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Different Surface Areas (different + surface_area)
Selected AbstractsComparison of binding energies of SrcSH2-phosphotyrosyl peptides with structure-based prediction using surface area based empirical parameterizationPROTEIN SCIENCE, Issue 10 2000Denise A. Henriques Abstract The prediction of binding energies from the three-dimensional (3D) structure of a protein,ligand complex is an important goal of biophysics and structural biology. Here, we critically assess the use of empirical, solvent-accessible surface area-based calculations for the prediction of the binding of Src-SH2 domain with a series of tyrosyl phosphopeptides based on the high-affinity ligand from the hamster middle T antigen (hmT), where the residue in the pY+3 position has been changed. Two other peptides based on the C-terminal regulatory site of the Src protein and the platelet-derived growth factor receptor (PDGFR) are also investigated. Here, we take into account the effects of proton linkage on binding, and test five different surface area-based models that include different treatments for the contributions to conformational change and protein solvation. These differences relate to the treatment of conformational flexibility in the peptide ligand and the inclusion of proximal ordered solvent molecules in the surface area calculations. This allowed the calculation of a range of thermodynamic state functions (,Cp, ,S, ,H, and ,G) directly from structure. Comparison with the experimentally derived data shows little agreement for the interaction of SrcSH2 domain and the range of tyrosyl phosphopeptides. Furthermore, the adoption of the different models to treat conformational change and solvation has a dramatic effect on the calculated thermodynamic functions, making the predicted binding energies highly model dependent. While empirical, solvent-accessible surface area based calculations are becoming widely adopted to interpret thermodynamic data, this study highlights potential problems with application and interpretation of this type of approach. There is undoubtedly some agreement between predicted and experimentally determined thermodynamic parameters; however, the tolerance of this approach is not sufficient to make it ubiquitously applicable. [source] Preparation and characterization of highly polar polymeric sorbents from styrene,divinylbenzene and vinylpyridine,divinylbenzene for the solid-phase extraction of polar organic pollutantsJOURNAL OF POLYMER SCIENCE (IN TWO SECTIONS), Issue 13 2003Núria Fontanals Abstract This article explores the synthesis of styrene,divinylbenzene resins with different surface areas and the influence of these surface areas on their performance in the solid-phase extraction of polar compounds from water samples. As expected, increasing the surface areas increases the retention capability of polar compounds. To improve the retention properties, we have used 4-vinylpyridine instead of styrene in the polymerization and evaluated the influence of the sorbent polarity and surface area on the retention properties. We have found that a compromise is required between the percentage of 4-vinylpyridine, which increases the polarity of the sorbent, and the percentage of divinylbenzene, which increases the surface area. In the solid-phase extraction of polar compounds, the results are best for a polymer containing 2.14% N and having a surface area of 710 m2/g. © 2003 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 41: 1927,1933, 2003 [source] Influence of the pore structure on the properties of silica based reversed phase packings for LCJOURNAL OF SEPARATION SCIENCE, JSS, Issue 4 2005Zoltan Szabó Abstract This paper describes the preparation and investigation of new, highly loaded, monomeric, silica based, reversed phase C18 and C30 packings. The influence of pore structure and endcapping on the properties of C18 and C30 packings is described. Using hydrothermal procedures, silicas with predictable pore size (9.3,25.5 nm) and surface area have been prepared. Silylation with long chain silanes substantially alters the pore structure of the silica: pore size and pore volume decrease. A new parameter, the volumetric surface coverage [mm3×m,2] has been introduced. This parameter , calculated from on-column measured porosity data , indicates the pore volume portion occupied by the hydrocarbon chains. Endcapping does not significantly change the pore structure of the bonded phases. The reduced retentions (reduced with respect to unit area: [k/m2]) , a good measure for comparing the retention behaviour of packings with different surface areas , are similar for most of the phases, demonstrating good accessibility of the pores for the solutes. Slightly lower retentions were found on the endcapped than on the non-endcapped phases for probes with dense ,-electron system (e. g. polyaromatic hydrocarbons) demonstrating the contribution of silanophilic interactions to the retention. The phases had been successfully used for various demanding separations, e. g. for the separation of flavonoids, carotenoids, resveratrol, and tocopherol isomers, fullerenes, and anions. [source] Surface Enthalpy, Enthalpy of Water Adsorption, and Phase Stability in Nanocrystalline Monoclinic ZirconiaJOURNAL OF THE AMERICAN CERAMIC SOCIETY, Issue 1 2009A. V. Radha A fundamental issue that remains to be solved when approaching the nanoscale is how the size induces transformation among different polymorphic structures. Understanding the size-induced transformation among the different polymorphic structures is essential for widespread use of nanostructured materials in technological applications. Herein, we report water adsorption and high-temperature solution calorimetry experiments on a set of samples of single-phase monoclinic zirconia with different surface areas. Essential to the success of the study has been the use of a new ternary water-in-oil/water liquid solvothermal method that allows the preparation of monoclinic zirconia nanoparticles with a broad range of (BET) Brunauer,Emmett,Teller surface area values. Thus, the surface enthalpy for anhydrous monoclinic zirconia is reported for the first time, while that for the hydrous surface is a significant improvement over the previously reported value. Combining these data with previously published surface enthalpy for nanocrystalline tetragonal zirconia, we have calculated the stability crossovers between monoclinic and tetragonal phases to take place at a particle size of 28 ± 6 nm for hydrous zirconia and 34 ± 5 nm for anhydrous zirconia. Below these particle sizes, tetragonal hydrous and anhydrous phases of zirconia become thermodynamically stable. These results are within the margin of the theoretical estimation and confirm the importance of the presence of water vapor on the transformation of nanostructured materials. [source] | |||||||||||||