Spin-labeled hemoglobin crystals.

Abstract

This work has demonstrated that strong anisotropic paramagnetic resonance spectra can be obtained from nitrocide-malemide spin-labeled hemoglobin crystals. The spectra show the known twofold symmetry of the hemoglobin molecule. The orientation of the labeling molecule relative to the hemoglobin molecule deduced from the paramagnetic resonance spectra can be accounted for in terms of a rough atomic model of oxyhemoglobin, based on the work of Perutz and co-workers. The model also accounts for previously observed "allosteric" effects of O2 on the immobilization of nitroxide-maleimide spin-labels.