CHARGE-INDUCED CHROMATIC TRANSITION OF AMINO ACID-DERIVATIZED POLYDIACETYLENE LIPOSOMES

Polydiacetylene liposomes have useful potential in biosensor research. To investigate the role of the headgroup in the colorimetric transiti on, a series of amino acid-derivatized 10,12-pentacosadyanoic acid lip ids have been synthesized. The UV-polymerized liposomes undergo an irr eversible color change from blue to red in response to a change of spe cific solution pH. In this system, the color change appears to be due to charge-induced headgroup rearrangement which perturbs the conjugate d backbone assembly. Considering the reduced degree of freedom for lip id molecules in polymeric liposomes, a rigid, staggered conformational change in polydiacetylene conjugation is suggested as a likely mechan ism for the colorimetric transition.