Interaction of Astramol Poly(propyleneimine) Dendrimers with DNA and Poly(methacrylate) Anion in Water and Water–Salt Solutions

Interaction of poly­(propyleneimine) dendrimers DAB-<i>dendr-</i>(NH₂)_<i>x</i> of five generations (<i>x</i> = 4, 8, 16, 32, and 64) with either calf thymus DNA or tagged by pyrenyl groups poly­(methacrylate) anion (PMA*) as well as destruction of formed polyelectrolyte complexes by the added sodium chloride were studied by fluorescence quenching techniques. DNA-containing complexes (dendriplexes) were investigated by ethidium bromide assay, whereas formation of PMA* complexes was estimated by fluorescence of the pyrenyl groups that remained free of contact with the dendrimers-quenchers. The ion pairing with DNA phosphate groups was pH-sensitive and accompanied by inaccessibility of a part of the dendrimer amino groups even in slightly acidic media. The growth of the generation number resulted in successive stabilization of the dendriplexes against the added salt. The dendriplexes of all dendrimers except DAB-<i>dendr-</i>(NH₂)₄ were stable at physiological ionic strength. In contrast to the highly charged cationic polymer poly­(<i>N</i>-ethyl-4-vinylpyridinium) bromide of different degrees of polymerization, the dendrimers formed more stable complexes with flexible PMA* rather than with DNA, proving the inaccessibility of a part of the amino groups for the rigid double helix. The revealed regularities appear to be a platform for design of dendriplexes with controllable stability, in particular fulfilling the requirements imposed for gene delivery vehicles

Interaction of polyelectrolytes with proteins, 3 Influence of complexing polycations on the thermoaggregation of oligomeric enzymes

The ability of quaternized polyamines (poly-N-alkyl-4-vinylpyridinium bromides possessing a number, m, of methylene groups in the N-alkyl substituent or a degree of alkylation, beta, and n,n-ionene bromides) to suppress the thermoaggregation of glyceraldehyde-3-phosphate dehydrogenase increased in the order m = 1 < 3 < 5, beta = 95 < 85 < 70 << 45 < 35 < 20 and n = 3 < 6 < 10, which agrees well with the increase, in the same order, in the hydrophobicity of the chains. Complexing suppressed thermoaggregation, but not thermodenaturation of the enzyme, which was even encouraged by the polycations and occurred at room temperature when the most efficient suppressor (with beta = 20) was used. The adverse effect was reduced by the addition of sodium chloride which destroyed the complex and resulted in a noticeable reactivation

Light Scattering Study of the Antibody-Poly(methacrylic acid) and Antibody-Poly(acrylic acid) Conjugates in Aqueous Solutions

The effect of the conformational state of the polymer coil on the properties of protein-polymer conjugates has been studied for the conjugates of antibody (monoclonal antibody from 6C5 clone against inactivated rabbit muscle glyceraldehyde-3-phosphate dehydrogenase; Ab) with poly(methacrylic acid) (PMAA) or poly-(acrylic acid) (PAA). The pH-dependencies of molecular properties and structural parameters of aqueous solutions (radius of gyration, intensity of scattered light, hydrodynamic diameter, and polydisperisty index) of Ab, PMAA, and PAA, have been studied using static and dynamic light scattering techniques. While free Ab aggregates in solution and precipitates at its isoelectric point, the covalent attachment of a charged polymer to Ab prevents its association and shifts the precipitation point towards more acidic values (from pH 5.95 for Ab to pH ∼ 4.8 for Ab- PMAA). The predominant role of the conformational status of the polymer in the process of conjugate precipitation has been considered. Contrary to the precipitation of Ab-PMAA, the formation of stable colloidal particles was suggested for Ab-PAA at pH < 4.8. In the conjugates, polymer chains surround the protein globule in an extremely compact manner while Ab significantly affects the polymer conformation. The essentially larger hydrodynamic radii of conjugates, when compared with their radii of gyration, confirm the strong interaction of conjugates with solvent molecules

Supercharged Polyplexes: Full-Atom Molecular Dynamics Simulations and Experimental Study

Quite recently, we reported the synthesis of supercharged polycations bearing pH-insensitive double-charged repeat units with either three or five methylene groups in the space between charges. The developed approach is based on the quaternization of the parent poly­(4-vinylpyridine) with different alkylating agents, providing the possibility to perform the modification as a one-step reaction, which occurs in mild conditions with a controllable degree of conversion. In the present work, we used the above approach for preparing and investigating supercharged polyplexes (polyelectrolyte complexes of nucleic acids), in particular to elucidate the reason for the key feature, i.e., the clearly defined stability of the polyplexes formed by supercharged polyamines. The main findings of the experimental study were confirmed by the results of full atomic modeling, and the principal regularities responsible for the structure, stability, and properties of the supercharged polyplexes have been elucidated for the first time