Micellization of Lactosylammonium Surfactants with Different Counter Ions and Their Interaction with DNA

Abstract

So far, the studies about the physical chemical properties of sugar-based surfactants have been still unsystematic; most of the studies have been focused on nonionic sugar-based surfactants. In the present work, we studied the micellization of four lactose-based surfactants, with the same headgroup (lactosylammonium) and the same hydrophobic alkyl chain (dodecyl) but different counterions (malonate, adipate, propionate, and hexanoate), at 25.0 and/or 50.0 °C. We found that these four surfactants could decrease the surface tension of water to ca. 30 mN/m. When the number of carboxylate groups in the counterion was the same, the counterion having a shorter alkyl chain could lead to a smaller minimum area per surfactant molecule. Moreover, the surfactants with monocarboxylates as counterions had much lower critical micelle concentrations than those with dicarboxylates as counterions, and the micelles from the former surfactants had a lower counterion binding degree. The lactosylammonium surfactants could bind with DNA, and low content of the surfactant could decrease the CD signal of DNA, while high content of the surfactant could make DNA unfold somewhat.