Isoprenoids and Bacteriorhodopsin in Halobacteria

Photocurrent kinetics of purple-membrane sheets bound to planar bilayer membranes

“…The maximum energy per flash falling onto the membrane was approximately l0 pJ, corresponding to an energy density of about 2 mJ/cm 2, or about n_ ~5.8 x 10 is quanta/cm 2 (at 575 nm). Since the absorption cross-section of bacteriorhodopsin at 575 nm is about a-~2.1 x 10 -1. cm 2, corresponding to an extinction coefficient of e--_54000 u -1 cm -1 (Oesterhelt, 1976), one has an-~l.2, meaning that at the highest light intensity used in these experiments almost every chromophore becomes excited by a single flash. In most experiments, the light intensity was reduced with grey filters to 2-20 % of the maximum value.…”

The Family Halobacteriaceae

“…Under conditions of oxygen limitation, halobacteria may form the pigment bacteriorhodopsin, which has been shown to be a key element in a system capable of converting light energy to chemical energy without the participation of chlorophyll, which is lacking in the halobacteria (Oesterhelt, 1976).…”

Photocurrents generated by bacteriorhodopsin on planar bilayer membranes

“…In the bacterial membrane bacteriorhodopsin forms two-dimensional cristalline patches which may be isolated in form of the so-called purple-membrane fragments. Considerable effort has been spent in the last years to elucidate the structure and the photochemistry of the purple membrane (for recent reviews, see Oesterhelt, 1976;Henderson, 1977). Most of the work so far has been devoted to the analysis of the photochemical reaction cycle of isolated purple membrane fragments in aqueous phase (Oesterhelt and Stoeekenius, 1973;Oesterhelt and Hess, 1973;Lewis et al, 1974;Dencher and Wilms, 1975;Kung et al, 1975;Lozier et al, 1975;Hirsch et al, 1976;Kaufmann et al, 1976;Lozier et al, 1976;Sherman et al, 1976;Becher and Ebrey, 1977;Goldschmidt et al, 1977;Marcus and Lewis, 1977;Renthal, 1977;Campion et al, 1977).…”