A cascade through spin states in the ultrafast haem relaxation of met-myoglobin.
We report on a study of the early relaxation processes of met-Myoglobin in aqueous solution, using a combination of ultrafast broadband fluorescence detection and transient absorption with a broad UV-visible continuum probe at different pump energies. Reconstruction of the spectra of the transient species unravels the details of the haem photocycle in the absence of photolysis. Besides identifying a branching in the ultrafast relaxation of the haem, we show clear evidence for an electronic character of the intermediates, contrary to the commonly accepted idea that the early time relaxation of the haem is only due to cooling. The decay back to the ground state proceeds partially as a cascade through iron spin states, which seems to be a general characteristic of haem systems.
Laboratoire de Spectroscopie Ultrarapide, ISIC, Ecole Polytechnique Fédérale de Lausanne, CH-1015 Lausanne, Switzerland.
Cristina
C
Consani
Laboratoire de Spectroscopie Ultrarapide, ISIC, Ecole Polytechnique Fédérale de Lausanne, CH-1015 Lausanne, Switzerland.
Gerald
G
Auböck
Laboratoire de Spectroscopie Ultrarapide, ISIC, Ecole Polytechnique Fédérale de Lausanne, CH-1015 Lausanne, Switzerland.
Olivier
O
Bräm
Laboratoire de Spectroscopie Ultrarapide, ISIC, Ecole Polytechnique Fédérale de Lausanne, CH-1015 Lausanne, Switzerland.
Frank
F
van Mourik
Laboratoire de Spectroscopie Ultrarapide, ISIC, Ecole Polytechnique Fédérale de Lausanne, CH-1015 Lausanne, Switzerland.
Majed
M
Chergui
D006418:Heme / Q000737:chemistry*; D007501:Iron / Q000737:chemistry; D008786:Metmyoglobin / Q000737:chemistry*; D011166:Porphyrins / Q000737:chemistry; D013050:Spectrometry, Fluorescence
D011166:Porphyrins; D008786:Metmyoglobin; D006418:Heme; D007501:Iron