COVID-19: inflammatory responses,structure-based drug design and potential therapeutics

Molecular Diversity - The COVID-19 pandemic caused by SARS-CoV-2 is responsible for the global health emergency. Here, we explore the diverse mechanisms of SARS-CoV-induced inflammation. We presume...     

Does the classically chaotic Henon-Heiles oscillator exhibit quantum chaos under intense laser fields?

The quantum dynamics of an electron moving under the Henon-Heiles (HH) potential in the presence of external time-dependent (TD) laser fields of varying intensities have been studied by evolving in real time the unperturbed ground-state wave function φ (x, y, t) of the HH oscillator. The TD Schrödinger equation is solved numerically and the system is allowed to generate its own wave packet. Two kinds of sensitivities, namely, sensitivity to the initial quantum state and to the Hamiltonian, are examined. The threshold intensity of the laser field for an electron moving in the HH potential to reach its continuum is identified and in this region quantum chaos has been diagnosed through a combination of various dynamical signatures such as the autocorrelation function, quantum ‘phase-space’ volume, ‘phase-space’ trajectory, distance function and overlap integral (akin to quantum fidelity or Loschmidt echo), in terms of the sensitivity towards an initial state characterized by a mixture of quantum states (wave packet) brought about by small changes in the Hamiltonian, rather than a ‘pure’ quantum state (a single eigenstate). The similarity between the HH potential and atoms/molecules in intense laser fields is also analyzed.     

A Comparative Study of the PFP and BAB Models in Predicting the Surface and Transport Properties of Liquid Ternary Systems

Measurements of the surface tension, viscosity and density were carried out for three ternary and their nine contributing binary liquid systems, namely: (1) toluene + cyclohexane + carbon tetrachloride and its contributing binaries (toluene + cyclohexane), (cyclohexane + carbon tetrachloride), and (carbon tetrachloride + toluene); (2) benzene + cyclohexane  + toluene and its contributing binaries (benzene + cyclohexane), (cyclohexane  + toluene), and (toluene + benzene); and (3) carbon tetrachloride + cyclohexane + benzene and its contributing binaries, (carbon tetrachloride + cyclohexane), (cyclohexane + benzene) and (benzene + carbon tetrachloride), all at 298.15 K over a wide range of compositions. The surface and transport properties of these liquid ternary systems were also studied theoretically by two liquid models, those of PFP (Prigogine-Flory-Patterson) and BAB (Bertrand-Acree-Bruchfield). The excess surface thermodynamic and excess transport properties predicted with the use of these two models agree well with the experimental results. An attempt has also been made to explain the nature of the molecular interactions and forces involved in these liquid ternary systems.     

Mild and Ecofriendly Tandem Synthesis,and Spectral and Antimicrobial Studies of N1-Acetyl-5-aryl-3-(substituted styryl)pyrazolines

N¹-acetyl-5-aryl-3-(substituted styryl)pyrazolines were synthesized by the cyclocondensation of 1,5-substituted diphenyl-1,4-pentadien-3-ones with hydrazine hydrate and a cyclizing agent such as acetic acid in ethanol. The title compounds were synthesized using conventional and solvent-free approaches, which involves mechano-chemical mixing, microwave-irradiation, and ultrasound-irradiation methods in the presence of a solid support. The synthesized compounds have been characterized by elemental analyses and spectral data (IR, PMR, and FAB-mass). All the synthesized compounds have been evaluated for their antibacterial and antifungal activities. Some compounds have shown promising biological activity.     

Organosilicon backbone containing pyridyl/quinolyl ligands: Synthesis, complexation reactions and single crystal structures of metallamacrocyclic Pd(II) and Cu(II) complexes

Organosilicon backbone containing ligands 1,2-bis(dimethyl(2-pyridyl)silyl)ethane (L¹) and 1,2-bis(dimethyl(3-quinolyl)silyl) ethane (L²) have been synthesized by treating 2-bromopyridine and 3-bromoquinoline with n-butyllithium and reacting the resulting lithiated products with 1,2-bis(chlorodimethylsilyl)ethane. The ligation of L¹ and L² with Pd(II), Ag(I) and Cu(II) has been investigated. The single crystal structures of L², [Pd(L¹)Cl₂] (1), [Cu(L¹)Br₂] (3) and [PdCl₂(L²)]₂ (4) have been solved. All the three complexes are metallamacrocyclic in nature. The last one is 22-membered and the first example which has ligands containing organosilicon backbone. The geometry of Pd as well as Cu is very close to square planar. The Pd–N, Pd–Cl, Cu–N and Cu–Br bond distances (2.010(1)–2.027(3), 2.3063(10)–2.3114(4), 2.004(4)–2.018(5) and 2.4137(10)–2.4172(10) Å) are very close to sum of covalent radii, indicating strong ligation of L¹ and L² with the metal ions.     

Tuning the multiferroic properties of Pb(Fe1/2Nb1/2)O3 by cationic substitution

A series of substituted lead iron niobate compounds with the general formula Pb²⁺_(1−x)A^Z_x(Fe_{{(1−(2−Z)x)/2}}Nb_{{(1+(2−Z)x)/2}})O₃ (0<x<0.6 and A=La³⁺, K⁺ or Sr²⁺) were prepared by a modified solid-state synthesis. The relative concentrations of Fe³⁺ and Nb⁵⁺ were adjusted to compensate the charge imbalance due to the aliovalent substitution. The dielectric constant and magnetic susceptibilities were studied as a function of temperature. The temperature of the dielectric maximum, T_M, of the substituted compounds decreased linearly with increasing concentration of the substituent ions. The magnetic measurements showed an antiferromagnetic transition at temperatures T_N1 due to the superexchange interactions mediated by Fe–O–Fe and an additional antiferromagnetic-type transition at T_N2. T_N1 linearly increased with the increasing concentration of Fe³⁺ ion at the B-site of ABO₃-type substituted compounds. T_M is shown to be directly dependent on the concentration of the ferroactive Nb⁵⁺ ions at the B-site and Pb²⁺ ions at the A-site.     

Formation of high nuclearity mixed-valent polyoxovanadates in the presence of copper amine complexes

Two new Müller-type clusters, a one-dimensional solid [Cu(en)]_{2 4}[Cl ⊂V₁₅O₃₆]−12H₂O1, and a three-dimensional solid [Cu(pn)]_{2 4}[Cl ⊂V₁₈O₄₂]·12H₂O2, have been synthesised by employing identical hydrothermal conditions e_xcept varying the nature of organic diamine.1 crystallised in a chiral space groupP2₁2₁2₁ witha = 12.757(1),b = 18.927(2) andc = 28.590(3) ?, andZ =4.2 crystallised in a tetragonal system with space groupP4/nnc,a = 15.113(1) andc = 18.542(3) ?, andZ = 2. Mixed-valent vanadium ions in structures1 and2 have been established both by magnetisation and bond-length bond-valence measurements. Chemistry of formation of high nuclearity polyoxovanadate clusters is discussed. Dedicated to Prof J Gopalakrishnan on his 62nd birthday.     

One-dimensional multiple-well oscillators: A time-dependent quantum mechanical approach

Time-dependent Schrödinger equation (TDSE) is solved numerically to calculate the ground- and first three excited-state energies, expectation values 〈x ^2j 〉, j=1, 2 …, 6, and probability densities of quantum mechanical multiple-well oscillators. An imaginary-time evolution technique, coupled with the minimization of energy expectation value to reach a global minimum, subject to orthogonality constraint (for excited states) has been employed. Pseudodegeneracy in symmetric, deep multiple-well potentials, probability densities and the effect of an asymmetry parameter on pseudodegeneracy are discussed.     

Structural evolution and stability of hydrogenated Li(n) (n = 1-30) clusters: a density functional study

The structure and electronic and optical properties of hydrogenated lithium clusters Li(n)H(m) (n = 1-30, m ≤ n) have been investigated by density functional theory (DFT). The structural optimizations are performed with the Becke 3 Lee-Yang-Parr (B3LYP) exchange-correlation functional with 6-311G++(d, p) basis set. The reliability of the method employed has been established by excellent agreement with computational and experimental data, wherever available. The turn over from two- to three-dimensional geometry in Li(n)H(m) clusters is found to occur at size n = 4 and m = 3. Interestingly, a rock-salt-like face-centered cubic structure is seen in Li(13)H(14). The sequential addition of hydrogen to small-sized Li clusters predicted regions of regular lattice in saturated hydrogenated clusters. This led us to focus on large-sized saturated clusters rather than to increase the number of hydrogen atoms monotonically. The lattice constants of Li(9)H(9), Li(18)H(18), Li(20)H(20), and Li(30)H(30) calculated at their optimized geometry are found to gradually approach the corresponding bulk values of 4.083. The sequential addition of hydrogen stabilizes the cluster, irrespective of the cluster size. A significant increase in stability is seen in the case of completely hydrogenated clusters, i.e., when the number of hydrogen atoms equals Li atoms. The enhanced stability has been interpreted in terms of various electronic and optical properties like adiabatic and vertical ionization potential, HOMO-LUMO gap, and polarizability.     

Miniemulsion synthesis of metal-oxo cluster containing copolymer nanobeads

Hybrid nanobeads containing either a manganese-oxo or manganese-iron-oxo cluster have been prepared via the miniemulsion polymerization technique. Two new ligand substituted oxo clusters, Mn(12)O(12)(VBA)(16)(H(2)O)(4) and Mn(8)Fe(4)O(12)(VBA)(16)(H(2)O)(4) (where VBA = 4-vinylbenzoate), have been prepared and characterized. Polymerization of the functionalized metal-oxo clusters with styrene under miniemulsion conditions produced monodispersed polymer nanoparticles as small as ~60 nm in diameter. The metal-oxo polymer nanobeads were fully characterized in terms of synthetic parameters, composition, structure, and magnetic properties.