rhodopsin

History and Etymology for rhodopsin

borrowed from German Rhodopsin, from rhod- rhod- + Greek ópsis "appearance, sight, vision" + German -in -in entry 1 — more at optic entry 1

Note: Term introduced by the German physiologist Wilhelm Kühne (1837-1900) and his assistant August Ewald (1849-1924) in "Untersuchungen über den Sehpurpur," Untersuchungen aus dem Physiologischen Institute der Universität Heidelberg, 1. Band (1878), p. 181: "Was den Sehpurpur im Dunkel ändert, pflegt es z. Th. in derselben Weise zu thun, wie das Licht, d.h. erst eine gelbe Materie, dann farblose Substanz hervorzubringen. Der Kürze wegen und um dem Auslande unsere Bezeichnungen zugänglich zu machen, kann man sagen, Rhodopsin werde erst in Xanthopsin, dieses in Leukopsin zersetzt." ("Those things [i.e., reagents] that convert visual purple in darkness in part act in the same manner as light, that is, they first produce a yellow material, then a colorless substance. For the sake of brevity, and in order to make our designations more accessible to foreigners, we can say that rhodopsin is first broken down into xanthopsin ['visual yellow'], and this into leucopsin ['visual white'].") Kühne's selection of the combining element rhod-, usually meaning "red," is somewhat idiosyncratic, given that he is rendering German Sehpurpur ("visual purple") and not Sehrot ("visual red").