Spectral evidence for sub-picosecond iron displacement after ligand detachment from hemoproteins by femtosecond light pulses.
AUTOR(ES)
Martin, J L
RESUMO
We have measured spectral and kinetic differences in protoheme, sperm whale or horse heart myoglobin and human hemoglobin following photodissociation induced by optical pulses of 80 fs duration. Full ligation was performed with oxygen or carbon monoxide. Femtosecond kinetics and transient difference spectra revealed the appearance of a deoxy species with tau approximately equal to 250-300 fs. The transient deoxy species in myoglobin and hemoglobin evidenced a 3-4 nm red shift of their delta A spectra compared with the equilibrium delta A spectrum. This shift was not observed after photodissociation of the carbon monoxide liganded protoheme. We proposed that the 250 fs time constant corresponding to the appearance of the deoxy-like species is related to the displacement of the ferrous iron out of the heme plane. Consequently, the small red shift of the delta A spectra observed in photodissociated hemoproteins may be tentatively attributed to changes in the vibrational modes of either the proximal histidine-Fe2+ bond and/or of the N4 porph-Fe-N epsilon His (F8) bent.
ACESSO AO ARTIGO
http://www.pubmedcentral.nih.gov/articlerender.fcgi?artid=555364Documentos Relacionados
- Direct observation of sub-picosecond equilibration of excitation energy in the light-harvesting antenna of Rhodospirillum rubrum.
- Crosslinking of progesterone receptor to DNA using tuneable nanosecond, picosecond and femtosecond UV laser pulses.
- Molecular structures from femtosecond x-ray pulses
- Observer variability in recording the peripheral pulses.
- Microphotocoagulation: selective effects of repetitive short laser pulses.