The endothermic effects during denaturation of lysozyme by temperature modulated calorimetry and an intermediate reaction equilibrium (Articolo in rivista)

Type
Label
  • The endothermic effects during denaturation of lysozyme by temperature modulated calorimetry and an intermediate reaction equilibrium (Articolo in rivista) (literal)
Anno
  • 2002-01-01T00:00:00+01:00 (literal)
Alternative label
  • Salvetti G. (1), Tombari E. (1), Mikheeva L. (2), Johari G.P.(3) (2002)
    The endothermic effects during denaturation of lysozyme by temperature modulated calorimetry and an intermediate reaction equilibrium
    (literal)
Http://www.cnr.it/ontology/cnr/pubblicazioni.owl#autori
  • Salvetti G. (1), Tombari E. (1), Mikheeva L. (2), Johari G.P.(3) (literal)
Pagina inizio
  • 6081 (literal)
Pagina fine
  • 6087 (literal)
Http://www.cnr.it/ontology/cnr/pubblicazioni.owl#numeroVolume
  • 106 (literal)
Http://www.cnr.it/ontology/cnr/pubblicazioni.owl#descrizioneSinteticaDelProdotto
  • Studio mediante calorimetria a scansione e modulata del processo di Folding-unfolding di una proteina modello (Lisozima). (literal)
Note
  • ISI Web of Science (WOS) (literal)
Http://www.cnr.it/ontology/cnr/pubblicazioni.owl#affiliazioni
  • (1) IPCF-CNR, via G. Moruzzi 1 56124 Pisa; (2) Russian Academy of Sciences, Moscow, Russia ; (3) McMaster Univ, Dept Mat Sci & Engn, Hamilton, ON L8S 4L7, Canada (literal)
Titolo
  • The endothermic effects during denaturation of lysozyme by temperature modulated calorimetry and an intermediate reaction equilibrium (literal)
Abstract
  • To gain insight into the thermodynamics of protein denaturation, the complex heat capacity, C-p* (= C-p' - iC(p)\") of lysozyme-water system has been measured at pH 2.5 in the 293-368 K range by using temperature-modulated scanning calorimetry (TMSC), a technique in which the thermally reversible enthalpy changes are measured separately and simultaneously with the thermally irreversible enthalpy changes. The plot of C-p' against the temperature T shows a broad peak, which is similar to that observed in C-p.DSC, measured here and elsewhere by differential scanning calorimetry (DSC), a technique which gives the sum of both the reversible and irreversible contributions in the apparent heat capacity value. This peak in C-p.DSC has been generally attributed to endothermic heat absorption on reversible and irreversible unfolding processes and irreversible thermal denaturation. It is shown that the observed C-p' peak results from heat absorption when the equilibrium constant between the native lysozyme state and a conformationally different intermediate state increases with T. The plot of C-p' versus T is subdivided into four regions, corresponding to the dominance of a certain process. Thermal denaturation of lysozyme was found to occur according to a scheme, native state - unfolded (intermediate) state - denatured state. This conclusion is consistent with the general view that the first step of denaturation of small one-domain globular protein like lysozyme is a reversible conformational (unfolding) transition, and the second step is irreversible denaturation. It is shown that when kept isothermally at T > 341 K, i.e., within the transition temperature range, C-p' of lysozyme decreases. This decrease is exponential in time and corresponds to a rate constant, which varies according to the Arrhenius-type equation, with a preexponential factor of 5 x 10(20) s(-1) and energy of 167 kJ/mol. The overall kinetics of the denaturation reaction is of the first order. (literal)
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