| Abstract
| - In this paper, we report on the original global fit procedure of synchrotron small-angle X-ray scattering (SAXS)data applied to a model protein, met-myoglobin, in dilute solution during temperature- and pressure-induceddenaturation processes at pH 4.5. Starting from the thermodynamic description of the protein unfolding pathwaydeveloped by Hawley (Hawley, S. A. Biochemistry1971, 10, 2436), we have developed a new method foranalyzing the set of SAXS curves using a global fitting procedure, which allows us to derive the form factorof all the met-myoglobin species present in the solution, their aggregation state, and the set of thermodynamicparameters, with their p and T dependence. This method also overcomes a reasonably poor quality of theexperimental data, and it is found to be very powerful in analyzing SAXS data. SAXS experiments wereperformed at four different temperatures from hydrostatic pressures up to about 2000 bar. As a result, thepresence of an intermediate, partially unfolded, dimeric state of met-myoglobin that forms during denaturationhas been evidenced. The obtained parameters were then used to derive the met-myoglobin p, T phase diagramthat fully agrees with the corresponding phase diagram obtained by spectroscopic measurements.
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