Osman M, Høiland H, Holmsen H, Ishigami Y
School of Science and Technology (HIS), Ullandhaug, Stavanger, Norway.
J Pept Sci. 1998 Nov;4(7):449-58. doi: 10.1002/(sici)1099-1387(199811)4:7<449::aid-psc164>3.0.co;2-#.
We have studied the effects of extrinsic environmental conditions on the conformation of surfactin, a heptapeptide biosurfactant from Bacillus subtilis, in aqueous solutions. It has been made clear that temperature, pH, Ca2+ ions and the synthetic nonionic surfactant hepta-ethylene glycol (C12E7) affect the conformation of surfactin in aqueous solutions. The beta-sheet formation reached a maximum at 40 degrees C both in presence and absence of (C12E7) and the nonionic surfactant enhances the beta-sheet formation even at 25 degrees C. Ca2 + induced the formation of alpha-helices and caused this transition at 0.3 mM with surfactin monomers or at 0.5 mM with surfactin micelles, but above these transition concentrations of Ca2+ beta-sheets were observed. In micellar solution the beta-sheet structure was stabilized at pH values below 7 or upon addition of Ca2+ in concentrations above 0.5 mM. Our results indicated that the bioactive conformation of surfactin is most likely the beta-sheets when the molecules are assembled in micelles. The beta-sheet structure in micelles could be retained by tuning the micelles. Surfactin micelles could be tuned in the bioactive conformation by manipulating pH, temperature, Ca2+ or (C12E7) concentrations in surfactin solutions. Our results strongly indicated that Ca2+ and other molecules (such as C12E7) may function as directing templates in the assembly and conformation of surfactin in micelles. Thus, we suggest environmental manipulation and template-aided micellation (TAM) as a new approach for preparing predesigned micelles, microemulsions or micro-spheres for specific application purposes.
我们研究了外在环境条件对枯草芽孢杆菌七肽生物表面活性剂表面活性素在水溶液中构象的影响。已经明确，温度、pH值、Ca2+离子以及合成非离子表面活性剂七乙二醇（C12E7）会影响表面活性素在水溶液中的构象。无论有无（C12E7），β-折叠的形成在40℃时达到最大值，并且即使在25℃时非离子表面活性剂也能增强β-折叠的形成。Ca2+诱导α-螺旋的形成，在表面活性素单体浓度为0.3 mM或表面活性素胶束浓度为0.5 mM时引发这种转变，但在这些Ca2+的转变浓度以上会观察到β-折叠。在胶束溶液中，β-折叠结构在pH值低于7或添加浓度高于0.5 mM的Ca2+时会稳定下来。我们的结果表明，当分子组装成胶束时，表面活性素的生物活性构象最有可能是β-折叠。胶束中的β-折叠结构可以通过调节胶束来保留。通过控制表面活性素溶液中的pH值、温度、Ca2+或（C12E7）浓度，可以将表面活性素胶束调节为生物活性构象。我们的结果有力地表明，Ca2+和其他分子（如C12E7）可能在表面活性素在胶束中的组装和构象中起指导模板的作用。因此，我们建议将环境调控和模板辅助胶束化（TAM）作为一种新方法，用于制备用于特定应用目的的预设计胶束、微乳液或微球。
