| Budget Amount *help |
¥1,900,000 (Direct Cost: ¥1,900,000)
Fiscal Year 1995: ¥500,000 (Direct Cost: ¥500,000)
Fiscal Year 1994: ¥1,400,000 (Direct Cost: ¥1,400,000)
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| Research Abstract |
This project was planned for aiming to estimate thermodynamic stabillity of a membrane protein, OmpA solubilized in a binary surfactant mixed system composed of an ionic surfactant, sodium dodecyl sulfate (SDS) and a nonionic one, octylglucoside. We have so far investigated various solution properties of OmpA in the mixed surfactant system with various compositions by means of a multiple detection system involving low-angle light scattering measurement combined with size exclusion chromatography. We have thus measured the change of molar mass and specific refractive index increment of the membrane protein with composition of the mixed surfactant system. According to those measurements, we could show that OmpA denatured in the presence of SDS restores its non-denatured structure via two cooperative transitions, and are going to analyze the results in terms of interaction between the protein and the surfactants. We believe that the structural change of the membrane protein must be interpreted according to conventional formulation of solvent denaturation. In this fiscal year, hence, we investigated the conformational change of a soluble protein, bovine pancreatic ribonuclease A,in this binary surfactant system to find that the denaturation and renaturation can be well described nominally according to the conventional formulation of solvent denaturation of proteins. The resulted stability was however significantly smaller than that estimated obtained via urea denaturation, and the mode of binding of surfactants was evidently different from the model. This shows another formulation should be necessary to interpret the denaturation of a protein by the surfactant. Those interactions between proteins and surfactants must be clarified in order to evaluate the stability of the membrane protein properly, and therefore it is significant to accumulate knowledge about the behavior of soluble proteins in the mixed surfactant system in parallel with membrane proteins.
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