Figure 3.

Chemical structures of selective histidine-rich polymers. (a) Histidylated polylysine, (b) four-branched histidine-lysine peptide with a 3-lysine core, (c) protonated and buffering subunits (Gtt-H, Stp-H, and Sph-H) incorporated into linear and branched polymers, (d) urocanic-modified chitosan, (e) cyclodextrin-containing polycation modified by two imidazole groups, (f) the imidazole ring of polyhistidine modified by methylation. The number of unmodified (X) and modified (Y, Z, X’) monomeric units in the polymer (a,d–f) are indicated.