Chain length effects of oligo(l-lysine)-shelled dendrimers on interaction with DNA

The interaction of novel oligo(l-lysine)-shelled dendrimers (G3-PLL) with DNA was studied by means of circular dichroism spectroscopy, dynamic light scattering, and melting behavior of double-stranded DNA. G3-PLLs having various oligo(l-lysine) (PLL) segment (n = 5–40) were successfully synthesized by graft-polymerization of l-lysine NCA initiated with amino groups at the 3rd-generation poly(amidoamine) dendrimer surface. The ionization property of the newly prepared G3-PLLs were first examined. The evaluated pKa values (8.3–8.5) for G3-PLLs were found to be significantly lower than those (9.2–9.4) for the corresponding linear PLLs, probably due to alignment of PLL segments on the three-dimensional core surface. The binding experiments of G3-PLLs to DNA showed that doublestranded DNAs were fairly strongly bound to G3-PLLs primarily through electrostatic interactions. In addition, G3-PLLs served as a DNA cross-linker. A longer PLL-containing G3-PLL was found to interact with DNA more effectively than a shorter one.