Nucleic Acids Research Advance Access originally published online on November 22, 2007
Nucleic Acids Research 2008 36(1):342-351; doi:10.1093/nar/gkm1035
| ||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
Nucleic Acids Research, 2008, Vol. 36, No. 1 342-351
© 2007 The Author(s)
This is an Open Access article distributed under the terms of the Creative Commons Attribution Non-Commercial License (http://creativecommons.org/licenses/by-nc/2.0/uk/) which permits unrestricted non-commercial use, distribution, and reproduction in any medium, provided the original work is properly cited.
Molecular Biology |
Activation of DNA strand exchange by cationic comb-type copolymers: effect of cationic moieties of the copolymers
1Institute for Materials Chemistry and Engineering, Kyushu University, 744-CE11 Motooka, Nishi, Fukuoka 819-0395 and 2CREST, Japan Science and Technology Agency, 4-1-8 Honcho, Kawaguchi, Saitama 332-0012, Japan
*To whom correspondence should be addressed. Tel: +81 92 802 2522; Fax: +81 92 802 2523; Email: maruyama{at}ms.ifoc.kyushu-u.ac.jp
Received August 20, 2007. Revised October 30, 2007. Accepted October 30, 2007.
We have previously reported that poly(L-lysine)-graft-dextran cationic comb-type copolymers accelerate strand exchange reaction between duplex DNA and its complementary single strand by >4 orders of magnitude, while stabilizing duplex. However, the stabilization of the duplex is considered principally unfavourable for the accelerating activity since the strand exchange reaction requires, at least, partial melting of the initial duplex. Here we report the effects of different cationic moieties of cationic comb-type copolymers on the accelerating activity. The copolymer having guanidino groups exhibited markedly higher accelerating effect on strand exchange reactions than that having primary amino groups. The high accelerating effect of the former is considered to be due to its lower stabilizing effect on duplex DNA, resulting from its increased affinity to single-stranded DNA. The difference in affinity was clearly demonstrated by a fluorescence correlation spectroscopy study; the interaction of the former with single-stranded DNA still remained high even at 1 M NaCl, while that of the latter completely disappeared. These results suggest that some modes of interactions, such as hydrogen bonding, other than electrostatic interactions between the copolymers having guanidino groups and DNAs may be involved in strand exchange activation.