Wasu WitoonsaridsilpBusaba PanyarachunNarong SarisutaChristel C. Müller-GoymannMahidol UniversitySrinakharinwirot UniversityTechnische Universitat Braunschweig2018-09-242018-09-242010-02-01Colloids and Surfaces B: Biointerfaces. Vol.75, No.2 (2010), 501-509092777652-s2.0-70549107962https://repository.li.mahidol.ac.th/handle/20.500.14594/28795The conformation of peptide and protein drugs in various microenvironments and the interaction with drug carriers such as liposomes are of considerable interest. In this study the influence of microenvironments such as pH, salt concentration, and surface charge on the secondary structure of a model protein, lysozyme, either in solution or entrapped in liposomes with various molar ratios of phosphatidylcholine (PC):cholesterol (Chol) was investigated. It was found that entrapment efficiency was more pronounced in negatively charged liposomes than in non-charged liposomes, which was independent of Chol content and pH of hydration medium. The occurrence of aggregation, decrease in zeta potential, and alteration of31P NMR chemical shift of negatively charged lysozyme liposomes compared to blank liposomes suggested that the electrostatic interaction plays a major role in protein-lipid binding. Addition of sodium chloride could impair the neutralizing ability of positively charged lysozyme on negatively charged membrane via chloride counterion binding. Neither lysozyme in various buffer solutions with sodium chloride nor that entrapped in liposomes showed any significant change in their secondary structures. However, significant decrease in α-helical content of lysozyme in non-charged liposomes at higher pH and salt concentrations was discovered. © 2009.Mahidol UniversityBiochemistry, Genetics and Molecular BiologyChemical EngineeringChemistryPhysics and AstronomyArticleSCOPUS10.1016/j.colsurfb.2009.09.027