Abstract：
Binary systems of citrus peel pectin (a major food carbohydrate) and mucin (a principal oral-gastrointestinal glycoprotein) are studied, as to understand the interactions and thermodynamics between food and biofluids during oral processing and digestion. The fluorimetry emission spectra of mucin were quenched by pectin addition at 293, 301, 310 and 318 K, indicating direct contact between the two macromolecular populations. A red shift, suggesting pectin-induced alterations on mucin conformation, has been observed at 318 K. Intensity-based Stern - Volmer plots fitted second-order polynomial equations, suggesting the coexistence of both static and dynamic quenching, while the increase of the slopes with temperature points to the predominance of dynamic phenomena. Time-resolved fluorescence measurements also point to dynamic quenching related to transient interactions, rather than to specific bonding. Thermodynamic analysis yields negative free energy changes in all cases, with positive changes for enthalpy and large positive values for TΔS. These are in agreement with the Stern - Volmer analysis, suggesting the predominance of transient, dynamic (here entropic) interactions. These provide an image of mucin interacting with pectin macromolecules during the oral processing and digestion of foods, and can relate to the texture, flavor (e.g. astringency) and bioavailability of polysaccharide-based foods.
摘要：
研究了柑橘皮果胶（一种主要的食物碳水化合物）和粘蛋白（一种主要的口服胃肠道糖蛋白）的二元系统，了解口腔加工和消化过程中食物和生物流体之间的相互作用和热力学。通过在293、301、310和318K添加果胶来淬灭粘蛋白的荧光发射光谱，表明两个大分子群体之间的直接接触。一个红色的转变，提示果胶诱导的粘蛋白构象改变，在318K观察到基于强度的斯特恩-沃尔默图拟合二阶多项式方程，表明静态和动态淬火共存，而斜率随温度的增加表明动力学现象占优势。时间分辨荧光测量还指向与瞬态相互作用相关的动态猝灭，而不是特定的结合。热力学分析在所有情况下都会产生负自由能变化，焓的正变化和TΔS的大正值。这些与斯特恩-沃尔默的分析一致，表明了短暂的优势，动态(这里是熵)相互作用。这些提供了在食物的口腔加工和消化过程中粘蛋白与果胶大分子相互作用的图像，并且可以与纹理相关，以多糖为基础的食物的风味(如收敛性)和生物利用度。
