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The crystal structure of the complex between rat-prostatic acid phosphatase (PAP) and L-(+)-tartrate (Lindqvist et al., J. Biol. Chem., 1993, 268, 20744-20746) contains the model of the ligand with incorrect chirality. We report here the correct model and discuss the relation between this model and the model of the inhibitory complexes between PAP and oxy-anions.
The crystal structure of the acyclonucleoside, 9-[4-hydroxy-2-(hydroxymethyl)- butyljguanine (2HM-HBG), has been compared with related acyclonucleosides, and that of the acyclonucleotide, 9-1(1,3-dihydroxy-2-propoxy)methyl]guanine-3',5'-cyclic phosphate (DlIPG-cMP), also with its parent second messenger cGMP and cyclic monophosphate nucleotides. There is considerable conformational flexibility in the acyclic chain of these compounds with several conformations coexisting in the solid state. This flexibility together with the narrow range of the glycosidic torsion angles (from 69° to 94°, with an average of 83(3)° for 11 molecules when the aglycon is guanine, and from 92° to 108° with an average of 103(3)° for 4 molecules when the aglycon is adenine) may be essential for the antiviral activity of these compounds and their ability to act as substrates. The mechanism of antiviral activity of, 9-1(1,3-dihydro- xy-2-propoxy)methyllguanine-3',5'-cyclic phosphate is different from that of the acyclonucleosides, and is discussed in the light of it being a close structural analogue to the second messenger cGMP.
In the crystal structures of N3-protonated cytidinium and 2'-deoxycytidinium salts with composite XYn anions capable of accepting hydrogen bonds through their Y atoms, the dominating motif of cytosinium...anion interactions consists of a pair of hydrogen bonds donated from the N3+-H protonation site and from the exoamino N4-H41 group cis to N3, and accepted by two Y centers of one anion. This multi-point recognition pattern is stable and robust and thus can be classified as a supramolecular synthon. In a broader group of N3-protonated, N1-substituted cytosinium salts with composite anions it occurs with 70% frequency. The C5 side of the cytosine ring mimics the N3+-H type synthon and shows a propensity to form an analogous motif in which a C5-H5...Y hydrogen bond replaces the strong N3+-H...Y interaction. Since the C-H...Y bond is much weaker, the secondary motif shows higher deformability and is less frequent (44%).
The small angle X-ray scattering (SAXS) pattern of the homotetrameric aspa­raginase II from Escherichia coli was measured in solution in conditions resembling those in which its crystal form was obtained and compared with that calculated from the crystallographic model. The radius of gyration measured by SAXS is about 5% larger and the maximum dimension in the distance distribution function about 12% larger than the corresponding value calculated from the crystal structure. A compari­son of the experimental and calculated distance distribution functions suggests that the overall quaternary structure in the crystal and in solution are similar but that the homotetramer is less compact in solution than in the crystal.
The samples containing rapeseed oil and palm stearin, both initial blends and interesterified products, crystallised in the ß form. The partial substitution of palm stearin for hydrogenated palm stearin caused that besides the ß crystal form also ß crystal form occurred in the reaction products. The amount of the ß form was the greater, the more palm stearin was replaced with partially hydrogenated stearin. The presence of trans isomers, but not the sample content of palmitic acid, was the main factor that delayed the ß to ß transition. In addition, the amount of ß crystal form was found to be greater in products containing partial acylglycerols (mostly diacylglycerols) besides triacylglycerols than in pure respective triacylglycerols.
The ribosome is a macromolecular assembly that is responsible for protein biosynthesis in all organisms. It is composed of two-subunit, ribonucleoprotein particles that translate the genetic material into an encoded polypeptides. The small subunit is the site of codon-anticodon interaction between the messenger RNA (mRNA) and transfer RNA (tRNA) substrates, and the large subunit catalyses peptide bond formation. The peptidyl- transferase activity is fulfilled by 23S rRNA, which means that ribosome is a ribozyme. 5S rRNA is a conserved component of the large ribosomal subunit that is thought to enhance protein synthesis by stabilizing ribosome structure. This paper shortly summarises new results obtained on the structure and function of 5S rRNA.
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