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B–Z DNA Transition Triggered by a Cationic Comb‐Type Copolymer
Author(s) -
Shimada Naohiko,
Kano Arihiro,
Maruyama Atsushi
Publication year - 2009
Publication title -
advanced functional materials
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 6.069
H-Index - 322
eISSN - 1616-3028
pISSN - 1616-301X
DOI - 10.1002/adfm.200901169
Subject(s) - cationic polymerization , copolymer , circular dichroism , polyelectrolyte , materials science , polymer chemistry , dna , polymer , crystallography , stereochemistry , chemistry , biochemistry , composite material
The conformational transition from right‐handed B–DNA to left‐handed Z–DNA—the B–Z transition—has received increased attention recently because of its potential roles in biological systems and its applicability to bionanotechnology. Though the B–Z transition of poly(dG–dC) · poly(dG–dC) is inducible under high salt concentration conditions (over 4 M NaCl) or by addition of multivalent cations, such as hexaamminecobalt(III), no cationic polymer were known to induce the transition. In this study, it is shown by circular dichroism and UV spectroscopy that the cationic comb‐type copolymer, poly( L ‐lysine)‐ graft ‐dextran, but not poly( L ‐lysine) homopolymer or a basic peptide, induces the B–Z transition of poly(dG–dC) · poly(dG–dC). At a cationic amino group concentration of 10 −4 M the copolymer stabilizes Z–DNA. The transition pathway from the B to the Z form is different to that observed previously. We speculate that the cationic backbone of the copolymer, which reduces electrostatic repulsion among DNA phosphate groups, and the hydrophilic dextran chains, which reduce activity of water, cooperate to induce the B–Z transition. The copolymer specifically modified the micro‐environment around DNA molecules to induce Z–DNA formation through stable and spontaneous inter‐polyelectrolyte complex formation.