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71.
Sandeep K. Vaishanav Jyoti Korram Rekha Nagwanshi Kallol K. Ghosh Manmohan L. Satnami 《Journal of fluorescence》2016,26(3):855-865
Protein Quantum dots interaction is crucial to investigate for better understanding of the biological interactions of QDs. Here in, the model protein Bovine serum albumin (BSA) was used to evaluate the process of protein QDs interaction and adsorption on QDs surface. The modified Stern-Volmer quenching constant (Ka), number of binding sites (n) at different temperatures (298 308 and 318 K?±?1) and corresponding thermodynamic parameters (ΔG?<?0, ΔH?<?0, and ΔS?>?0) were calculated. The quenching constant (Ks) and number of binding sites (n) is found to be inversely proportional to temperature. It signified that static quenching mechanism is dominant over dynamic quenching. The standard free energy change (ΔG?<?0) implies that the binding process is spontaneous, while the enthalpy change (ΔH?<?0) suggest that the binding of QDs to BSA is an enthalpy-driven process. The standard entropy change (ΔS?>?0) suggest that hydrophobic force played a pivotal role in the interaction process. The adsorption process were assessed and evaluated by pseudofirst-order, pseudosecond-order kinetic model, and intraparticle diffusion model. 相似文献
72.
Clavulanic acid is a naturally occurring antibiotic produced by Streptomyces clavuligerus. The present work reports on clavulanic acid production by Streptomyces clavuligerus MTCC 1142 using one-factor-at-a-time and L25 orthogonal array. The one-factor-at-a-time method was adopted to investigate the effect of media components (i.e., carbon
source, nitrogen source and inoculum concentration) and environmental factors such as pH for clavulanic acid production. Production
of clavulanic acid by Streptomyces clavuligerus was investigated using seven different carbon sources (viz. glucose, sucrose, modified starch, rice-bran oil, soybean oil, palm oil, and glycerol) and six different nitrogen sources
(viz. peptone, yeast extract, ammonium chloride, ammonium carbonate, sodium nitrate and potassium nitrate). A maximum yield of
140 μg/mL clavulanic acid was obtained in the medium containing soybean oil as a carbon source and yeast extract as nitrogen
source. Subsequently, the concentration of soybean flour, soybean oil, dextrin, yeast extract and K2HPO4 were optimized using L25 orthogonal array method. The final optimized medium produced 500 μg/mL clavulanic acid at the end of 96 h as compared to
140 μg/mL before optimization. Synthesis of precursor molecules as a metabolic driving force is of considerable importance
in antibiotic synthesis. Attempts to increase the clavulanic acid synthesis by manipulating the anaplerotic flux on C3 and C5 precursors by supplementing the medium with arginine, ornithine, proline, valine, leucine, isoleucine, pyruvic acid and á-ketoglutarate
were successful. Supplementing the optimized medium with 0.1 M arginine and 0.1 M leucine increased the yield of clavulanic acid further to 1100 μg/mL and 1384 μg/mL respectively. 相似文献
73.
Nipun Mahajan Rekha Chadda Kevin Calabro Hiren Solanki Enda O Connell Paul V. Murphy Olivier P. Thomas 《Tetrahedron letters》2017,58(12):1237-1239
A library of 864 extracts prepared from Irish marine organisms was screened in the search for novel antioxidants. Chemical investigation of the most promising extract obtained from the common lichen Lichina pygmaea led to the isolation of five resorcinol derivatives. An unusual urea moiety was found embedded in two of these compounds, pygmanilines A (1) and B (2) and their structures were confirmed by one-step chemical syntheses. 相似文献
74.
Craw Alastair; Maclagan Diane; Thomas Rekha R. 《Proceedings London Mathematical Society》2007,95(1):179-198
For a finite abelian group G GL (n, ), we describe the coherent component Y of the moduli space of-stable McKay quiver representations. This is a not-necessarily-normaltoric variety that admits a projective birational morphism obtained by variation of GeometricInvariant Theory quotient. As a special case, this gives a newconstruction of Nakamura's G-Hilbert scheme HilbG that avoidsthe (typically highly singular) Hilbert scheme of |G|-pointsin . To conclude, we describe the toric fan of Y and hence calculate the quiver representationcorresponding to any point of Y. 相似文献
75.
Qian Guan Jennifer Atsma Rekha Tulsan Sergey Voronov Julia Ding Jeff Beckman Zheng Jian Li 《Electrophoresis》2020,41(13-14):1245-1252
In the biopharmaceutical industry, CE-SDS assesses the purity, heterogeneity, and stability of therapeutic proteins. However, for mAb-1 and mAb-2, typical CE-SDS under reducing conditions produced atypical protein peak profiles, which led to biased purity results, thus were not acceptable for biologics manufacturing. This bias was caused by the formation of method-induced higher molecular weight artifacts, the levels of which correlated with protein concentration. Here we show that adding sodium tetradecyl and hexadecyl sulfates to the sample and the sieving gel buffer solutions was required to prevent formation of aggregate artifacts and to maintain detergent:protein uniformity, suggesting their importance during the sample preparation steps of heat denaturation and subsequent cooling as well as during capillary migration. For these proteins, we show that this uniformity was likely due to the ability of these detergents to bind proteins with markedly higher affinities compared to SDS. “CE-SCXS” methods (where CE-SCXS is CGE using detergent composed of a sodium sulfate head group and a hydrocarbon tail, with “CX” representing various tail lengths), were developed with a sodium tetradecyl sulfate sample buffer and a sodium hexadecyl sulfate containing sieving gel buffer that minimized artifacts and provided robust characterization and release results for mAb-1 and mAb-2. 相似文献
76.
77.
Speeds of sound have been measured in dipropylene glycol monopropyl ether mixtures with methanol, 1-propanol, 1-pentanol,
and 1-heptanol as a function of composition at 288.15, 298.15, and 308.15 K and atmospheric pressure. Measurements of viscosity
at 298.15 K and atmospheric pressure have also been made for the same mixtures over the whole composition range. The speeds
of sound were combined with our previous densitity results to obtain the isentropic compressibility κ
S
. The molar volumes were multiplied by the isentropic compressibilities to obtain estimates of K
S,m
and its excess counterparts KS,mEK_{S,m}^{\mathrm{E}}. The KS,mEK_{S,m}^{\mathrm{E}} values are negative over the entire range of composition for all mixtures. Deviations in viscosity η from the mixing relation ∑x
i
ln η
i
and excess Gibbs energies of activation for viscous flow ΔG
∗E have been derived for all of these systems. Also, from the speed of sound results, the apparent molar compressibilities [`(K)]f,i0\overline{K}_{\phi ,i}^{0} of the components have been calculated at infinite dilution. The variations of these properties with the composition, temperature
and the number of carbon atoms in the alcohol molecule are discussed in terms of molecular interactions. The experimental
results have also been discussed on the basis of IR measurements. 相似文献
78.
Dimethylsulfonium methylide mediated olefination of 2-phenylethenylidene phosphonoacetate followed by the Horner-Wadsworth-Emmons reaction with aromatic aldehydes provided access to reactive 1,5-diaryl-2-ethoxycarbonyl [3]dendralenes which in situ underwent Diels-Alder cyclodimerisation leading to highly functionalised cyclohexenes with very high regio- and stereoselectivity. 相似文献
79.
Shrestha RG Abezgauz L Danino D Sakai K Sakai H Abe M 《Langmuir : the ACS journal of surfaces and colloids》2011,27(21):12877-12883
In this article, we provide direct evidence for 1-D micellar growth and the formation of a network structure in an aqueous system of poly(oxyethylene) cholesteryl ether (ChEO(20)) and lauryl diethanolamide (L-02) by rheometry, small-angle X-ray scattering (SAXS), and cryo-transmission electron microscopy (cryo-TEM). The ChEO(20) self-assembles into spheroid micelles above the critical micelle concentration and undergoes a 1-D microstructural transition upon the incorporation of L-02, which because of its lipophilic nature tends to be solubilized into the micellar palisade layer and reduces the micellar curvature. The elongated micelles entangle with each other, forming network structures of wormlike micelles, and the system shows viscoelastic properties, which could be described by the Maxwell model. A peak observed in the zero-shear viscosity (η(0)) versus L-02 concentration curve shifted toward higher L-02 concentrations and the value of maximum viscosity (η(0?max)) increased with the increasing ChEO(20) mixing fraction with water. We observed that η(0?max) increased by 2 to 4 orders of magnitude as a function of the ChEO(20) concentration. The Maxwell relaxation time (τ(R)) shows a maximum value at a concentration corresponding to η(0?max) (i.e., τ(R) increases with L-02 concentration and then decreases after attaining a maximum value, whereas the plateau modulus (G(0)) shows monotonous growth). These observations demonstrate microstructural transitions in two different modes: L-02 first induces 1-D micellar growth and as a result the viscosity increases, and finally after the system attains its maximum viscosity, L-02 causes branching in the network structures. The microstructure transitions are confirmed by SAXS and cryo-TEM techniques. 相似文献