Mössbauer and EPR study of nitrosyl hemoglobin

Nitrosyl hemoglobin was prepared by bubbling fresh57Fe-enriched rat hemoglobin with NO. S- and X-band EPR spectra at 77 K are typical for anS=1/2 system with an anisotropicg-tensor and exhibit hyperfine interactions of14N with the electronic spin. Mossbauer spectra at 4.2 and 100 K consist of a superposition of spectra from high- and low-spin Fe(III), deoxygenated hemoglobin and a component corresponding toS=1/2,g=2, hyperfine constantsA xx /g n Β n =A yy /g n Β n =−19.6 T,A zz /g n Β n =6.8 T, quadrupole splitting δE Q=1.5 mm s−1, isomer shiftI s=0.42 mm s−1 and linewidth 0.4 mm s−1. The spin-lattice relaxation rate at 100 K is