BISTABLE AGGREGATE OF ALL-TRANS-ASTAXANTHIN IN AN AQUEOUS-SOLUTION

The temperature dependence of the optical absorption spectra for astax anthin aggregate has been studied between 2 and 32 degrees C, Red-shif ted absorption bands as compared to the monomer absorption band are fo und above 21 degrees C in addition to the blue-shifted band of the agg regate. The spectra suggest that the molecular arrangement in the aggr egate is a bistable one consisting of head-to-tail and card-packed arr angements, A diagram describing the bistability together with the mono mer state is proposed in the space defined by the free energy and the quantity of Sigma(i=1)(N)[[theta(i)](2) + [delta theta(i)(2)]] for the angle theta(i) of the ith molecule in the N-molecule aggregate.