Spectrometric-based techniques for metal-binding protein assessment in clinical, environmental, and food samples

Metalloproteins and metal–protein complexes play key roles in all organisms. For example, certain metalloproteins are involved in metal homeostasis and detoxification, or oxidative stress protection; whereas, metals serve as essential cofactors in a large number of metal–protein complexes. Advances in analytical instrumentation as well as informatics have allowed a complete characterization/assessment of both metalloproteins and metal–protein complexes. In some cases, the identification of the protein is a key factor for understanding its physiological function, such as when assessing protein corona in nanoparticles–protein assemblies. On other occasions, the identification of the binding sites in the peptide chain and conformational changes as a consequence of the metal–protein interaction, as well as the lability of this interaction, can explain the role of these metal-based biomolecules in living organisms. This article attempts to critically review the current state-of-the-art of the available analytical techniques for characterizing metalloproteins and metal–protein complexes. Methods for assessing the structure, characterization of the metal-binding sites, as well as the class of proteins involved in some metal (metallic nanoparticle)-binding proteins are discussed. Recent developments when assessing metalloproteins and metal–protein complexes in the clinical, environmental, and food fields, and pioneering research regarding nanoparticle–protein characterization, are also reviewed.