Figure 7.

Stability of polymer:DNA complexes at pH 6.5 and 4.5. The amount of HK or HHK4b associated with DNA-bound beads was measured after 30 min of incubation at pH 6.5 and 4.5. The greater association numbers correlate with reduced release of the polymer from the DNA. The polymers were labeled with flurorescein and the amount of bound polymer was measured with a flurorescent microplate reader (485 nm excitation/530 nm emission). The graph indicates that the branched polymers bind DNA with substantially higher affinity at low pH than linear polymers. *P < 0.01, HHK4b (pH 4.5) versus HHK4b (pH 6.5) or HK (pH 6.5, 4.5).