Structural Changes Of Dha-Containing Phospholipids By K+ And Na+ Cations In Nerve Cell Membranes

Understanding the structure and dynamics of a docosa hexaenoic acid (DHA) containing phospholipid monomer within membranes is essential for recognizing the bilayer function in central nervous system. It has been recognized that the electrical impulses in nerve cells arise from the movement of electrical charges in the form of ions across the plasma membrane. In this study, we have modeled a novel DHA-containing phosphatidylcholine (PC) found in a marine single cell eukaryote, >Schizochytrium sp F26-b> and we were focused on understanding the physico-chemical nature of K+ and Na+ movement toward DHA-containing phospholipid through its structural changes. To know more about the temperature dependence of the structural stability of 1-pentadecanoyl-2-docosahexaenoyl-sn-glycerol-3-phosphocholin frequently calculations have been carried out at different biological temperatures and the plotted graphs of energy values at all employed temperatures have been analyzed. Our findings confirmed the usefulness of Quantum chemical calculations for determination of dynamics of a phospholipid and prediction of their biological activity in bio-membranes.Chemistr

THE COMPARISON OF STRUCTURE AND PROPERTY OF AZT CONFORMERS AND ITS ANALOGUE CS-87 USING DENSITY FUNCTIONAL THEORY CALCULATIONS: A STUDY OF ANTI-AIDS

The compounds 3'-azido-3'-deoxythymidine (AZT), 3'-azido-2',3'-dideoxyuridine (CS-87) are active inhibitors of HIV-1 replication, the causative agents of AIDS. We report Abinitio, DFT results of two AZT conformers; A-AZT and CS-87 by different basis sets and on structural and electronic properties. It is shown that A-AZT and CS-87 are similar in structure and properties. The B-AZT conformer is different from them interestingly and it is predicted that B-AZT is to be the active form of AZT. KEY WORDS: 3'-Azido-3'-deoxythymidine (AZT), 3'-Azido-2',3'-dideoxyuridine (CS-87), Inhibitors of HIV-1 replication, Causative agents of AIDS, AZT conformers, Abinitio, Density functional theory Bull. Chem. Soc. Ethiop. 2006, 20(1), 133-142

Solvent effect on 14N NMR shielding of glycine, serine, leucine, and threonine: comparison between chemical shifts and energy versus dielectric constant

The polarizable continuum model (PCM) is employed to describe the system in the condensed phase. The performance of DFT and PCM in describing high order nonlinear mixed electric and magnetic effects in condensed phase are described. In this paper we consider the effect of 10 solvents with a wide range of dielectric constants on 4 amino acids. NMR shielding values (ppm), isotropic and anisotropic effects, energy interaction between solute and solvent, and the effect of hydrogen bond on shielding are described. Direct and indirect solvent effects on shielding are also calculated. The observed solvent-induced shielding variation is more strongly related to the intensity of the solvent reaction field rather than on the change of molecular geometry induced by the solvent. KEY WORDS: Solvent effect, 14N NMR shielding, Solvent-induced shielding, Polarizable continuum model, Amino acids   Bull. Chem. Soc. Ethiop. 2007, 21(1), 111-116

Investigation of solvent effect and NMR shielding tensors of p53 tumor-suppressor gene in drug design

The p53 tumor-suppressor gene encodes a nuclear phosphoprotein with cancer- inhibiting properties. The most probable cancerous mutations occur as point mutations in exons 5 up to 8 of p53, as a base pair substitution that encompasses CUA and GAT sequences. As DNA drug design represents a direct genetic treatment of cancer, in the research reported computational drug design was carried out to explore, at the Hartree–Fock level, effects of solvents on the thermochemical properties and nuclear magnetic resonance (NMR) shielding tensors of some atoms of CUA involved in the hydrogen-bonding network. The observed NMR shielding variations of the solutes caused by solvent change seemed significant and were attributed to solvent polarity, and solute–solvent and solvent–solute hydrogen-bonding interactions. The results provide a reliable insight into the nature of mutation processes. However, to improve our knowledge of the hydration pattern more rigorous computations of the hydrated complexes are needed

Density Functional Theory Study of B 6 C 4 Si Cluster as a Novel Drug Carrier

ABSTRACT The aim of the present study was to prepare new cluster (B 6 C 4 Si) as an antibiotic carrier. Density functional theory (DFT) method at the B3LYP level of theory in conjugate with the 6-311G** basis set was used to evaluate the interaction between B 6 C 4 Si cluster and Penicillin. From NMR shielding calculations, it can be seen that the penicillin connects stronger to B 6 C 4 Si cluster in positive charges than negative charge. Thus by creating positive field, penicillin can be connected to the B 6 C 4 Si cluster and delivered easily by using a negative filed

THEORETICAL STUDY OF SOLVENT EFFECTS AND NMR SHIELDING TENSORS OF DLPC

ABSTRACT The effect of the polarity of the environment on the conformation zwitterionic membrane dilauroyl phosphatidylcholine (DLPC) has been investigated with calculation at the Hatree-Fock level using the 6-31G* basis set with Onsager continuum solvation model. The \u27Gauge Including Atomic Orbital\u27 (GIAO) approach is used to investigate Ab initio GIAO calculations of NMR chemical shielding tensors carried out within SCF-Hartree-Fock approximation are described. In order to compare the calculated chemical shifts with experimental ones, it is important to use consistent nuclear shielding for NMR reference compounds like TMS. Conformation of DLPC was evaluated with four different solvents with different dielectric constant (Water (£ = 78.39), Dimethyl Sulfoxide (£ = 46.7), Acetone (£ = 20.7) and Heptane (£ = 1.92). In concern with conformational energy, Water could be the most suitable solvent for DLPC. Moreover, as the polarity of the medium increase, the conformational stability of this molecule increases faster than that of DLPC in the gas phase. Consequently, the relative energy of DLPC also depends on the polarity of the environment. This subject was considered as well as the most variable in some dihedral angles degree and NM.R isotropic shift were in the less dielectric constant (£ = 1.92). It could be in polar medium DLPC conformer becomes additionally stabilized by intermolecular ionic and hydrogen bond interactions with polar neighboring molecules. On the basis of this work it can be concluded that the effect of the polarity of the environment clearly are influenced on the isotropic values by geometry variation due to intermolecular motion in molecule. Keywords: Onsager continuum model, DLPC ,NMR shielding, isotropic, solvent models, anisotropi

THEORETICAL STUDY OF SOLVENT EFFECTS AND NMR SHIELDING TENSORS OF DLPC

The effect of the polarity of the environment on the conformation zwitterionic membrane dilauroyl phosphatidylcholine (DLPC) has been investigated with calculation at the Hatree-Fock level using the 6-31G* basis set with Onsager continuum solvation model. The ‘Gauge Including Atomic Orbital' (GIAO) approach is used to investigate Ab initio GIAO calculations of NMR chemical shielding tensors carried out within SCF-Hartree-Fock approximation are described. In order to compare the calculated chemical shifts with experimental ones, it is important to use consistent nuclear shielding for NMR reference compounds like TMS. Conformation of DLPC was evaluated with four different solvents with different dielectric constant (Water (ε = 78.39), Dimethyl Sulfoxide (ε = 46.7), Acetone (ε = 20.7) and Heptane (ε = 1.92). In concern with conformational energy, Water could be the most suitable solvent for DLPC. Moreover, as the polarity of the medium increase, the conformational stability of this molecule increases faster than that of DLPC in the gas phase. Consequently, the relative energy of DLPC also depends on the polarity of the environment. This subject was considered as well as the most variable in some dihedral angles degree and NMR isotropic shift were in the less dielectric constant (ε = 1.92). It could be in polar medium DLPC conformer becomes additionally stabilized by intermolecular ionic and hydrogen bond interactions with polar neighboring molecules. On the basis of this work it can be concluded that the effect of the polarity of the environment clearly are influenced on the isotropic values by geometry variation due to intermolecular motion in molecule.   Keywords: Onsager continuum model, DLPC ,NMR shielding, isotropic, solvent models, anisotropi