The objectives of these studies (1) were: (a) to search for experimental evidence that would allow a choice between different models ('egg-box' model of Grant et al. (1973) (2), models of Mackie et al. (1983) (3)); and (b) to find out what the 'cooperativity' in cation-binding by pectates means from a thermodynamic point of view.
Debongnie, Ph., Mestdagh, M., Domard, A., & Rinaudo, M. (1991). Interactions between pectins and multivalent cations. Food Hydrocolloids, 5(1-2), 109-111. https://doi.org/10.1016/S0268-005X(09)80294-4 (Original work published 1991)