Emoproteine e Neuroglobina
Il nucleo
di eogni
emoproteina
Funzione biologica ↔
formare
rompere
legami è
costituito da uno ione di ferro,
Specie deoxy
che ne determina
le
funzionalitàesacoordinata
biologiche.
Specie deoxy
pentacoordinata
Amminoacidi
Ligando gassoso
(O2, CO, NO)
Heme
Ferro
Dinamica Ultraveloce
Studiare dinamiche di
campioni fotoeccitati
∆t<1ps
Dinamica Ultraveloce
Neuroglobina
Citocromo cdeoxy
Fotolisi della
Jean-Louis Martin et al. 2007 Metionina
????
“…However, such studies are extremely challenging for the
physiologically relevant ligand oxygen and have not been
reported yet, even for the well studied oxygen carriers
myoglobin and hemoglobin, presumably at least in part
because of technical difficulties”
“…Because of the decreased spectral resolution in the
subpicosecond Raman experiments, lines in these spectra are
broader than in the steady-state spectra obtained with cw
excitation.”
Stati
transienti ??
δω≈10cm-1 δt=2ps
Dinamica Ultraveloce
“Transient spectra indicate the
formation of a 5-c domed species upon
photoexcitation of the 6-c species, and
thus photodissociation of an internal
residue. The process appears similar to
the way small ligands like CO can be
photodissociated from ferrous hemeHis-CO complexes. As, in contrast to
small gaseous ligands, the internal
ligands are restrained to heme
proximity, full rebinding is observed on
the picosecond time scale for all
proteins.”
Femtosecond Stimulated Raman Scattering
Actinic Pum
Raman
Probe
∆t
Timeline
Photochemical Pump
Energy
Raman
Pulse
Risoluzione
temporale illimitata
Raman spontaneo
“transform limited”
δωδt>15ps·cm-1
“Reaction” coordinate
Raman
Pulse
Femtosecond Stimulated Raman Scattering
Timing cycle – 1 ms timebase:
Raman Pump
Raman
Pulse
WL Probe
WLG
WLC
ON ON ON ON ….
RAMAN PULSE
ON OFF
PHOTOCHEM PUMP
ON ON OFF
ON OFF ….
OFF ….
Femtosecond Stimulated Raman Scattering
Conclusioni
Conclusioni