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Several fluorescence and colorimetric chemosensory for Sn 2+ detection in an aqueous media have been reported, but applications remain limited for discriminative Sn 2+ detection in live human cells and zebrafish larvae. Herein, a mitochondria-targeted Sn 2+ "turn-on" colorimetric and fluorescence chemosensor, 2CTA, with an aggregation-induced emission (AIE) response was developed. The sensing of Sn 2+ was enabled by a reduction-enabled binding pathway, with the conversion of -C˭O groups to -C-OH groups at the naphthoquinone moiety. The color changed from light maroon to milky white in a buffered aqueous solution. The chemosensor 2CTA possessed the excellent characteristics of good water solubility, fast response (less than 10 s), and high sensitivity (79 nM) and selectivity for Sn 2+ over other metal ions, amino acids, and peptides. The proposed binding mechanism was experimentally verified by means of FT-IR and NMR studies. The chemosensor 2CTA was successfully employed to recognize Sn 2+ in live human cells and in zebrafish larvae. In addition, a colocalization study proved that the chemosensor had the ability to target mitochondria and overlapped almost completely with MitoTracker Red. Furthermore, a bioimaging study of live cells demonstrated the discriminative detection of Sn 2+ in human cancer cells and the practical applications of 2CTA in biological systems., (Copyright © 2021 Elsevier B.V. All rights reserved.)

A new chemosensor (NANH) based on naphthyl moiety was synthesized with good selectivity and sensitivity towards Al 3+ ions via the inhibition by operating through dual mechanisms like photo-induced electron transfer (PET) and excited-state intramolecular proton transfer (ESIPT). The synthesized NANH was validated by various techniques such as 1 H, 13 C NMR and mass spectrum. While prominent fluorescent enhancement was observed from the NANH upon binding with Al 3+ ions, however, other metal ions have not responded in the emission spectrum. Detection limit and association constant of NANH for Al 3+ were calculated as 1.2 × 10 -7  M and 4.09 × 10 4  M -1 by using fluorescence titration method. Binding ratio (1:1) of NANH with Al 3+ ions were proved by Job's plot and DFT studies. Furthermore, aluminium in variety of water samples was determined, and NANH could be used for biosensing of Al 3+ in living cells., Competing Interests: Declaration of competing interest The authors declared there are no conflicts of interest., (Copyright © 2020 Elsevier B.V. All rights reserved.)

Influenza virus of different subtypes H1N1, H2N2, H3N2 and H5N1 cause many human pandemic deaths and threatening the people worldwide. The Hemagglutinin (HA) protein mediates viral attachment to host receptors act as an attractive target. The sixteen natural compounds have been chosen to target the HA protein. Molecular docking studies have been performed to find binding affinity of the compounds. Out of the sixteen, three compounds CI, CII and CIII found to posses a higher binding affinity. The molecular dynamics (MD) simulation has been performed to study the structural, dynamical properties for the nine different complexes CI, CII, CIII bound with H1, H2, H3 proteins and the results were compared. The molecular mechanics Poission-Boltzmann surface area (MM-PBSA) method is used to compare the binding free energy, its different energy components and per residue binding contribution. The H1 subtype shows higher binding preference for all the curcumin derivatives than H2 and H3. The binding capability of protein subtypes with curcumin derivatives and the binding affinity of curcumin compounds are in the order H1>H2>H3 and CI>CII>CIII respectively. The two -O-CH3- groups present in the CI compound help to have strong binding with HA protein than CII and CIII. The van der Waals interaction energy plays a significant role for binding in all the complexes. The hydrogen bonding interactions were monitored throughout the MD simulation. The conserved region (153-155) and the helix region (193-194) of H1, H2, H3 protein subtypes are found to possess higher binding susceptibility for binding of the curcumin derivatives., (Copyright © 2017 Elsevier Ltd. All rights reserved.)

In this work, using ab initio and density functional theory (DFT) methods halogen substituted formic acid (FA) dimer is studied. The dimer stability is due to the hydrogen bonds, either conventional (OH⋯O, OH⋯F, OH⋯Cl) or non-conventional (CH⋯O, CH⋯F, CH⋯Cl). Among all the dimers, trans-trans form is more stable than the trans-cis, and cis-cis form. Basis set extrapolated counterpoise corrected interaction energy results for the FA dimer are in excellent agreement with BSSE corrected MP2 interaction energy. Symmetry Adopted Perturbation Theory (SAPT) analysis reveals that the electrostatic effect plays a dominant role in stabilization among the dimers with maximum interaction energy. Chlorine substituted FA dimer has high hyperpolarizability, which makes them excellent candidate for nonlinear optical materials (NLO). The halogen substituted formic acid dimers have higher stability and polarizability value than the unsubstituted formic acid dimer. The hyperpolarizability values depend on the geometrical structures of halogenated formic acid dimers than the type of hydrogen bonds. The small excitation energy and HOMO-LUMO gap in the halogenated formic acid dimer has led to the strong nonlinear optical response. The depolarization ratio and Rayleigh scattering increases in formic acid dimer after the halogen atom substitution., (Copyright © 2014 Elsevier B.V. All rights reserved.)

The conformational dependence of nonplanarity of the peptide bond of formylglycinamide has been studied using ab initio and density functional theory methods. Hartree-Fock self-consistent field theory (HF), Møller-Plesset perturbation theory (MP2) of ab initio and B3LYP level of theory of dft method have been used employing 6-31++G** basis set. The MP2 method predicts better results than HF and B3LYP levels of theory for conformational stability dependence of nonplanarity. Systematic dependence of planarity deviation has been observed in MP2 theory. The chemical hardness values successfully predict the conformational region, but fail to obey maximum hardness principle. It is concluded that the most reliable dft method could not successfully predict the planarity of peptide bond in comparison with electron correlated method of ab initio method.

Molecular structure and conformational stability of chair and twist conformers of 1,2-dioxane and halogen substituted compounds of the 1,2-dioxane have been studied using ab initio and density functional theory (DFT) methods. The molecular geometries of 1,2-dioxane, 3,6-difluoro, 3,6-dichloro, 3,3,6,6-tetrafluoro and 3,3,6,6-tetrachloro 1,2-dioxane compounds were optimized at HF, MP2, B3LYP and B3PW91 levels of theory by implementing 6-31G* basis set. To study the effect of polar medium, self-consistent reaction field theory is used to optimize the conformers at B3LYP/6-31G* level of theory. The geometrical parameters of chair and twist conformers have been discussed in the light of interaction between lone pair electrons present in the oxygen and substituted halogen atoms. The relative stability of the conformers have been studied using relative energy, maximum hardness principle and thermodynamical quantities. The 13C-NMR chemical shift study for carbon atoms in the title compounds are calculated and the results have been discussed.