Ultraviolet-visible spectroscopy has been used to follow the solubilization of the dark-adapted purple membrane of Halobacterium halobium by Triton X-100. Turbidity of purple membrane fragments and absorbance of bacteriorhodopsin variations during continuous addition of detergent give solubilization profiles exhibiting several break points corresponding to different equilibrium stages of the solubilization process. The present method allows the determination of the detergent to protein + lipid ratio in mixed aggregates at the corresponding break points. It was concluded that, when performed systematically, this technique is a very convenient and powerful tool for the quantitative study of biomembrane-to-micelle transition.
