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    Wyświetlanie 1-5 z 5
    Tytuł:
    Structural basis of negative cooperativity in transthyretin
    Autorzy:
    Neumann, Piotr
    Cody, Vivian
    Wojtczak, Andrzej
    Powiązania:
    https://bibliotekanauki.pl/articles/1044029.pdf
    Data publikacji:
    2001
    Wydawca:
    Polskie Towarzystwo Biochemiczne
    Tematy:
    negative cooperativity
    transthyretin
    Opis:
    A comparison of the AC and BD binding sites of transthyretin (TTR) was made in terms of the interatomic distances between the Cα atoms of equivalent amino acids, measured across the tetramer channel in each binding site. The comparison of the channel diameter for apo TTR from different sources revealed that in the unliganded transthyretin tetramers the distances between the A, D and H β-strands are consistently larger, while the distances between the G β-strands are smaller in one site than in the other. These differences might be described to have a 'wave' character. An analogous analysis performed for transthyretin complexes reveals that the shape of the plot is similar, although the amplitudes of the changes are smaller. The analysis leads us to a model of the changes in the binding sites caused by ligand binding. The sequence of events includes ligand binding in the first site, followed by a slight collapse of this site and concomitant opening of the second site, binding of the second molecule and collapse of the second site. The following opening of the first, already occupied site upon ligand binding in the second site is smaller because of the bridging interactions already formed by the first ligand. This explains the negative cooperativity (NC) effect observed for many ligands in transthyretin.
    Źródło:
    Acta Biochimica Polonica; 2001, 48, 4; 867-875
    0001-527X
    Pojawia się w:
    Acta Biochimica Polonica
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    Structural determinants of cooperativity in acto-myosin interactions.
    Autorzy:
    Moraczewska, Joanna
    Powiązania:
    https://bibliotekanauki.pl/articles/1043682.pdf
    Data publikacji:
    2002
    Wydawca:
    Polskie Towarzystwo Biochemiczne
    Tematy:
    cooperativity
    acto-myosin regulation
    tropomyosin
    contraction
    Opis:
    Regulation of muscle contraction is a very cooperative process. The presence of tropomyosin on the thin filament is both necessary and sufficient for cooperativity to occur. Data recently obtained with various tropomyosin isoforms and mutants help us to understand better the structural requirements in the thin filament for cooperative protein interactions. Forming an end-to-end overlap between neighboring tropomyosin molecules is not necessary for the cooperativity of the thin filament activation. When direct contacts between tropomyosin molecules are disrupted, the conformational changes in the filament are most probably transmitted cooperatively through actin subunits, although the exact nature of these changes is not known. The function of tropomyosin ends, alternatively expressed in various isoforms, is to confer specific actin affinity. Tropomyosin's affinity or actin is directly related to the size of the apparent cooperative unit defined as the number of actin subunits turned into the active state by binding of one myosin head. Inner sequences of tropomyosin, particularly actin-binding periods 3 to 5, play crucial role in myosin-induced activation of the thin filament. A plausible mechanism of tropomyosin function in this process is that inner tropomyosin regions are either specifically recognized by myosin or they define the right actin conformation required for tropomyosin movement from its blocking position.
    Źródło:
    Acta Biochimica Polonica; 2002, 49, 4; 805-812
    0001-527X
    Pojawia się w:
    Acta Biochimica Polonica
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    Analysis of ligand binding process using binding capacity concept.
    Autorzy:
    Bordbar, A
    Saadati, Z
    Sohrabi, N
    Powiązania:
    https://bibliotekanauki.pl/articles/1041509.pdf
    Data publikacji:
    2004
    Wydawca:
    Polskie Towarzystwo Biochemiczne
    Tematy:
    cooperativity
    ligand binding
    binding capacity
    stoichiometry of binding
    Opis:
    Binding capacity is the homotropic second derivative of the binding potential with respect to the chemical potential of the ligand. It provides a measure of steepness of the binding isotherm and represents the extent of cooperativity. In the present study, the shape of the binding capacity curve for various systems was investigated and the relation between binding capacity and the extent of cooperativity examined. In this regard, a novel linear graphical method was introduced for binding data analysis. The stoichiometry of binding and the extent of cooperativity can be determined by this method. This method has been successfully applied to various systems such as binding of oxygen to hemoglobin, warfarin to human serum albumin and dodecyltrimethylammonium bromide to α-amylase.
    Źródło:
    Acta Biochimica Polonica; 2004, 51, 4; 963-970
    0001-527X
    Pojawia się w:
    Acta Biochimica Polonica
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    Analysis of oxygen binding by hemoglobin on the basis of mean intrinsic thermodynamic quantities
    Autorzy:
    Bordbar, Abdol-Khalegh
    Mousavi, Sayed
    Dazhampanah, Hamid
    Powiązania:
    https://bibliotekanauki.pl/articles/1041216.pdf
    Data publikacji:
    2006
    Wydawca:
    Polskie Towarzystwo Biochemiczne
    Tematy:
    cooperativity
    mean intrinsic Gibbs free energy
    linkage phenomena
    hemoglobin
    Opis:
    The binding data for oxygenation of human hemoglobin, Hb, at various temperatures and in the absence and presence of 2,3-diphosphoglycerate, DPG, and inositol hexakis phosphate, IHP, were analyzed for extraction of mean intrinsic Gibbs free energy, ΔGo, enthalpy, ΔHo, and entropy, ΔSo, of binding at various partial oxygen pressures. This method of analysis considers all the protein species present such as dimer and tetramer forms which were not considered by Imai et al. (Imai K et al., 1970, Biochim Biophys Acta 200: 189 - 196) , in their analysis which was based on Adair equation. In this regard, the values of Hill equation parameters were estimated with high precision at all points of the binding curve and used for calculation of ΔGo, ΔHo and ΔSo were also calculated by analysis of ΔGo values at various temperatures using van't Hoff equation. The results represent the enthalpic nature of the cooperativity in Hb oxygenation and the compensation effect of intrinsic entropy. The interpretation of results also to be, into account the decrease of the binding affinity of sites for oxygen in the presence of DPG and IHP without any considerable changes in the site - site interaction (extent of cooperativity). In other words, the interactions between bound ligands, organic phosphates and oxygen, are more due to a decreasing binding affinity and not to the reduction of the cooperative interaction between sites. The results also document the more heterotropic effect of IHP compared to DPG.
    Źródło:
    Acta Biochimica Polonica; 2006, 53, 3; 563-568
    0001-527X
    Pojawia się w:
    Acta Biochimica Polonica
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    Efekt kooperatywności oddziaływań iekowalencyjnych w wybranych układach molekularnych stabilizowanych wiązaniami wodorowymi i halogenowymi
    Cooperativity effect in noncovalent interactions of selected molecular complexes stabilised by hydrogen and halogen bonds
    Autorzy:
    Domagała, Małgorzata
    Dominikowska, Justyna
    Palusiak, Marcin
    Powiązania:
    https://bibliotekanauki.pl/articles/172440.pdf
    Data publikacji:
    2019
    Wydawca:
    Polskie Towarzystwo Chemiczne
    Tematy:
    wiązanie halogenowe
    wiązanie wodorowe
    energia oddziaływania
    efekt kooperatywny
    modelowanie molekularne
    halogen bond
    hydrogen bond
    interaction energy
    cooperativity effect
    molecular modelling
    Opis:
    Among various so-called weak interactions, a halogen bond [8 and references therein] is currently probably one of more explored by researchers. This is due to the fact that it has several properties in common with the hydrogen bonding, and thus, similarly as already well characterised H-bond, it may have a crucial role in different physical, chemical, and biological processes. This bond is formed due to stabilising interactions between a region of positive charge located on a surface of the halogen atom and the other atomic center possessing the electron charge surplus (e.g. a lone pair) [8]. The region of positive charge appears on the halogen atom surface due to deformation of its electron cloud resulting in its ellipsoidal shape with the short axis opposite the covalent bond and the long axis in the perpendicular direction [11]. This results in a particular distribution of local charges on the atomic surface, as shown in Figure 1. As a consequence the halogen atom may exhibit a dual character, acting as either electron charge donor or acceptor, depending on the type of interaction and the direction of the appearing interactomic contact. A good example of such situation is shown in Figure 2. Thus, one may consider the situation when two interactions are formed simultaneously and the halogen atom acts as an electron charge donor and acceptor at the same time. For such situation the synergism of both interactions may strengthen complexation. In order to analyze that case, various representative complexes were investigated [13, 17, 18, 20, 21] by means of many-body interaction approach [5, 6]. In general, it appears that as distinct to hydrogen bond [2–4], the synergism is rather weak, with some exceptions for iodine atom due to stronger halogen bonds formed by that atomic centre [13, 17, 18]. In the case of halo-amine tetramers [21] the additional stabilising effect derived from back bonding of π type was found – for the first time for a halogen bond.
    Źródło:
    Wiadomości Chemiczne; 2019, 73, 1-2; 33-52
    0043-5104
    2300-0295
    Pojawia się w:
    Wiadomości Chemiczne
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
      Wyświetlanie 1-5 z 5

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