Comparative binding study of steroidal adenine with flavin and uracil derivatives

A comparative binding study of a steroidal adenine derivative based on lithocholic acid with N(10)-benzylisoalloxazine (flavin) and N(1)-iso-propyluracil has been described.     

Improved Absorbance and Near-Infrared Dispersion of AuGe Nanoparticles over Au Nanoparticles Prepared with Similar Thermal Annealing Environment

The difficulty in patterning the structures at sub-wavelength range leads to employ the bottom-up approach to form nanostructures of metals as well as dielectric components that disperse them in host media. The optical properties of nanoparticles are studied with UV-Vis 750 (lambda) NIR spectroscopy and fit with empirical relations. The refractive index is about the volume fraction of particles. The AuGe nanoparticles demonstrate improved absorbance, lower refractive index, and higher extinction than Au nanoparticles formed with similar thermal process. Surface plasmon resonance (SPR) phenomena are highly sensitive to the bonding between atoms, atomic structure, and the electronic configuration in atoms of the given material. If one takes into account the structure of materials, then the literature on eutectic alloys predicts that alloying gold with germanium (AuGe) with varying compositions will also change the x-ray diffraction peak positions of gold itself. The peak shift can be interpreted as the change in grain size or shift in grain boundaries implying a corresponding change in material’s atomic arrangement within lattice structure. As a result, there will be a change in the charge distribution of free electron cloud in original gold ultimately affecting a change in the plasmon resonance frequency and thereby modulating the various optical phenomena such as absorbance, reflectance, and refractive index. This alloying also brings a change in the dielectric constant of the material such that the plasmonic behavior may shift among different regions (UV, visible, NIR, MWIR, and LWIR). Metal semiconductor eutectic alloy which is widely popular as a soldering material would have scope in futuristic photonic applications due to its tuneable optical properties. In this work, we study the effects of Au and AuGe nanoparticle deposition on GaAs films grown by molecular beam epitaxy (MBE). Au and AuGe thin films (12-nm thick) were annealed in the temperature ranges of 400–800 and 300–700 °C, respectively, to form Au and AuGe nanoparticles. The formation of these nanoparticles was confirmed by scanning electron microscopy (SEM) measurements. Optical absorption spectroscopy measurements showed plasmon resonance peaks at around 670 and 535 nm for the AuGe-deposited 300 °C-annealed sample and Au-deposited 600 °C-annealed sample on sapphire, respectively, thereby confirming the plasmonic effect. Correlation of Raman spectroscopy measurement results with X-ray diffraction measurement results reveal that the transverse optical mode intensity and full width at half maximum of the GaAs (400) peak increased with an increase in annealing temperature, indicating degradation of the crystalline properties of GaAs film at higher annealing temperatures. The highest increments of the photoluminescence (PL) intensities in comparison to that of the bare GaAs film were observed to be 37 and 77% for the Au-deposited 600 °C-annealed and AuGe-deposited 300 °C-annealed samples, respectively. These enhancements of PL spectra are an indication of the significant scattering of photons by Au and AuGe nanoparticles, and they are attributed mainly to the contribution of the local surface plasmon resonance of these nanoparticles. A comparative analysis of PL enhancements revealed that AuGe nanoparticles induced a greater enhancement than Au nanoparticles. The calculated activation energies of the Au-deposited 600 °C-annealed sample, AuGe-deposited 300 °C-annealed sample, and bare GaAs sample were around 18, 24, and 33 meV, respectively. We found one-order increment in peak responsivity of AuGe plasmonic-based trilayer InAs quantum dot detector in comparison to as-grown detector at 80 K. Therefore, this study is expected to be very useful in the realization of high-performance plasmonic-based optoelectronic and sensing devices.     

Genetic and substrate-level modulation of Bacillus subtilis physiology for enhanced extracellular human interferon gamma production

Human interferon-gamma (hIFNG) production is limited by various gene-level bottlenecks including translation, protein folding, and secretion which depends upon the physiological state of the organism. In this study gene-level and substrate-level modulations have been used to control Bacillus subtilis physiology for >15 fold extracellular soluble hIFNG production. Two variants of the native human interferon-gamma gene (hifng) were designed and synthesized, namely, cohifng_his and cohifng having codon adaptation index 25.33 and 26.89% higher than the native gene, respectively. BScoIFNG and BScoIFNGhis with ΔG of ?100.0 and ?113.7?kcal?mol^?1 resulted in 30 and 6.5% higher hIFNG compared to the native gene in complex medium. BScoIFNG produced 1.53 fold higher hIFNG using glucose-based defined medium as compared to the complex medium by modulating the physiological parameter growth rate from 0.35 to 0.26?hr^?1. Further modulatory effect of various phosphotransferase transport system (PTS) and no-PTS sugars, sugar alcohols, and organic acids was quantified on the physiology of B. subtilis WB800N for extracellular hIFNG production. Sorbitol and glycerol emerged as the best hIFNG producers with lowest growth and substrate consumption rates. BScoIFNG produced maximum 3.15?mg?L^?1 hIFNG at 50?g?L^?1 glycerol with highest hIFNG yield (Y_p/x?=?0.136) and lowest substrate uptake rate (q_s?=?0.26).     

Comprehensive Identification and Spatial Mapping of Habenular Neuronal Types Using Single-Cell RNA-Seq

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Mechanisms of Lipid Scrambling by the G Protein-Coupled Receptor Opsin

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Solvent based optimization for extraction and stability of thymoquinone from <Emphasis Type="Italic">Nigella sativa</Emphasis> Linn. and its quantification using RP-HPLC

The Nigella sativa pharmacological properties are mainly ascribed to its volatile oil, of which thymoquinone is an important bioactive component. Surprisingly, till date, no standard formulation or thymoquinone rich N. sativa extract is under clinical use probably due to its poor extraction and lesser stability in the already used solvents. In the present investigation solubility, extraction, percent composition and total antioxidant activity from the seeds of N. sativa was explored using five solvents. An HPLC method was standardized in an isocratic system (C-18 column, flow rate of 1.0 ml/min, mobile phase—water:methanol: 30:70, detection wavelength—254 nm, retention time—8.77 min) for quantification of thymoquinone. To further confirm the presence of thymoquinone in the respective extracts absorbance spectra analysis has been carried out and compared with pure thymoquinone. Additionally total antioxidant activity of Nigella sativa extracts has been evaluated using ascorbic acid as standard. Our results showed maximum percentage yield in aqueous extract while methanol having the least yield and the ethanol, benzene and hexane extracts exhibited moderate yields. A linear standard calibration curve of thymoquinone showed R² as 0.999 and % RSD as 7.166. The HPLC analysis revealed maximum percentage composition of thymoquinone in the benzene extract, whereas in the hexane and methanol extracts the content was less. Aqueous and ethanol extracts displayed insignificant thymoquinone content. Absorbance spectra analysis confirms the presence of thymoquinone peak in the benzene, hexane and methanol extracts while aqueous and ethanol extracts showed minimal absorbance. Maximum total antioxidant activity was observed in the aqueous extract while minimum was observed in the methanolic extract. Weak positive (+?0.3676) correlation was established between percent composition of thymoquinone and antioxidant activity among different extracts indicating that thymoquinone may not be the only factor for antioxidant activity, but other phytochemicals might also contribute. However, we for the first time demonstrated that the benzene extract of N. sativa has better solubility and percent composition of thymoquinone as compared to other solvents. It can be concluded that the solubility, differential composition of bioactive components among these extracts may have diverse effects on the total antiradical activity. Thus, our study provides insights on optimization and standardization of bioactive rich formulation of N. sativa.     

Heme metabolism in promastigotes of Leishmania donovani

Promastigotes of Leishmania donovani (Dd-8 strain) showed presence of important key enzymes of heme synthesizing (d-aminolevulinic acid synthase and ferrochelatase) and degrading (heme oxygenase and biliverdin reductase) systems, classical leishmanicidal drugs viz allopurinol, amphotericin B, pentamidine and CDRI compound 93/202 inhibited the heme oxygenase activity of the parasite, whereas, -aminolevulinic acid synthase activity practically remained unaffected. The Km, Vmax ad pH values of heme oxygenase of promastigotes were found to be 1666 M hemin, 625 nmol of bilirubin formed h-1 mg protein-1 and 7.5 respectively. The findings suggest the presence and importance of heme metabolism in the de novo synthesis of different hemoproteins of the Leishmania parasite as well as the detoxification and its defence against biological insults.     

Influence of amino acids on the biosynthesis of cyclosporin A by Tolypocladium inflatum

 An indigenously isolated strain of Tolypocladium inflatum, when grown as a suspension culture in semi-synthetic and synthetic media, produced cyclosporin A. Biosynthesis of this well-known immunosuppressive agent was found to be influenced heavily by the external addition of the amino acid constituents of the molecule. In synthetic media, L-leucine and L-valine were found to act as strong inducers of drug production. L-Valine increased the specific production of cyclosporin A by 75% in semi-synthetic medium and by ten times in synthetic medium compared to an unsupplemented control culture. D-Valine had no stimulating effect on the production. The presence of amino acids in the exponential growth phase ensured optimal production, as was indicated in the experiment in which L-valine was added at different times; 4 g/l was the optimum concentration of exogenous L-valine. On the other hand, exogenous sarcosine and L-methionine tended to diminish drug production. Received: 23 October 1995/Received revision: 23 January 1996/Accepted: 29 January 1996     

Isoalantolactone derivatives and germacranolides from Blumea densiflora

The germacranolides tagitinin A and tirotundin ethyl ether and a series of new ring A-hydroxylated isoalantolactone derivatives were isolated from Blumea densiflora. Structures were established by spectroscopic methods and chemical transformations.     

Studies in pectic enzymes of parasitic fungi VI. Factors affecting the secretion of pectic enzymes byAlternaria tenuis

The effects of various cultural factors on the secretion of three pectic enzymes (PP, PG and PE) byAlternaria tenuis on synthetic media were studied. The results can be summarised as follow:

1. 1.
   No definite correlation between the secretion of pectic enzymes, pH of the medium and the growth of the fungus was observed.