Physiological concentrations (ppb-range) of Fe, Cu, Zn, Ni, Mo, Pd, Co, Mn, Pt, Cr, Cd and other metal cofactor species can be identified and absolutely quantified in an aliquot of a fraction by inductively coupled plasma mass spectrometry (ICP-MS) or total reflection X-ray fluorescence (TXRF), for example. In case of ICP-MS the structural information of the associated metallobiomolecules is irreversibly lost due to ionization of the sample with plasma. Another established high sensitive detection method for the determination of trace elements in biological samples is graphite furnace atomic absorption spectrometry (GF-AAS) (cf. fig. Electropherogram). Because of high purity and optimized concentration of the separated metalloproteins, for example, therapeutic recombinant plant-made pharmaceuticals such as copper chaperone for superoxide dismutase (CCS) from medicinal plants, in a few specific PAGE fractions, the related structures of these bioactive analytes can be elucidated quantitatively by using solution NMR spectroscopy under non-denaturing conditions.