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We present a reinvestigation of sulfate--water clusters Due to image rights restrictions, multiple line equation(s) cannot be graphically displayed. (H2O)n=3-7, which involves several new aspects. Using a joint molecular mechanics/first principles approach, we perform exhaustive searches for stable cluster geometries, showing that the sulfate--water landscape is much richer than anticipated previously. We check the compatibility of the new structures with experiment by comparing vertical detachment energies (VDEs) calculated at the B3LYP/6-311++G** level of theory and determine the energetic ordering of the isomers at the RI-MP2/aug-cc-pVTZ level. Our results are benchmarked carefully against reference energies of estimated CCSD(T)/aug-cc-VTZ quality and VDEs of CCSD(T)/aug-cc-pVDZ quality. Furthermore, we calculate anharmonic vibrational corrections for up to the n = 6 clusters, which are shown to be significant for isomer energy ordering. We use energy decomposition analysis (EDA) based on the absolutely localized fragment (ALMO) expansion to gain chemical insight into the binding motifs. [ABSTRACT FROM AUTHOR]

Incorporation of Zn2+ into bayerite results in the formation of a cation-ordered layered double hydroxide (LDH) of monoclinic symmetry in which about half the vacancies of Al(OH)3 are occupied by Zn2+ giving rise to positively charged layers. Charge compensation takes place by the incorporation of sulfate ions in the interlayer region. Structure refinement reveals that the adjacent layers in the crystal are related by a 21 axis (we call it 2M1 polytype) with sulfate coordinating in the D2d symmetry in the interlayer region. Another polytype in which adjacent layers are related by a 2-fold axis (2M2 polytype) can also be envisaged. Faulted crystals arising from intergrowths of the 2M2 polytype within the 2M1 structure were also obtained. These bayerite-based LDHs have a distinctly different interlayer chemistry when compared to the better known brucite-based LDHs, in that they have a strong affinity for tetrahedral ions such as SO42-, CrO42-, and MoO42- and a poor affinity for CO32- ions. These observations have implications for the use of LDHs in applications related to chromate sorption. [ABSTRACT FROM AUTHOR]

Structural elucidation of glycosaminoglycans (GAGs) is one of the major challenges in biochemical analysis. This is mainly because of the diversity of GAG sulfation and N-acetylation patterns and variations in uronate isomers. ESI-MS and recently MALDI-MS methodologies are important strategies for investigating the molecular structure of GAGs. However, the interpretation of MS data produced by these strategies must take into account a large number of variables (including the number of monosaccharide residues, acetylations, sulfate groups, multiple charges, and exchanges between different cations). We have developed a bioinformatics tool to assist this complex interpretation task. The software is based on Glyco Workbench, a tool for semiautomatic interpretation of glycan MS data. The tool generates the sugar backbones in all their variants (GAG family, composition, acetylation positions, and number of sulfates) and automatically matches them with the selected MS peaks. The backbones corresponding to a given peak are validated against the selected MS/MS peaks by generating all possible fragmentations. Native chondroitin sulfate and heparin oligosaccharides as well as chemically modified heparin oligomers have been successfully analyzed by MALDI. and ESI-MS and MS/MS, and the results of the semiautomated annotation of these mass spectra are presented here. [ABSTRACT FROM AUTHOR]

Demonstrates that dynamic combinatorial chemistry can be used to optimize the binding properties of bis(cyclopeptide) complex 2 toward anions in aqueous solution. Resulting receptors that bind iodide and sulfate anions with, for neutral species, unprecedented affinities; Reversible disulfide chemistry; Thermodynamic analysis of the binding.