Alpern M, Fulton A B, Baker B N
Vision Research Laboratory, W.K. Kellogg Eye Center, University of Michigan, Ann Arbor 48105.
Vision Res. 1987;27(9):1459-70. doi: 10.1016/0042-6989(87)90155-6.
Microspectrophotometry (MSP) shows rhodopsin highly concentrated (about 3.0 mmol/l) in rod outer segments (ROS). Calculation of the in vivo absorption spectrum of human rhodopsin from such data reveals a striking failure to agree with the action spectrum of human rod vision. Agreement is good between the spectral distribution of absorption coefficients and the action spectrum, but the "concentration-broadening" (or "self-screening") introduced by the high end on absorbance at this concentration results in a misfit among the largest in the 93 years comparisons of this kind have been made! To deal with this anomaly, it has been suggested that "concentration-broadening" is inappropriate for rhodopsin in rod vision. This proposal was tested by comparing rod action spectra of 15-day-old and adult rats, since the lengths of ROS increase by a factor of about two in maturation. Three lines of evidence are inconsistent with it. Although the conundrum remains unexplained, it cannot be dismissed by supposing "self-screening" inappropriate for night vision.
显微分光光度测定法（MSP）显示，视紫红质在视杆细胞外段（ROS）中高度浓缩（约3.0 mmol/l）。根据这些数据计算出的人类视紫红质的体内吸收光谱，结果令人惊讶地与人类视杆细胞视觉的作用光谱不一致。吸收系数的光谱分布与作用光谱之间吻合良好，但在该浓度下吸光度的高端所引入的“浓度展宽”（或“自屏蔽”）导致了这种93年来同类比较中最大的不匹配！为了解决这一异常现象，有人提出“浓度展宽”不适用于视杆细胞视觉中的视紫红质。通过比较15日龄和成年大鼠的视杆细胞作用光谱对这一假设进行了检验，因为在成熟过程中视杆细胞外段的长度增加了约两倍。有三条证据与该假设不一致。尽管这个难题仍然无法解释，但不能通过假定“自屏蔽”不适用于夜间视觉来将其忽略。
