Density function M06 method has been used to optimize the geometries of shikonin -thymine at 6-311++G** basis. Finally, fourteen stabilized complexes have been obtained. Theories of atoms in molecules (AIM) and natural bond orbital (NBO) have been utilized to investigate the hydrogen bonds involved in all the systems. The interaction energies of all the complexes were corrected by basis set sup...

We show here that an economic basis set can describe nucleic acid base pairs involving the hydrogen bond interactions in density functional calculations. The economic basis set in which the polarization function is added only to oxygen and nitrogen atoms of strong electronegativity can predict reliable geometric structures and dipole moment of nucleic acid base pairs, comparable to those obtain...

The series of fifteen synthesized 4-hydroxycoumarin derivatives was subjected to antioxidant activity evaluation in vitro, through total antioxidant capacity, 1,1-diphenyl-2-picryl-hydrazyl (DPPH), hydroxyl radical, lipid peroxide scavenging and chelating activity. The highest activity was detected during the radicals scavenging, with 2b, 6b, 2c, and 4c noticed as the most active. The antioxida...

UV resonance Raman excitation profiles and Raman depolarization ratios were measured for trialanine and tetraalanine between 198 and 210 nm. Excitation within the pi --> pi* electronic transitions of the peptide bond results in UVRR spectra dominated by amide peptide bond vibrations. In addition to the resonance enhancement of the normal amide vibrations, we find enhancement of the symmetric te...

We report the synthesis of penicillamine-protected Ag20 nanoclusters (NCs), with properties of high monodispersity, red fluorescence and water solubility. Full characterization of the Ag20 NCs is addressed, along with first-principles optimization calculations, revealing the chemical composition and structure of the as-prepared Ag NCs within a molecular formula [Ag20(DPA)18-H]-. Moreover, natur...

The chiral self-discrimination of twelve molecules showing axial chirality has been studied. They included peroxides, hydrazines, carboxylic acids, amides, and allenes. The homo and heterochiral dimers of the selected compounds, that present two hydrogen bonds, have been studied by means of density functional theory ~B3LYP/6-311G**! and ab initio ~MP2/6-311G** and MP2/6-31111G**! methods. The e...

Mercaptopurine is a medicine used to prevent the formation and spread of cancer cells. Mercaptopurine, known chemically as 1,7-dihydro-6H-purine-6-thione, is an analogue of the purine bases adenine and hypoxanthine. This work reports an investigation of anticancer drug Mercaptopurine with the combined density functional theory and Its structure were optimized at B3LYP/6-31G*, level and The mole...

in this paper geometry optimization of two ionic complexes such as cr042-gly+1, and mo042- gly+i have been carried out at the hf and b3lyp levels oftheory with 6-31g* basis set in the gas phase. moreover, chemical shift andnatural bond of orbital (nbo) of these compounds have been obtainedusing nmr and nbo methods. finally, the obtained theoretical results werecompared with each other.

An equation relating the strength (bondforming power) of an spd hybrid bond orbital to the angles it makes with other bond orbitals is formulated and applied in the discussion of the structures of transition-metal carbonyls and other substances by the valence-bond method. The rather simple theory gives results that agree well with those obtained by the complicated and laborious calculation of s...

In three 9-silyltriptycenes bearing chlorine, bromine and the methyl group in one of the peri positions, the silyl group suffers extreme hindrance of its reorientational motion. Owing to this, separate signals of the individual silyl group protons could be observed in NMR spectra at relatively high temperatures. For each compound, the measured values of J couplings of these protons to the 29Si ...