Library

feed icon rss

Your email was sent successfully. Check your inbox.

An error occurred while sending the email. Please try again.

Proceed reservation?

Export
  • 1
    Electronic Resource
    Electronic Resource
    s.l. : American Chemical Society
    Chemical reviews 95 (1995), S. 829-847 
    ISSN: 1520-6890
    Source: ACS Legacy Archives
    Topics: Chemistry and Pharmacology
    Type of Medium: Electronic Resource
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
  • 2
    Electronic Resource
    Electronic Resource
    Copenhagen : International Union of Crystallography (IUCr)
    Acta crystallographica 54 (1998), S. 1414-1415 
    ISSN: 1399-0047
    Source: Crystallography Journals Online : IUCR Backfile Archive 1948-2001
    Topics: Chemistry and Pharmacology , Geosciences , Physics
    Notes: Prolyl oligopeptidase from pig muscle has been crystallized in complex with an inhibitor, using PEG 8000 and calcium acetate as precipitants. The crystals are orthorombic and the space group is P212121 with cell dimensions a = 111.8, b = 101.8, c = 72.4 Å. The asymmetric unit contains a single chain of prolyl oligopeptidase, corresponding to a specific volume of 2.55 Å3 Da−1 and a solvent content of 52%. The observed diffraction pattern extends to 2.3 Å resolution and the native crystals are well suited for structural analysis by X-ray diffraction methods.
    Type of Medium: Electronic Resource
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
  • 3
    Electronic Resource
    Electronic Resource
    Springer
    JBIC 2 (1997), S. 135-138 
    ISSN: 1432-1327
    Keywords: Key words Heme peroxidases ; Protein electrostatics ; Free radical location ; Molecular orbital calculations
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Chemistry and Pharmacology
    Notes: Abstract  The heme enyzmes cytochrome c peroxidase (CCP) and pea cytosolic ascorbate peroxidase (APX) show a high level of sequence identity. The main difference near the active sites is the presence of a cation binding site in APX located about 1 nm from the Trp-179 side chain, which is hydrogen-bonded to Asp-208. It is possible that this difference in electrostatics provided by the protein environment is an essential determinant of the stabilization of the ion-pair or neutral form of the Trp...Asp couple in APX and CCP. Semiempirical molecular orbital calculations support the hypothesis that the position of the moving proton inside the couple influences the location of the free electron, leading to radical formation either on the heme or on the Trp side chain of these enzymes.
    Type of Medium: Electronic Resource
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
  • 4
    ISSN: 1432-1327
    Keywords: Key words Protein electrostatistics ; Electron-proton coupling ; Redox-Bohr effect ; pKa calculations ; Cytochrome c3
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Chemistry and Pharmacology
    Notes: Abstract  A comparative study of the pH-dependent redox mechanisms of several members of the cytochrome c 3 family has been carried out. In a previous work, the molecular determinants of this dependency (the so-called redox-Bohr effect) were investigated for one species using continuum electrostatic methods to find groups with a titrating range and strength of interaction compatible with a mediating role in the redox-Bohr effect. Here we clarify these aspects in the light of new and improved pK a calculations, our findings supporting the hypothesis of propionate D from heme I being the main effector in the pH-dependent modulation of the cytochrome c 3 redox potentials in all the c 3 molecules studied here. However, the weaker (but significant) role of other titrating groups cannot be excluded, their importance and identity changing with the particular molecule under study. We also calculate the relative redox potentials of the four heme centers among the selected members of the c 3 family, using a continuum electrostatic method that takes into account both solvation and interaction effects. Comparison of the calculated values with available data for the microscopic redox potentials was undertaken, the quality of the agreement being dependent upon the choice of the dielectric constant for the protein interior. We find that high dielectric constants give best correlations, while low values result in better magnitudes for the calculated potentials. The possibility that the crystallographic calcium ion in c 3 from Desulfovibrio gigas may be present in the solution structure was tested, and found to be likely.
    Type of Medium: Electronic Resource
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
  • 5
    ISSN: 1432-2234
    Keywords: Carboxyl ; Carboxylate dyad ; Geometry ; Transferability ; Crystals ; Proteins
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary Simple models of the -COO− ... HOOC- moiety were studied byab initio and semiempirical MNDO/PM3 methods combined with retrieval from the Cambridge Crystallographic Database and Protein Data Bank in order to check transferability of the non-bonded geometry. We found that the gas-phase O ... O distance (252 pm) elongates in crystals and proteins to 256±14 and 262±27 pm, respectively. C-O ... O-C dihedral angles are much more variable, however, energetically excluded values appear only exceptionally in crystals and less frequently in proteins. Most probably due to packing effects -COO− ... HOOC-conformations, preferred in the gas phase, are poorly populated in crystals
    Type of Medium: Electronic Resource
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
  • 6
    Electronic Resource
    Electronic Resource
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Computational Chemistry 19 (1998), S. 38-50 
    ISSN: 0192-8651
    Keywords: quantum mechanics ; molecular mechanics ; self-consistent Madelung potential ; polar molecular crystals ; Chemistry ; Theoretical, Physical and Computational Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Computer Science
    Notes: The self-consistent Madelung potential (SCMP) approach for calculating molecular wave functions for a subunit embedded in a symmetrical environment constituted by the copies of the subunit is implemented with semiempirical NDDO model Hamiltonians and supplemented with empirically parameterized dispersion-repulsion interaction potentials. This model yields sublimation enthalpies in good agreement with available experimental data for a series of molecular crystals, including imidazol, benzimidazole, urea, urethane, dicyaneamide, formamide, uracil, cytosine, maleic anhydride, succinic anhydride, and 1,3,5-triamino-2,4,6-trinitro-benzene. The SCMP-NDDO method, which avoids difficulties concerning the parametrization of charges in the molecular mechanics force fields, is proposed mainly for the treatment of molecular crystals with large unit cells. It might be particularly useful where important charge reorganization is expected under the effect of the crystal field. Charge distributions, obtained by the SCMP and the simple dielectric cavity self-consistent reaction field models, are compared and analyzed.   © 1998 John Wiley & Sons, Inc.   J Comput Chem 19: 38-50, 1998
    Additional Material: 2 Ill.
    Type of Medium: Electronic Resource
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
  • 7
    ISSN: 0887-3585
    Keywords: D-xylose isomerase ; protein crystallography ; enzyme kinetics ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine
    Notes: The catalytic metal binding site of xylose isomerase from Arthrobacter B3728 was modified by protein engineering to diminish the inhibitory effect of Ca2+ and to study the competence of metals on catalysis. To exclude Ca2+ from Site 2 a double mutant D254E/D256E was designed with reduced space available for binding. In order to elucidate structural consequences of the mutation the binary complex of the mutant with Mg2+ as well as ternary complexes with bivalent metal ions and the open-chain inhibitor xylitol were crystallized for x-ray studies. We determined the crystal structures of the ternary complexes containing Mg2+, Mn2+, and Ca2+ at 2.2 to 2.5 Å resolutions, and refined them to R factors of 16.3, 16.6, and 19.1, respectively. We found that all metals are liganded by both engineered glutamates as well as by atoms O1 and O2 of the inhibitor. The similarity of the coordination of Ca2+ to that of the cofactors as well as results with Be2+ weaken the assumption that geometry differences should account for the catalytic noncompetence of this ion. Kinetic results of the D254E/D256E mutant enzyme showed that the significant decrease in Ca2+ inhibition was accompanied by a similar reduction in the enzymatic activity. Qualitative argumentation, based on the protein electrostatic potential, indicates that the proximity of the negative side chains to the substrate significantly reduces the electrostatic stabilization of the transition state. Furthermore, due to the smaller size of the catalytic metal site, no water molecule, coordinating the metal, could be observed in ternary complexes of the double mutant. Consequently, the proton shuttle step in the overall mechanism should differ from that in the wild type. These effects can account for the observed decrease in catalytic efficiency of the D254E/D256E mutant enzyme. Proteins 28:183-193, 1997. © 1997 Wiley-Liss Inc.
    Additional Material: 5 Ill.
    Type of Medium: Electronic Resource
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
  • 8
    Electronic Resource
    Electronic Resource
    New York, NY : Wiley-Blackwell
    Proteins: Structure, Function, and Genetics 28 (1997), S. 131-134 
    ISSN: 0887-3585
    Keywords: apocalmodulin ; calmodulin antagonists ; bisindol alkaloids ; fendiline analogues ; circular dichroism spectroscopy ; protein crystallization ; X-ray diffraction ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine
    Notes: Ca2+-calmodulin is crystallized with two new and potent drugs: a bisindol derivative (KAR-2, 3”-(β-chloroethyl)-2”,4”-dioxo-3,5”-spiro-oxazolidino-4-deacetoxy-vinblastine) with antitumor activity and an arylalkylamine fendiline analogue (N-(3,3-diphenylpropyl)-N'-[1-(3,4-di-n-butoxy-phenyl)-ethyl]-1,3-diaminopropane) with anticalmodulin activity. The crystals diffract beyond 2.8 Å and differ in unit cell parameters from each other as well as from crystals of Ca2+-calmodulin or Ca2+-calmodulin-ligand complexes, as reported thus far. Attempts to crystallize Ca2+-free calmodulin without drugs failed, in consonance with earlier results; however, single Ca2+-free calmodulin crystals diffracting beyond 2.5 Å resolution were grown in the presence of KAR-2. Results indicate that binding of the two drugs to apocalmodulin or Ca2+-calmodulin may induce unique novel protein conformers, targets of further detailed X-ray studies. © 1997 Wiley-Liss Inc.
    Additional Material: 1 Tab.
    Type of Medium: Electronic Resource
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
Close ⊗
This website uses cookies and the analysis tool Matomo. More information can be found here...