Pyridones as NNRTIs against HIV-1 mutants: 3D-QSAR and protein informatics

CoMFA and CoMSIA based 3D-QSAR of HIV-1 RT wild and mutant (K103, Y181C, and Y188L) inhibitory activities of 4-benzyl/benzoyl pyridin-2-ones followed by protein informatics of corresponding non-nucleoside inhibitors’ binding pockets from pdbs 2BAN, 3MED, 1JKH, and 2YNF were analysed to discover consensus features of the compounds for broad-spectrum activity. The CoMFA/CoMSIA models indicated that compounds with groups which lend steric-cum-electropositive fields in the vicinity of C5, hydrophobic field in the vicinity of C3 of pyridone region and steric field in aryl region produce broad-spectrum anti-HIV-1 RT activity. Also, a linker rendering electronegative field between pyridone and aryl moieties is common requirement for the activities. The protein informatics showed considerable alteration in residues 181 and 188 characteristics on mutation. Also, mutants’ isoelectric points shifted in acidic direction. The study offered fresh avenues for broad-spectrum anti-HIV-1 agents through designing new molecules seeded with groups satisfying common molecular fields and concerns of mutating residues.     

Completing extended metric spaces: An alternative approach

This paper proves the completion of extended metric spaces using the concept of $\epsilon$-approach nearness spaces, in terms of clusters that are a generalization of Cauchy sequences.     

Ultrafilter Completeness in {{\varepsilon}} -approach Nearness Spaces

This paper presents a new approach to the proof of the Niemytzki–Tychonoff theorem for symmetric topological spaces. The proof uses the concept of completeness in ${\varepsilon}$ -approach nearness spaces which was introduced by Peters and Tiwari (Appl Math Lett 25:1544–1547, 2012), and of clusters that are a generalization of Cauchy sequences.     

A 3-approximation algorithm for the facility location problem with uniform capacities

We consider the facility location problem where each facility can serve at most U clients. We analyze a local search algorithm for this problem which uses only the operations of add, delete and swap and prove that any locally optimum solution is no more than 3 times the global optimum. This improves on a result of Chudak and Williamson who proved an approximation ratio of ${3+2\sqrt{2}}$ for the same algorithm. We also provide an example which shows that any local search algorithm which uses only these three operations cannot achieve an approximation guarantee better than 3.     

Holstein–Primakoff (H-P) Approach to Determine the Optical Response of Hybrid Optomechanical System Containing Multiple Quantum Dots

A theoretical model is presented to study the hybrid optomechanical system comprising an ensemble of N number of quantum dots (QDs). Utilizing the Holstein–Primakoff (H-P) transformation formalism, the calculations become easily scalable. The bistability in this hybrid optomechanical system is studied in the presence of third order nonlinear χ⁽³⁾ medium using the H-P transformation method and to verify the results, numerical method has also been utilized. It is also demonstrated that the system's parameters may be tuned to alter the bistability phenomenon and absorption spectrum's response, which exhibits both positive and negative absorption (emission). This alternative approach (H-P transform) is demonstrated to solve analytically the system containing multiple QDs in an elegant manner.     

Targeted Synthesis of 3,3′-, 3,4′- and 3,6′-Phenylpropanoid Sucrose Esters

In this study, we report on an orthogonal strategy for the precise synthesis of 3,3′-, 3,4′-, and 3,6′-phenylpropanoid sucrose esters (PSEs). The strategy relies on carefully selected protecting groups and deprotecting agents, taking into consideration the reactivity of the four free hydroxyl groups of the key starting material: di-isopropylidene sucrose 2. The synthetic strategy is general, and potentially applies to the preparation of many natural and unnatural PSEs, especially those substituted at 3-, 3′-, 4′- and 6′-positions of PSEs.     

Amine grafted Fe3O4 immobilized graphene oxide as a recyclable and effectual nanocomposite for the regioselective ring opening reaction

Research on Chemical Intermediates - This work describes the synthesis of magnetic graphene oxide (MGO), where iron oxide (Fe3O4) nanoparticles were uniformly deposited over the sheets of the...     

Solar Light Responsive Graphitic Carbon Nitride Coupled Porphyrin Photocatalyst that Uses for Solar Fine Chemical Production

Photocatalysis is a defendable manner for production of several organic chemicals, energy and its storage from solar energy. For the evolution of metal free, cost-effective catalyst a 2D composite has been appear as a photocatalyst. Here, we had reported the synthesis of a light harvesting composite as a photocatalyst which was assembled by a poly-condensation mechanism between graphitic carbon nitride and tetrakis(4-nitrophenyl) porphyrin and the resulting composite manifest the excellent light harvesting properties, suitable energy band and low charge recombination. The photocatalyst [(NO₂)₄TPP@g-C₃N₄] enables the efficient photocatalytic production of nicotinamide adenine dinucleotide (NADH) from consumed NAD⁺ also the production of organic chemicals like 4-methoxybenzylimines from 4-methoxybenzylamines. The photocatalytic efficiency of the photocatalyst was estimated by the percentage of NADH regeneration and the percentage yield of organic transformations. It shows the tetrakis(4-nitrophenyl) porphyrin could enhance the charge transfer capacity of graphitic carbon nitride which shows excellent photocatalysis activities and organic transformations.     

Improved solubility and stability of trialkylammonium selenocarboxylate in organic solvents for efficient amidation with azides

Trialkylammonium selenocarboxylate, formed in situ from the reaction of diacyl diselenide with piperidine in the presence of diisopropylethylamine, was found to react readily at room temperature with electron-deficient azides to form amides in excellent yields. The trialkylammonium selenocarboxylate salt formed has good solubility and stability in organic solvents. The enhanced stability allowed mild heating to improve the amidation yields with electron-rich azides.     

Identical-location Transmission Electron Microscopy of Pt Nanoparticle Electrocatalysts Using Iridium-coated Au Grids for Fuel Cell Durability Tests Simulating Start-up and Shutdown Conditions

In an identical-location TEM (IL-TEM) analysis of an electrocatalyst, an Au grid is usually selected owing to its chemical stability under potential cycling conditions. A potential cycle between 1.0 and 1.5 V is applied to the catalyst-cast Au grid for cathode durability testing that simulates the start-up and shutdown conditions of fuel cells. Because of the redox potential of Au (1.36 V vs. RHE), the grid dissolves and redeposits on the catalyst under the applied potential, making it complicated to evaluate the catalyst nanoparticle shape and size after degradation. We fabricated an Au grid coated with an iridium oxide layer (Ir-coated Au grid) to suppress the dissolution of Au. The Ir-coated Au grid with carbon support was compared to the Au grid to confirm the effect of the iridium oxide layer. No Au deposition was observed, even after 3000 cycles at 60 °C for the Ir-coated Au grid, but Au was deposited on carbon on the Au grid after 1000 cycles. Consequently, the alkylamine-modified Pt nanoparticle catalyst (unwashed catalyst) was observed along with the Ir-coated Au grid using IL-TEM under durability tests simulating start-up and shutdown conditions. A catalyst with less alkylamine content was prepared by butylamine washing (washed catalyst) and observed using IL-TEM for comparison. The Pt nanoparticles of the washed catalyst aggregated and changed their morphology after 1000 cycles, while the alkylamine-modified nanoparticles of the unwashed catalyst almost maintained their original size and shape up to 1000 cycles. The Ir-coated gold grids allow proper IL-TEM analysis of catalysts in durability tests without the interference of Au dissolution.