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Structure and stoichiometry of CTAB-DNA complexes
S Madhukar1, A V Radhakrishnan1, A K Majhi1
1Raman Research Institute, Bangalore 560 080, India.
The Journal of Chemical Physics
|December 15, 2020
Summary
We studied cetyltrimethylammonium bromide-DNA complexes, finding a 1:2 micelle-DNA ratio best explains their hexagonal structure. This structure is supported by elemental analysis and electrostatic stability calculations.
Area of Science:
- Biophysics
- Materials Science
- Structural Biology
Background:
- Cetyltrimethylammonium bromide (CTAB) is a cationic surfactant.
- DNA is a key biomolecule with a double helix structure.
- Complexes formed between surfactants and DNA are of interest for structural and material properties.
Purpose of the Study:
- To elucidate the structure of cetyltrimethylammonium bromide-DNA complexes.
- To determine the micelle to DNA stoichiometry within these complexes.
- To assess the relative stability of different proposed complex structures.
Main Methods:
- Small-angle X-ray diffraction (SAXRD) was used to probe the complex structure.
- Elemental analysis was performed to determine the precise stoichiometry.
- Madelung energy calculations were employed to evaluate electrostatic stability.
Main Results:
- The complexes were found to exhibit a two-dimensional hexagonal phase.
- SAXRD data strongly supported a 1:2 micelle-DNA stoichiometry.
- Elemental analysis confirmed the 1:2 stoichiometry.
- Electrostatic calculations indicated this structure is relatively stable.
Conclusions:
- The 1:2 micelle-DNA stoichiometry is the most consistent model for CTAB-DNA complexes.
- Structural and elemental analyses provide converging evidence for this stoichiometry.
- Electrostatic interactions play a role in the stability of these complexes.
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