“…NMR spectra of paramagnetic hemoproteins are unique in that not only can they, under appropriate conditions, be interpreted almost as effectively as for a diamagnetic analogue to yield the molecular structure, − but the resulting hyperfine shifts near the active site yield a wealth of information on the electronic structure and magnetic properties of the active site not available for a diamagnetic derivative. ,, The majority of the systems studied possess low-spin, ferric hemin for which there exist relatively robust quantitative interpretive bases for both the contact and dipolar shifts. − While fewer high-spin ferric hemoproteins have been investigated in detail, the results provide a relatively simple, and for the contact shifts only empirical, correlation between molecular structure and electronic/magnetic properties. ,− The least understood iron oxidation/spin state is high-spin iron(II) heme, which is the only functional paramagnetic state of globins, , one of two functional states 27 of ferricytochromes c ‘, as well as one in many heme enzymes. , …”