Biophysical characterization of complexation of DNA with oppositely charged Gemini surfactant 12-3-12.
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(CMC(mix)) 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.
State Key Laboratory of Chemical Engineering and Department of Chemistry, East China University of Science and Technology, Shanghai 200237, China.
Xiaofang
X
Zhao
Yazhuo
Y
Shang
Jun
J
Hu
Honglai
H
Liu
Ying
Y
Hu
D055592:Biophysical Phenomena; D002412:Cations; D002942:Circular Dichroism; D004247:DNA / Q000737:chemistry*; D004563:Electrochemistry; D057927:Hydrophobic and Hydrophilic Interactions; D000644:Quaternary Ammonium Compounds / Q000737:chemistry*; D012996:Solutions; D013050:Spectrometry, Fluorescence; D013500:Surface Tension; D013501:Surface-Active Agents / Q000737:chemistry*
D002412:Cations; D000644:Quaternary Ammonium Compounds; D012996:Solutions; D013501:Surface-Active Agents; C533917:trimethylene-1, 3-bis (dodecyldimethylammonium bromide); D004247:DNA