Hyperbranched poly(L-lysine) modified with histidine residues via lysine terminal amino groups:: Synthesis and structure

A method for preparing hyperbranched poly(L-lysine) via the polymerization of N-epsilon-carbobenzoxy-L-lysine-N-carboxyanhydride has been developed in order to regulate the molecular mass and size of this polymer and to modify amino groups of its N-terminal lysine residues. This method includes the reductive removal of an N-epsilon-carbobenzoxy group by hydrogen over activated palladium in the presence of a chain termination agent, which is the activated ether of N-alpha-tert-butyloxycarbonylhistidine. The structure of the polymers has been studied by capillary electrophoresis, circular dichroism, and molecular hydrodynamics.