Poly (dipeptamidines) are polypeptide derivatives in which the carbonyl oxygen of each second backbone amide group is replaced by an imine nitrogen (see A). So far, such derivatives have been unknown. Polyprotonated salts of them (= poly (dipeptamidinium) salts) are of interest in view of their intrinsic constitutional relationship to the structure of polynucleotides: the number of covalent bonds between neighboring centers of positive ...