EPR investigation of libration motion of spin labeled hemerythrin

• Room-temperature X-band EPR spectra of site directed spin labeled hemerythrin, reported for first time.
• Viscous media (glycerol, PEG4000, BSA) affect the the mobility (rotational correlation time τc) differently.
• Effects on multimeric organization noted.
• This study is as part of efforts to design a hemerythrin-based blood substitute.

Reported here are room-temperature continuous wave X-band Electron Paramagnetic Resonance (EPR) spectra of the non-heme di-iron protein hemerythrin (Hr), spin labeled at position 51C in different viscous media, illustrating the mobility and oligomeric recombination tendency of the Phascolopsis gouldii Hr. The mobility of a spin labeled Hr depends on the local viscosity and its connectivity to the nature of the molecular environment (glycerol, PEG4000 and BSA). This provides the basis for a tool useful in directly monitoring Hr in ex vivo samples upon injection within the bloodstream of test animals, for blood substitute research.

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