Reversibility and Hierarchy of Thermal Transition of Hen Egg-White Lysozyme Studied by Small-Angle X-Ray Scattering

摘要: To clarify mechanisms of folding and unfolding proteins, many studies thermal denaturation proteins have been carried out at low protein concentrations because in cases accompanies a great tendency aggregation. As small-angle x-ray scattering (SAXS) measurements are liable to use low-concentration solutions avoid aggregation, SAXS has regarded as very difficult observe detailed features structural transitions such intramolecular changes. By using synchrotron radiation SAXS, we found that the presence repulsive interparticle interaction between can maintain solute particles separately prevent further aggregation processes under conditions transition hen egg-white lysozyme (HEWL) holds high reversibility even 5% w/v HEWL below pH approximately 5. Because concentration solutions, data enough high-statistical accuracy discuss depending on hierarchy. Thus, tertiary change starts from mostly onset temperature determined by differential scanning calorimetry measurement, which large heat absorption, whereas change, corresponding interdomain correlation polypeptide chain arrangement, much prior above main transition. The present finding reversible is expected enable us analyze multiplicity transitions.