpy)2(L)]2+ (L = CNOIP, HPIP, DPPZ, TAPIP)

The structures and solvent dependence of electronic spectra of four Ru(II) polypyridyl complexes: [Ru(bpy)2CNOIP]2+, bpy = 2,2-bipyridine and CNOIP = 2-(2-chloro-5-nitrophenyl)imidazo[4,5-f][1,10]phenanthroline (Ru-1); [Ru(bpy)2HPIP]2+, HPIP = 2-(2-hydroxyphenyl) imidazo[4,5-f][1,10]phenanthroline (Ru-2); [Ru(bpy)2DPPZ]2+, DPPZ = dipyrido[3,2:a-2′,3′:c]-phenazine (Ru-3); [Ru(bpy)2TAPIP]2+, TAPTP = 4,5,9,18-tetraazaphenanthreno-[9,10-b]triphenylene (Ru-4) have been carried out by density functional theory/time-dependent density functional theory in vacuum and nine solvents are described by the conductor-like polarized continuum model. The calculated results show that the solvent has a strong effect on the electron distribution of molecular orbitals and character of charge transfer. In water, the simulated absorption spectra (λmax) are in accordance with experimental data. The computational results also indicate the electronic spectra of Ru(II) polypyridyl complexes: [Ru(bpy)2(L)]2+ is very sensitive to the intercalative ligands L = CNOIP, HPIP, DPPZ, TAPIP in the presence of solvent. It was noted that the trend of transition intensity of complexes strongly depends on the polarity of solvents. In the present polar solvents, the transition intensity trend of Ru-4 > Ru-1 > Ru-2 > Ru-3 was obtained, but in the case of nonpolar solvents, the transition intensity trend is Ru-4 > Ru-3 > Ru-1 > Ru-2. Among the four polypyridyl complexes, [Ru(bpy)2TAPIP]2+(Ru-4) exhibits the strongest oscillator strength in all nine solvents.

Improved thermal and mechanical properties of silicone resin composites by liquid crystal functionalized graphene nanoplatelets

A liquid crystalline molecule, 4′-allyloxy-biphenyl-4-ol (AOBPO), was synthesized from 4,4′-dihydroxybiphenyl and allyl bromide as raw materials and then used to functionalize graphene nanoplatelets (GNS) via covalent bond and π–π interactions. The AOBPO functionalized graphene nanoplatelets (AOBPO–GNS) were characterized by fluorescence spectroscopy, thermal gravimetric analysis, Fourier transform infrared spectroscopy (FTIR), X-ray diffraction and Raman spectroscopy, and then mixed with silicone resin as fillers to fabricate silicon resin nanocomposites. The drastic quenching of the AOBPO fluorescence elucidated that the biphenyl anchoring unit of liquid crystalline AOBPO was strongly interacted with the surface of graphene sheets via π–π interactions. FTIR and Raman spectroscopy proved the existence of covalent interaction between the AOBPO and GNS. The thermal and mechanical properties testing indicated that the tensile strength of silicon resin nanocomposites increased by 463xa0% over that of neat silicon resin when the mass fraction of AOBPO–GNS was 1.0xa0%, and the elastic modulus of silicon resin nanocomposite increased by 1080xa0% over that of neat silicon resin if it came up to 2.0xa0%. The thermal conductivity of the resin filled with the AOBPO–GNS was improved to be 3.105xa0W/(mxa0K) at the mass fraction of 15.0xa0%, which was enhanced more than 38 times over that of neat silicon resin. The resulted thermally conductive and mechanically applicable silicon resin nanocomposites could be significant in a wide variety of electronic packaging applications.

First principle simulation on oxidation mechanism of diethyl ether by nitrogen dioxide

The oxidation mechanism of diethyl ethers by NO2 was carried out using density functional theory (DFT) at the B3LYP/6-31+G (d, p) level. The oxidation process of ether follows four steps. First, the diethyl ether reacts with NO2 to produce HNO2 and diethyl ether radical with an energy barrier of 20.62 kcal ⋅ mol-1. Then, the diethyl ether radical formed in the first step directly combines with NO2 to form CH3CH(ONO)OCH2CH3. In the third step, the CH3CH(ONO)OCH2CH3 was further decomposed into the CH3CH2ONO and CH3CHO with a moderately high energy barrier of 32.87 kcal ⋅ mol-1. Finally, the CH3CH2ONO continues to react with NO2 to yield CH3CHO, HNO2 and NO with an energy barrier of 28.13 kcal ⋅ mol-1. The calculated oxidation mechanism agrees well with Nishiguchi and Okamotos experiment and proposal.

Preparation and thermo-mechanical properties of functionalized graphene/silicone rubber nanocomposites

Silicone rubber is widely used in electronic packaging materials. Electronic appliances have become miniaturized which need more outstanding packaging materials. Functionalized grapheme/scilicon rubber composites is one of the development to improve the performance of the silicone rubber. Graphite oxide (GO) was modified by KH-550, and then the modified graphite oxide was reduced by hydrazine hydrate to get functionalized graphene (FG). In order to get functionalized graphene /silicon rubber nanocomposites, FG was dispersed into 107 gum. The structure and morphology of both the nanocomposites and FG were characterized by FTIR, SEM, XRD and TG. The results show that KH-550 was bonded with GO, the layer of FG was expanded to 0.4nm. Compared with the pure silicon rubber, the initial decomposition temperature of all the functionalized graphene/silicon rubber nanocomposites were improved. Mechanical property tests show that the tensile strength of the nanocomposites with 0.7wt% FG are 2.46 MPa which increases by 198.39% compared with neat silicone rubber, and the elongation at break of composite increases by 171.89%, which is about triple of the pure silicone rubber. Thermal conductivity test shows that the thermal conductivity of the composites with 1.0wt% FG reaches 0.18 W /(m·K).

Preparation of graphene aerogel and its electrochemical properties as the electrode materials for supercapacitors

Graphene oxide was prepared through an improved method, and then three-dimensional graphene aerogel was (GA) synthesized by an organic sol-gel process. The morphological characteristics and textural properties of the GA were investigated by scanning electron microscope (SEM), X-ray diffraction (XRD) and Fourier transform infrared spectrum (FT-IR), respectively. For capacitive properties tests, cyclic voltammetry (CV), galvanostatic charge/discharge and electrochemical impedance spectroscopy (EIS) were carried out in a two-electrode system with a working potential window from 0 to 1V. Moreover, a specific capacitance of 176 F/g was determined at a constant current density of 1 A/g in 1 mol L-1 Na2SO4 electrolyte. The advantageous properties such as high specific surface areas, high specific capacitance, high conductivity and well-connected 3D mesoporous structure of the GA, permit excellent performance as electrode materials for supercapacitors.

Fast single mode microwave-assisted synthesis of porous carbon aerogel for supercapacitors

Carbon materials are, in general, very good absorbents of microwaves. The microwave-assisted synthesis illustrated in this work allows carbon aerogels (CA) to be synthesized in a much shorter time than by conventional methods. Resorcinol-formaldehyde xerogels were synthesized using single mode microwave synthesis system at 85°C for less than an hour. Then, carbonization was performed to obtain carbon xerogels. The effect of the microwave radiation time involved in the process on the textural and electrochemical performance of the final materials was evaluated. It can be concluded that it is possible to control their textural characteristics of carbon xerogels by modifying radiation time. The electrochemical performance of synthesized carbon xerogels as electrode materials in electric double-layer capacitors was studied by cyclic voltammetry and charge/discharge experiments in an alkali medium (6MKOH). It can be seen that single mode microwave-assisted synthesis helps the carbon xerogels display good cycle durability and the specific capacitance of the CA which was radiation for 40minutes is 96.22F/g even without any activation and doping treatments.

Preparation of nickel oxide/graphene aerogel composites and its electrochemical performance for supercapacitor

In this paper, nickel oxide/graphene aerogel composites (NiO/GA) have been synthesized by a simple solvothermal route starting with graphene oxide (GO). The morphology, composition and microstructure of the as-obtained samples are systematically characterized by Fourier Transform infrared spectroscopy (FTIR), X-ray diffraction (XRD) and field emission scanning electron microscopy (FESEM). Moreover, the electrochemical performances of composites were evaluated by cyclic voltammogram (CV) and galvanostatic charge-discharge. The nickel oxide was electrochemically deposited into the highly porous GA to form NiO/GA composites. NiO/GA electrodes exhibit excellent electrochemical performance with a maximum specific capacitance of 489.9 F g-1 at the charge/discharge current density of 1 A g-1 in 2 M KOH electrolyte.