TentaGel® resins are grafted copolymers consisting of a low crosslinked polystyrene matrix on which polyethylene glycol (PEG or POE) is grafted via an ethyl ether group which increases stability towards acid treatment and minimizes PEG-leaching. The graft copolymer shows modified physicochemical properties which are highly dominated by the PEG moiety (and no longer by the polystyrene matrix) and has hydrophobic and hydrophilic properties. These copolymers are pressure stable and can be used in batch processes as well as under continuous flow conditions. The PEG spacer is in the range of MW 3000 Da. TentaGel® resins have high diffusion rates and excellent swelling in a wide range of solvents from e.g. toluene to water. Multiple Antigenic Peptides (MAPs) are peptides that are branched artificially, in which Lys residues are used as the scaffolding core. MAPs have a high molar ratio of the peptide antigen to the core molecule, and no carrier protein is needed to elicit an antibody response. Acid treatment liberates the MAP-system, modified by ß-Ala at the C terminus.