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Effect of charge density of cationic polyelectrolytes on complex formation with DNA
Author(s) -
Mita Kazuei,
Zama Mitsuo,
Ichimura Sachiko
Publication year - 1977
Publication title -
biopolymers
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.556
H-Index - 125
eISSN - 1097-0282
pISSN - 0006-3525
DOI - 10.1002/bip.1977.360160913
Subject(s) - chemistry , polymer , cationic polymerization , dna , polyelectrolyte , molecule , charge density , phosphate , polymer chemistry , crystallography , organic chemistry , biochemistry , physics , quantum mechanics
The interaction between DNA and ionen polymers, ‐[N + (CH 3 ) 2 (CH 2 ) m N + (CH 3 ) 2 (CH 2 ) n ] l −, with m‐n of 3–3, 6–6, and 6–10 were examined in order to know how the binding behavior of cationic polymers with DNA depends on the charge density of polycation. The ionen polymer has no bulky side chain and the binding forces with DNA would be attributed mainly to electrostatic interaction. When 3–3 ionen polymers were added to DNA solution, precipitable complexes with the ratio of cationic residue to DNA phosphate (+/−) of 1/1 and the free DNA molecules were segregated, while 6–6 and 6–10 ionen polymers formed soluble complexes with DNA molecules up to (+/−) = 0.5. This suggests that 3–3 ionen polymers bind cooperatively with DNA while 6–6 and 6–10 ionen polymers bind noncooperatively. The cooperative binding of 3–3 ionen polymer and the noncooperative binding of 6–6 ionen polymer were also supported by the thermal melting and recooling profiles from the midpoint between first and second meltings. It was concluded that the charge density of DNA phosphate is a critical value determining whether the ionen polymers bind to DNA by a cooperative or by a noncooperative binding, since the distance between successive cationic charges of 3–3 ionen polymer is shorter than that between successive phosphate charges on DNA double helix and those of 6–6 and 6–10 ionen polymers are longer.