Search

We present a model for quasielastic neutron scattering (QENS) by an aqueous solution of compact and inflexible molecules. This model accounts for time-dependent spatial pair correlations between the atoms of the same as well as of distinct molecules and includes all coherent and incoherent neutron scattering contributions. The extension of the static theory of the excluded volume effect [A. K. Soper, J. Phys.: Condens. Matter 9, 2399 (1997)] to the time-dependent (dynamic) case allows us to obtain simplified model expressions for QENS spectra in the low Q region in the uniform fluid approximation. The resulting expressions describe the quasielastic small-angle neutron scattering (QESANS) spectra of D2O solutions of native and methylated cyclodextrins well, yielding in particular translational and rotational diffusion coefficients of these compounds in aqueous solution. Finally, we discuss the full potential of the QESANS analysis (that is, beyond the uniform fluid approximation), in particular, the information on solute-solvent interactions (e.g., hydration shell properties) that such an analysis can provide, in principle. [ABSTRACT FROM AUTHOR]

The 2.1 Angstrom resolution structure of unliganded Clostridium perfringens conjugated bile acid hydrolase (CBAH) apoenzyme and the 1.7 Angstrom resolution crystal structure of the complex formed between CBAH and the substrate taurodeoxycholic acid is presented. The structure analysis of C. perfringens CBAH identifies critical residues in catalysis, substrate recognition, and tetramer formation, which may serve in further biochemical characterization of bile acid hydrolases.

Water oxidation generating atmospheric oxygen occurs in photosystem II (PSII), a large protein-pigment complex located in the thylakoid membrane. The redox potentials for one-electron oxidation of the chlorophyll a molecules in PSII is calculated, considering the protein environment in atomic detail.

The 2.6 angstrom resolution X-ray crystal structure of a decameric HNA/RNA duplex containing all four Watson-Crick base pairs and representing the physiologically active state of an HNA antisense oligonucleotide hybridized with target RNA is determined. The asymmetric unit contains four distinct hybrid duplexes that differ only slightly in their overall helical conformation.

The guanine specificity of ribonuclease T1 (RNase T1) alteration by rational and random mutagenesis have not been successful yet and it is important to note that the high flexibility of Trp45 and Asn46 within the three asymmetric unit. The studies reveal that the variant RV is the first variant of RNaseT1 and was easy to determine the single kinetic constant variant for Gpc and Apc but the mode of adenine recognition needs to be analyzed.

The molecular structures of peracylated beta-cyclodextrins (CDs) -heptakis (2,3,6-tri-O-acetyl)-beta-CD (TA), heptakis (2,3,6-tri-O-propanoyl)-beta-CD (TD) and, heptakis (2,3,6-tri-butanoyl)-B-CD- (TB)-are determined by single crystal X-ray structure analysis. No inclusion complexes are formed, which is attributed to the intramolecular closure of the molecular cavity by one of the acyl chains.