Murray State University

Poster Title

Cooperative Interactions in the Laser-Induced Purple-to-Blue Transition of Bacterial Purple Membranes: Implications for Degenerative Diseases of the Retina

Institution

Murray State University

Abstract

Epidemiological evidence suggests that age-related macular degeneration (AMD), the leading cause of blindness in the elderly, is caused in part by toxic free radicals generated when the visual pigment rhodopsin absorbs light. Characterizing these free radicals has proved difficult because of the difficulty of obtaining large quantities of rhodopsin, and because of its photolability under laboratory conditions. Hence the use of model visual pigments in free radical studies is highly desirable. We are characterizing the laser-induced purple to blue color change of the model visual pigment bacteriorhodopsin (BR), which imparts the purple color to halobacterial purple membrane (PM). BR - which is a close structural relative of rhodopsin - is both readily available and photostable. PM - which consists of a tightly packed lattice of BR molecules - converts to “laser-induced blue membrane” (LIBM) upon exposure to green laser pulses. Our studies to date indicate that the generation of LIBM is photocooperative (i.e., that photodamaged BR molecules facilitate the photodamage of other BR molecules in their immediate vicinity). In this poster, we describe results from recent experiments designed to test this “PM-to-LIBM photocooperativity” hypothesis. Because the PM to LIBM photoconversion appears to be mediated by free radicals, these studies may provide new insights regarding the origin and treatment of AMD.

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Cooperative Interactions in the Laser-Induced Purple-to-Blue Transition of Bacterial Purple Membranes: Implications for Degenerative Diseases of the Retina

Epidemiological evidence suggests that age-related macular degeneration (AMD), the leading cause of blindness in the elderly, is caused in part by toxic free radicals generated when the visual pigment rhodopsin absorbs light. Characterizing these free radicals has proved difficult because of the difficulty of obtaining large quantities of rhodopsin, and because of its photolability under laboratory conditions. Hence the use of model visual pigments in free radical studies is highly desirable. We are characterizing the laser-induced purple to blue color change of the model visual pigment bacteriorhodopsin (BR), which imparts the purple color to halobacterial purple membrane (PM). BR - which is a close structural relative of rhodopsin - is both readily available and photostable. PM - which consists of a tightly packed lattice of BR molecules - converts to “laser-induced blue membrane” (LIBM) upon exposure to green laser pulses. Our studies to date indicate that the generation of LIBM is photocooperative (i.e., that photodamaged BR molecules facilitate the photodamage of other BR molecules in their immediate vicinity). In this poster, we describe results from recent experiments designed to test this “PM-to-LIBM photocooperativity” hypothesis. Because the PM to LIBM photoconversion appears to be mediated by free radicals, these studies may provide new insights regarding the origin and treatment of AMD.