Studies on rhodopsin. 8. Retinylidenemethylamine, an indicator yellow analogue

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Abstract
A crystalline compound showing the spectroscopic characteristics of indicator yellow was prepared from retinene and methyiamine. Analytical results showed this to be a Schiff''s base, to which the trivial name of retinylidenemethylamine has been given. (The C19H27CH=radical has been named retinylidene -this nomenclature is discussed.) The spectroscopic properties and antimony trichloride color reactions of retinene oxime are reported, and confirm the Schiff''s base structure of the indicator yellow analogue. Corresponding Schiff''s bases have been prepared in solution from methyiamine and other aldehydes and show similar shifts of [lambda] maximum in acid. Retinylidene-methylamine reacted with methyl iodide to give retinylidene-dimethylammonium iodide, which has [lambda] maximum (chloroform) 485/z. Results show that the bathochromic shift of retinylidenemethylamine in acid is due to the formation of a retinylidene-ammonium salt. Indicatory yellow derived directly from rhodopsin is therefore N-retinylidene-opsin and "acid indicator yellow" the corresponding ammonium salt. Unusual chromo-gens were produced from retinylidenamino compounds by the action of antimony trichloride and concentrated H2SO4. Their resemblance to the rhodopsin chromophore is discussed.