Comparison of hydrophobicity studies of silica aerogels using contact angle measurements with water drop method and adsorbed water content measurements made by Karl Fischer’s titration method

Hydrophobic silica aerogels possesses potential applications as insulating materials for refrigerators, furnaces and thermos flasks. In such applications, aerogel materials may get exposed for longer time to atmosphere and the adsorbed water content from surroundings may deteriorate its properties. Therefore, hydrophobicity of the arogels becomes crucial parameter and needs to be evaluated critically. In the present works, silica alcogels were prepared using the mixture of tetramethoxysilane and methyltrimethoxysilane (MTMS) as precursor chemicals for silica. The concentration of MTMS, which is used as hydrophobic reagent, in the said mixture of silicon alkoxide was varied between 0 and 100% in steps of 25%. After gelation, the alcogels were dried supercritically by solvent extraction method. Resulted aerogels were exposed to relative humidity of 90% for a period of one month which were then characterized to assess hydrophobicity by the contact angle using water drop method and adsorbed water content measurements by Karl Fischer’s Titration method. Observed contact angle and water content measurements were compared and the results are reported in the present research paper.     

Study of the interaction of unaggregated and aggregated amyloid β protein (10-21) with outward potassium channel

Metal ion-induced aggregation of Aβ into insoluble plaques is a central factor in Alzheimer’s disease. Zn2 is the only physiologically available transition metal ion responsible for aggregating Aβ at pH 7.4. To make it clear that the neurotoxicity of Zn2 -induced aggregation of Aβ on neurons is the key to un- derstand Aβ mechanism of action further. In this paper, we choose Aβ (10-21) as the model fragment to research hippocampal CA1 pyramidal neurons. For the first time, we adopt the combination of spectral analysis with patch-clamp technique for the preliminary study of the mutual relations of Zn2 , Aβ and ion channel from the cell level. The following expounds upon the effects and mode of action of two forms (unaggregated and aggregated) of Aβ (10-21) on hippocampus outward potassium channel three processes (activation, inactivation and reactivation). It also shows the molecular mechanics of AD from the channel level. These results are significant for the further study of Aβ nosogenesis and the devel- opment of new types of target drugs for the treatment of AD.     

Exploring the H-abstraction reactions of CHCl·-/CCl2·- with CX3H（X = F,Cl,Br and I） using the density functional theory method

Gas-phase hydrogen abstraction reactions have been compared using the popular density functional theory(DFT) functional BHandHLYP/aug-cc-pVTZ/RECP level of theory,on the basis of the model reaction CHCl·-/CCl2·-+ CX3H(X = F,Cl,Br and I).Our theoretical findings suggest the efficiency of the H-abstraction reactions induced by either CHCl·-or CCl2·-increases as the substrate is changed from CF3H to CI3H,and that CHCl·-has a higher activity in hydrogen abstraction than CCl2·-for a given substrate.The entropy effect at 298 K does not significantly change the trend in reactivity of the various reactions,which is in general controlled by the heights of activation energies △E≠.Therefore,we have explored the origin of the energy barriers △E≠ of the reactions using the activation strain model of chemical reactivity.     

A high performance method for thermodynamic study on the binding of copper ion and glycine with Alzheimer’s amyloid β peptide

The interaction of Cu²⁺ to the first 16 residues of the Alzheimer’s amyloid β peptide, Aβ(1–16) was studied by isothermal titration calorimetry at pH 7.2 and 37°C in aqueous solution. The Gholamreza Rezaei Behbehani (GRB) solvation model was used to reproduce the enthalpies of interactions of Aβ(1–16) with glycine, Gly+Aβ(1–16), and Cu²⁺ ions, Cu²⁺ +Aβ(1–16), over the whole range of Cu2+ concentrations. The binding parameters recovered from the solvation model were attributed to the structural change of Aβ(1–16) due to the glycine and Cu²⁺ interactions. It was found that there is a set of two identical binding sites for Cu²⁺ ions. p=2 indicates that the binding has positive cooperativity in the two binding sites. Aβ(1–16) structure is destabilized greatly as a result of binding to Cu²⁺ ions.     

Application of Bader’s atoms in molecules theory to the description of coordination bonds in the complex compounds of Ca2+ and Mg2+ with methylidene rhodanine and its anion

In the framework of Bader??s atoms in molecules theory a complete analysis of the distribution function of electron density in molecules of complexes of Ca²⁺ and Mg²⁺ with methylidene rhodanine and its anion was carried out. The role of mutual polarization of the metal cation and the ligand in the formation of coordination bonds was demonstrated. The accumulation of electron density in the interatomic space of coordination bonds is assumed to be a consequence of the deformation of the ligand electron shell under the influence of the cation electric field. Based on the magnitude and sign of the Laplacian and the electron energy density at the critical points of coordination bonds the interactions were classified the in terms of the atoms in molecules theory. The energy of the coordination bonds was evaluated using the Espinoza??s formula. The stability of metal-containing rings was considered basing on the values of the bond ellipticity.