Retinal

Literature References: Carotenoid component of the visual pigments. Of the 16 possible stereoisomers, 13 have been synthesized. The 11-cis isomer is the chromophore of the majority of naturally occurring opsins, q.v. Isoln from retinas: G. Wald, J. Gen. Physiol. 19, 351 (1935); recognition as vitamin A aldehyde: R. A. Morton, Nature 153, 69 (1944). Prepd by the oxidation of vitamin A: Ball et al., Biochem. J. 42, 516 (1948); by the oxidation of b-carotene: Wendler et al., J. Am. Chem. Soc. 72, 234 (1950); from b-ionone: Eiter, Truscheit, US 3060229 (1962 to Bayer); Jacobs et al., Rec. Trav. Chim. 84, 1113 (1965). Synthesis in vitro from vitamin A1: G. Wald, R. Hubbard, Proc. Natl. Acad. Sci. USA 36, 92 (1950). Synthesis of 11-cis isomer: J. M. Dieterle, C. D. Robeson, Science 120, 219 (1954). X-ray crystallography of retinals: R. Gilardi et al., Nature 232, 187 (1971); H. Matsumoto et al., J. Am. Chem. Soc. 102, 4259 (1980). Exposure of opsin-bound retinal to light initiates the cis-trans isomerization and resultant dissociation of retinal from the apoprotein. This catalyzes an enzyme cascade which leads to visual excitation: R. Hubbard, A. Kropf, Proc. Natl. Acad. Sci. USA 44, 130 (1958); B. Honig et al., ibid. 76, 2503 (1979). Bioregulation of absorption maxima: B. Honig et al., J. Am. Chem. Soc. 101, 7084 (1979). HPLC determn in biological material: T. Suzuki, M. Makino-Tasaka, Anal. Biochem. 129, 111 (1983). Review of syntheses: V. Balogh-Nair, K. Nakanishi, Methods Enzymol. 88, 496-506 (1982); R. Liu, A. Asata, ibid. 506-516. Role in vision: D. F. O'Brien, Science 218, 961-966 (1982); P. S. Zurer, Chem. Eng. News 61, 24-35 (Nov. 28, 1983). Book: The Retinoids Vol. 1-2, M. B. Sporn et al., Eds. (Academic Press, New York, 1984).