text: By definition, these compounds occur in nature, but the subfield includes anthropogenic species, such as pollutants (e.g., methylmercury) and drugs (e.g., Cisplatin).  The field, which incorporates many aspects of biochemistry, includes many kinds of compounds, e.g., the phosphates in DNA, and also metal complexes containing ligands that range from biological macromolecules, commonly peptides, to ill-defined species such as humic acid, and to water (e.g., coordinated to gadolinium complexes employed for MRI).  Traditionally bioinorganic chemistry focuses on electron- and energy-transfer in proteins relevant to respiration.  Medicinal inorganic chemistry includes the study of both non-essential and essential elements with applications to diagnosis and therapies.
  * Examples: hemoglobin, methylmercury, carboxypeptidase