Dai Qingyuan, Zhu Xiuling, Yu Jingyang, Karangwa Eric, Xia Shuqin, Zhang Xiaoming, Jia Chengsheng
State Key Laboratory of Food Science and Technology, School of Food Science and Technology, Jiangnan University , Lihu Road 1800, Wuxi, Jiangsu 214122, People's Republic of China.
College of Biological and Chemical Engineering, Anhui Polytechnic University , Beijing Middle Road, Wuhu, Anhui 241000, People's Republic of China.
J Agric Food Chem. 2016 Jul 13;64(27):5539-48. doi: 10.1021/acs.jafc.6b01213. Epub 2016 Jul 1.
Protein conformational changes were demonstrated in biopolymer nanoparticles, and molecular forces were studied to elucidate the formation and stabilization mechanism of biopolymer nanoparticles. The biopolymer nanoparticles were prepared by heating electrostatic complexes of whey protein isolate (WPI)-dextran conjugate (WD) and chondroitin sulfate (ChS) above the denaturation temperature and near the isoelectric point of WPI. The internal characteristics of biopolymer nanoparticles were analyzed by several spectroscopic techniques. Results showed that grafted dextran significantly (p < 0.05) prevented the formation of large aggregates of WD dispersion during heat treatment. However, heat treatment slightly induced the hydrophobicity changes of the microenvironment around fluorophores of WD. ChS electrostatic interaction with WD changed the fluorescence intensity of WD regardless of heat treatment. Far-UV circular dichroism (CD) and attenuated total reflectance Fourier transform infrared (ATR-FTIR) spectroscopies confirmed that glycosylation and ionic polysaccharide did not significantly cause protein conformational changes in WD and ChS (WDC) during heat treatment. In addition, hydrophobic bonds were the major molecular force for the formation and stabilization of biopolymer nanoparticles. However, hydrogen bonds slightly influenced their formation and stabilization. Ionic bonds only promoted the formation of biopolymer nanoparticles, while disulfide bonds partly contributed to their stability. This work will be beneficial to understand protein conformational changes and molecular forces in biopolymer nanoparticles, and to prepare the stable biopolymer nanoparticles from heating electrostatic complexes of native or glycosylated protein and polysaccharide.
在生物聚合物纳米颗粒中证实了蛋白质构象变化，并研究了分子力以阐明生物聚合物纳米颗粒的形成和稳定机制。通过将乳清蛋白分离物（WPI）-葡聚糖共轭物（WD）与硫酸软骨素（ChS）的静电复合物在高于变性温度且接近WPI的等电点的条件下加热来制备生物聚合物纳米颗粒。通过几种光谱技术分析了生物聚合物纳米颗粒的内部特征。结果表明，接枝的葡聚糖在热处理过程中显著（p<0.05）阻止了WD分散体大聚集体的形成。然而，热处理略微诱导了WD荧光团周围微环境的疏水性变化。无论是否进行热处理，ChS与WD的静电相互作用都会改变WD的荧光强度。远紫外圆二色性（CD）和衰减全反射傅里叶变换红外（ATR-FTIR）光谱证实，糖基化和离子多糖在热处理过程中不会显著引起WD和ChS（WDC）中的蛋白质构象变化。此外，疏水键是生物聚合物纳米颗粒形成和稳定的主要分子力。然而，氢键对它们的形成和稳定有轻微影响。离子键仅促进生物聚合物纳米颗粒的形成，而二硫键部分有助于它们的稳定性。这项工作将有助于理解生物聚合物纳米颗粒中的蛋白质构象变化和分子力，并有助于从天然或糖基化蛋白质与多糖的加热静电复合物制备稳定的生物聚合物纳米颗粒。
