Kinetics of the outer-sphere oxidation of thiourea by heteropoly-α<Subscript>2</Subscript>-17-tungsto-1-vanadodiphosphate anion

Kinetics of the oxidation of thiourea (tu) by heteropoly-α₂-17-tungsto-1-vanadodiphosphate anion, α₂-[P₂V^VW₁₇O₆₂]^7?, have been studied spectrophotometrically in aqueous acidic medium at 25 °C. At low pH (2.4–3.0), the neutral form of tu is the only reactive species. At higher pH (4.2–4.9), both neutral and deprotonated forms of tu participate in the reaction. The observed mixed-order kinetics suggest two parallel reactions: one in which the order in [tu] is unity, and a second in which it is two. In both cases, the order in [α₂-[P₂V^VW₁₇O₆₂]^7?] is unity. Based on the kinetic studies, a mechanism is proposed, in which a second-order proton-coupled electron transfer involving NH₂CSNH₂ and α₂-[P₂V^VW₁₇O₆₂]^7? proceeds through a sequential electron transfer, followed by proton transfer such that the reaction is an “activation-controlled” outer-sphere electron transfer process. By applying the Marcus equation, the self-exchange rate constants for the couples \({\text{NH}}_{2} {\text{CSNH}}_{2}^{ \cdot + }\)/NH₂CSNH₂ and α₂-[P₂V^VW₁₇O₆₂]^7?/α₂-[P₂V^IVW₁₇O₆₂]^8? were evaluated.     

Design,synthesis and exploration of in silico α-amylase and α-glucosidase binding studies of pyrrolidine-appended quinoline-constrained compounds

Research on Chemical Intermediates - A series of new pyrrolidine-appended phenoxy-substituted quinoline derivatives were synthesized using 2-chloro-3-formyl quinoline. Initially, the second...     

A numerical method for singularly perturbed weakly coupled system of two second order ordinary differential equations with discontinuous source term

In this paper, a numerical method based on finite difference scheme and Shishkin mesh for singularly perturbed two second order weakly coupled system of ordinary differential equations with discontinuous source term is presented. An error estimate is derived to show that the method is uniformly convergent with respect to the singular perturbation parameter. Numerical results are presented to illustrate the theoretical results.     

Structural Stability Among Hybrid Antimicrobial Peptide Cecropin A(1–8)–Magainin 2(1–12) and Its Analogues: A Computational Approach

Cecropin A–Magainin 2 (CA–MA) hybrid antimicrobial peptide (AMP), a combination of two naturally occurring AMPs, cecropin A and magainin 2 is preferred widely in biotechnological, nano and pharmaceutical applications. It exhibits a strong antibacterial activity with a characteristic reduced cytotoxic effect towards mammalian cells. In this study, three AMP structures native CA–MA hybrid and its tryptophan substitutes CA–MA L2 and CA–MA A2 was computationally studied to analyze their structural stability and functionality. Computational analysis like, intra-molecular interactions (25), relative stability (3.22) and instability index (?14.28) showed an increase in structural stability of native CA–MA hybrid. Additionally, the generated peptide ensembles showed a RMSD (3.98 Å), RMSF (0.202 Å), radius of gyration (11.98 Å), ovality (3.33) and hydrophobicity (69.7%) supporting native CA–MA along with hydrogen bond strength (?4.212 kcal/mol) and distribution comparatively. The distribution of secondary structure in native CA–MA hybrid showed the sequential maintenance of stable helical content along with helical stability (52.25%) and computed free energy (?1.74 kcal/mol) in membrane mimicking environment proving its functional activity comparatively. This study aids in designing stable AMP biodrugs with low cytotoxicity in future, the result can be potentially extended to other AMPs to assist in their exploitation as peptide and nano drugs.     

Influence of niobium doping on the electrical properties of 0.58Pb(Sc1/2Nb1/2)O3-0.42PbTiO3 single crystal

Piezoelectric single crystals of 0.58Pb(Sc_1/2Nb_1/2)-0.42PbTiO₃ and Nb⁵⁺-doped PSN-PT have been grown using flux technique. It is believed that the addition of Nb⁵⁺ creates lead vacancy in order to compensate charge neutrality. The structural distortion that occured in the doped crystals has been revealed through broadening of some peaks in X-ray diffraction studies. Niobium content that increased from 0.50 to 1.00 mol% might have induced more defect dipoles associated with . This plays a significant role in improving the ferroelectric, dielectric and piezoelectric properties. Our observations clearly show an increase in the spontaneous polarization (P_r), dielectric constant at room temperature, degree of diffuseness and transition temperature (T_c) and also a decrease in coercive field. The reasons behind these enhanced electrical properties are discussed in detail.     

Generation of 532 nm laser radiation and phase matching properties of organic nonlinear optical material

Organic nonlinear optical single crystal of l-asparagine-l-tartaric acid (LAsT) was grown by slow evaporation technique at room temperature. The grown crystal was confirmed by single crystal X-ray diffraction and FT-IR studies. The direct band gap energy was found to be 5.4 eV. The SHG efficiency of the sample is 3 times higher than that of KDP crystal. The laser damage threshold of the grown crystal was 5.7 GW/cm². The grown crystal was thermally stable up to 141 °C. Low dielectric constant at higher frequency was found by dielectric measurements. The activation energy was calculated from Arrhenius relation and it was found to be 0.088 eV. Negative photoconducting nature was obtained by photoconductivity measurements.     

Highly stereoselective cyclopropanation of glycals with cyclic diazoamides: a facile synthesis of spirooxindolyl sugar derivatives

Rhodium(II) acetate catalyzed intermolecular cyclopropanation of glycals with cyclic carbenoids generated from 3-diazo-2-oxindole has been achieved to produce a novel series of spirooxindolyl sugar derivatives in good yields under mild experimental conditions.     

Free vibration analysis of axially functionally graded tapered Timoshenko beams using differential transformation element method and differential quadrature element method of lowest-order

The present paper investigates the free vibration characteristics of Timoshenko beams whose cross-sectional profile and material properties vary along the beam axis with any arbitrary functions. Free vibration analysis of these beams is carried out through solving the governing differential equations of motion. Since the application of differential transformation method (DTM) does not necessarily converge to satisfactory results, an element-based differential transformation method, namely differential transformation element method (DTEM), is introduced which significantly enhances the accuracy of the results. Furthermore, differential quadrature element of the lowest order (DQEL) is introduced which is based on differential quadrature element method (DQEM). DQEL formulates the problem on the basis of the interpolation of the first differential of the functions; therefore, in contrast with DQEM higher differentials of functions are not employed in DQEL. The competency of DQEL and DTEM in free vibration analysis is verified through several numerical examples. The effects of taper ratio and material non-homogeneity on natural frequencies are investigated.     

Engineered Cyclotides with Potent Broad in Vitro and in Vivo Antimicrobial Activity

The search for novel antimicrobial agents to combat microbial pathogens is intensifying in response to the rapid development of drug resistance to current antibiotic therapeutics. Respiratory failure and septicemia are the leading causes of mortality among hospitalized patients. Here, the development of a novel engineered cyclotide with effective broad-spectrum antibacterial activity against several ESKAPE bacterial strains and clinical isolates is reported. The most active antibacterial cyclotide was extremely stable in serum, showed little hemolytic activity, and provided protection in vivo in a murine model of P. aeruginosa peritonitis. These results highlight the potential of the cyclotide scaffold for the development of novel antimicrobial therapeutic leads for the treatment of bacteremia.