Influence of terminal substituent on non-linear S-shaped oligomers consisting of azobenzene moieties at the peripheral arm: Synthesis,characterisation and phase transition behaviour

A series of symmetrical S-shaped mesogens based on 4,4′-bis-(6-bromohexyloxy)biphenyl as a central unit containing two 2-{6-[4-(4-substitutedphenylazo)phenoxy]hexyloxy}phenol as side-chain groups has been successfully synthesised. The terminal substituent was varied from halogen (X = F, Cl, Br and I) to non-halogen (X = C₂H₅ and OC₂H₅). The oligomers with C₂H₅ and OC₂H₅ substituents exhibit predominantly the monotropic nematic (N) phase. The OC₂H₅-containing derivatives possess long-range stability of N phase than its C₂H₅-containing analogue in which it has small range of N phase stability. As for halogen-containing analogues, oligomer with F exhibits monotropic N phase whilst oligomers with Cl and Br exhibit monotropic N and smectic A (SmA) phases. In addition, homologue with Br shows additional phase which is smectic B (SmB) phase upon further cooling. However, the oligomers in which F, Cl and Br were substituted by I exhibits purely monotropic SmA and SmB phases. X-ray diffraction measurements reveal that the smectic phase is inclined to the monolayer structure.     

Molecular Docking and Dynamics Investigations for Identifying Potential Inhibitors of the 3-Chymotrypsin-like Protease of SARS-CoV-2: Repurposing of Approved Pyrimidonic Pharmaceuticals for COVID-19 Treatment

This study demonstrates the inhibitory effect of 42 pyrimidonic pharmaceuticals (PPs) on the 3-chymotrypsin-like protease of SARS-CoV-2 (3CL^pro) through molecular docking, molecular dynamics simulations, and free binding energies by means of molecular mechanics–Poisson Boltzmann surface area (MM-PBSA) and molecular mechanics–generalized Born surface area (MM-GBSA). Of these tested PPs, 11 drugs approved by the US Food and Drug Administration showed an excellent binding affinity to the catalytic residues of 3CL^pro of His41 and Cys145: uracil mustard, cytarabine, floxuridine, trifluridine, stavudine, lamivudine, zalcitabine, telbivudine, tipiracil, citicoline, and uridine triacetate. Their percentage of residues involved in binding at the active sites ranged from 56 to 100, and their binding affinities were in the range from −4.6 ± 0.14 to −7.0 ± 0.19 kcal/mol. The molecular dynamics as determined by a 200 ns simulation run of solvated docked complexes confirmed the stability of PP conformations that bound to the catalytic dyad and the active sites of 3CL^pro. The free energy of binding also demonstrates the stability of the PP–3CL^pro complexes. Citicoline and uridine triacetate showed free binding energies of −25.53 and −7.07 kcal/mol, respectively. Therefore, I recommend that they be repurposed for the fight against COVID-19, following proper experimental and clinical validation.     

Electronic structure of 4H-pyrido[1,2-a]pyrimidin-4-ones

The characteristic features of ir and uv spectra of 43 4H-pyrido[1,2-a]pyrimidin-4-one derivatives with electron donor or acceptor groups in position 3, and positions 6, 7, 8, or 9, respectively, have been systematically studied. On the basis of the spectra some conclusions have been drawn for the molecular structure. The negative solvent effect of the lowest-energy π → π* transition is investigated by the PPP method.     

Characterization of the barrier parameter of homogeneous convex cones

We characterize the smallest (best) barrier parameter of self-concordant barriers for homogeneous convex cones. In particular, we prove that this parameter is the same as the rank of the cone which is the number of steps in a recursive construction of the cone (Siegel domain construction). We also provide lower bounds on the barrier parameter in terms of the Carathéodory number of the cone. The bounds are tight for homogeneous self-dual cones. © 1998 The Mathematical Programming Society, Inc. Published by Elsevier Science B.V.Research supported in part by an operating grant from NSERC of Canada.Research supported in part by the National Science Foundation under grant DMS-9306318.     

Polymerization of monoisocyanates by the Pruitt–Baggett adduct

n-Butyl isocyanate (nBIC) was polymerized in bulk by the Pruitt–Baggett adduct (PBA) at ?23, 0.0, and 25.0°C. Polymerization was accompanied by trimerization to the cyclicisocyanurates at all temperatures. Spectroscopic evidences supported the nylon-1 structure for both trimer and polymer. The polymer/trimer ratio and the molecular weight of produced polymers were found to increase with decreasing temperature. The Pruitt–Baggett catalyst (PBC), which is the reaction product of (PBA + H₂O) system, also polymerized nBIC, but with a relatively slower rate. In aromatic and etheric solutions, nBIC was only trimerized by PBA. Copolymerization of nBIC with propylene oxide by PBA and PBC failed. Some selected monoisocyanates were also polymerized by PBA. © 1993 John Wiley & Sons, Inc.     

Shear viscosity of hydrogen and helium fluids at extended regions of temperatures and pressures

Shear viscosities of hydrogen (H₂) and helium (He) fluids are investigated at extended regions of temperature and pressure using an improved equation of state, in which the the long-range attractive forces are incorporated into the formalism via the double Yukawa (DY) potential fitted to the empirical H₂ and He potentials. Quantum effects, which become paramount at low temperatures, are taken into account through a first-order quantum correction based on the Wigner–kirkwood expansion. The dimerization of H₂ is treated as a hard convex body for which an equation of state can be derived based on the scaled particle theory.     

Complexes of N-(2 Hydroxy-1-Naphthalidene) Antharanilic Acid with Some Lanthanides

The complexes of N-(2-hydroxy-1-naphthalidene)anthranilic acid abbreviated (H₂NA) with some trivalent rare earth elements (Pr, Nd, Sm, Gd, Dy, Er and Yb) were prepared. The complexes were characterized by chemical and thermal analysis, ir and conductimetric methods. Two types of ionic complexes; Ln(HNA)₂OH·2H₂O with Dy, Er and Yb, and Ln(HNA)₂OH with Pr, Nd, Sm and Gd were isolated. Coordination of the ligand with metal-ions occurs through the carboxy group and the nitrogen atom. The acid dissociation constants K₁ and K₂ of H₂NA and the overall stability constants β₁ and β₂ of some lanthanide complexes in 75% (v/v) dioxan-water solutions were determined by the potentiometric method.     

Evaluation of infection imaging potential of <Superscript>131</Superscript>I-labeled imidazolium salt

Effective antimicrobial compounds are necessary due to increased resistance of antibiotics against microorganisms causing infectious diseases. In this study, imidazolium-TFSI salt [ITFSI: octyl-bis(3-methylimidazolium)-di(bis(trifluoromethane)sulfonimide)] was labeled with ¹³¹I with high efficiency. In vitro uptake experiments of ¹³¹I-ITFSI showed high uptake in gram-positive Staphylococcus aureus bacteria. ¹³¹I-ITFSI was also evaluated for comparison between bacterial infection and sterile inflammation by in vivo studies. The biodistribution results revealed that ¹³¹I-ITFSI might be used as a nuclear imaging agent for detection of bacterial infection.