Enzymatic Synthesis of Nucleoside‐5′‐O‐(1‐thiophosphates) and (SP)‐Adenosine‐5′‐O‐(1‐thiotriphosphate)

Treatment of adenosine with PSCl₃ in trimethyl phosphate gave, after ion‐exchange chromatography, adenosine‐5′‐O‐monophosphate (AMP; 28%) and adenosine‐5′‐O‐monothiophosphate (AMPS; 48%). AMPS was studied as a thiophosphate residue donor in an enzymatic transphosphorylation with nucleoside phosphotransferase (NPase) of the whole cells of Erwinia herbicola. As exemplified by a number of natural and sugar‐ and base‐modified nucleosides, it was demonstrated that NPase of the whole cells of Erwinia herbicola catalyzes the transfer of both thiophosphate and phosphate residues with a similar efficiency. An incubation of AMPS in a phosphorylating extract of Saccharomyces cerevisiae (K‐phosphate buffer (0.3 M , pH 7.0); 3% glucose; 15 mM MgCl₂; 28°, 8 h), followed by ion‐exchange column chromatography afforded AMP (8%), AMPS (recovered, 23%), ATP (11%), and (S_P)‐adenosine‐5′‐O‐(1‐thiotriphosphate) ((S_P)‐ATPαS); (total yield 37%; 48% based on the consumed AMPS). For comparison of physicochemical properties, adenosine was chemically transformed into ATPαS as a mixture of the (S_P) (53%) and (R_P) (44%) diastereoisomers.     

A brief and convergent synthetic route to defucogilvocarcin M chromophore: the formal synthesis of WS-5995 A and C

[reaction: see text] Densely substituted styryl sulfone 20 is shown to undergo double annulation with phthalide 21 to give, in one-pot operation and in excellent yield, the benzonaphthopyranone scaffold 22 of gilvocarcins.     

Regiospecific synthesis of isopestacin, a naturally occurring isobenzofuranone antioxidant

A DBU promoted aldol cyclocondensation of hydroxyisobenzofuranone 15 with cyclohexane-1,3-dione, followed by aromatization has resulted in the first short synthesis of isopestacin (1).     

Effect of phenols and carboxylic acids on photochromism of 1-alkyl-2-(arylazo)imidazoles

Light irradiated trans-to-cis isomerization of 1-alkyl-2-(arylazo)imidazole in the presence of phenol, catechol, benzoic acid and salicylic acid (called co-factors) has been studied in this work. The rate of trans→cis photoisomerization is decreased in the presence of co-factor in the medium and is dependent on the concentration of active quotient about photochrome. The decrease in rate follows catechol>benzoic acid>phenol>salicylic acid. This trend is due to the effects of dissociation ability of –O–H/–COOH, intermolecular association of the molecules etc. The reverse change, cis-to-trans, is very slow in light irradiation and has been carried out by a thermal process in the dark. The quantum yield of isomerization follows the same sequence of effects of co-factors.     

Quantification of piperine in different varieties of Piper nigrum by a validated high-performance thin-layer chromatography‒densitometry method

JPC – Journal of Planar Chromatography – Modern TLC - Piperine is the most important alkaloid molecule present in Piper nigrum. In this study, a simple, rapid, quantitative...     

Synthesis of platestacks and microtowers of zinc by thermal evaporation

Zinc microtower and platestacks were synthesized by thermal evaporation of zinc. This synthesis was carried out under high vacuum conditions in the absence of catalyst and carrier gas. The morphology, composition and microstructural properties of the Zn nanostructures were studied by XRD, SEM and TEM. The synthesized microtowers and platestacks were single crystalline in nature. These microtowers and platestacks showed a layered structures consisting of several hexagonal nanoplates. Based on the morphological and composition analysis, we have proposed a vapor–solid mechanism to explain the growth of these nanostructures.     

Trichosanthes dioica root possesses stimulant laxative activity in mice

Trichosanthes dioica Roxb. (Cucurbitaceae), named 'pointed gourd' in English, is a dioecious climber grown in India. This study was aimed at evaluating the laxative activity of the aqueous extract of T. dioica root (TDA) in Swiss albino mice. The laxative activity of TDA (100 and 200?mg?kg(-1) body weight per os) was evaluated by assessing the excretory bowel activities in naive (non-constipated) and in drug (loperamide)-induced constipation in mice. Further, the gastrointestinal transit was measured in both naive and in constipated mice. Castor oil (0.5?mL/mouse per os) was used as the reference. TDA significantly and dose-dependently increased all the excretory bowel activities and gastrointestinal transit in both naive and constipated mice. TDA at 200?mg?kg(-1) body weight was found to be the most active, causing diarrhoea in mice. Thus, T. dioica root demonstrated stimulant laxative activity in Swiss mice, validating its traditional usage in India.     

Effects of heat treatment on evolution of microstructure of boron free and boron containing biomedical Ti-13Zr-13Nb alloys

In the present study, the effects of heat treatment on the microstructure of Ti-13Zr-13Nb (TZN) and Ti-13Zr-13Nb-0.5B (TZNB) alloys have been investigated. Depending on the heat treatment conditions, the microstructure of the heat treated TZN alloy consisted mainly of elongated and/or equiaxed α, β or martensite. Slow cooling (furnace or air cooling) from the solution treatment temperature produced α and β phases in the microstructure. Rapid cooling (water quenching) resulted in martensite and retained β when the solution treatment temperature was above or close to β transus. However, martensite was not formed after water quenching from a solution treatment temperature which was below β transus due to partitioning effect of the alloying elements. Increasing the cooling rate from the furnace cooling to the air cooling led to finer microstructure. Aging of water quenched samples transformed the martensite, if present, into α and β, and the morphology of α phase changed from elongated to equiaxed and enhanced the growth of α. The microstructure of all the TZNB samples consisted of dispersed precipitated particles of TiB in the matrix. The majority of the boride particles showed an acicular (needle like) morphology. The other phases present in the TZNB alloy were similar to those in the similarly heat treated TZN alloy. Moreover, a growth of α phase was observed in the microstructure of TZNB alloy when compared with that of TZN alloy.     

Integrability lost: Chaotic dynamics of classical strings on a confining holographic background

It is known that classical string dynamics on pure AdS₅×S⁵${\mathit{AdS}}_5\times S^5$ is integrable and plays an important role in solvability. This is a deep and central issue in holography. Here we investigate similar classical integrability for a more realistic confining background and provide a negative answer. The dynamics of a class of simple string configurations on AdS soliton background can be mapped to the dynamics of a set of non-linearly coupled oscillators. In a suitable limit of small fluctuations we discuss a quasi-periodic analytic solution of the system. Numerics indicates chaotic behavior as the fluctuations are not small. Integrability implies the existence of a regular foliation of the phase space by invariant manifolds. Our numerics shows how this nice foliation structure is eventually lost due to chaotic motion. We also verify a positive Lyapunov index for chaotic orbits. Our dynamics is roughly similar to other known non-integrable coupled oscillator systems like Hénon–Heiles equations.