Cloning,Expression, and Biochemical Characterization of a Novel Acidic GH16 β-Agarase,AgaJ11, from <Emphasis Type="Italic">Gayadomonas joobiniege</Emphasis> G7

A novel β-agarase AgaJ11 belonging to the glycoside hydrolase (GH) 16 family was identified from an agar-degrading bacterium Gayadomonas joobiniege G7. AgaJ11 was composed of 317 amino acids (35 kDa), including a 26-amino acid signal peptide, and had the highest similarity (44 % identity) to a putative β-agarase from an agarolytic marine bacterium Agarivorans albus MKT 106. The agarase activity of purified AgaJ11 was confirmed by zymogram analysis. The optimum pH and temperature for AgaJ11 activity were determined to be 4.5 and 40 °C, respectively. Notably, AgaJ11 is an acidic β-agarase that was active only at a narrow pH range from 4 to 5, and less than 30 % of its enzymatic activity was retained at other pH conditions. The K _m and V _max of AgaJ11 for agarose were 21.42 mg/ml and 25 U/mg, respectively. AgaJ11 did not require metal ions for its activity, but severe inhibition by several metal ions was observed. Thin layer chromatography and agarose-liquefying analyses revealed that AgaJ11 is an endo-type β-agarase that hydrolyzes agarose into neoagarohexaose, neoagarotetraose, and neoagarobiose. Therefore, this study shows that AgaJ11 from G. joobiniege G7 is a novel GH16 β-agarase with an acidic enzymatic feature that may be useful for industrial applications.     

Determination of Enantiomeric Purity of GSK962040 Based on Liquid Chromatography Using Chiral Stationary Phase Combined with a Pre-column Derivatization Procedure

A sensitive and accurate LC method was developed and further validated for the determination of enantiomeric purity of GSK962040. Before separation, a pre-column derivatization procedure was performed. Baseline separation with a resolution higher than 1.9 was accomplished within 15 min using a Chiralpak AD-H (250 × 4.6 mm; particle size 5 μm) column, with n-hexane: 2-propanol (85:15 v/v) as mobile phase at a flow rate of 1 mL min^?1. The eluted analytes were subsequently detected with a UV detector at 260 nm. The effects of mobile phase components and temperature on enantiomeric selectivity as well as resolution of enantiomers were thoroughly investigated. The calibration curves were plotted within the concentration range between 4 and 200 μg mL^?1 (n = 8), and recoveries between 98.15 and 101.48% were obtained, with relative standard deviation (RSD) lower than 1.42%. The LOD and LOQ for the Boc-GSK962040 were 1.23 and 4.15 μg mL^?1 and for its enantiomer were 1.38 and 4.76 μg mL^?1, respectively. The developed method was also evaluated and validated by analyzing bulk samples with different enantiomeric ratios of GSK962040. It was demonstrated that the method was accurate, robust and sensitive, and also had practical utilities for real analysis.     

Effect of Light/Dark Regimens on Hydrogen Production by <Emphasis Type="Italic">Tetraselmis subcordiformis</Emphasis> Coupled with an Alkaline Fuel Cell System

To improve the photoproduction of hydrogen (H₂) by a green algae-based system, the effect of light/dark regimens on H₂ photoproduction regulated by carbonyl cyanide m-chlorophenylhydrazone (CCCP) was investigated. A fuel cell was integrated into a photobioreactor to allow online monitoring of the H₂ evolution rate and decrease potential H₂ feedback inhibition by consuming the generated H₂ in situ. During the first 15 h of H₂ evolution, the system was subjected to dark treatment after initial light illumination (L/D = 6/9 h, 9/6 h, and 12/3 h). After the dark period, all systems were again exposed to light illumination until H₂ evolution stopped. Two peaks were observed in the H₂ evolution rate under all three light/dark regimens. Additionally, a high H₂ yield of 126 ± 10 mL L^?1 was achieved using a light/dark regimen of L 9 h/D 6 h/L until H₂ production ceased, which was 1.6 times higher than that obtained under continuous illumination. H₂ production was accompanied by some physiological and morphological changes in the cells. The results indicated that light/dark regimens improved the duration and yield of H₂ photoproduction by the CCCP-regulated process of Tetraselmis subcordiformis.     

The kinetics of the reduction reaction of plutonium(IV) with <Emphasis Type="Italic">N</Emphasis>,<Emphasis Type="Italic">N</Emphasis>-dimethylhydroxylamine

Development of the petroleum industry has resulted in increasing production of oil sludge, the disposal of which risks introducing hazardous elements into the environment. In the frames of these studies the presence of the toxic metals arsenic, chromium and zinc in oil sludge and the leachability of those toxins. Samples were obtained from a refinery plant in Sg Udang, Melaka and from the Miri Crude Oil Terminal, Sarawak, both in Malaysia. k ₀-Instrumental Neutron Activation Analysis was used to measure mass fractions of elements. The samples were packed and irradiated in a TRIGA Mark II reactor. Mass fraction of arsenic in the oil sludge samples were found to be higher than the EPA pollutant mass fraction limit; mass fractions of chromium and zinc were below of this limit. Samples were also tested for leachability, which was found to be contributed to by controlled diffusion. Slow leachability of arsenic was found to be higher than the EPA limit in these oil sludge samples, influenced by such factors as redox condition. It was found however, that the most leachable of these elements in all samples from both sites was zinc, followed by arsenic and chromium, indicating that zinc may present a more serious threat of environmental contamination than the other two.     

Effect of environmental conditions on the sorption of radiocobalt from aqueous solution to treated eggshell as biosorbent

Carbonate hydroxylapatite (CHAP), prepared from eggshell waste, was used to remove ⁶⁰Co(II) from aqueous solutions. The sorption of ⁶⁰Co(II) on CHAP as a function of contact time, pH, ionic strength and foreign ions in the absence and presence of humic acid and fulvic acid under ambient conditions was studied. The sorption of ⁶⁰Co(II) on CHAP was strongly dependent on pH and ionic strength. The thermodynamic parameters (ΔH ⁰, ΔS ⁰, ΔG ⁰) of ⁶⁰Co(II) sorption on CHAP were calculated from the temperature-dependent sorption isotherms, and the results indicated that the sorption process of ⁶⁰Co(II) on CHAP was endothermic and spontaneous. At low pH, the sorption of ⁶⁰Co(II) was dominated by outer-sphere surface complexation and ion exchange with Na⁺/H⁺ on CHAP surfaces, whereas inner-sphere surface complexation was the main sorption mechanism at high pH. Experimental results also indicated that CHAP was a suitable low-cost adsorbent for pre-concentration and solidification of ⁶⁰Co(II) from large volumes of aqueous solutions.     

Statins: 3-Hydroxy-3-methylglutaryl-CoA (HMG-CoA) Reductase Inhibitors Demonstrate Anti-Atherosclerotic Character due to Their Antioxidant Capacity

Atherosclerosis is a chronic inflammatory disease of multiple etiologies. It is associated with the accumulation of oxidized lipids in arterial lesions leading to coronary heart disease. 3-Hydroxy-3-methylglutaryl coenzyme A (HMG-CoA) reductase inhibitors (commonly known as statins) are widely used in cardiovascular disease prevention to lower the cholesterol. The antioxidant activity of HMG-CoA reductase inhibitors was studied by lipid peroxidation inhibition assay, DPPH, and hydroxyl radical scavenging-activity methods. The lovastatin (93%) and simvastatin (96%) showed significant action of lipid peroxidation inhibition compared to other HMG-CoA reductase inhibitors. The DPPH radical and hydroxyl radical scavenging activity of simvastatin was 38% and 33%, respectively. The oxidative modification of serum lipid due to reactive oxygen species causes atherosclerosis. This study revealed the importance of lovastatin and simvastatin to prevent oxidative stress-related cardiovascular diseases.     

Effect of Biosurfactants on Laccase Production and Phenol Biodegradation in Solid-State Fermentation

The effects of two biosurfactants, tea saponin (TS) and rhamnolipid (RL), on the production of laccase and the degradation of phenol by P. simplicissimum were investigated in solid-state fermentation consisting of rice straw, rice bran, and sawdust. Firstly, the effects of phenol on the fermentation process were studied in the absence of surfactants. Then, a phenol concentration of 3 mg/g in the fermentation was selected for detailed research with the addition of biosurfactants. The results showed that TS and RL at different concentrations had stimulative effects on the enzyme activity of laccase. The highest laccase activities during the fermentation were enhanced by 163.7%, 68.2%, and 23.3% by TS at concentrations of 0.02%, 0.06%, and 0.10%, respectively. As a result of the enhanced laccase activity, the efficiency of phenol degradation was also improved by both biosurfactants. RL caused a significant increase of fungal biomass in the early stage of the fermentation, while TS had an inhibitory effect in the whole process. These results indicated that RL could mitigate the negative effects of phenol on fungal growth and consequently improve laccase production and phenol degradation. TS was potentially applicable to phenol-polluted solid-state fermentation.     

Special wetting behavior of a graphitic nanofiber-modified epoxy generalized for rough textured fabric surfaces

Wetting behavior of a polymer resin used as matrix on fabric surfaces is one of the key attributes for making high quality structural composites. Though incorporation of various functionalized nanoparticles can stimulate improvements to many properties of epoxy resins, there has not been any report on wettability of any nano-modified epoxy on rough inclined fabric surfaces. In this research work, wetting behavior of a previously developed nano-epoxy resin modified by a type of reactive graphitic nanofibers (r-GNFs) was investigated. The observation results revealed that a unique wetting behavior was discovered from the nano-epoxy on rough fabric surfaces due to the contribution of the r-GNFs. Based on this dramatically improved wettability of the epoxy, a concept of dry–wet contact model was proposed to interpret the different wetting phenomenon observed from the nano-epoxy and that of the pure epoxy. The improved wetting characteristics of the nano-epoxy system will be essential for enabling future energy efficient infusion processing for manufacturing high quality and high-performance structural composite applications.     

Synthesis,structure, CMC values,thermodynamics of micellization,steady-state photolysis and biological activities of hexadecylamine cobalt(III) dimethyl glyoximato complexes

Metallosurfactant complexes of the type trans- [Co(DH)₂(HA)X], where DH = Dimethyl glyoxime, HA = Hexadecyl amine and X = Cl⁻, Br⁻, I⁻, N₃ ⁻, NO₂ ⁻ or SCN⁻, were synthesized and characterized by physico-chemical and spectroscopic methods. In addition, the single crystal X-ray structure of the ionic complex trans-[Co(DH)₂(HA)₂][Co(DH)₂(I)₂)] is presented. The critical micelle concentration values of the complexes in ethanol were obtained by measuring the absorption at 290 nm. Specific conductivity data (at 303–313 K) served for the evaluation of the thermodynamics of micellization ) \left( {\Updelta G^{0}_{{{\text{m}}}}, \Updelta H^{0}_{{{\text{m}}}}, \Updelta S^{0}_{\text{m}} } \right) . Steady-state photolysis, cyclic voltammetry and biological activities of the complexes were studied. The compounds were tested for antimicrobial activity.     

Synthesis,structure, and DNA-binding properties of manganese(II) and zinc(II) complexes with tris(<Emphasis Type="Italic">N</Emphasis>-methylbenzimidazol-2-ylmethyl)amine ligand

Tris(N-methylbenzimidazol-2-ylmethyl)amine (Mentb) and its two complexes, [Mn(Mentb)(DMF)(H₂O)](pic)₂ 1 and [Zn(Mentb)(pic)](pic) 2 (pic = picrate), have been synthesized and characterized by physico-chemical and spectroscopic methods. Single crystal X-ray diffraction revealed that the two complexes have different structures. In complex 1, the coordination sphere around Mn(II) is distorted octahedral, whereas in complex 2 the coordination sphere around Zn(II) is distorted trigonal bipyramidal. The DNA-binding properties of the free ligand and its two complexes have been investigated by electronic absorption, fluorescence, and viscosity measurements. The results suggest that the ligand and its two complexes bind to DNA via an intercalation binding mode, and their binding affinity for DNA follows the order 1 > 2 > ligand.