Green Enzymatic Synthesis of L-Ascorbyl Fatty Acid Ester: An Antioxidant

In green chemistry, biocatalysis using microwaves is a very attractive tool for various regioselective syntheses. L-Ascorbyl fatty acid esters were synthesized by an immobilized lipase from Bulkholderia multivorans using microwaves, with a dynamically enhanced rate of reaction and appreciable yield of around 80%. Microwave radiation had no effect on enzymic inactivation, however, synergism between microwaves and biocatalyst was observed.     

Regioselective Photocyclization Reactions of 3‐Allyloxy‐6‐chloro‐2‐(thiophen‐3‐yl)‐4H‐chromen‐4‐one: Solvent Effect

The photo‐irradiation of thienylchromenone resulted in the regioselective cyclization which is exclusively controlled by the nature of solvent used as reaction medium. Compared to nonpolar medium, polar solvent furnished a diverse array of novel angular tetracyclic photoproducts with gem‐dihydro functionality and exocyclic double bonds on the fused pyran ring, which is unprecedented to best of our knowledge.     

Use of NAD(P)H Fluorescence Measurement for On-Line Monitoring of Metabolic State of Azohydromonas australica in Poly(3-hydroxybutyrate) Production

Culture fluorescence measurement is an indirect and non-invasive method of biomass estimation to assess the metabolic state of the microorganism in a fermentation process. In the present investigation, NAD(P)H fluorescence has been used for on-line in situ characterization of metabolic changes occurring during different phases of batch cultivation of Azohydromonas australica in growth associated poly(3-hydroxybutyrate) or PHB production. A linear correlation between biomass concentration and net NAD(P)H fluorescence was obtained during early log phase (3–12 h) and late log phase (24–39 h) of PHB fermentation. After 12 h (mid log phase) cultivation PHB accumulation shot up and a drop in culture fluorescence was observed which synchronously exhibited continuous utilization of NAD(P)H for the synthesis of biomass and PHB formation simultaneously. A decrease in the observed net fluorescence value was observed again towards the end of fermentation (at 39 h) which corresponded very well with the culture starvation and substrate depletion towards the end of cultivation inside the bioreactor. It was therefore concluded that NAD(P)H fluorescence measurements could be used for indication of the time of fresh nutrient (substrate) feed during substrate limitation to further enhance the PHB production.     

Ring opening of epoxides with alcohols using Fe(Cp)2BF4 as catalyst

Fe(Cp)₂BF₄ is an efficient catalyst for the alcoholysis of aromatic, aliphatic, and cyclic epoxides giving excellent yields of the corresponding β-alkoxy alcohols under ambient conditions. The methanolysis of styrene oxide using Fe(Cp)₂BF₄ as a catalyst (5 mol %) gave excellent yield of 2-methoxy-2-phenylethanol with complete regio-selectivity. The ring opening of cyclic epoxides gave 77–97% yields of trans-β-methoxy alcohols, in 0.5–6 h. The use of 1,2-epoxyhexane and 1,2-epoxydodecane as substrates gave both regioisomers in excellent yields. The first order rate of reaction with respect to catalyst was observed for the kinetics of ring opening of 1,2-epoxyhexane with methanol.     

Facile ion-exchange synthesis of Gd-doped K2Ta2O6 photocatalysts with enhanced visible light activity

One of the well-known ways of increasing the visible light absorption capability of semiconducting materials is cation doping. This study aims to use Gd doping to tailor the bandgap energy of K₂Ta₂O₆ (KTO) for photocatalytic degradation of organic pollutants under visible light irradiation. Accordingly, the parent KTO and Gd-doped KTO with different Gd concentrations (K_2-3xGd_xTa₂O₆; x = 0.025, 0.05, 0.075 and 0.1 mol%) were synthesized by hydrothermal and facile ion-exchange methods, respectively. The powder XRD, FT-IR, SEM-EDS, TEM-SAED, N₂ adsorption-desorption, XPS, UV–Vis DRS, PL and ESR techniques were used to investigate the effect of Gd dopant concentration on the structural and photocatalytic properties of KTO. The photocatalytic activity of these samples was investigated for the photocatalytic degradation of methylene blue (MB) dye in an aqueous solution at room temperature under visible light irradiation. The experimental results show that all Gd-doped KTO samples exhibit enhanced photocatalytic activity compared with parent KTO toward MB degradation. In particular, Gd-KTO obtained by doping of 0.075 mol% shows the highest photocatalytic activity among the Gd-doped samples and the degradation efficiency of MB was 79% after 180 min of visible light irradiation, which is approximately 1.5 times as high as that by parent KTO (53%). In addition, trapping experiments and electron spin resonance (ESR) analysis demonstrated that the hydroxyl radicals (^?OH) have played a crucial role in the photocatalytic degradation of MB. The reusability and stability of Gd doped-KTO with a Gd content of 0.075 mol% against MB degradation were examined for five cycles. Based on the present study results, a visible light induced photocatalytic mechanism has been proposed for Gd0075-KTO sample.     

Plasmonic photoelectrochemical reactions on noble metal electrodes of nanostructures

Plasmonic noble metal nanostructures have been targeted due to their strong surface plasmon resonance at photoelectrochemical interfaces. Recently, it has been concluded that, the plasmonic noble metal nanostructures on photoexcitation permit the transfer of effective hot carriers (hot electron/hole pair) to nearby adsorbed molecules where, the transformed hot carriers can efficiently decrease the activation barrier of a reaction. In this review, our recent achievements in the plasmon-mediated chemical reactions of organic molecules such as para-aminothiophenol, substituted para-aminothiophenol and para-nitrothiophenol at nanostructures modified noble metal electrodes using surface enhanced Raman spectroscopy, electrochemical methods, and theoretical calculations will be discussed.     

BMIM[BF4]: An Efficient Ionic Liquid Medium for the Synthesis of Chromeno[b]pyridines as Potential Anticancer Agents

Russian Journal of Organic Chemistry - A series of 2-amino-4-aryl-5-oxochromeno[4,3-b]pyridine-3-carbonitriles have been synthesized with good yields (85–90%) by reacting...     

Development of two-step radioimmunoassay (RIA) for the measurement of free triiodothyronine in human serum based on antibody coated tubes

Journal of Radioanalytical and Nuclear Chemistry - We describe a simple, user friendly two-step radioimmunoassay (RIA) based on antibody coated tubes for the measurement of free triiodothyronine in...     

Effect of salicin on induction and carbon catabolite repression of endoxylanase synthesis in Penicillium janthinellum MTCC 10889

Amongst various carbon sources, xylan was found to be the sole inducer of endoxylanase production by Penicillium janthinellum MTCC 10889 in submerged cultivation. Endoxylanase synthesis by a xylan induced culture was initially repressed after a simultaneous addition of xylose, probably by the inducer exclusion mechanism, but it was resumed and achieved its highest level at a much later stage of growth (at 120 h). Xylose added after 30 h of growth cannot exert its full repressive effect. Although glucose was proved to be a more potent repressor than xylose, supplementation of salicin, an alcoholic β-glycoside containing d-glucose, with pure xylan resulted in an about 3.22 fold increase in the enzyme synthesis at 72 h followed by constant high production of the enzyme at least until the 144th h of growth. Inducing capacity of salicin in a xylan induced culture was significantly reduced when it was added after 30 h of growth. Addition of salicin and xylan help to partially overcome the repressive effect of xylose and glucose. Failure of salicin in recovering the endoxylanase synthesis in actinomycin D and cyclohexamide inhibited the xylan induced culture indicating that salicin cannot initiate the de novo synthesis of the enzyme.     

Role of graphene in structural transformation of zirconium oxide

Fine powders of zirconium oxide (ZrO₂) were prepared using zirconium oxychloride by combustion method. The crystalline size of pure ZrO₂ was in range of 14–45 nm. Graphene was incorporated in ZrO₂ using graphene oxide as precursor and reducing it with hydrazine hydrate. X-Ray diffraction, Fourier transform infra-red spectroscopy, thermogravimetric analysis and Raman spectroscopy methods were used to characterize the samples. The role of graphene in structural transformation of ZrO₂ to monoclinic phase was clearly observed.