Ohta Akio, Miyazato Yuya, Sasaki Hiroyasu, Yasuhara Kazuma, Asakawa Tsuyoshi
School of Chemistry, College of Science and Engineering, Kanazawa University, Kakuma, Kanazawa, Ishikawa 920-1192, JAPAN.
J Oleo Sci. 2009;58(12):607-15. doi: 10.5650/jos.58.607.
The incorporation behaviors of some N-dodecanoyl amino acid-type surfactants into L-alpha-dipalmitoylphosphatidylcholine (DPPC) vesicles in aqueous solution were investigated. From the leakage measurements of a vesicle-entrapped fluorescence probe, it was found that these surfactants did not affect the DPPC vesicle so much at a very low concentration less than a one-tenth of the critical micelle concentration (CMC), but caused a significant release of the probe form the vesicles even at just below the CMC. The leakage induced by amino acid-type surfactants was promoted by increasing hydrophobicity of the amino acid. However the polarization of DPH embedded in the DPPC membrane was almost unchanged by incorporation of the surfactants at the concentration below the CMC except for the N-dodecanoylphenylalanine system. The binding enthalpy and the binding constant of the surfactant to DPPC vesicles were estimated by isothermal titration calorimetry. While the binding enthalpy was independent of the kind of surfactant, the binding constant increases with increasing hydrophobicity of the amino acid species in the surfactants. The molar ratio of bound surfactant to DPPC molecule in the saturated state was much greater than that for sodium dodecyl sulfate system. Further the ratio was not influenced by the structure of the amino acid side chain.
研究了一些N-十二烷酰氨基酸型表面活性剂在水溶液中掺入L-α-二棕榈酰磷脂酰胆碱（DPPC）囊泡的行为。通过对包封在囊泡中的荧光探针的泄漏测量发现，在低于临界胶束浓度（CMC）十分之一的极低浓度下，这些表面活性剂对DPPC囊泡的影响不大，但即使在略低于CMC时，也会导致探针从囊泡中大量释放。氨基酸型表面活性剂引起的泄漏随着氨基酸疏水性的增加而加剧。然而，除了N-十二烷酰苯丙氨酸体系外，在低于CMC的浓度下掺入表面活性剂时，嵌入DPPC膜中的DPH的极化几乎没有变化。通过等温滴定量热法估算了表面活性剂与DPPC囊泡的结合焓和结合常数。虽然结合焓与表面活性剂的种类无关，但结合常数随着表面活性剂中氨基酸种类疏水性的增加而增大。饱和状态下结合的表面活性剂与DPPC分子的摩尔比远大于十二烷基硫酸钠体系。此外，该比例不受氨基酸侧链结构的影响。
