Chromatographic interactions between proteins and sulfoalkylbetaine-based zwitterionic copolymers in fully aqueous low-salt buffers

Macroporous monoliths containing N,N-dimethyl-Nmethacryloyloxyethyl-N-(3-su lfopropyl)am betaine (SPE) have been synthesized via in situ photo-polymeri zation, yielding a stoichiometric balance between sulfur and nitrogen in th e final polymer, which is indicative of a genuine strong/strong zwitterioni c character. The chromatographic properties of these zwitterionic resins we re evaluated with respect to the retention behavior of inorganic ions and p roteins. The weak electrostatic nature of the interaction between the sulfo betaine monoliths and proteins provided a high selectivity between basic pr oteins and peptides, Elution was accomplished with low-ionic-strength fully aqueous mobile phases, whereby high recovery was obtained, even for hydrop hobic proteins. Chaotropic ions such as perchlorate or thiocyanate were use d as mobile phase modifiers to modulate the apparent ion exchange group den sity, thus introducing a route for the modulation of the ionic strength tha t is required to competitively elute the protein. The promising features of polymeric sulfoalkylbetaine interaction layers for separation and analysis of biological extracts was also manifested in an application involving pur ification of biologically active peptide-pheromone obtained from Enterococc us faecium.