Wang Xiaoyong, Fan Min
School of Chemistry & Molecular Engineering, East China University of Science and Technology Shanghai 200237 China
RSC Adv. 2019 Feb 15;9(10):5748-5755. doi: 10.1039/c9ra00005d. eCollection 2019 Feb 11.
Bile salts are biosurfactants distributed in the human gastrointestinal tract, which can significantly influence the structure and functions of orally administrated components. This work has studied the interaction and conformation changes of zein with sodium taurocholate (NaTC) in the formation of zein/NaTC nanoparticles. When the NaTC concentration ( ) increases from 0 to 0.24 g L, the particle size of zein/NaTC nanoparticles decreases from 97 to 76 nm, but markedly increases from 76 to 137 nm as increases from 0.24 to 0.4 g L. At = 0-0.24 g L, the sharply decreased zeta potential of zein/NaTC nanoparticles suggests that NaTC monomers electrostatically bind with zein molecules to form zein/NaTC complexes, which have high steric repulsion and thus aggregate into smaller zein/NaTC nanoparticles. Nevertheless, at = 0.24-0.4 g L, the less changed zeta potential of zein/NaTC nanoparticles together with the surface tension result suggests that NaTC dimers formed on zein polypeptide chains due to the hydrophobic interaction cause zein/NaTC complexes to undergo more aggregation into larger zein/NaTC nanoparticles. Compared to little changes in the secondary and tertiary structures of zein molecules at = 0-0.24 g L, the absorption, fluorescence, and circular dichroism measurements disclose that the addition of NaTC above 0.24 g L can greatly unfold the compact structure of zein molecules with decreased α-helix content.
胆汁盐是分布于人体胃肠道的生物表面活性剂，可显著影响口服成分的结构和功能。本研究考察了玉米醇溶蛋白与牛磺胆酸钠（NaTC）在形成玉米醇溶蛋白/NaTC纳米颗粒过程中的相互作用和构象变化。当NaTC浓度（ ）从0增加到0.24 g/L时，玉米醇溶蛋白/NaTC纳米颗粒的粒径从97 nm减小到76 nm，但当 从0.24增加到0.4 g/L时，粒径显著从76 nm增加到137 nm。在 = 0 - 0.24 g/L时，玉米醇溶蛋白/NaTC纳米颗粒的zeta电位急剧下降，表明NaTC单体与玉米醇溶蛋白分子静电结合形成玉米醇溶蛋白/NaTC复合物，该复合物具有较高的空间排斥力，因此聚集成较小的玉米醇溶蛋白/NaTC纳米颗粒。然而，在 = 0.24 - 0.4 g/L时，玉米醇溶蛋白/NaTC纳米颗粒的zeta电位变化较小，结合表面张力结果表明，由于疏水相互作用在玉米醇溶蛋白多肽链上形成的NaTC二聚体导致玉米醇溶蛋白/NaTC复合物进一步聚集形成更大的玉米醇溶蛋白/NaTC纳米颗粒。与 = 0 - 0.24 g/L时玉米醇溶蛋白分子二级和三级结构变化较小相比，吸收、荧光和圆二色性测量结果表明，添加0.24 g/L以上的NaTC可显著展开玉米醇溶蛋白分子的紧密结构，同时α-螺旋含量降低。
