Size-Exclusion Chromatography of Carboxyl-terminated Dendrimers as a Model for Permeation of Charged Particles into Like-Charged Cavities

(6) or silica (7, 8). SEC partition coefficients of proteins In order to examine the permeation of small charged colloids on polymer-based chromatographic gels also display clear into cavities of like charge, size-exclusion chromatography was evidence of repulsive effects when pH is larger than the carried out with carboxyl-terminated dendritic polymers on a po- protein isoelectric points (9, 10). rous glass stationary phase. Chromatographic partition coef®-While there are numerous qualitative reports of the dimi-cients KSEC were measured for solute diameters ranging from 2 to nution of permeation by electrostatic repulsion, quantitative8 nm, at neutral pH, and ionic strengths from 0.01 to 0.09 M, and treatments are less common. Lin and Deen (11) measuredwere reported relative to those of noninteracting solutes of equal the diffusivity of polystyrene sulfonate through track-etchedsize (pullulan and Ficoll). The experimental results were com-pared to values calculated using the treatment of F. G. Smith III nucleopore membranes as a function of ionic strength and and W. M. Deen for charged spheres in cylindrical pores of like membrane pore radius, and compared the data to theoretical charge (J. Colloid Interface Sci. 78, 44 (1980) ; 91, 571 (1983)). results obtained from a model that incorporates long-range The measured degrees of permeation were typically 20±100 % solute-pore interactions into the partitioning of flexible chain larger than the calculated values, the discrepancies being greatest macromolecules in like-charged pores (12). The reductio