Download Fe-Fe hydrogenase enzymes catalyze the reversible oxidation of

Quantification of Carbon Monoxide from a Photochemical Carbon Monoxide Releasing
Molecule (PhotoCORM) using a Binuclear Rhodium(II) Compound
Kim Trevino, Meghan McCurry & Carmen F. Works
Department of Chemistry, Sonoma State University
Detection of CO in vitro:
• Myoglobin assay is standard but is sensitive to oxidation.
• Binuclear Rh-compounds present a colormetric solution.
Background:
•
Fe-Fe hydrogenase enzymes catalyze the
reversible oxidation of molecule
hydrogen.
The active site of Fe-Fe hydrogenase
enzymes are organometallic.
1.2
1.0
0.8
Abs
•
0.6
[Fe 4S4]
S
OC
NC
X
S
S
0.4
CO
0.2
Fe
Fe
C
O
CN
OH 2
Enzyme Active Site
•
•
•
•
•
Model compounds of Fe-Fe Hydrogenase
have been shown to release CO upon
irradiation.
CO is best known as a silent killer, but it is
also recognized as a small molecule
signaling agent produced through heme
catabolism which is catalyzed by heme
oxygenase.
There are two isozymes of heme
oxygenase (HO) known as HO-1 and HO-2
and both generate CO in vivo.
Photochemical carbon monoxide
releasing molecules (PhotoCORMs) have
the potential for achieving a safe and
controlled delivery of CO to specific
targets.
To help quantitate the photochemistry of
CO release we’ve employed a binuclear
rhodium(II) compound, [Rh2
{(C6H4)P(C6H5)2}2 (02CCH3)2] • (CH3CO2H)2 .
Scheme 1. The oxidation of heme by heme
oxygense producing CO in vivo. Chem.
Commun., 2007, 4197-4208
0.0
400
Figure 2. Color changes observed with the addition
of CO to the rhodium compound.
Synthetic approach to develop PhotoCORMs using
Fe-Fe Hydrogenase model compounds, which
allow for a versatile synthetic platform:
hn
S
S
OC
-CO
Fe
OC
OC
OC
Fe
OC
L
700
800
Figure 3. Changes in the optical spectra
of both (µ-pdt)Fe2(CO)6 and [Rh2
irradiation of 365 nm light.
O
Fe
CO
Table 1. Quantum Yield Data for PDT and
Rhodium in methylene chloride, upon
irradiation of 365 nm light.
CO
CO
Fe
600
{(C6H4)P(C6H5)2}2 (02CCH3)2] •
(CH3CO2H)2 in methylene chloride, upon
Fe2(m-pdt)(CO)6
S
S
500
nm
CO
L
L = CO, CN- or PR3
PDT
Rh
0.17
0.13
0.16
0.11
0.13
0.09
0.15
0.10
Wavelength
365 nm
Quantum Yield
0.15 ± 0.08
1.0
0.8
0.6
Absorbance
Cys
0.4
0.2
0.0
250
Figure 1. Spectral changes of Fe2(m-pdt)(CO)6 in
THF when irradiated with 365 nm light. Monitored
by IR.
300
350
Wavelength (nm)
400
450
Figure 1. Top: Spectral changes of Fe2(mpdt)(CO)6 in THF when irradiated with 365
nm light. Bottom: Spectral changes for FeMET in acetonitrile when irradiated with
334 nm light
500
Acknowledgments:
We would like to thank the Chemistry Division of the National
Science Foundation (NSFCHE-1057808) , LSAMP NSF grant
HRD-1302873, McNair Scholars Program, Presidential Scholar
Jaimey Homen, and CSUPERB for support.