Abstract
The change in protein conformational structure and retinal chromophore binding state have been examined by using in situ UV−vis, FTIR, and CD spectroscopies during the thermal denaturation and refolding processes in bacteriorhodopsin (bR) of purple membrane (PM), in its native trimeric and in Triton X-100 solubilized monomeric form. For the trimeric bR, it is found that heating bR through its premelting transition (T > 78 °C, Tm‘) does not cause any permanent damage in the protein secondary structure, and a reversible refolding occurs when it cools back to room temperature. For the monomeric bR, it is found that it is less thermally stable than the trimer. There is a significant change in its protein secondary structure and a complete dissociation of retinal occurs irreversibly at a temperature as low as 66 °C. In addition, it is found that heating the trimeric bR through its main molten state (T > 96 °C, Tm) changes the protein secondary structure so that bR does not refold fully into its original second...
Published Version
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