This work explored the influence of the citrus pectin degree and pattern of methylesterification on its interaction with Zn²⁺ 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_abs) were produced through enzymatic (blockwise pattern) or alkaline (random pattern) demethylesterification. The pectin-Zn²⁺ 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 Zn²⁺. Decreasing pectin DM or increasing DB_abs promoted Zn²⁺ binding, with the estimated binding capacity (mol Zn²⁺/mol GalA) and binding constant (mM⁻¹) being mainly determined by pectin DB_abs, 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.

这项工作使用等温滴定量热法（ITC）探索了柑橘果胶的程度和甲基酯化方式对其与Zn ²⁺相互作用的影响。通过酶促（逐段模式）或碱性（无规模式）脱甲基酯化生产具有可比的甲基酯化度（DM）但非甲基酯化的羧基具有不同分布模式（绝对嵌段度，DB _abs）的果胶样品。发现果胶-Zn ²⁺相互作用是吸热的，其中正熵变化补偿了不利的吸热焓变，从而驱动果胶与Zn ²⁺之间的相互作用。果胶DM降低或DB _Abs升高促进锌²⁺结合，估计的结合能力（mol Zn ²⁺ / mol GalA）和结合常数（mM ^-1）主要由果胶DB _Abs而非DM确定。已发现ITC是研究果胶与阳离子相互作用的有用技术，但是，低DM的果胶样品对胶凝敏感，因此较难研究。