Haem localization in haemoproteins by spin and triplet tools

The rate constants of efficient exchange interaction (Kex) of spin‐labelled lysozyme and the triplet probes perylene, eosine and anthracene butanoic acid with the haemoproteins were measured in microsomes and in solution by electron paramagnetic resonance and by the registration of delayed annihilation fluorescence. Constants of efficient exchange interactions with the haem groups of myoglobin, haemoglobin, cytochrome c and b5 are 3–22 × 107 M−1 s−1 in solution. The experiments with membrane‐bound cytochrome P‐450 revealed no exchange interactions with the probes located in solution or in the membrane. These results can be accounted for by the deeper incorporation of cytochrome P‐450 haem into the protein globule as compared to the other haemoprotein haems studied.