Enantioselective Binding and Stable Encapsulation of α-Amino Acids in a Helical Poly(L-glutamic acid)-Shelled Dendrimer in Aqueous Solutions

摘要

A novel water-soluble peptide-shelled dendrimer containing a poly(L-glutamic acid) segment grafted on the third-generation poly(amido amine) dendrimer was successfully synthesized, and its secondary structural properties and interaction with α-amino acids (Trp, Phe, and Tyr) were revealed by spectroscopic measurements. In the lower pH region, this peptide-dendrimer adopted an α-helix conformation with almost 100% helicity resulting from the three-dimensional aggregation of the segment. Interactions with α-amino acids proceeded with positive cooperativity on the basis of a Hill plot, and as a result, D isomers preferentially bound to the α-helical segments relative to L isomers. The bound α-amino acids were not released into the water phase but were transferred into the inner core of the dendrimer where they remained stable, even when a conformational change of the helix segment was caused by pH variation.