title: Photoselection and aggregation in purple membrane of Halobacterium halobium.
abstract: Preparations of the purple membrane of Halobacterium halobium suspended in dilute buffer and basal salt have been examined by circular dichroism spectroscopy and correlation analysis of scattered laser light. Dark adapted samples suspended in basal salt show photoselection when examined by circular dichroism. This was confirmed by irradiation with plane polarized light. Light-adapted samples or dark-adapted samples suspended in dilute buffer did not show this phenomenon. The reaction responsible for photoselection was shown to be the light induced cis-trans isomerization of bacteriorhodopsin. The stability of the induced anisotropy was due to aggregation in the basal salt suspensions which occurred despite little or no visual indication. This aggregation was confirmed by correlation analysis of scattered laser light.
mesh_terms: D001436:Bacteriorhodopsins; D002338:Carotenoids; D002942:Circular Dichroism; D003623:Dark Adaptation; D006217:Halobacterium / Q000648:ultrastructure; D007834:Lasers; D009904:Optical Rotation; D012542:Scattering, Radiation; D012995:Solubility
chemical_list: D002338:Carotenoids; D001436:Bacteriorhodopsins