Journal
BIOPHYSICAL CHEMISTRY
Volume 138, Issue 3, Pages 144-149Publisher
ELSEVIER
DOI: 10.1016/j.bpc.2008.09.014
Keywords
Gemini surfactant; DNA; Interaction; Surface tension; Circular dichroism
Funding
- National Natural Science Foundation of China [20706013, 20736002]
- Program for Changjiang Scholars and Innovative Research Team in University
- 111 Project of Ministry of Education of China [B08021]
- [IRT0721]
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The interaction between DNA and cationic gemini surfactant trimethylene-1, 3-bis (dodecyldimethylammonium bromide) (12-3-12) has been investigated by the measurements of fluorescence, surface tension, UV spectrum and circular dichroism (CD). Micelle-like structure of 12-3-12 induced by DNA appears at critical aggregation concentration (CAC), which is much lower than critical micelle concentration (CMC) of 12-3-12 in DNA-free solution. CAC is independent of DNA concentration, but the CMC of the mixed solutions of DNA and 12-3-12(CMCmix) increases with the increasing of DNA concentration. The surface tensions of the mixed system are higher than that of the pure surfactant solution, much different from the so-called synergistic lowering of the surface tension for other polymer-surfactant systems. Phase separation occurs after the neutralization point and the precipitate redissolves with superfluous 12-3-12. Cationic surfactant 12-3-12 can exclude ethidium bromide (EB) from the DNA/EB complex, and this process does not depend on the DNA concentration but on the charge ratio of 12-3-12 to DNA. The binding constant of EB to DNA decreases sharply at the charge ratio from 0.5 to 1.0. Circular dichroism (CD) spectra show that DNA undergoes a conformational transition from native B-form to chiral Psi-phase with increasing of 12-3-12. (C) 2008 Elsevier B.V. All rights reserved.
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