Dendrimer Folding in Aqueous Media: An Example of Solvent-Mediated Chirality Switching

摘要

Allosteric proteins exhibit highly nonlinear responses to external stimuli that cause small perturbations of a particular parameter to effect very large changes in protein structure and function. This behavior is a direct consequence of the structural cooperativity that correlates the conformational equilibria of multiple subunits within the protein structure. Such allosteric phenomena are commonly observed in biomacromolecules and are critical for their function. There are relatively few synthetic materials, however, that exhibit this conformational cooperativity. The creation of such conformational adaptability in synthetic systems requires the allosteric transmission of local structural or chiral information to the next hierarchical level of structural organization. We have recently developed a dendrimeric system that adopts a compact, helical shape governed by the syn,syn conformational preference of the pyridine-2,6-dicarboxamide repeat unit. We report herein that water-soluble versions of these dendrons fold in water. Furthermore, the terminal pentaethylene glycol chains and the dendron secondary structure exhibit highly correlated conformational equilibria. Accordingly, solvent-induced conformational fluctuations of the terminal pentaethylene glycol chains are correlated with an inversion in the sense of helical chirality expressed by the dendrons.