Abstract
The water retention properties of the phosphatidilcholine (PC) bilayer were evaluated by measuring the bound water content and water permeability in the presence of various kinds of amino acids. The presence of proline (Pro), a hydrophilic amino acid, significantly increased the bound water content of the PC bilayer. On the other hand, the presence of isoleucine (Ile) or leucine (Leu), hydrophobic amino acids, not only increased the bound water content but also decreased the water permeability of the PC bilayer. In addition, the coexistence of Pro and Ile or Leu, produced a extremely marked increase in the bound water content and a decrease in the water permeability of the PC bilayer. Furthermore, long-standing water retention was observed in the PC bilayer membrane containing mixed amino acids such as Pro/Ile and Pro/Leu. These results suggest that the combination of these amino acids acts synergistically to increase the water content of the PC bilayer membrane due to enhancement of both the water holding capacity and the barrier function of the PC bilayer. Therefore, it is considered that the PC bilayers containing Pro/Ile or Pro/Leu are highly effective moisturizing agents for cosmetics.
