Spin relaxation of iron in mixed state hemoproteins

In hemoproteins the relaxation mechanism of iron is Orbach for high spin (HS) and Raman for low spin (LS). We found that in met-hemoglobin and met-myoglobin, under conditions in which the two spin states coexist, both the HS and the LS states relax to the lattice through Orbach-like processes. Alos, very short (approximately 1 ns) and temperature independent transverse relaxation times T2 were estimated. This may result from the unusual electronic structure of mixed states hemoproteins that allows thermal equilibrium and interconversion of the spin states.