Biocidal activity of polystyrenes that are cationic by virtue of protonation.

[structure: see text] Poly(1) kills bacteria (Gram-positive and -negative) and lyses human erythrocytes; this biocidal profile is similar to that of the peptide toxin mellitin. Poly(1) has antibacterial activity comparable to that of a potent derivative of the host defense peptide magainin II, but lacks magainin's selectivity for bacteria over erythrocytes. An analogous N-quaternized polymer, poly(3), is less biocidal than poly(1), suggesting that reversible N-protonation leads to greater biocidal activity than does irreversible N-quaternization.