Alloxazine, structure

Allene, perfluoro-, cycloaddition to phenylsydnone, 59, 12 Allene, phenylsulfinyl-, cycloaddition of nitrile oxides, 60, 276 Alloxan, structure, 55, 133 Alloxazines, synthesis, 55, 186 Allyl alcohols, ethers, chiral,... 

Using surfactant chromophores, trans-bilayer electron transfer can also be observed, although in the absence of a mediator, the chromophore must be embedded in both surfaces of the bilayer structure. Thus, MV " in the bulk aqueous phase can be reduced by EDTA or sodium ascorbate in the inner water pools if they are separated by a bilayer consisting of 5,10,15-tris(l-methyl-pyridine)-4-yl-20-(4-stearoxyphenyl)porphinatozinc colyophilized with dipalmitoyl-L-phos-phatidylcholine (DPPC). l imilar results are obtained using surfactant derivatives of [Ru(bipy)3] and increased rates of formation are observed if mediators such as hexadecyl-viologen, 2-methyl-1,4-naphthoquinone (vitamin didodecyl- or dibutyl-alloxazine... 

This structure is quite analogous to that of the pyrimidine nucleotide anhydrides mentioned above. FAD, which also contains a pyrophosphate bond, is converted by alkali into an alloxazine mononucleotide with doubly esterified phosphate at carbons 4 and 5 of the ribityl moiety. 

Structure of the Flavins.— When riboflavin is irradiated in alcohol, a sugar, D-ribose, is split off, leaving a crystallisable residue, lumi-chrome. Alkaline hydrolysis of lumichrome yields urea and a dimethyl benzpyrazine, which suggests the presence of three rings in the original flavin, one of which has yielded the urea. This has led to the w-alloxazine formula now adopted for the lyoehromes, according to which lumichrome is the 6 7-dimethyl derivative. 

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