Purified rhodopsin was incorporated into phospholipid bilayers of egg phosphatidylcholine to give recombinant membrane vesicles, which were examined by proton and phosphorus nuclear magnetic resonance spectroscopy. Increased rhodopsin content in the membranes appears to progressively inhibit the molecular motions of the methyl, methylene, and phosphate groups of the phospholipid molecules. This indicates that regions of the rhodopsin molecule interact in a manner that affects the phospholipids from the aqueous interface to the bilayer midline. In the dark, the recombinant vesicles were sealed to europium, manganese, or cobalt ions. Light exposure allowed rapid equilibration of Mn2+ and Co2+, and somewhat slower equilibration of Eu3+ across the membrane. Light changed the membrane permeability, and the gradient in chemica tential resulted in a net ion movement across the rhodopsin:phospholipid recombinant membrane. The results suggest rhodopsin is a transmembrane protein.

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The successful syntheses and characterizations of the novel bicyclic C-P heterocycles 1,1,5,5,8-pentamethylphosphalilolidine (3) and 1,1,6,6,8-pentamethylphosphajulolidine (4) are described. Cyclization of 1-(methyl-p-tolylphosphinoyl)-3-methylbutan-2-01(7) by using polyphoephoric acid at 120 "C produced an inseparable, isomeric mixture (83% yield) of 1,4,4,7-and 1,4,4,6-tetramethylphosphinoline oxides (8 and 9) in ratio of ca. 3:l. This isomerization is rationalized by a mechanism which involves the cationic ipso cyclization followed by migration of the phosphinoyl group. Cyclic voltammetric and UV spectroscopic data suggest that both phosphajulolidine and phosphalilolidine have essentially no n-?r interaction between the lone-pair electrons on the phosphorus and the adjacent aromatic ?r system. (8) Tsvetkov, E. N. J. Gen. Chem. USSR (Engl. Transl.) 1976,45,489. (9) The systematic nomenclature names for phoephalilolidine A (n = 2, m = 3) and phosphajulolidine A (n = m = 3) would be phospholano [3,2,1-ij]tetrahydrophosphinoline and phmphorinano[3,2,1-i~']tetrahydrophoephinoline, respectively. (For reference, see: Mann, F. G. "The Heterocyclic Derivatives of Phosphorus, Arsenic, Antimony, and Bismuth", 2nd ed.; Wiley-Interscience: New York, 1970; p 124.) We feel to name them as nitrogen analogues of lilolidine (Almond, C. Y.; Mann, F. G.

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Kinetics and Mechanism of Chelation of Nickel(II) by a Tridentate a-[(2-Hydroxyphenyl)azo]-a-acetoacetonitrile and an a-(8-Quinolylazo)-a-acetoacetonitrile Dye