Low-temperature spectrophotometry
نویسندگان
چکیده
Photoreactions of the fourth rhodopsin-like pigment, phoborhodopsin (pR480), of Hulobacrerium halobium were studied by low-temperature spectrophotometry. Upon irradiation of pR480 at -80 as well as 170°C with 436 nm light, a new intermediate having a difference absorption maximum at about 520 nm was produced. We designate this intermediate ‘P520’. Prolonged irradiation caused the formation of a photosteady-state mixture composed of P520 and pR480, indicating that P520 was photoreversible to pR480 at 80°C. P520 was thermally converted back to pR480 through P350 and P530, both of which were detected previously [(1986) Biochem. Biophys. Res. Commun. 139, 389-3951. Based on these results. a new photochemical reaction cycle of pR is presented.
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