Phosphonate-Stabilized Titanium-Oxo Clusters with Ferrocene Photosensitizer: Structures, Photophysical and Photoelectrochemical Properties, and DFT/TDDFT Calculations.

The metal-to-core charge transfer (MCCT) transition in sensitized titanium-oxo clusters is an important process for photoinduced electron injection in photovoltaic conversion. This process resembles most closely the Type II photoinjection in dye-sensitized solar cells. Herein we report the synthesis and photophysical and photoelectrochemical (PEC) properties of the phosphonate-stabilized titanium-oxo clusters containing the ferrocenecarboxylate ligands. These ferrocene-containing clusters exhibit intense visible absorption extended up to 600 nm along with low optical band gaps of ∼2.2 eV. The low-energy transitions of these clusters were systematically investigated by UV-vis spectroscopy and DFT/TDDFT calculations. The combined experimental and computational studies suggest that the ferrocenecarboxylate-substituted titanium-oxo clusters form a donor-acceptor (D-A) system. The low-energy transition of these clusters primarily involves the MCCT from the iron center to TiO cluster core. The TiO core structure and phosphonate ligands both have great influence on the PEC properties of the clusters. This work provides valuable examples for the sensitized titanium-oxo clusters in which electron injection takes place via MCCT transition.

[Effect of Jiangzhi Kangyanghua mixture on high-sensitivity C-reactive protein and vascular endothelial functions of hypertension patients].

To observe the effect of Jiangzhikangyanghua Mixture on high-sensitivity CRP (hs-CRP) and vascular endothelial functions of essential hypertension (EH) patients. In this study, 72 cases of out-patients with EH were selected from department of cardiology of Wujin hospital of traditional Chinese Medicine, and randomly divided into the control group (n= 36, amlodipine 5 mg qd + valsartan 80 mg qd) and the test group (n =36 amlodipine 5 mg qd + valsartan 80 mg qd + Jiangzhikangyanghua mixture 20 mL tid). The contents of hs-CRP, ET-1 and NO were measured before and after treatment for two months. The result showed that the contents of hs-CRP, ET-1 in both groups reduced (P <0. 05) , while the test group show a more significant reduction than the control group (P <0. 05). After the treatment, the content of NO raised in both group, while the test group show a more significant increase than that of the control group (P <0. 05). This study indicated that Jiangzhi Kangyanghua mixture could reduce the contents of hs-CRP and ET-1 and raise NO of EH patients.

catena-Poly[[(2,2'-bipyridine-κN,N')cadmium]-µ(3)-4-nitro-phthalato-κO:O',O'':O'''].

In the title polymeric compound, [Cd(C(8)H(3)NO(6))(C(10)H(8)N(2))](n), two O atoms from both carboxyl-ate groups of a nitro-phthalate anion coordinate to the Cd(II) cation, forming a seven-membered chelate ring and two carboxyl-ate O atoms from another two nitro-phthalate anions and a 2,2'-bipyridine ligand coordinate to the Cd cation to complete the distorted octa-hedral coordination geometry. The carboxyl-ate groups of the nitro-phthalate anion adopt a syn-anti bridging mode, linking adjacent Cd(II) cations and forming a polymeric chain running along the a axis. Weak intra- and inter-molecular C-H⋯O hydrogen bonding is present in the crystal structure.

Dynamic structures of phosphodiesterase-5 active site by combined molecular dynamics simulations and hybrid quantum mechanical/molecular mechanical calculations.

Various quantum mechanical/molecular mechanical (QM/MM) geometry optimizations starting from an x-ray crystal structure and from the snapshot structures of constrained molecular dynamics (MD) simulations have been performed to characterize two dynamically stable active site structures of phosphodiesterase-5 (PDE5) in solution. The only difference between the two PDE5 structures exists in the catalytic, second bridging ligand (BL2) which is HO- or H2O. It has been shown that, whereas BL2 (i.e. HO-) in the PDE5(BL2 = HO-) structure can really bridge the two positively charged metal ions (Zn2+ and Mg2+), BL2 (i.e. H2O) in the PDE5(BL2 = H2O) structure can only coordinate Mg2+. It has been demonstrated that the results of the QM/MM geometry optimizations are remarkably affected by the solvent water molecules, the dynamics of the protein environment, and the electronic embedding charges of the MM region in the QM part of the QMM/MM calculation. The PDE5(BL2 = H2O) geometries optimized by using the QM/MM method in different ways show strong couplings between these important factors. It is interesting to note that the PDE5(BL2 = HO-) and PDE5(BL2 = H2O) geometries determined by the QM/MM calculations neglecting these three factors are all consistent with the corresponding geometries determined by the QM/MM calculations that account for all of these three factors. These results suggest the overall effects of these three important factors on the optimized geometries can roughly cancel out. However, the QM/MM calculations that only account for some of these factors could lead to considerably different geometries. These results might be useful also in guiding future QM/MM geometry optimizations on other enzymes.

Electrochemical behavior and voltammetric determination of paracetamol on Nafion/TiO2-graphene modified glassy carbon electrode.

The TiO(2)-graphene (TiO(2)-GR) nanocomposite for paracetamol electrochemical sensing is described. The electrochemical behavior of paracetamol at the Nafion/TiO(2)-GR composite film modified glassy carbon electrode (GCE) was investigated by cyclic voltammetry. The results showed that the incorporation of TiO(2) nanoparticles with graphene significantly enhanced the electrochemical reactivity and voltammetric response of paracetamol. In addition, Nafion acts as an effective solubilizing agent and antifouling coating in the fabrication of the modified electrode. This electrochemical sensor exhibits excellent analytical performance for paracetamol detection at physiological pH with detection limit of 2.1×10(-7) M, linear range of 1-100 µM and reproducibility of 3.6% relative standard deviation.

Hydrothermal preparation and electrochemical sensing properties of TiO(2)-graphene nanocomposite.

A facile hydrothermal method has been developed and shown to be effective for the preparation of TiO(2)-graphene nanocomposite. The as-prepared nanocomposite was characterized using FT-IR spectroscopy, powder X-ray diffraction (XRD) and scanning electron microscopy (SEM). The TiO(2)-graphene modified glassy carbon electrode (GCE) exhibited remarkable electron transfer kinetics and electrocatalytic activity toward the oxidation of dopamine (DA). Furthermore, the oxidation of common interfering agent such as ascorbic acid (AA) was significantly suppressed at this modified electrode, which resulted in good selectivity and sensitivity for electrochemical sensing of DA. These results demonstrate that the TiO(2)-graphene hybrid material has promising potential applications in electrochemical sensors and biosensors design.

Understanding the structure-activity and structure-selectivity correlation of cyclic guanine derivatives as phosphodiesterase-5 inhibitors by molecular docking, CoMFA and CoMSIA analyses.

Molecular docking and 3D-QSAR analyses were performed to understand how PDE5 and PDE6 interact with a series of (49) cyclic guanine derivatives. Using the conformations of the compounds revealed by molecular docking, CoMFA and CoMSIA analyses resulted in the first quantitative structure-activity relationship (QSAR) and first quantitative structure-selectivity relationship (QSSR) models (with high cross-validated correlation coefficient q(2) and conventional correlation coefficient r(2) values) for predicting the inhibitory activity against PDE5 and the selectivity against PDE6. The high q(2) and r(2) values, along with further testing, indicate that the obtained 3D-QSAR and 3D-QSSR models will be valuable in predicting both the inhibitory activity and selectivity of cyclic guanine derivatives for these protein targets. A set of 3D contour plots drawn based on the 3D-QSAR and 3D-QSSR models reveal some useful clues to improve both the activity and selectivity by modifying structures of the compounds. It has been demonstrated that both the steric and electrostatic factors should appropriately be taken into account in future rational design and development of more active and more selective PDE5 inhibitors for the therapeutic treatment of erectile dysfunction (ED).

Characterization of a catalytic ligand bridging metal ions in phosphodiesterases 4 and 5 by molecular dynamics simulations and hybrid quantum mechanical/molecular mechanical calculations.

Cyclic nucleotide phosphodiesterases (PDEs) constitute a large superfamily of enzymes regulating concentrations of intracellular second messengers cAMP and cGMP through PDE-catalyzed hydrolysis. Although three-dimensional x-ray crystal structures of PDE4 and PDE5 have been reported, it is uncertain whether a critical, second bridging ligand (BL2) in the active site is H2O or HO- because hydrogen atoms cannot be determined by x-ray diffraction. The identity of BL2 is theoretically determined by performing molecular dynamics simulations and hybrid quantum mechanical/molecular mechanical (QM/MM) calculations, for the first time, on the protein structures resolved by x-ray diffraction. The computational results confirm our previous suggestion, which was based on QM calculations on a simplified active site model, that BL2 in PDE4 should be HO-, rather than H2O, serving as the nucleophile to initialize the catalytic hydrolysis of cAMP. The molecular dynamics simulations and QM/MM calculations on PDE5 demonstrate for the first time that the BL2 in PDE5 should also be HO- rather than H2O as proposed in recently published reports on the x-ray crystal structures, which serves as the nucleophile to initialize the PDE5-catalyzed hydrolysis of cGMP. These fundamental structural insights provide a rational basis for future structure-based drug design targeting PDEs.