In this study, the effect of the secondary structure of the protein on the acid strength of three structures of random (R), alpha helix (α) and beta sheet (b) were investigated theoretically. These structures are related to the cationic amino acids of histidine and lysine in the polypeptide chain of eight-glycine residue. Computational methods at the HF, B3LYP, X3LYP and M05-2X levels in t...

The influence of cation-π interactions on the strength and nature of intramolecular O...H hydrogen bond has been investigated by quantum chemical calculations in orthohydroxy benzaldehyde (HBA) compound. Ab initio calculations have been performed at MP2/6-311++G** level of theory. Vibrational frequencies and physical properties such as chemical potential and chemical hardness of these compounds...

The bonding in monomeric and dimeric molecular compounds of Cr, Mo, W and U is explored using the Quantum Theory of Atoms-in-Molecules (QTAIM). The metal-ligand and metal-metal bond critical point properties ρb, ∇(2)ρb and Hb, and also the bond delocalisation indices δ(A, B), are correlated with the data from previous Ziegler-Rauk energy decomposition studies of the same systems. For M2X6 (M = ...

The intramolecular [3+2] cycloaddition (32CA) reactions of azido alkynes leading to spirocyclic, tricyclic, and bicyclic triazolooxazines has been studied within the molecular electron density theory (MEDT) at MPWB1K/6-311G(d,p) level. localization function (ELF) characterizes as zwitterionic species. Analysis conceptual DFT indices allows classifying azide moiety electrophilic counterpart alky...

This study focuses on selected members of the general salen-analogues family possessing two O-H?N hydrogen bonds, namely three isomers N,N’-bis(salicylidene)-X-phenylenediamine, denoted as ortho, meta and para. Two are not planar in published crystal structures. The current tackles problem symmetry interactions within molecules, well lattice. aromaticity phenyl rings is evaluated using Harmonic...

The recently reported cationic titanocene complex [Cp2TiMe(OH2)](+) was subjected to detailed computational studies using density functional theory (DFT). The calculated NMR spectra revealed the importance of including the anion and the solvent (CD2Cl2) in order to calculate spectra which were in good agreement with the experimental data. Specifically, two organic solvent molecules were require...

dft-gga method of perdew-burke-ernzerhof (pbe) is used with aug-cc-pvtz, 6-311++g**, and def2-tzvp large basis sets to study the hydrogen bond interactions between oxygen lone pair as a donor electron with hydrogen atom connected to the aniline’s nitrogen as an electron acceptor (h2o···hnh-ph), and nitrogen lone pair with hydrogen of water molecule (ph-h2n···hoh), both in the gas phase. in some...