Reduced monoclinic BiVO4 for improved photoelectrochemical oxidation of water under visible light.

A monoclinic BiVO4 film was grown on a transparent conducting substrate for photoelectrochemical oxidation of water. A photocurrent up to 2.3 mA cm(-2) under visible light (λ > 420 nm) was achieved after treating the sample simply by electrochemical reduction followed by NaBH4. The high photocurrent is believed to be due to the improved carrier separation and transportation as a result of increased donor density.

De novo tyrosinase inhibitor: 4-(6,7-dihydro-5H-indeno[5,6-d]thiazol-2-yl)benzene-1,3-diol (MHY1556).

In this study, we have synthesized and studied de novo tyrosinase inhibitor, MHY1556, which showed significantly better efficacy than other pre-existing tyrosinase inhibitors in vitro experiments. The IC50 value of MHY1556 was 0.50µM which was significantly lower than that of kojic acid (IC50=53.95µM), which is a well-known tyrosinase inhibitor and was used as a positive control in this study. We predicted the tertiary structure of tyrosinase, simulated the docking with compound MHY1556 and confirmed that the compound strongly interacts with mushroom tyrosinase residues. Substitutions with a hydroxy group at both R1 and R3 of the phenyl ring indicated that these groups play a major role in the high binding affinity to tyrosinase, especially through the hydrogen bonding interaction of the hydroxyl group at R1 with GLY281. In addition, MHY1556 showed concentration-dependent inhibitory effects in melanin content assay where B16F10 melanoma cells were treated with α-melanocyte stimulating hormone (α-MSH), and also there is no significant cytotoxicity of this compound in cell viability assay conducted in B16F10 melanoma cells. The tyrosinase activity assay results with MHY1556 also support its potent inhibitory effects. Therefore, our data strongly suggest MHY1556 suppresses the melanogenesis via a tyrosinase inhibitory effect.

[Photochromic properties of complexes of curcumin aniline schiff base with rare earth].

Using Ce, La, Nd (III) nitrate and a curcumin aniline schiff base and a curcumin bis (4-methyl aniline) schiff base as raw materials, six complexes were synthesized. Through the molar conductance, IR, TG-DTA and element analysis motheds, the structures of complexes were characterized. Moreover, the properties of UV-Visible spectra and photochromic properties of the complex, and the solvatechromic performance in organic solvents were explored. The experiments showed that the complexes have good photochromic and solvate-chromic properties. The fluorescence intensity and UV-Visible spectra intensity were reduced under exposure,and the color of the complex solution became light. The complexes have different UV-Visible spectra in difference organic solvents. The relationship between photochromic properties and time was also studied.

Poly[diaqua-[µ-1,4-bis-(1H-imidazol-1-yl)benzene-κ(2)N(3):N(3')](µ-fumarato-κ(2)O(1):O(4))nickel(II)].

In the title compound, [Ni(C(4)H(2)O(4))(C(12)H(10)N(4))(H(2)O)(2)](n), the Ni(II) ion has a distorted octa-hedral coordination geometry. The asymmetric unit is composed of an Ni(2+) ion, located on a twofold rotation axis, one half of a 1,4-bis-(1H-imidazol-1-yl)benzene (BIMB) ligand and one half of a fumarte (fum(2-)) dianion, both ligands being located about inversion centers, and a coordinating water mol-ecule. The Ni(II) ions are linked by two BIMB ligands and two fum(2-) dianions, forming a four-connected layered structure parallel to (010) with a 4(4)-sql topology. Within each layer, there are rhombic grids with dimensions of ca 13.5 × 9.0 Šand approximate angles of 109 and 70°. The crystal packing features a two-dimensional → two-dimensional parallel/parallel interpenetration in which one undulating layer is catenated to another equivalent one, forming a new bilayer. Moreover, the entangled two-dimensional layers are connected by O-H⋯O and C-H⋯O hydrogen bonds, generating a three-dimensional structure.

Synthesis of novel azo-resveratrol, azo-oxyresveratrol and their derivatives as potent tyrosinase inhibitors.

Ten azo compounds including azo-resveratrol (5) and azo-oxyresveratrol (9) were synthesized using a modified Curtius rearrangement and diazotization followed by coupling reactions with various phenolic analogs. All synthesized compounds were evaluated for their mushroom tyrosinase inhibitory activity. Compounds 4 and 5 exhibited high tyrosinase inhibitory activity (56.25% and 72.75% at 50 µM, respectively). The results of mushroom tyrosinase inhibition assays indicate that the 4-hydroxyphenyl moiety is essential for high inhibition and that 3,5-dihydroxyphenyl and 3,5-dimethoxyphenyl derivatives are better for tyrosinase inhibition than 2,5-dimethoxyphenyl derivatives. Particularly, introduction of hydroxyl or methoxy group into the 4-hydroxyphenyl moiety diminished or significantly reduced mushroom tryosinase inhibition. Among the synthesized azo compounds, azo-resveratrol (5) showed the most potent mushroom tyrosinase inhibition with an IC(50) value of IC(50)=36.28 ± 0.72 µM, comparable to that of resveratrol, a well-known tyrosinase inhibitor.

Design, synthesis, and evaluation of (E)-N-substituted benzylidene-aniline derivatives as tyrosinase inhibitors.

We attempted to design and synthesize (E)-N-substituted benzylidene-hydroxy or methoxy-aniline derivatives and to evaluate their inhibitory effect on tyrosinase activity and anti-melanogenesis activity in murine B16F10 melanoma cells. Derivatives with a 4-methoxy- or 4-hydroxy-anilino group exerted more potent inhibition against mushroom tyrosinase than those with a 2-hydroxyanilino group. (E)-4-((4-Hydroxyphenylimino)methyl)benzene-1,2-diol exhibited the most potent and non-competitive inhibition on mushroom tyrosinase showing an IC(50) of 17.22 ± 0.38 µM and being more effective than kojic acid (51.11 ± 1.42 µM). This compound decreased melanin production stimulated by the alpha-melanocyte-stimulating hormone and inhibited murine tyrosinase activity in a dose-dependent manner. Therefore, we propose (E)-4-((4-hydroxyphenylimino)methyl)benzene-1,2-diol as a new candidate of potent tyrosinase inhibitors that could be used as therapeutic agent with safe skin-whitening efficiency.

Suppression of melanogenesis by a newly synthesized compound, MHY966 via the nitric oxide/protein kinase G signaling pathway in murine skin.

BACKGROUND: Ultraviolet B (UVB) radiation is the main physiological stimulus for skin pigmentation. Nitric oxide (NO) and the NO/PKG signaling pathway play an important role in UVB-induced melanogenesis, which is related to the induction of expression of tyrosinase. In an attempt to find a novel anti-melanogenic agent, we synthesized a new compound, 2-bromo-4-(5-chloro-benzo[d]thiazol-2-yl) phenol (MHY966). OBJECTIVE: The purpose of this study was to investigate the action of MHY966 on NO and the NO-mediated signaling pathway using in vitro and in vivo models of melanogenesis. METHODS: NO generation, melanin synthesis, and the expression of tyrosinase and PKG were measured in B16F10 melanoma cells to verify the anti-melanogenic effect of MHY966 in vitro. Next, melanin-possessing hairless mice were pre-treated with MHY966 and then irradiated with UVB repeatedly. Morphological, histological, and biochemical analyses including the expressions of PKG, tryosinase and nuclear MITF, and productions of nitric oxide, peroxynitrite and ROS were conducted. RESULTS: MHY966 effectively inhibited NO generation and subsequent melanin synthesis induced by sodium nitroprusside, an NO donor, and suppressed the expression of tyrosinase and PKG. Topical application of MHY966 dose-dependently attenuated UVB-induced pigmentation in a mouse model. This hypopigmentation effect induced by MHY966 treatment was mediated by the down-regulation of tyrosinase, PKG, and nuclear MITF, which was accompanied by decreased NO and NO-related oxidative stress. CONCLUSION: The novel compound, MHY966 had an inhibitory effect on NO generation and the NO-mediated signaling pathway leading to the down-regulation of tyrosinase. The significance of the present study is the finding of a promising anti-melanogenic agent targeting the NO/PKG signaling pathway.

Synthesis and preliminary in vitro biological evaluation of 5-chloro-2-(substituted phenyl)benzo[d]thiazole derivatives designed as novel antimelanogenesis agents.

We describe the design, synthesis, and biological activities of 5-chloro-2-(substituted phenyl)benzo[d]thiazole derivatives as novel tyrosinase inhibitors. Among them, 4-(5-chloro-2,3-dihydrobenzo[d]thiazol-2-yl)-2,6-dimethoxyphenol (MHY884) and 2-bromo-4-(5-chloro-benzo[d]thiazol-2-yl)phenol (MHY966) showed inhibitory activity higher than or similar to kojic acid, against mushroom tyrosinase. Therefore, we carried out kinetic studies on the two compounds with potent tyrosinase inhibitory effects. Kinetic analysis of tyrosinase inhibition revealed that all of these compounds are competitive inhibitors. MHY884 and MHY966 effectively inhibited tyrosinase activity and reduced melanin levels in B16 cells treated with α-melanocyte stimulating hormone (α-MSH). These data strongly suggest that the newly synthesized compounds MHY884 and MHY966 could suppress production of melanin via inhibition of tyrosinase activity.

Inhibitory effect of mTOR activator MHY1485 on autophagy: suppression of lysosomal fusion.

Autophagy is a major degradative process responsible for the disposal of cytoplasmic proteins and dysfunctional organelles via the lysosomal pathway. During the autophagic process, cells form double-membraned vesicles called autophagosomes that sequester disposable materials in the cytoplasm and finally fuse with lysosomes. In the present study, we investigated the inhibition of autophagy by a synthesized compound, MHY1485, in a culture system by using Ac2F rat hepatocytes. Autophagic flux was measured to evaluate the autophagic activity. Autophagosomes were visualized in Ac2F cells transfected with AdGFP-LC3 by live-cell confocal microscopy. In addition, activity of mTOR, a major regulatory protein of autophagy, was assessed by western blot and docking simulation using AutoDock 4.2. In the result, treatment with MHY1485 suppressed the basal autophagic flux, and this inhibitory effect was clearly confirmed in cells under starvation, a strong physiological inducer of autophagy. The levels of p62 and beclin-1 did not show significant change after treatment with MHY1485. Decreased co-localization of autophagosomes and lysosomes in confocal microscopic images revealed the inhibitory effect of MHY1485 on lysosomal fusion during starvation-induced autophagy. These effects of MHY1485 led to the accumulation of LC3II and enlargement of the autophagosomes in a dose- and time-dependent manner. Furthermore, MHY1485 induced mTOR activation and correspondingly showed a higher docking score than PP242, a well-known ATP-competitive mTOR inhibitor, in docking simulation. In conclusion, MHY1485 has an inhibitory effect on the autophagic process by inhibition of fusion between autophagosomes and lysosomes leading to the accumulation of LC3II protein and enlarged autophagosomes. MHY1485 also induces mTOR activity, providing a possibility for another regulatory mechanism of autophagy by the MHY compound. The significance of this study is the finding of a novel inhibitor of autophagy with an mTOR activating effect.

[Fluorescence property of a chemical probe for naked-eye and detection of Fe3+].

A higher selective and sensitive probe for the detection of Fe(III) in aqueous media was made using 2,4-Diisocyanatotoluene (TDI) as a bridge to couple Fe3 O4 nanoparticles(NPs) and Rhodamine-6G hydrazide. The characterization of composite materials with Infrared spectra(IR), Thermal Gravimetric analysis(TGA) and Transmission Emission Microscopy(TEM) points to the graft of Rhodamine-6G hydrazide onto the surface of the Fe3O4. The obvious color change of the probe solution from light grey to pink upon the addition of Fe3+ demonstrated the probe could be used for "naked-eye" detection of Fe3+ in water at pH 7. The presence of 1 equivalent (10 micromol x L(-1) microm) of each of these metal ions, including Mn2+, Ni2+, Y2+, Eu3+, Ce3+, La3+, Pr3+, Cd2+, Cr3+, Sm3+, Fe2+, Cu2+ and Zn2+ ions, did not demonstrate any obvious fluorescence change of the probe water solution, which confirmed the probe was a probe with remarkable selectivity for Fe3+. And the fluorescence images of HeLa cells in physiological solutions after incubation with Fe3+ and then further incubated with the probe leading to a strong intracellular fluorescence, which suggested the probe could penetrate the HeLa cell membrane and could respond to Fe3+ in intracellular within living cells.

Study on syntheses and anticoagulant action of heparin/rare earth nano-oxides hybrid material.

Four hybrid materials of RE2O3-TDI-Heparin (TDI=Toluene 2,4-diisocyanate, RE=La, Eu, Nd, Sc) were prepared by the method of graft. The materials were characterized by IR, TG, and SEM, which confirmed that the heparin was grafted on the surface of TDI modified rare earth nano-oxides. The cell adhesion experiment and the anticoagulant experiment demonstrated that the materials have lower cell toxicity, better cell adhesion as well as better anticoagulant action. In addition, the clotting time of hybrid materials were shortened compared with the heparin.

[Study on the interaction of Sm(III) complexes of rutin with serum albumin].

The binding reaction of rutin-Sm with serum albumin (SA) was investigated by the fluorescence method in physiological condition. The authors studied mainly the quenching mechanism of the fluorescence of SA by rutin-Sm, and calculation of the binding constants K(LB) of human serum albumin (HSA) and bovine serum albumin (BSA) with rutin-Sm by Lineweaver-Burk equation at different temperatures respectively, then obtained the thermodynamic parameters of HSA and BSA with rutin-Sm according to the calculated binding constants K(LB) at different temperature, meanwhile the type of binding forces of HSA and BSA with rutin-Sm was determined. The results showed that the emission spectra of BSA (HSA) in the presence and absence of rutin-Sm are different. The emission spectra of BSA (HSA) in the presence of rutin-Sm can be quenched. The quenching mechanism of rutin-Sm to SA was static quenching with non-radiation energy transfer for new complex of SA and rutin-Sm. The binding constants K(LB) (L x moL(-1)) were 6.540 x 10(5) and 3.265 x 10(5) for BSA, and 6.830 x 10(5) and 4.665 x 10(5) for HSA at 295 K and 310 K respectively. And the type of bonding forces was estimated by the calculation of thermodynamic parameters of the reaction of rutin-Sm with SA at different temperatures, and the result showed that the binding forces were mainly H-bond and Van der Waals between BSA and rutin-Sm due to the deltaH < 0 and deltaS < 0, and the main electrostatic interaction of rutin-Sm and HSA because of deltaH < 0 and deltaS > 0. The effect of rutin-Sm on the conformation of serum albumin was also studied by using synchronous fluorescence spectroscopy. Results indicated that rutin-Sm could be deposited and transported by serum protein in vivo.

Syntheses, characterization and biological activities of rare earth metal complexes with curcumin and 1,10-phenanthroline-5,6-dione.

Three new solid complexes have been synthesized by the reaction of rare earth(III) nitrate with the first ligand curcumin (HL) and the second ligand 1,10-phenanthroline-5,6-dione (L') in alcohol solution (pH=6.5-7.0). The composition of the complexes has been characterized by elemental analysis, molar conductivity, thermogravimetric analysis, IR, UV-vis methods. The results reveal that beta-diketone group of the first ligand to coordinates with rare earth ions in bidentate mode after deprotonated. But the second ligand uses its two N atoms coordinates with rare earth ions in bidentate mode. The general formula of the complexes is REL(3)L' (RE=Sm, Eu, Dy). The results of antibacterial activity indicated that the complexes have excellent antibacterial ability for the testing bacterium than that of curcumin. The result of agarose gel electrophoresis suggested that the complex of SmL(3)L' can cleave the plasmid DNA at physiological pH and temperature. And it was found that the cleavage process of plasmid DNA was sensitive to pH, however, adding radical scavengers almost had no effect on the DNA cleavage reaction, therefore, the cleavage of DNA by SmL(3)L' does not produce diffusible hydroxyl radicals via the Fenton reaction.

Biodegradation of Swainsonine by Acinetobacter calcoaceticus strain YLZZ-1 and its isolation and identification.

Eight swainsonine (SW)-degrading bacteria were isolated from the soil where locoweed was buried for 6 months and one of the strains (YLZZ-1) was selected for further study. Based on morphology, physiologic tests, 16S rRNA gene sequence, and phylogenetic characteristics, the strain showed the greatest similarity to members of the order Acinetobacters and within the order to members of the Acinetobacter calcoaceticus group. The ability of the strain for degrading SW, as sole carbon source, was investigated under different culture conditions. The preferential temperature and initial pH for the strain were 25-35 degrees C and 6-9, respectively. The optimal temperature for the strain was 30 degrees C and the optimal pH was 7.0. There was a positive correlation between degradation rate and inoculation amount. The concentration of SW affected the degradation ability. When the concentration of SW was lower than 100 mg/l, SW decreased immediately after incubation, and when the concentration of SW was 200 mg/l, there was an inhibiting effect for bacteria growth and SW degradation. The strain could degrade SW completely within 14 h when the concentration of SW was 50 mg/l. These results highlight the potential of this bacterium to be used in detoxifying of SW in livestock consuming locoweed.

[Thermodynamics studies on the binding of rutin and serum albumin].

To study the binding of rutin and serum albumin (SA) in physiological condition and the quenching mechanism of the fluorescence of SA by rutin, the fluorescence method was used. The results shows that the emission spectra of BSA (HSA) in the presence and absence of rutin are different. The emission spectra of BSA (HSA) in the presence of rutin can be quenched. The quenching mechanism of rutin to SA was static quenching with non-radiation energy transfer with single molecule. The binding constants K(A), the number of binding sites n and the thermodynamic parameters of the reaction of rutin with SA were determined at different temperatures. At 295 and 310 K, for BSA, K(A)(L * moL(-1)) = 4.215 x 10(4) and 6.996 x 10(3) and n = 0.75 and 0.64, respectively; for HSA, K(A)(L * moL (-1)) = 2.660 x 10(4) and 4.110 x 10(3) and n = 0.70 and 0.60, respectively. The binding constants K(A) decreased with the increase in temperature, which means that rutin and SA have a quite strong ability to form a new complex-system. The main binding force was discussed by thermodynamic equation, and the result is that deltaH < 0 and deltaS < 0 for the reaction of rutin with SA. So the binding forces was mainly H-bond and Van der Waals. The effect of the drug on the conformation of serum albumin was also studied by using synchronous fluorescence spectroscopy. Rutin could be deposited and transported by serum protein in vivo. Rutin had nearly no effect on the serum protein conformation.

[Influence of rutin on conformation of serum albumin].

We studied the effect of the rutin on the conformation of bovine serum albumin (BSA) and human serum albumin (HSA) by synchronous fluorescence spectrum (Alambda = lambda(em) - lambda(ex) = 15 nm and deltalambda = lambda(em) -lambda(ex) = 60 nm) and circular dichroism spectra. The results showed that rutin had hardly effect on the serum protein conformation, but influenced the secondary structure of serum albumin (SA) molecule with the addition of rutin into BSA and HSA solution. The alpha-helix structure of BSA and HSA was decreased and the beta-sheet was increased with the increase in rutin concentration. At the same time, we studied the binding of rutin and bovine serum albumin (BSA) and human serum albumin (HSA) by electrochemistry under physiological condition. Cyclic voltammograms of rutin demonstrated a pair of well-reversible peaks in the solution of Tris-NaCl buffer at pH 7.38 (sweep rate: 50 mV x s(-1); a glassy carbon working electrode, a platinum auxiliary electrode, and a saturated calomel reference electrode). Both peak potentials of rutin were E(pc) = 0.103 2 V and E(pa) = 0.150 6 V, ipc : ipa = 1 : 1.2, the dispersion of peak potential was 47.4 mV (deltaE(prutin) = deltaE(pc) - E(pa) = 47.4 mV). In addition, with the addition of BSA and HSA into the rutin solution, both the reduction and oxidation currents decreased only at the peak potentials of rutin (BSA: E(pc) = 0.114 1 V, E(pa) = 0.168 5 V, ipc : ipa = 1 : 1.2; HSA: E(pc) = 0.114 2 V, E(pa) = 0.168 8 V, ipc : ipa= 1 : 1.1), the dispersions of peak potential were changed: for BSA deltaE(prutin) = [E(pc) - E(pa)] = 54.4 mV, and for HSA: deltaE(prutin) = [E(pc) - E(pa)] = 54.6 mV. The results showed that there was an interaction of rutin with BSA and HSA, forming a kind of nonelectroactive supramolecular complex, and indicated that rutin could be deposited and transported by serum protein in vivo.

[Studies on the mechanism of the interaction between hydrazide-podophyllic Ni(II), Co(II), Zn(II) metal complexes and DNA].

The mechanism of the interaction between hydrazide-podophyllic (HDPP) metal (Me) complexes and calf thymus (ct) DNA in Tris buffer (pH 7.08) was studied by viscosity measurements, electronic absorption, gel electrophoresis, and ethidium bromide (EB) fluorescence spectroscopy. The results from varied experiments show that the intensity of the maximal absorption peaks from absorption spectra is weakened in the presence of DNA compared with that in the absence of DNA. Meanwhile, DNA can remarkably quench the emission intensity of the complex Me-HDPP system. The Me-HDPP complexes can increase the viscosity of ct DNA slightly and catalyze the cleavage of super coiled pBR322 DNA to the nicked form. The complexes of Ni-HDPP and Co-HDPP can be bound to ct DNA mainly by interaction, while the partial interaction of Zn-HDPP and ct DNA is the major modes. The binding constant of Me-HDPP complexes with ct DNA was determined.

[Studies on the interaction of the metal complex of hydrazide of podophyllic acid with DNA].

The interaction between the metal complex of hydrazide of podophyllic acid and calf thymus (CT) DNA was studied by using absorption spectra, fluorescence spectra and DNA heat denaturation. It was found that the intensity of the maximal absorption peaks from absorption spectra is weakened in the presence of the metal complex of hydrazide of podophyllic acid compared with that in the absence of the metal complex. All the experimental results show that the intercalation mode was proved to exist between HDPP-Ni complexes and CT DNA.

DNA Binding and cleavage activity of Ni(II) complex with all-trans retinoic acid.

Absorption, fluorescence spectral, cyclic voltammetry and agarose gel electrophoresis studies have been carried out on the interaction of Ni(II) complex with all-trans retinoic acid ([Ni(RA)(2)(H(2)O)(2)] * H(2)O) with DNA. The results indicate that the [Ni(RA)(2)(H(2)O)(2)] * H(2)O can more effectively promote the cleavage of plasmid DNA than that of all-trans retinoic acid (HRA) and Ni(II) at physiological pH and temperature, which may be one of the reasons why the inhibitory effect of [Ni(RA)(2)(H(2)O)(2)] * H(2)O on the human bladder line EJ cells is much greater than that of retinoic acid. It was found that the process of plasmid DNA cleavage was sensitive to ionic strength and pH, however, these radical scavengers almost had no effect on the DNA cleavage reaction. The above results suggested that the cleavage of plasmid DNA by [Ni(RA)(2)(H(2)O)(2)]* H(2)O did not produce diffusible hydroxyl radicals via the Fenton reaction. The results of UV-absorption studies and fluorescence characterization of the interaction of [Ni(RA)(2)(H(2)O)(2)] * H(2)O with Calf thymus DNA show that the [Ni(RA)(2)(H(2)O)(2)] * H(2)O binds to DNA mainly in an intercalating mode.