Binding Affinity of Cationic Gemini Surfactants to Insulin: Effect of the Spacer Length

Gemini surfactants are composed of two surfactants that are chemically linked together by a spacer attheir hydrophilic head groups.Because of their applications in academic and industrial fields, Geminisurfactants have drawn great attention of scientists of various communities, since 1991.Some of Geminishave reported as food stabilizers [1]. Others are claimed to be potential candidates for gene delivery [2].The interaction of Gemini surfactants with nucleic acids have also studied widely. However, theinteraction of Geminis with proteins has been the subject of only recent studies[3]. In this research, theinteraction of two cationic Gemini surfactants with insulin is investigated by fluorescence spectroscopy.The two Gemini surfactants differ in their spacer length (C6, C4). Titration of insulin solution with theGemini dispersion (C6 or C4) was performed and then, the fluorescence spectra recorded. The binding ofboth surfactants to the protein was evidencedby quenching the intrinsic fluorescence of protein uponaddition of the surfactants.The Stern-volmer plots were applied to derive the binding parameters such asKa and n. Results demonstrate that the longer the spacer length of the surfactant, the lower the bindingaffinity to insulin is. The number of binding sites for surfactant per protein molecule also decreases, as thespacer length increases.

کلیدواژه ها:

Cationic Gemini Surfactant ، fluorescence spectroscopy ، insulin ، interaction