Chain length cationic surfactant binding

K. Hayakawa and J.C.T. Kwak Surfacatant-Polyelectrolyte Interactions. 4. Surfactant Chain Length Dependence on the Binding of Alkylpyridinium Cations to Dextran Sulfate. J. Phys. Chem. 88, 1930 (1984). 

Malovikova A, Hayakawa K, Kwak JCT. Surfactant—polyelectrolyte interactions. 4. Surfactant chain length dependence of the binding of alkylpyridinium cations to dextran sulfate. J Phys Chem 1984 88 1930-1933. 

To summarize, the complex formation between cationic polypeptides and anionic surfactants is initiated through coulombic interaction and followed by a cooperative binding of successive surfactant ions. The nonpolar tails of clustered surfactant molecules can provide a hydrophobic environment that stabilizes an ordered conformation — a helix or a 8-form, which depends not only on the number of methylene groups of lysine and its homologs but also on the chain length of the surfactants. Excess surfactant molecules may cluster onto the bound surfactant ions in a "double layer" fashion with their polar heads exposed to the aqueous medium and nonpolar tails shielded from the polar environment. For the 8-pleated sheets a bilayer can also be formed between bound surfactant molecules which are sandwiched between two polypeptide chains. 

Fluorescence microscopy has been used extensively to monitor the compaction of DNA in the presence of several cationic species [16-23] as well as some other cosolutes [24]. For cationic surfactants, compaction starts at concentrations only slightly above the onset of binding, as characterized by the cac [19] and shows the same dependence of surfactant alkyl chain length as other self-assembly processes [25]. 

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