Structure and solubilization behaviors of micellar aggregates composed of peptide-based amphiphiles

Two amphiphilic polypeptides, poly(gamma-methyl L-glutamate)-block-poly(eth ylene glycol), PMLG-PEG, and poly(gamma-benzyl L-glutamate)-block-poly(ethy lene glycol), PBLG-PEG, were prepared and their aggregation structures and solubilization behavior were investigated. These amphiphilic polypeptides w ere soluble in water to form spherical aggregates in which the hydrophobic alpha-helical peptide tails were orderly packed in the hexagonal manner. Th e solubilization of 1-naphthol into these aggregates was characterized by t he semiequilibrium dialysis (SED) method. Values of the solubilization equi librium constant (K) decrease as the mole fraction of I-naphthol in the agg regate (X) increases. The solubilization isotherm of PBLG-PEG-1-naphthol sy stem is higher than that of PMLG-PEG-1-naphthol system. That is, the aromat ic-aromatic interaction in the former system may enhance the solubilization affinity between the aggregate and solute. It is shown, therefore, that th e interaction between peptide side chains and solutes is the effective fact or to control the solubilization behavior of micellar aggregates composed o f peptide-based amphiphiles.