Association of DNA with Multivalent Organic Counterions: From Flowers to Rods and Toroids

Abstract

In this study, complexes of DNA with different organic di- and tetravalent counterions were systematically investigated in solution and on a surface. The complexation behavior was studied by dynamic light scattering, static light scattering, atomic force microscopy, analytical ultracentrifugation, and UV-vis spectroscopy. Results show that both divalent and tetravalent counterions can induce the formation of DNA complexes. Divalent counterions cause aggregation only at high counterion excess, with charge ratios of 50:1 for supercoiled DNA and 200:1 for linear DNA, while for different tetravalent counterions aggregation is already observed for charge ratios of about 1:1. Flower-like aggregates are observed with divalent counterions. For a tetravalent perylene based counterion, a transition from flower-like aggregates at low charge ratios to toroids and rods at high charge ratios is observed. A transition regime for intermediate charge ratios is found. The influence of concentration, added salt, and preparation method is also discussed. It is concluded that it is the interplay of electrostatics and component architectures that directs the structure formation.

Fluorescent Nanoparticles through Self‐Assembly of Linear Ionenes and Pyrenetetrasulfonate

“…The findings extend other recent results that showed that aggregates of defined size and shape can be obtained when polyelectrolytes with special architectures are used, [54][55][56][57][58][59][60] while this was not the case for more flexible systems with more conformational freedom. [42][43][44][45][46][47][48][49] The present study showed that linear polyelectrolytes with multivalent aromatic counterions can also lead to assemblies of a defined size, but only in certain cases when the polyelectrolyte chain provides certain constraints.…”

“…Recently we could show that this can be achieved using polyelectrolytes of certain architectures in combination with stiff, multivalent, organic counterions. [54][55][56][57][58][59][60] It was found that in this type of ''electrostatic self-assembly'' the interplay of electrostatic interaction between counterion and macroion and additional mutual secondary interaction of the counterions, in particular ''p-p-stacking,'' can yield welldefined nanoassemblies in solution. Association of poly-(amidoamine) (PAMAM) dendrimers with the two isomeric naphthalene dicarboxylic acids resulted in cylindrical and spherical aggregates.…”

Isothermal titration calorimetry study of the polyelectrolyte complexation of xanthan and chitosan samples of different degree of polymerization

“…3,4 For stiff polymers, with DNA being the most widely used example, the polyelectrolyte complexes formed upon combination with multivalent ions (such as cobalt hexamine, polyethylenimine and polylysine) or lipids have characteristic shapes such as toroids and rods. [5][6][7][8][9] However, adoption of such well-defined structural geometries associated with complexation appears to be prominent only at low polymer concentrations and certain polymer pairs. Theoretical studies and numerical simulations also show that the formation of well-defined structures is not restricted to DNA, but depends on the chain stiffness of the polyelectrolyte as well as the intersegment attraction.…”

Evaluation and Elucidation of DNA‐Containing Viologen Dendrimer Complex Formation

“…[23] It is known that a high excess of counter ion (-/+ ratio: 0.002) caused by small methylviologens induces the formation of flower-like aggregates. [38] Dendriplexes with -/+ in the range of 0.05 to 20 can be seen in Figure 7 and Figure 8 (b, c). The dimensions of the primary complexes on gold can be determined from Figure 8 (b): length 98.5-136 nm, width 68-91 nm, and height 20-21 nm.…”