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RESEARCH PRODUCT

Complex Formation of DNA with Oppositely Charged Polyelectrolytes of Different Chain Topology:  Cylindrical Brushes and Dendrimers

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The complex formation between DNA (pUC19-supercoiled DNA, 2686 base pairs) and some polycations of different chain topologies in aqueous solution was studied by light scattering, gel electrophoresis, and AFM. The investigated polycations comprised cylindrical brush polymers with quaternized poly(vinylpyridine) and polyethylene imine side chains as well as a fifth generation dendrimer thus covering a broad molar mass regime of 3 × 104 g mol-1 < Mw < 1 × 107 g mol-1 and very different chemical charges/molecule, Z+, of 127 < Z+ < 5500. Irrespective of the polycation, the complexes formed in dilute solution exhibited a similar size in terms of the mean square radius of gyration, 〈Rg2〉, i.e., 30 nm < Rg < 40 nm (excess of DNA) and 40 nm < Rg < 55 nm (excess of polycation). At a large excess of either DNA or polycation, the complexes were shown to coexist with the uncomplexed molecules of the excess component and did not vary in size with increasing weight fraction of the minority component. Only if the number ...