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A bioinformatics study is conducted to analyze the polyelectrolyte domains, as well as the intrinsic disorder observed within the intrinsically disordered proteins (IDP) family, Asprich. The functions of the domains of these proteins are shown to be highly controlled by the structural and surface charge density features.

The bioinformatics studies related to the identification of the molecular traits that classify 12 amelogenin proteins as members of the intrinsically disordered or unstructured protein family (IDPs) which are capable of transformation to a folded state as part of their overall function is described. The studies confirmed labile structure of one of the amelogenins, recombinant porcine rP172, that facilitated interactions of amelogenin with other macromolecules or with minerals to yield stable internal protein assembly.

The role of amines in catalyzing the hydrolysis process that precedes condensation is analyzed by studying the hydrolysis rates of trimethylethoxysilane (TMES). The results show that amine catalysis of TMES is primarily a consequence of the amine's acidity at neutral pH, the proton released by the amine is transferred to the organosilicate producing a protonated ethoxy leaving group that can be displaced by water in an [S.sub.N]2 reaction.

Abstract: Quantitative kinetic studies of silicon sol–gel chemistry have proven difficult in the past because the analytical methods currently available are often incapable of providing the requisite temporal resolution or structural information. In the case of 29Si NMR spectroscopy, low isotopic abundance, a small, negative magnetogyric ratio, and long relaxation times contribute to experimental difficulty. Typically this can be overcome through the use of paramagnetic relaxation agents, but we find at neutral pH that the relaxation agents Cr(acac)3 and MnCl2 influence reaction rates. In an effort to avoid the use of potentially reactive relaxation agents, we investigate the quantitative accuracy of the polarization transfer pulse sequence, 29Si RINEPT+ (Refocused Insensitive Nuclei by Polarization Transfer). Due to signal enhancement and shorter acquisition time, RINEPT+ holds promise for use in the study of silicon reaction kinetics when methylated organosilicate starting compounds are used. [Copyright &y& Elsevier]

It is widely known that macromolecules, such as proteins, can control the nucleation and growth of inorganic solids in biomineralizing organisms. However, what is not known are the complementary molecular interactions, organization, and rearrangements that occur when proteins interact with inorganic solids during the formation of biominerals. The organic-mineral interface (OMI) is expected to be the site for these phenomena, and is therefore extraordinarily interesting to investigate. In this report, we employ X-ray absorption near edge (XANES) spectromicroscopy to investigate the electronic structure of both calcium carbonate mineral crystals and polypeptides, and detect changing bonds at the OMI during crystal growth in the presence of polypeptides. We acquired XANES spectra from calcium carbonate crystals grown in the presence of three mollusk nacre-associated polypeptides (AP7N, AP24N, n16N) and in the presence of a sea urchin spicule matrix protein, LSM34. All these model biominerals gave similar results, including the disruption of CO bonds in calcite and enhancement of the peaks associated with C-H bonds and C-O bonds in peptides, indicating ordering of the amino acid side chains in the mineral-associated polypeptides and carboxylate binding. This is the first evidence of the mutual effect of calcite on peptide chain and peptide chain on calcite during biomineralization. We also show that these changes do not occur when Asp and Glu are replaced in the n16N sequence with Asn and Gln, respectively, demonstrating that carboxyl groups in Asp and Glu do participate in polypeptide-mineral molecular associations.