Zeaxanthin分子集合体の分光学的挙動とその形態

Lutein, one of the xanthophylls, can be dispersed in various aqueous solutions, for example, protein solution, dilute acetone solution, dilute sodium dodecyl sulfate (SDS) solution, dodecyl trimethylammonium bromide solution, hen egg yolk phosphatidyl-choline (PC) liposome, or digalactosyldiglyceride liposome, to from chiral helical aggregates which acquire an optical activity in the visible region, and have a left handed helical structure. In this report, zeaxanthin, a structural isomer of lutein, was subjected to investigation as to whether zeaxanthin formed the chiral helical aggregate. When zeaxanthin was dispersed in SDS solution, some differences from lutein were obserbed. (1) CD spectrum of positive Cotten effect was shown, which was the reverse of lutein. (2) SDS concentration giving the reversion of the CD spectrum pattern was higher (3.5mM) than that of lutein (0.6mM). IN spite of these differences, however, the results showed that zeaxanthin molecules also associated to from molecular aggregate in such a manner performing π*-π*interaction at conjjugated polyene sites. zeaxanthin dispersed in PC liposome gave both left and right-handed helical structure under presence of Ca2+ at alkaline condition in comparison with lutein's left-handed structure. This result may depend on the fact that synthesized racemic zeaxanthin is subjected to this experiment. Those results gave the general conclusion that xanthophylls had the same basic types of behavior for making molecular aggregate in aqueous dispersion.