Irradiation of myoglobin by intense, ultrashort laser pulses

We probe the interaction of myoglobin with intense, femtosecond laser pulses. Significant spectral differences are found between native and the irradiated myoglobin. These arise from the disruption of the heme prosthetic group: geometrical restructuring results in alteration of the oxidation state of Fe (from its initial +3 state) which is found to be reversible on timescales of ~4–6 h. Measurements taken upon addition of OH scavengers establish the key role played by these radicals in the overall dynamics. Myoglobin remains intact upon intense field irradiation, demonstrating the structural robustness of the polypeptide backbone. Experiments utilizing intense, ultrashort laser pulses are expected to open new horizons for following, with high sensitivity, changes in the oxidation state, chemical environment, and electronic state of biomolecules in the aqueous phase.