Molecular structure of agarose chains in thermoreversible hydrogels revealed by means of a fluorescent probe technique

Thermoreversible hydrogels of agarose with both high and low molecular weights were studied by means of a fluorescence probe method using 1-anilino-8-naphthalene sulfonic acid (ANS). The fluorescence spectra of ANS in agarose/water changed markedly with agarose concentration. Analysis of the spectra shows that this change is not due to a shift of the whole spectrum, but that there are two fluorescent components of ANS in addition to the fluorescence peak at 542 nm due to free ANS molecules in water. The fluorescence component at 461 nm is assumed to be from ANS intercalated within either a single 31 helix-form agarose chain or nonpolar region produced by chemical defect, and the fluorescence component between 507 and 522 nm is assumed to be from ANS in aggregated regions of agarose chains having a loose helical structure. There is no doubt that a certain number of water molecules are included in the aggregated region. (C) 2005 Wiley Periodicals, Inc.