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

AB Initio Studies of Adsorption of Some Organic Inhibitors (Pyridine and Its derivatives) at the Aluminum Surface in hydrochloric acid (HCl)

ABSTRACT A quantum chemical study of the corrosion inhibition properties of some organic inhibitor molecules, pyridine, 2-picoline, 3-picoline, 4-picoline, 2, 4-lutidine at the aluminum surface in hydrochloric acid (HCl) was carried out. The models of the inhibitors adsorption on the Al-surface were optimized with the HF and B3LYP level using the 6-31G and LANL2DZ basis sets from the program package Gaussian 98 (A.7 Public Domain version). Based on the calculated results the compound was adsorbed on the metal surface mainly in their protonated forms. In the Alsurface is transferred to the inhibitor and organic inhibitor is adsorbed at the Al-surface in an inclined state. INTRODUCTION The inhibition efficiency depends on the parameters of system: metal composition, pH and structure of inhibitor molecule. It is well known that heterocyclic Compounds containing nitrogen atoms are good corrosion inhibitors for many metals in various acidic media In this paper is discussed the effect of five organic inhibitors(Pyridine,2-Picoline,3-Picoline,4-Picoline,2,4-Lutidine) on the inhibition of Al-surface in acidic media by means of an advanced quantum chemical method(HF and B3LYP).The electronic structure of the organic inhibitors has a key influence on the corrosion inhibition efficiency the metal

Proton-Coupled Electron-Transfer Mechanism for the Radical Scavenging Activity of Cardiovascular Drug Dipyridamole

Dipyridamole (DIP) is a well-known pharmaceutical drug used as a coronary vasodilator and anti-platelet agent in clinics for treating several cardiovascular diseases. Primarily, the therapeutic effects of the drug are attributed to its antioxidant potency. In this research, we aim to declare the unknown antioxidant mechanism of DIP as well as its potent chain-breaking antioxidant activity in polar aqueous medium inside the cells, using different experimental methods and theoretical quantum calculations. Data demonstrated the higher antioxidant capacity of DIP against ROS and free radicals in polar cell's interior. DIP is capable of generating long living and noninvasive DIP• radicals in oxidant condition that leads to an effective “chain-breaking antioxidant” activity. Quantum computational data indicated that DIP antioxidant has more favorable ionization potential than trolox which means DIP has higher antioxidant activity. Also, data showed that the direct hydrogen-transfer is not a favorable process to construct DIP• because of high barrier energy, though electron-transfer process can more easily to produce DIP•+ with the lowest barrier energy. Altogether, the electron donating potency of DIP to reduce ferric ion, having the low anodic oxidation peak potential, producing long lived stable DIP• radicals and protecting myoblast cells from oxidation, proposed the excellent “chain-breaking antioxidant” potency via electron-transfer mechanism of this vasodilator DIP drug in polar aqueous medium

<b>Characterization of nanocrystalline silicon germanium film and nanotube in adsorption gas by Monte Carlo and Langevin dynamic simulation</b>

The nanocrystalline silicon-germanium films (Si/Ge) and Si/Ge nanotubes have low band gaps and high carrier mobility, thus offering appealing potential for absorbing gas molecules. Interaction between hydrogen molecules and bare as well as functionalized Si/Ge nanofilm and nanotube was investigated using Monte Carlo (MC) and Langevin dynamic (LD) simulation methods. It was found that the binding energy of the H₂ on the Si/Ge surface is weak, and be enhanced by increasing curvature of surface to tube form and increasing temperature. The structural, total energy and energy band gaps of H₂ absorbed nanocrystalline silicon germanium film (Si/Ge) and as it passes through Si/Ge nanotube was also studied. They are computed with MC and LD simulation the methods at different temperatures. All the calculations were carried out using HyperChem 7.0 program package

Quantum mechanic study of basis set effect on NMR chemical shielding and hydrogen bonding of some amino acids in gaseous phase and solvent

Amino Acids can be defined separately by the unique characteristic rendered to each amino acid molecule as a result of the varying reactive abilities of their side chains. Structural analysis is performed using ab initio calculations in GAUSSIAN 98 program. The behavior of every atom as well as that of molecular fragments COOH, CH2, NH2 show that atoms in molecules (AIM) and Natural Population Analyses (NPA) charges exhibit not only a good conformational independence but also provide a meaningful picture of the electron charge distribution in this system. In this paper relative energies, dipole moments, rotational constants, vibration frequencies, charges of important atoms in structure of amino acids, NMR chemical shielding (symmetric & asymmetric: &#8710;&#963; , &#951; and hydrogen bonded have been studied by systematic ab initio calculations in three levels of theory: Hartree- Fock(HF), DFT (B3LYP) and MP2. Nine amino acids consist of: alanine, asparagine, glycine, cysteine, methionine, serine, proline, threonine and valine were studied in gaseous phase and in two aprotic Solvent and different basis sets: 6-31g*, 6-311+g*, 3-21g* and 6-311++g** were tested and compared to determine Which basis set is the most efficient to model these particular amino acids. A series of gauge independent atomic orbiter\'s (GIAO) magnetic shielding calculations also have been done in solution and gaseous phase. Egyptian Journal of Biochemistry and Molecular Biology Vol. 25 (2) 2007: pp. 154-17

NMR and Solvent Effect Study on the Thymine-Adenine-Thymine Sequence: A Theoretical Investigation on chemical behavior of Nucleotides in solution

In our current research, we have taken into account nuclear shielding parameters of Thymine-Adenine-Thymine (TAT) sequence using GIAO and Self-Consistent Reaction Field (SCRF) method at the level of HF/ 3-21G theory both in the gas phase and in different solvents such as water, ethanol, methanol, nitromethane and DMSO. These solvents represent a wide range of solvent propertis from the point of view of polarity as well as hydrogen bonding interactions. Our results reveal that NMR chemical shielding parameters are strongly affected by inducing different solvent media. Regarding to our plotted graphs of &#963;iso and &#916;E relatives versus &#1108;, the lowest &#963;iso values obtained in methanol for nitrogen atoms. However, the opposite trend yielded for the graph of asymmetry parameter (&#951;) versus &#1108;. Hydrogen bonding environment strongly affects the chemical shielding tensors and orientation of nuclei. It is noteworthy that the small variation in the position of atoms, eventually yields considerable change in the NMR shielding tensors of the various intermolecular hydrogen bonds. So, solute to solvent hydrogen-bonding effects on the calculated NMR shielding tensors has been concerned. According to our theoretical results of energy values, some important relationships have been found between the dielectric constant and structural stability of TAT sequence. For further evidences, we have discussed about the plotted graphs of relative energies versus dielectric constants of our considered solvents. Thus, we can drastically conclude that the dielectric permittivity of the solvent is a key factor that determines the chemical behavior of DNA in solution. Keywords: TAT sequence; solvent effect; NMR parameters; Ab initio Egyptian Journal of Biochemistry and Molecular Biology Vol. 26 (1) 2008 pp. 83-10