The invention provides a synthetic macromolecular conjugate for selective interaction with proteins, comprising a synthetic copolymer, and at least one binding group and at least one further group selected from an affinity tag and an imaging probe, said at least one binding group and at least one further group being bound via covalent bond to said synthetic copolymer. The macromolecular conjugate is suitable in particular for identification, visualization, quantification or isolation of proteins and/or cells.