THERMAL TRANSITIONS IN THE PURPLE MEMBRANE FROM HALOBACTERIUM-HALOBIUM

The application of a successive annealing procedure to the scanning ca lorimetric endotherm of the purple membrane from Halobacterium halobiu m in phosphate buffer, pH 7.5, leads to five thermal transitions benea th the overall endotherm. Circular dichroism and fluorescence experime nts have also been carried out with the native membrane heated at the same scan rate as in calorimetric runs (1-degrees-C/min) as well as wi th previously heated membrane samples. These results, together with ot hers from the literature, have been used to suggest a preliminary expl anation of the five thermal transitions.