Internal charge transfer based ratiometric interaction of anionic surfactant with calf thymus DNA bound cationic surfactant: Study I

• Cationic surfactant CTAB binds with DNA electrostatically.
• CTAB–DNA forms a stable ground as well as excited state equilibrium.
• Anionic surfactant SDS interact with cationic CTAB but not with DNA.
• ICT based ratiometric interaction of SDS with DNA bound CTAB.

Cetyl trimethyl ammonium bromide (CTAB) binds calf thymus (ct-) DNA like anionic biopolymers electrostatically and established equilibrium both in the ground as well as in excited state in aqueous medium at pH 7. Anionic sodium dodecyl sulfate (SDS) does not show even hydrophobic interaction with ct-DNA at low concentration. On contrary, SDS can establish well defined equilibrium with DNA bound CTAB in ground state where the same CTAB–DNA isosbestic point reappears. First report of internal charge transfer (ICT) based binding of CTAB with ct-DNA as well as ICT based interaction of anionic SDS with DNA bound CTAB that shows dynamic quenching contribution also. The reappearance of anodic peak and slight increase in cathodic peak current with increasing concentration (at lower range) of anionic SDS, possibly reflect the release of CTAB from DNA bound CTAB by SDS.

Compaction and decompaction of DNA in presence of cationic and anionic surfactants, respectively. Decompaction produces N-DNA and catanionic amphiphile (CTA+ −SD). N-DNA: Normal DNA; C-DNA: Complexed DNA.Figure optionsDownload as PowerPoint slide