Acta Chimica Sinica ›› 2013, Vol. 71 ›› Issue (9): 1293-1300.DOI: 10.6023/A13040401 Previous Articles     Next Articles



杨静, 孙润广, 郝长春, 乔进京, 何光晓   

  1. 陕西师范大学物理学与信息技术学院生物物理与生物医学工程研究室 西安 710062
  • 投稿日期:2013-04-12 发布日期:2013-05-16
  • 通讯作者: 孙润广,
  • 基金资助:

    项目受国家自然科学基金(No. 20772077)、教育部高等学校博士学科点专项科研基金(No. 200807180001)、陕西省自然科学基础研究计划(No. 2012JQ1002)和中央高校基本科研业务费专项(No. GK201102029)资助.

A Monolayer Study on the Interfacial Behavior of DPPC with β-sitosterol and Stigmasterol

Yang Jing, Sun Runguang, Hao Changchun, Qiao Jinjing, He Guangxiao   

  1. Laboratory of Biophysics and Biomedical Engineering, College of Physics and Information Technology, Shaanxi Normal University, Xi'an 710062
  • Received:2013-04-12 Published:2013-05-16
  • Supported by:

    Project supported by the National Natural Science Foundation of China (No. 20772077), the Doctoral Fund of Ministry of Education of China (No. 200807180001), the Natural Science Basic Research Plan in Shaanxi Province of China (No. 2012JQ1002) and the Fundamental Research Funds for the Central Universities (No. GK201102029).

It is known that sterols are key components of cellular membranes, which can modulate membrane properties and induce influence on the organization of membrane phospholipids. Howerer, the influence of these sterols on membrane properties sees to be unclear. It is worth studying. The interactions between β-sitosterol and stigmasterol and dipalmitoyl phosphatidycholine (DPPC) in mixed monolayers were studied by langmuir technique and atomic force microscopy (AFM). The influence of β-sitosterol and stigmasterol effects on properties of DPPC membrane on phase transition from the liquid expanded (LE) to liquid condensed (LC) state were investigated and the condensing and ordering potency of binary monolayers containing β-sitosterol and stigmasterol were thoroughly analyzed. Based on the analysis of mixing values as well as AFM images it was evidenced that the effect of the plant sterol depends on the composition of model membrane. The results show that the addition of the plant sterols into model membrane modifies the condensation, ordering and interactions in the system. Moreover, at their higher concentration Xsterols=0.8, the values of the excess molecular area and excess Gibbs enerqy displayed negative values, which indicate that between molecules in the mixed monolayer exist stronger attraction than in the respective one-component films and suggest β-sitosterol and stigmasterol in the mixed system have the similar effects on its properties. Examination of the excess free energy of mixing reveals an enhanced stability of binary monolayers. At lower content, Xsterols=0.2, 0.4, the values of the excess molecular area and excess Gibbs energy suggested stronger attractive interaction between stigmasterol and DPPC, while an intermolecular stronger repulsion interaction between β-sitosterol and DPPC. It shows that stigmasterol was found to modify the properties of model membrane more strongly than β-sitosterol. It reflects that side-chain can reduce packing effectiveness, increased tilt of the molecules with respect to the monolayer plane, and the presence of the double bond reduces the hydrophobicity of the branched hydrocarbon tail of stigmasterol, which could cause strols to have long axis parallel to the interface. The result of AFM supported the theoretic analysis.

Key words: phytosterol, interaction, phase transition, condensation, atomic force microscopy (AFM)