Kandori H, Mizukami T, Okada T, Imamoto Y, Fukada Y, Shichida Y, Yoshizawa T
Department of Biophysics, Faculty of Science, Kyoto University, Japan.
Proc Natl Acad Sci U S A. 1990 Nov;87(22):8908-12. doi: 10.1073/pnas.87.22.8908.
Measurement of the primary photochemical reaction of iodopsin, a chicken red-sensitive cone visual pigment, was carried out at room temperature by using picosecond (ps) laser photolysis. Excitation of iodopsin with a ps green pulse (pulse width, 21 ps) caused the instantaneous formation of a bathochromic product, which was stable on a ps time scale. This product may correspond to "bathoiodopsin," which was detected by low-temperature spectrophotometry. Although bathoiodopsin produced at the temperature of liquid nitrogen or helium reverted to the original pigment (iodopsin) on warming (above -170 degrees C), the bathoiodopsin produced at physiological temperature decayed to all-trans-retinal and R-photopsin (the protein moiety of iodopsin) presumably through several intermediates. The absorption maximum of bathoiodopsin at room temperature was at 625 nm, a wave-length slightly shorter than that measured at low temperature (lambda max, 640 nm). The extinction coefficient of bathoiodopsin at room temperature was lower than that at low temperature and close to that of the original iodopsin at room temperature.
利用皮秒（ps）激光光解技术在室温下对鸡的红色敏感视锥视觉色素视碘质的初级光化学反应进行了测量。用皮秒绿色脉冲（脉冲宽度为21 ps）激发视碘质会导致一种红移产物的瞬间形成，该产物在皮秒时间尺度上是稳定的。这种产物可能对应于通过低温分光光度法检测到的“视紫红质中间体”。尽管在液氮或液氦温度下产生的视紫红质中间体在升温时（高于 -170℃）会恢复为原始色素（视碘质），但在生理温度下产生的视紫红质中间体可能会通过几种中间体衰变为全反式视黄醛和R-视蛋白（视碘质的蛋白质部分）。室温下视紫红质中间体的最大吸收波长为625 nm，该波长略短于在低温下测得的波长（λmax，640 nm）。室温下视紫红质中间体的消光系数低于低温下的消光系数，且接近室温下原始视碘质的消光系数。
