Reversibility of the interactions between a novel surfactant derived from lysine and biomolecules

In this work the novel cationic surfactant derived from lysine (S)-5-acetamido-6-(dodecylamino)-N,N,N-trimethy1-6-oxohexan-1-ammonium chloride, LYCl, was prepared and the physicochemical characterization of its aqueous solutions was carried out. The binding of LYCl to bovine serum albumin, BSA, and to double stranded calf thymus DNA, ctDNA, was investigated using several techniques. Results show that LYCl binding to BSA is followed by a decrease in the alpha-helix content caused by the unfolding of the protein. LYCl association to ctDNA mainly occurs through groove binding and electrostatic interactions. These interactions cause morphological changes in the polynucleotide from an elongated coil structure to a more compact globular structure, resulting in the compaction of ctDNA. Addition of beta-cyclodextrin, beta-CD, to the BSA-LYCl and ctDNA-LYCl complexes is followed by the refolding of BSA and the decompaction of ctDNA. This can be explained by the ability of beta-CD to hinder BSA-LYCl and ctDNA-LYCl interactions due to the stronger and more specific beta-CD-LYCl hydrophobic interactions. The stoichiometry of the beta-CD:LYCl inclusion complex and its formation equilibrium constant were determined in this work. The reported procedure using beta-CD is an efficient way to refold proteins and to decompact DNA, after the morphological changes caused in the biomolecules by their interaction with cationic surfactants. (C) 2015 Elsevier B.V. All rights reserved.