Protein relaxation without a geminate phase in nanosecond photodissociatedCO carp hemoglobin

Transient heme-protein interactions upon passing from ligated to deligated carp hemoglobin were observed through time-resolved optical spectra followi ng nanosecond CO photodissociation. The spectral evolution of the heme, in the nanosecond and microsecond time ranges, shows a protein conformational relaxation and the absence of a geminate CO recombination in carp hemoglobi n. The comparison of the phenomena in carp and human hemoglobin implies tha t the physical basis of the geminate rebinding in human hemoglobin should i nvolve an out-of-equilibrium protein conformation, close to a dissipative s tructure defined by the thermodynamics of Prigogine. (C) 1999 Elsevier Scie nce B.V. All rights reserved.