Analysis of cationic comb-type copolymers/DNA interaction by the single molecular observation and intermolecular force measurement.

We have reported that poly(L-lysine)-graft-dextran (PLL-g-Dex) accelerates DNA hybridization and increases stability of a double stranded DNA (dsDNA). Furthermore, PLL-g-Dex was found to stimulate the DNA strand exchange reaction between dsDNA and its complementary single stranded DNA (ssDNA). In order to better understand these phenomena, we evaluate PLL-g-Dex/DNA interaction by the single molecular observation and intermolecular force measurement at single molecular level. We have been able to observe PLL-g-Dex/DNA complex at single molecular level. PLL-g-Dex was found to increases the dissociation force of a dsDNA.