Laboratory of Food Technology, Leuven Food Science and Nutrition Research Centre (LFoRCe), Department of Microbial and Molecular Systems (M2S), KU Leuven, Kasteelpark Arenberg 22, Box 2457, 3001 Leuven, Belgium.
Renewable Materials and Nanotechnology Research Group, Department of Chemical Engineering, KU Leuven, Campus Kulak Kortrijk, Etienne Sabbelaan 53, Box 7659, 8500 Kortrijk, Belgium.
Carbohydr Polym. 2018 Oct 1;197:460-468. doi: 10.1016/j.carbpol.2018.05.079. Epub 2018 May 28.
This work explored the influence of the citrus pectin degree and pattern of methylesterification on its interaction with Zn using isothermal titration calorimetry (ITC). Pectin samples with a comparable degree of methylesterification (DM) but distinct distribution patterns of non-methylesterified carboxylic groups (absolute degree of blockiness, DB) were produced through enzymatic (blockwise pattern) or alkaline (random pattern) demethylesterification. The pectin-Zn interaction was found to be endothermic, in which a positive entropy change compensated for the unfavorable endothermic enthalpy change, driving the interaction between pectin and Zn. Decreasing pectin DM or increasing DB promoted Zn binding, with the estimated binding capacity (mol Zn/mol GalA) and binding constant (mM) being mainly determined by pectin DB, rather than DM. ITC was found to be a useful technique to study the pectin-cation interaction, however, low DM pectin samples are sensitive to gelling and therefore more difficult to study.
本研究采用等温滴定微量热法（ITC）探究了桔皮果胶酯化度和酯化模式对其与锌相互作用的影响。通过酶解（块状模式）或碱解（随机模式）脱甲酯，制备了甲酯化度相当但非甲酯化羧酸基团分布模式不同（绝对嵌段度，DB）的果胶样品。果胶与锌的相互作用为吸热反应，其中正熵变补偿了不利的吸热焓变，驱动了果胶与锌之间的相互作用。降低果胶的甲酯化度或增加 DB 均促进了锌的结合，估计的结合容量（每摩尔半乳糖醛酸结合的锌摩尔数）和结合常数（毫摩尔）主要由果胶的 DB 决定，而不是甲酯化度。ITC 被发现是研究果胶-阳离子相互作用的有用技术，但甲酯化度低的果胶样品易凝胶化，因此更难研究。
