Using Gaussian 03, software the thermodynamic functions such as Gibbs free energy, G, Enthalpy, H, and Entropy, S, of Alanine and Valine amino acids were theoretically studied at different solvents. First, the Density Functional Theory (B3LYP) level with 3-21G, 6-31G and 6-31+G basis sets were employed to optimization of isolated Alanine and Valine amino acids in the gas phase. Moreover, Vib...

Subcritical crack growth in fused silica is treated as a stress assisted chemical reaction between water and strained bonds at the crack tip. In this work, the kinetics of the reaction is modeled by assuming the stress reduces the energy barrier of the activated complex by affecting both the activation enthalpy and entropy, where the stress dependence can take different forms. This theory is co...

Carbohydrate-protein interactions have been investigated for a model system of a monoclonal antibody, SYA/J6, which binds a trisaccharide epitope of the O-polysaccharide of the Shigella flexneri variant Y lipopolysaccharide. The thermodynamics of binding for the methyl glycoside of the native trisaccharide epitope, Rha-Rha-GlcNAc () to SYA/J6 over a range of temperatures exhibits strong, linear...

Titration calorimetry measurements of the binding of phenyl-alpha (alpha PhOGlu), 3-methoxy (3MeOGlu), fluorodeoxy and deoxy derivatives of alpha-D-glucopyranose (Glu) to concanavalin A (conA), pea lectin and lentil lectin were performed at approx. 10 and 25 degrees C in 0.01 M dimethylglutaric acid/NaOH buffer, pH 6.9, containing 0.15 M NaCl and Mn2+ and Ca2+ ions. Apparently the 3-deoxy, 4-de...

The interaction between isatin-β-thiosemicarbazone (IBT) and calf thymus DNA (CT-DNA) was investigated in physiological buffer (pH 7.4) using Neutral Red (NR) dye as a spectral probe by UV–Vis absorption and fluorescence spectroscopy, as well as viscosity measurements. The IBT is stabilized by intercalation in the DNA ( K [IBT –DNA] =1.03×105 M−1), and displaces the NR dye from the NR–DNA comple...

In the present work, the interaction of three water soluble porphyrins, tetra (p-trimethyle) ammoniumphenyl porphyrin iodide (TAPP) as a cationic porphyrin, tetra sodium meso-tetrakis (p-sulphonatophenyle) porphyrin (TSPP) as an anionic porphyrin and manganese tetrakis (p-sulphonato phenyl)porphinato acetate (MnTSPP) as a metal porphyrin, with DNA have been studied by isothermaltitration microc...

Free energy is the key quantity to describe the thermodynamics of biological systems. In this perspective we consider the calculation of free energy, enthalpy and entropy from end-point molecular dynamics simulations. Since the enthalpy may be calculated as the ensemble average over equilibrated simulation snapshots the difficulties related to free energy calculation are ultimately related to t...

The configurational entropy of a beta-heptapeptide in solution at four different temperatures is calculated. The contributions of the backbone and of the side-chain atoms to the total peptide entropy are analyzed separately and the effective contribution to the entropy arising from correlations between these terms determined. The correlation between the backbone and side-chain atoms amounts to ...