workshop on metabolomics in the context of ...ferredoxin p700+ 4fe-4s p700 on excitation p700...
TRANSCRIPT
WORKSHOP ON
METABOLOMICS IN THE CONTEXT OF
SYSTEMS BIOLOGY: A RATIONAL APPROACH
TO SEARCH FOR LEAD MOLECULES
25-26/02/10
Maria Fátima das Graças Fernandes da Silva
Federal University of São Carlos, SP, Brazil
NATURAL PRODUCTS
AND PHOTOSYNTHESIS
INTERACTION
N
O
OH
OH
OMe
O
OH
Me
N
O
OH
OOH
OH
OMeMe
AcO
O
H
OH
Photosynthesis is the primary
metabolic process disrupted by a
diverse range of herbicides.
However, other targets for herbicide action are
cell division, cell elongation, plant growth regulation
metabolism and biosynthesis of lipids, amino acids
and pigments.
As part of our efforts to find
potential lead compounds as herbicides,
we have been assayed natural products
as inhibitors of photosynthesis.
N
O
OH
OH
OMe
O
OH
Me
N
O
OH
OOH
OH
OMeMe
AcO
O
H
OH
Photosynthesis in green plants is mediated by two
linked photosystems: Photosystem II and I
Photosystem II, begins
with excitation of a special
pair of chlorophyll
molecules that are bound
by D1 and D2 subunits of
proteins system.
D1 D2
Thylakoid
membrane
The special pair of
chlorophyll a molecules absorb
light at 680 nm, thus it is
often called P680.
On excitation P680 rapidly
transfers an electron to a
pheophytin, which transfers it
to a bound plastoquinone at
site QA and then to a mobile
plastoquinone at site QB.
N
H
N
H
OMe
OO
N
N
H
H
O
H
O O
R
O
On
(n = 6 to 10)
O
On
(n = 6 to 10)
Light
QA
QB
MnO4
H2O O2
e-
P680* P680+
With the arrival of a
second electron and the
uptake of two protons, the
mobile plastoquinone is
reduced to QH2
O-
O.n
(n = 6 to 10)
e-
O-
O- n
(n = 6 to 10)
H+2OH
OH n
(n = 6 to 10)
N
H
N
H
OMe
OO
N
N
H
H
O
H
O O
R
O
On
(n = 6 to 10)
Light
QA
QB
MnO4
H2O O2
O-
O- n
(n = 6 to 10)
e-
P680*P680+
O
NH
NH-O
O
NH
NH.O
e-_
N
H
N
H
OMe
OO
N
N
H
H
O
H
O O
R
O
On
(n = 6 to 10)
O
On
(n = 6 to 10)
Light
QA
QB
e-
P680*
2 H2O + (Mn2+, Mn3+, Mn4+, Mn5+) O2 + 4 e- + 4 H+
O
NH
NH-O
O
NH
NH.O
e-_ P680+
The pair P680+
extracts electrons
from tyrosine
residue of subunit
D1 of PSII.
Oxidized tyrosin
removes electrons
from water
molecules bound to
the manganese
center.
Photosystem II
occurs in the thylakoid
membrane.
The manganese
center, or the water
oxidation occurs in the
thylacoide lumen
Stroma
Lumen
4H+
4H+
+ 4e-
In short
Electrons flow from H2O to QB (QH2)
1.0
0.0
- 1.0
Re
du
cti
on
po
ten
tia
l (V
)
Mn
center
H2O
P680
Photon 1
P680*
Ph
QA
QB
Photosystem II
O2
Cytochrome bf links Photosystem
II to Photosystem I
This complex catalyzes the
transfer of electrons from
plastoquinol (QH2) to plastocianin
(Pc), a small, soluble copper protein
in the thylakoid.1.0
0.0
- 1.0
Red
ucti
on
po
ten
tial (V
)
Mn
center
H2O
P680
Photon 1
P680*
Ph
QA
QB
Photosystem II
O2
PQ
1.0
0.0
- 1.0
Red
ucti
on
po
ten
tial (V
)
Mn
center
H2O
P680
Photon 1
P680*
Ph
QA
QB
Photosystem II
O2
1.0
0.0
- 1.0
Red
ucti
on
po
ten
tial (V
)
Mn
center
H2O
P680
Photon 1
P680*
Ph
QA
QB
Photosystem II
O2
PQ
Plastoquinol is oxidized to plastoquinone
(n = 6 to 10)
n
OH
OH
- H+
O-
OH n
(n = 6 to 10)
O.
OH
Cytochrome bf (Fe-S protein) PCox PCred
O.
O
- H+(n = 6 to 10)
n
O
O
_ e-
_ e-
(n = 6 to 10)
n
n
(n = 6 to 10)
The electrons flow through the iron-sulfur protein
of Cytochrome bf complex to convert oxidized
plastocyanin into its reduced form.
(n = 6 to 10)
n
OH
OH
- H+
O-
OH n
(n = 6 to 10)
O.
OH
Cytochrome bf (Fe-S protein) PCox PCred
O.
O
- H+(n = 6 to 10)
n
O
O
_ e-
_ e-
(n = 6 to 10)
n
n
(n = 6 to 10)
Stroma
Lumen
4H+
4H+
+ 4e-
These
protons are
released in the
thylakoide
lumen
Thylakoide lumen low pH
In short
Electrons flow from H2O to Plastocyanin, then to PSI
1.0
0.0
- 1.0
Re
du
cti
on
po
ten
tia
l (V
)
Mn
center
H2O
P680
Photon 1
P680*
Ph
QA
QBCytochrome
bf complexP700
Pc
Photosystem II
O2
PQ
Photosystem I
Photosystem I, begins with excitation of a special
pair of chlorophyll a molecules that are bound by
psaA and psaB subunits of proteins system.
The special pair of chlorophyll a molecules absorb light
at 700 nm, thus it is often called P700.
PsaAPsaB
Light
e-
P700*
Chlorophyll
(A0)
Quinone
(A1)
Ferredoxin
P700+
4Fe-4S
P700
On excitation P700
rapidly transfers an
electron to chlorophyll at
site A0, which transfers it
to quinone at site A1 and
then to a set of iron (Fe)-
Sulfur clusters, and
finally to ferredoxin (Fd) .
Photosystem I
Light
e-
P700*
Chlorophyll
(A0)
Quinone
(A1)
Ferredoxin
P700+
Plastocyanin (Cu+)
Plastocyanin (Cu2+)
e-
4Fe-4S
P700
P700+ captures
an electron from
reduced
plastocyanin to
return to P700.
PSII
Ferredoxin transfers electrons to NADP+ and
the reaction is catalyzed by ferredoxin-NADP+
reductase to form NADPH
1.0
0.0
- 1.0
Re
du
cti
on
po
ten
tia
l (V
)
Mn
center
H2O
P680
Photon 1
P680*
Ph
QA
QBCytochrome
bf complexP700
P700*
Pc
Photon 2
A0
A1
4Fe-4S
Fd-NADP+
reductase
NADPH
Photosystem II
Photosystem I
O2
PQ
*
The excess of protons flow out of
lumen through ATP synthase to
generate ATP from ADP and Pi in the
stroma.
ATP synthase is called
CF1-CF0 complex
Photosynthesis
*
A number of compounds isolated in our own
investigations of plants from Sapindales (Rutales)
were assayed.
Inhibition of photophosphorylation and
electron transport chain in thylakoids by
Natural Products
We use artificial electron donors and
acceptors, which bind in specific site of PSII or
PSI
e-
.
N
N
N
N
Paraquat
Methylviologen (MV)
MV
1.0
0.0
- 1.0
Re
du
cti
on
po
ten
tial (V
)
Mn
center
H2O
P680
Photon 1
P680*
Ph
QA
QBCytochrome
bf complexP700
P700*
Pc
Photon 2
A0
A1
4Fe-4S
Fd-NADP+
reductase
NADPH
Photosystem II
Photosystem I
O2
PQ
Lumen4 H+
1.0
0.0
- 1.0
Re
du
cti
on
po
ten
tial (V
)
Mn
center
H2O
P680
Photon 1
P680*
Ph
QA
QBCytochrome
bf complexP700
P700*
Pc
Photon 2
A0
A1
4Fe-4S
Fd-NADP+
reductase
NADPH
Photosystem II
Photosystem I
O2
PQ
1.0
0.0
- 1.0
Re
du
cti
on
po
ten
tial (V
)
Mn
center
H2O
P680
Photon 1
P680*
Ph
QA
QBCytochrome
bf complexP700
P700*
Pc
Photon 2
A0
A1
4Fe-4S
Fd-NADP+
reductase
NADPH
Photosystem II
Photosystem I
O2
PQ
Lumen4 H+
Measurement of ATP Synthesis
We use
methylviologen
(MV) as electron
acceptor, and
chlorophyll from
the intact
chloroplasts
freshly lysed.
Stock solution of NP is prepared using DMSO.
MV
1.0
0.0
- 1.0
Re
du
cti
on
po
ten
tial (V
)
Mn
center
H2O
P680
Photon 1
P680*
Ph
QA
QBCytochrome
bf complexP700
P700*
Pc
Photon 2
A0
A1
4Fe-4S
Fd-NADP+
reductase
NADPH
Photosystem II
Photosystem I
O2
PQ
Lumen4 H+
1.0
0.0
- 1.0
Red
ucti
on
po
ten
tial (V
)
Mn
center
H2O
P680
Photon 1
P680*
Ph
QA
QBCytochrome
bf complexP700
P700*
Pc
Photon 2
A0
A1
4Fe-4S
Fd-NADP+
reductase
NADPH
Photosystem II
Photosystem I
O2
PQ
1.0
0.0
- 1.0
Red
ucti
on
po
ten
tial (V
)
Mn
center
H2O
P680
Photon 1
P680*
Ph
QA
QBCytochrome
bf complexP700
P700*
Pc
Photon 2
A0
A1
4Fe-4S
Fd-NADP+
reductase
NADPH
Photosystem II
Photosystem I
O2
PQ
Lumen4 H+
1.0
0.0
- 1.0
Red
ucti
on
po
ten
tial (V
)
Mn
center
H2O
P680
Photon 1
P680*
Ph
QA
QBCytochrome
bf complexP700
P700*
Pc
Photon 2
A0
A1
4Fe-4S
Fd-NADP+
reductase
NADPH
Photosystem II
Photosystem I
O2
PQ
Lumen4 H+
1.0
0.0
- 1.0
Red
ucti
on
po
ten
tial (V
)
Mn
center
H2O
P680
Photon 1
P680*
Ph
QA
QBCytochrome
bf complexP700
P700*
Pc
Photon 2
A0
A1
4Fe-4S
Fd-NADP+
reductase
NADPH
Photosystem II
Photosystem I
O2
PQ
1.0
0.0
- 1.0
Red
ucti
on
po
ten
tial (V
)
Mn
center
H2O
P680
Photon 1
P680*
Ph
QA
QBCytochrome
bf complexP700
P700*
Pc
Photon 2
A0
A1
4Fe-4S
Fd-NADP+
reductase
NADPH
Photosystem II
Photosystem I
O2
PQ
Lumen4 H+
We analyzed the effect of N P on electron
transport from H2O to MV.
First of all, we measure the proton concentration,
or ATP synthesis
ATP
MV
Photosynthetic phosphorylation from water to MV
as electron acceptor was inhibited by siderin in a
concentration-dependent manner.
Effect of compounds 1 (), 2 (), 3 (), and 4 () on ATP synthesis.
O OMeO
OMe
1
Veiga, da Silva et al, Arch. Biochem. Biophys. 465, 38-43, 2007
The I50 value for siderin (1) was 27.0 M.
The other coumarins were almost inactive as
inhibitor to ATP synthesis.
Effect of compounds 1 (), 2 (), 3 (), and 4 () on ATP synthesis.
O OMeO
OMe
1
O OMeO
MeO
O OO
OMe
O O
OMe
O
2
3
4
1.0
0.0
- 1.0
Re
du
cti
on
po
ten
tial (V
)
Mn
center
H2O
P680
Photon 1
P680*
Ph
QA
QBCytochrome
bf complexP700
P700*
Pc
Photon 2
A0
A1
4Fe-4S
Fd-NADP+
reductase
NADPH
Photosystem II
Photosystem I
O2
PQ
Lumen4 H+
1.0
0.0
- 1.0
Re
du
cti
on
po
ten
tial (V
)
Mn
center
H2O
P680
Photon 1
P680*
Ph
QA
QBCytochrome
bf complexP700
P700*
Pc
Photon 2
A0
A1
4Fe-4S
Fd-NADP+
reductase
NADPH
Photosystem II
Photosystem I
O2
PQ
1.0
0.0
- 1.0
Re
du
cti
on
po
ten
tial (V
)
Mn
center
H2O
P680
Photon 1
P680*
Ph
QA
QBCytochrome
bf complexP700
P700*
Pc
Photon 2
A0
A1
4Fe-4S
Fd-NADP+
reductase
NADPH
Photosystem II
Photosystem I
O2
PQ
Lumen4 H+
We measure the oxygen concentration with an
oxygen electrode (Clark-type electrode)
Measurement of non-cyclic electron transport
MV
Siderin inhibited the phosphorylating electron
transport rate 100% at 400 M.
Effect of siderin on electron flow [basal (), phosphorylating (),
and uncoupled ()] from water to MV in spinach chloroplasts
O OMeO
OMe
1
1.0
0.0
- 1.0
Re
du
cti
on
po
ten
tial (V
)
Mn
center
H2O
P680
Photon 1
P680*
Ph
QA
QBCytochrome
bf complexP700
P700*
Pc
Photon 2
A0
A1
4Fe-4S
Fd-NADP+
reductase
NADPH
Photosystem II
Photosystem I
O2
PQ
Lumen4 H+
1.0
0.0
- 1.0
Re
du
cti
on
po
ten
tial (V
)
Mn
center
H2O
P680
Photon 1
P680*
Ph
QA
QBCytochrome
bf complexP700
P700*
Pc
Photon 2
A0
A1
4Fe-4S
Fd-NADP+
reductase
NADPH
Photosystem II
Photosystem I
O2
PQ
1.0
0.0
- 1.0
Re
du
cti
on
po
ten
tial (V
)
Mn
center
H2O
P680
Photon 1
P680*
Ph
QA
QBCytochrome
bf complexP700
P700*
Pc
Photon 2
A0
A1
4Fe-4S
Fd-NADP+
reductase
NADPH
Photosystem II
Photosystem I
O2
PQ
Lumen4 H+
We use artificial electron donors and acceptors,
which bind in specific site of PSII or PSI
LOCALIZATION OF SIDERIN SITES OF
INTERACTION ON PSII OR PSI
ELUCIDATION OF THE MECHANISM OF ACTION
MV
Dichlorophenol-
indophenol
DCPIPox DCPIPred
H2O
We analyzed the effect
of siderin on electron
transport from H2O to
DCPIPox; then to QB.
We measure the oxygen
concentration with an
oxygen electrode (Clark-
type electrode)
2 H+
e-
OH
ClCl
OH
N H
O
N
ClCl
OH
DCPIPox
1.0
0.0
- 1.0
Re
du
cti
on
po
ten
tial (V
)
Mn
center
H2O
P680
Photon 1
P680*
Ph
QA
QBCytochrome
bf complexP700
P700*
Pc
Photon 2
A0
A1
4Fe-4S
Fd-NADP+
reductase
NADPH
Photosystem II
Photosystem I
O2
PQ
Lumen4 H+
1.0
0.0
- 1.0
Re
du
cti
on
po
ten
tial (V
)
Mn
center
H2O
P680
Photon 1
P680*
Ph
QA
QBCytochrome
bf complexP700
P700*
Pc
Photon 2
A0
A1
4Fe-4S
Fd-NADP+
reductase
NADPH
Photosystem II
Photosystem I
O2
PQ
1.0
0.0
- 1.0
Re
du
cti
on
po
ten
tial (V
)
Mn
center
H2O
P680
Photon 1
P680*
Ph
QA
QBCytochrome
bf complexP700
P700*
Pc
Photon 2
A0
A1
4Fe-4S
Fd-NADP+
reductase
NADPH
Photosystem II
Photosystem I
O2
PQ
Lumen4 H+
1.0
0.0
- 1.0
Re
du
cti
on
po
ten
tial (V
)
Mn
center
H2O
P680
Photon 1
P680*
Ph
QA
QBCytochrome
bf complexP700
P700*
Pc
Photon 2
A0
A1
4Fe-4S
Fd-NADP+
reductase
NADPH
Photosystem II
Photosystem I
O2
PQ
Lumen4 H+
1.0
0.0
- 1.0
Re
du
cti
on
po
ten
tial (V
)
Mn
center
H2O
P680
Photon 1
P680*
Ph
QA
QBCytochrome
bf complexP700
P700*
Pc
Photon 2
A0
A1
4Fe-4S
Fd-NADP+
reductase
NADPH
Photosystem II
Photosystem I
O2
PQ
1.0
0.0
- 1.0
Re
du
cti
on
po
ten
tial (V
)
Mn
center
H2O
P680
Photon 1
P680*
Ph
QA
QBCytochrome
bf complexP700
P700*
Pc
Photon 2
A0
A1
4Fe-4S
Fd-NADP+
reductase
NADPH
Photosystem II
Photosystem I
O2
PQ
Lumen4 H+
We also add
DBMIB, which
binding in
Cytochrome bf
complex,
inhibiting the
electron
transport from
H2O to Quinone
pool (Qp).
O
O
Br
Br2,5-dibromo-3-methyl-
6-isopropyl-p-benzoquinone
Then, electrons flow to DCPIPox.
DCPIPox
1 Conc. M
0
100
200
300
400
PSII
H2O to DCPIPox (%)
100
78
70
52
0
Siderin inhibits electron transport
from H2O to DCPIPox, then to QB, by
100% at 400 M
Veiga, da Silva et al, Arch. Biochem. Biophys. 465, 38-43, 2007
1.0
0.0
- 1.0
Red
ucti
on
po
ten
tial (V
)
Mn
center
H2O
P680
Photon 1
P680*
Ph
QA
QBCytochrome
bf complexP700
P700*
Pc
Photon 2
A0
A1
4Fe-4S
Fd-NADP+
reductase
NADPH
Photosystem II
Photosystem I
O2
PQ
Lumen4 H+
1.0
0.0
- 1.0
Red
ucti
on
po
ten
tial (V
)
Mn
center
H2O
P680
Photon 1
P680*
Ph
QA
QBCytochrome
bf complexP700
P700*
Pc
Photon 2
A0
A1
4Fe-4S
Fd-NADP+
reductase
NADPH
Photosystem II
Photosystem I
O2
PQ
1.0
0.0
- 1.0
Red
ucti
on
po
ten
tial (V
)
Mn
center
H2O
P680
Photon 1
P680*
Ph
QA
QBCytochrome
bf complexP700
P700*
Pc
Photon 2
A0
A1
4Fe-4S
Fd-NADP+
reductase
NADPH
Photosystem II
Photosystem I
O2
PQ
Lumen4 H+
DCPIPox
MnO4
H2O O2
MnO4
H2O O2
P680+
P680Donor site
Acceptorsite
1.0
0.0
- 1.0
Red
ucti
on
po
ten
tial (V
)
Mn
center
H2O
P680
Photon 1
P680*
Ph
QA
QBCytochrome
bf complexP700
P700*
Pc
Photon 2
A0
A1
4Fe-4S
Fd-NADP+
reductase
NADPH
Photosystem II
Photosystem I
O2
PQ
Lumen4 H+
1.0
0.0
- 1.0
Red
ucti
on
po
ten
tial (V
)
Mn
center
H2O
P680
Photon 1
P680*
Ph
QA
QBCytochrome
bf complexP700
P700*
Pc
Photon 2
A0
A1
4Fe-4S
Fd-NADP+
reductase
NADPH
Photosystem II
Photosystem I
O2
PQ
1.0
0.0
- 1.0
Red
ucti
on
po
ten
tial (V
)
Mn
center
H2O
P680
Photon 1
P680*
Ph
QA
QBCytochrome
bf complexP700
P700*
Pc
Photon 2
A0
A1
4Fe-4S
Fd-NADP+
reductase
NADPH
Photosystem II
Photosystem I
O2
PQ
Lumen4 H+
DCPIPox
MnO4
H2O O2
MnO4
H2O O2
P680+
Donor site
SiMo
To localize the
siderin site of
interaction on
PSII between H2O
to QB, we use
electron acceptor
which binds in the
donor site of
PSII, as
silicomolybdate.
SiMo12O-4
40 + 2e- + 2 H+ H2SiMo12O-4
40
1.0
0.0
- 1.0
Re
du
cti
on
po
ten
tial
(V)
Mn
center
H2O
P680
Photon 1
P680*
Ph
QA
QBCytochrome
bf complexP700
P700*
Pc
Photon 2
A0
A1
4Fe-4S
Fd-NADP+
reductase
NADPH
Photosystem II
Photosystem I
O2
PQ
Lumen4 H+
1.0
0.0
- 1.0
Red
ucti
on
po
ten
tial (V
)
Mn
center
H2O
P680
Photon 1
P680*
Ph
QA
QBCytochrome
bf complexP700
P700*
Pc
Photon 2
A0
A1
4Fe-4S
Fd-NADP+
reductase
NADPH
Photosystem II
Photosystem I
O2
PQ
1.0
0.0
- 1.0
Red
ucti
on
po
ten
tial (V
)
Mn
center
H2O
P680
Photon 1
P680*
Ph
QA
QBCytochrome
bf complexP700
P700*
Pc
Photon 2
A0
A1
4Fe-4S
Fd-NADP+
reductase
NADPH
Photosystem II
Photosystem I
O2
PQ
Lumen4 H+
MnO4
H2O O2
MnO4
H2O O2
P680+
Donor site
SiMo
SiMo12O-4
40 + 2e- + 2 H+ H2SiMo12O-4
40
DCMU
N
Cl
Cl
N
O
H
We also add
DCMU, which binding
in plastoquinone site,
inhibiting the
electron transport
from H2O to QB.
Then, electrons flow to SiMo.
Dichlorophenyldimethylurea
1.0
0.0
- 1.0
Re
du
cti
on
po
ten
tial (V
)
Mn
center
H2O
P680
Photon 1
P680*
Ph
QA
QBCytochrome
bf complexP700
P700*
Pc
Photon 2
A0
A1
4Fe-4S
Fd-NADP+
reductase
NADPH
Photosystem II
Photosystem I
O2
PQ
Lumen4 H+
1.0
0.0
- 1.0
Re
du
cti
on
po
ten
tial (V
)
Mn
center
H2O
P680
Photon 1
P680*
Ph
QA
QBCytochrome
bf complexP700
P700*
Pc
Photon 2
A0
A1
4Fe-4S
Fd-NADP+
reductase
NADPH
Photosystem II
Photosystem I
O2
PQ
1.0
0.0
- 1.0
Re
du
cti
on
po
ten
tial (V
)
Mn
center
H2O
P680
Photon 1
P680*
Ph
QA
QBCytochrome
bf complexP700
P700*
Pc
Photon 2
A0
A1
4Fe-4S
Fd-NADP+
reductase
NADPH
Photosystem II
Photosystem I
O2
PQ
Lumen4 H+
MnO4
H2O O2
MnO4
H2O O2
P680+
Donor site
SiMo
1 Conc. M
0
100
200
300
400
PSII
H2O to SiMo (%)
100
75
50
12
0
Siderin inhibits electron transport from
H2O to SiMo by 100% at 400 M
DCMU
Veiga, da Silva et al, Arch. Biochem. Biophys. 465, 38-43, 2007
1.0
0.0
- 1.0R
ed
ucti
on
po
ten
tial (V
)
Mn
center
H2O
P680
Photon 1
P680*
Ph
QA
QBCytochrome
bf complexP700
P700*
Pc
Photon 2
A0
A1
4Fe-4S
Fd-NADP+
reductase
NADPH
Photosystem II
Photosystem I
O2
PQ
Lumen4 H+
1.0
0.0
- 1.0R
ed
ucti
on
po
ten
tial (V
)
Mn
center
H2O
P680
Photon 1
P680*
Ph
QA
QBCytochrome
bf complexP700
P700*
Pc
Photon 2
A0
A1
4Fe-4S
Fd-NADP+
reductase
NADPH
Photosystem II
Photosystem I
O2
PQ
1.0
0.0
- 1.0R
ed
ucti
on
po
ten
tial (V
)
Mn
center
H2O
P680
Photon 1
P680*
Ph
QA
QBCytochrome
bf complexP700
P700*
Pc
Photon 2
A0
A1
4Fe-4S
Fd-NADP+
reductase
NADPH
Photosystem II
Photosystem I
O2
PQ
Lumen4 H+
MnO4
H2O O2
MnO4
H2O O2
P680+
Donor site
DPC To confirm the siderin site
of interaction on PSII between
H2O to P680+, we use electron
donor which bind in the donor
site of PSII, as DPC,
diphenylcarbazide.
1.0
0.0
- 1.0
Re
du
cti
on
po
ten
tial (V
)
Mn
center
H2O
P680
Photon 1
P680*
Ph
QA
QBCytochrome
bf complexP700
P700*
Pc
Photon 2
A0
A1
4Fe-4S
Fd-NADP+
reductase
NADPH
Photosystem II
Photosystem I
O2
PQ
Lumen4 H+
1.0
0.0
- 1.0
Red
ucti
on
po
ten
tial (V
)
Mn
center
H2O
P680
Photon 1
P680*
Ph
QA
QBCytochrome
bf complexP700
P700*
Pc
Photon 2
A0
A1
4Fe-4S
Fd-NADP+
reductase
NADPH
Photosystem II
Photosystem I
O2
PQ
1.0
0.0
- 1.0
Red
ucti
on
po
ten
tial (V
)
Mn
center
H2O
P680
Photon 1
P680*
Ph
QA
QBCytochrome
bf complexP700
P700*
Pc
Photon 2
A0
A1
4Fe-4S
Fd-NADP+
reductase
NADPH
Photosystem II
Photosystem I
O2
PQ
Lumen4 H+
MnO4
H2O O2
MnO4
H2O O2
P680+
Donor site
DPC
With DPC, we use Tris-
treated chloroplasts that inhibit
the water-oxidation enzyme
activity, thus we do not have
the electron flow from water,
but from DPC.
X
1.0
0.0
- 1.0
Red
ucti
on
po
ten
tial (V
)
Mn
center
H2O
P680
Photon 1
P680*
Ph
QA
QBCytochrome
bf complexP700
P700*
Pc
Photon 2
A0
A1
4Fe-4S
Fd-NADP+
reductase
NADPH
Photosystem II
Photosystem I
O2
PQ
Lumen4 H+
1.0
0.0
- 1.0
Red
ucti
on
po
ten
tial (V
)
Mn
center
H2O
P680
Photon 1
P680*
Ph
QA
QBCytochrome
bf complexP700
P700*
Pc
Photon 2
A0
A1
4Fe-4S
Fd-NADP+
reductase
NADPH
Photosystem II
Photosystem I
O2
PQ
1.0
0.0
- 1.0
Red
ucti
on
po
ten
tial (V
)
Mn
center
H2O
P680
Photon 1
P680*
Ph
QA
QBCytochrome
bf complexP700
P700*
Pc
Photon 2
A0
A1
4Fe-4S
Fd-NADP+
reductase
NADPH
Photosystem II
Photosystem I
O2
PQ
Lumen4 H+
1.0
0.0
- 1.0
Re
du
cti
on
po
ten
tial (V
)
Mn
center
H2O
P680
Photon 1
P680*
Ph
QA
QBCytochrome
bf complexP700
P700*
Pc
Photon 2
A0
A1
4Fe-4S
Fd-NADP+
reductase
NADPH
Photosystem II
Photosystem I
O2
PQ
Lumen4 H+
1.0
0.0
- 1.0
Re
du
cti
on
po
ten
tial (V
)
Mn
center
H2O
P680
Photon 1
P680*
Ph
QA
QBCytochrome
bf complexP700
P700*
Pc
Photon 2
A0
A1
4Fe-4S
Fd-NADP+
reductase
NADPH
Photosystem II
Photosystem I
O2
PQ
1.0
0.0
- 1.0
Re
du
cti
on
po
ten
tial (V
)
Mn
center
H2O
P680
Photon 1
P680*
Ph
QA
QBCytochrome
bf complexP700
P700*
Pc
Photon 2
A0
A1
4Fe-4S
Fd-NADP+
reductase
NADPH
Photosystem II
Photosystem I
O2
PQ
Lumen4 H+
2 H+
e-
OH
ClCl
OH
N H
O
N
ClCl
OH
MnO4
H2O O2
MnO4
H2O O2
P680+
Donor site
DPCX
DCPIPox
We analyzed the effect of siderin
on electron transport from DPC to
DCPIPox; then to QB.
O
O
Br
Br
DBMIB
Dichlorophenol -
indophenol
DCPIPox DCPIPred
DPC
Reaction of electron transport from DPC
(diphenylcarbazide) to DCPIPox:
O
N
ClCl
OH OH
ClCl
OH
N H
e-
2 H+
2
- 2 H+
e-
e-
NN N
N
OH
H H
H
NN N
N
O
H
H
NN N
N
O
H
H
2e-
Reduction of DCPIPox
is quantified
spectrophotometrically
at 600 nm.
MnO4
H2O O2
MnO4
H2O O2
P680+
DPCX
MnO4
H2O O2
MnO4
H2O O2
P680+
Donor site
DPCX
1 Conc. M
0
50
100
200
PSII
DPC to DCPIP (%)
100
83
58
57
Electron transport from DPC to
DCPIPox was partially inhibited at
all concentrations tested.
DCPIPox
Veiga, da Silva et al, Arch. Biochem. Biophys. 465, 38-43, 2007
1.0
0.0
- 1.0R
ed
ucti
on
po
ten
tial (V
)
Mn
center
H2O
P680
Photon 1
P680*
Ph
QA
QBCytochrome
bf complexP700
P700*
Pc
Photon 2
A0
A1
4Fe-4S
Fd-NADP+
reductase
NADPH
Photosystem II
Photosystem I
O2
PQ
Lumen4 H+
1.0
0.0
- 1.0R
ed
ucti
on
po
ten
tial (V
)
Mn
center
H2O
P680
Photon 1
P680*
Ph
QA
QBCytochrome
bf complexP700
P700*
Pc
Photon 2
A0
A1
4Fe-4S
Fd-NADP+
reductase
NADPH
Photosystem II
Photosystem I
O2
PQ
1.0
0.0
- 1.0R
ed
ucti
on
po
ten
tial (V
)
Mn
center
H2O
P680
Photon 1
P680*
Ph
QA
QBCytochrome
bf complexP700
P700*
Pc
Photon 2
A0
A1
4Fe-4S
Fd-NADP+
reductase
NADPH
Photosystem II
Photosystem I
O2
PQ
Lumen4 H+
1.0
0.0
- 1.0
Red
ucti
on
po
ten
tial (V
)
Mn
center
H2O
P680
Photon 1
P680*
Ph
QA
QBCytochrome
bf complexP700
P700*
Pc
Photon 2
A0
A1
4Fe-4S
Fd-NADP+
reductase
NADPH
Photosystem II
Photosystem I
O2
PQ
Lumen4 H+
1.0
0.0
- 1.0
Red
ucti
on
po
ten
tial (V
)
Mn
center
H2O
P680
Photon 1
P680*
Ph
QA
QBCytochrome
bf complexP700
P700*
Pc
Photon 2
A0
A1
4Fe-4S
Fd-NADP+
reductase
NADPH
Photosystem II
Photosystem I
O2
PQ
1.0
0.0
- 1.0
Red
ucti
on
po
ten
tial (V
)
Mn
center
H2O
P680
Photon 1
P680*
Ph
QA
QBCytochrome
bf complexP700
P700*
Pc
Photon 2
A0
A1
4Fe-4S
Fd-NADP+
reductase
NADPH
Photosystem II
Photosystem I
O2
PQ
Lumen4 H+
1 Conc. M
0
50
100
200
PSII
DPC to DCPIP (%)
100
83
58
57
1 Conc. M
0
100
200
300
400
PSII
H2O to SiMo (%)
100
75
50
12
0
The two results indicated that the target of
siderin is located at the donor and acceptor
sides of PSII, between P680 to QA.
However, siderin did not affect PSI
1.0
0.0
- 1.0
Re
du
cti
on
po
ten
tia
l (V
)
Mn
center
H2O
P680
Photon 1
P680*
Ph
QA
QBCytochrome
bf complexP700
P700*
Pc
Photon 2
A0
A1
4Fe-4S
Fd-NADP+
reductase
NADPH
Photosystem II
Photosystem I
O2
PQ
Veiga, da Silva et al, Arch. Biochem. Biophys. 465, 38-43, 2007
N
O
O
Me
N-methylflindersine does not inhibit electron
transport from H2O to SiMo, but inhibited electron
transport from DCP to DCPIP.
N-Me-Flindersine
Veiga, da Silva et al, Allelopathy J. 21, 133-144, 2008
Thus, the results
indicated that the target
of N-methylflindersine is
located at the acceptor
side of PSII, between QA
and QB.
Cytochrome
bf complex
1.0
0.0
- 1.0
Red
ucti
on
po
ten
tial (V
)
Mn
center
H2O
P680
Photon 1
P680*
Ph
QA
QB
Photosystem II
O2
PQ
Veiga, da Silva et al, Allelopathy J. 21, 133-144, 2008
1.0
0.0
- 1.0
Red
ucti
on
po
ten
tial (V
)
Mn
center
H2O
P680
Photon 1
P680*
Ph
QA
QBCytochrome
bf complexP700
P700*
Pc
Photon 2
A0
A1
4Fe-4S
Fd-NADP+
reductase
NADPH
Photosystem II
Photosystem I
O2
PQ
Lumen4 H+
1.0
0.0
- 1.0
Red
ucti
on
po
ten
tial (V
)
Mn
center
H2O
P680
Photon 1
P680*
Ph
QA
QBCytochrome
bf complexP700
P700*
Pc
Photon 2
A0
A1
4Fe-4S
Fd-NADP+
reductase
NADPH
Photosystem II
Photosystem I
O2
PQ
1.0
0.0
- 1.0
Red
ucti
on
po
ten
tial (V
)
Mn
center
H2O
P680
Photon 1
P680*
Ph
QA
QBCytochrome
bf complexP700
P700*
Pc
Photon 2
A0
A1
4Fe-4S
Fd-NADP+
reductase
NADPH
Photosystem II
Photosystem I
O2
PQ
Lumen4 H+
We analyzed the effect of N-methylflindersine on
electron transport from PSII using TMQH2 to MV.
Localization of N-methylflindersine sites of
interaction on PSI
TMQH2MV
1.0
0.0
- 1.0
Red
ucti
on
po
ten
tial (V
)
Mn
center
H2O
P680
Photon 1
P680*
Ph
QA
QBCytochrome
bf complexP700
P700*
Pc
Photon 2
A0
A1
4Fe-4S
Fd-NADP+
reductase
NADPH
Photosystem II
Photosystem I
O2
PQ
Lumen4 H+
1.0
0.0
- 1.0
Red
ucti
on
po
ten
tial (V
)
Mn
center
H2O
P680
Photon 1
P680*
Ph
QA
QBCytochrome
bf complexP700
P700*
Pc
Photon 2
A0
A1
4Fe-4S
Fd-NADP+
reductase
NADPH
Photosystem II
Photosystem I
O2
PQ
1.0
0.0
- 1.0
Red
ucti
on
po
ten
tial (V
)
Mn
center
H2O
P680
Photon 1
P680*
Ph
QA
QBCytochrome
bf complexP700
P700*
Pc
Photon 2
A0
A1
4Fe-4S
Fd-NADP+
reductase
NADPH
Photosystem II
Photosystem I
O2
PQ
Lumen4 H+
We also add DCMU, which binding in
plastoquinone site, inhibiting the electron transport
from H2O to QB, or PSI.
Then, electrons flow from TMQH2 to MV.
DCMU
N
Cl
Cl
N
O
HTMQH2
MV
OHOH
OH
HO OH
O OHOH
OH
-O O
-
O
- 2 H+
OHOH
OH
.O O
.
O
- 2 e-
OHOH
OH
O O
O
+ 2H+
+ 2e-
O
O
OH
OH
- 2e-
O
O
- 2H+
2+ 2e
-
.
N
N+
+N
N
2
+
Ascorbic acid
TMQ TMQH2
Methylviologen (MV)
Tetramethylhydroquinone
(TMQH2) is oxidized to
tetramethylquinone and
transfer electrons to MV.
2MV.+ 2O2 2MV2+ + 2O2.-
2MV.+
.
N
N+
2
O2
O2.-
O2.-
OHOH
OH
HO OH
O OHOH
OH
-O O
-
O
- 2 H+
OHOH
OH
-O O
.
O
- e-
2H+
H2O2
Hydrogen peroxide
The oxygen
concentration
decrease.
We measure the oxygen
concentration with an oxygen
electrode (Clark-type electrode)
1.0
0.0
- 1.0
Re
du
cti
on
po
ten
tial (V
)
Mn
center
H2O
P680
Photon 1
P680*
Ph
QA
QBCytochrome
bf complexP700
P700*
Pc
Photon 2
A0
A1
4Fe-4S
Fd-NADP+
reductase
NADPH
Photosystem II
Photosystem I
O2
PQ
Lumen4 H+
1.0
0.0
- 1.0
Re
du
cti
on
po
ten
tial (V
)
Mn
center
H2O
P680
Photon 1
P680*
Ph
QA
QBCytochrome
bf complexP700
P700*
Pc
Photon 2
A0
A1
4Fe-4S
Fd-NADP+
reductase
NADPH
Photosystem II
Photosystem I
O2
PQ
1.0
0.0
- 1.0
Re
du
cti
on
po
ten
tial (V
)
Mn
center
H2O
P680
Photon 1
P680*
Ph
QA
QBCytochrome
bf complexP700
P700*
Pc
Photon 2
A0
A1
4Fe-4S
Fd-NADP+
reductase
NADPH
Photosystem II
Photosystem I
O2
PQ
Lumen4 H+
DCMU
N
Cl
Cl
N
O
HTMQH2
MV
O2
O2.-
O2.-
OHOH
OH
HO OH
O OHOH
OH
-O O
-
O
- 2 H+
OHOH
OH
-O O
.
O
- e-
2H+
H2O2
The oxygen concentration
decrease.
2 Conc. M
0
100
200
300
400
500
PSI
TMQH2 to MV (%)
100
82
73
45
36
0
At 500 M N-methylflindersine
completely inhibited electron
transport from TMQH2 to MV.
Localization of N-methylflindersin sites of
interaction on PSI
Veiga, da Silva et al, Allelopathy J. 21, 133-144, 2008
1.0
0.0
- 1.0
Re
du
cti
on
po
ten
tial (V
)
Mn
center
H2O
P680
Photon 1
P680*
Ph
QA
QBCytochrome
bf complexP700
P700*
Pc
Photon 2
A0
A1
4Fe-4S
Fd-NADP+
reductase
NADPH
Photosystem II
Photosystem I
O2
PQ
Lumen4 H+
1.0
0.0
- 1.0
Re
du
cti
on
po
ten
tial (V
)
Mn
center
H2O
P680
Photon 1
P680*
Ph
QA
QBCytochrome
bf complexP700
P700*
Pc
Photon 2
A0
A1
4Fe-4S
Fd-NADP+
reductase
NADPH
Photosystem II
Photosystem I
O2
PQ
1.0
0.0
- 1.0
Re
du
cti
on
po
ten
tial (V
)
Mn
center
H2O
P680
Photon 1
P680*
Ph
QA
QBCytochrome
bf complexP700
P700*
Pc
Photon 2
A0
A1
4Fe-4S
Fd-NADP+
reductase
NADPH
Photosystem II
Photosystem I
O2
PQ
Lumen4 H+
DCMU
N
Cl
Cl
N
O
HTMQH2
MV
1.0
0.0
- 1.0
Red
ucti
on
po
ten
tial (V
)
Mn
center
H2O
P680
Photon 1
P680*
Ph
QA
QBCytochrome
bf complexP700
P700*
Pc
Photon 2
A0
A1
4Fe-4S
Fd-NADP+
reductase
NADPH
Photosystem II
Photosystem I
O2
PQ
Lumen4 H+
1.0
0.0
- 1.0
Red
ucti
on
po
ten
tial (V
)
Mn
center
H2O
P680
Photon 1
P680*
Ph
QA
QBCytochrome
bf complexP700
P700*
Pc
Photon 2
A0
A1
4Fe-4S
Fd-NADP+
reductase
NADPH
Photosystem II
Photosystem I
O2
PQ
1.0
0.0
- 1.0
Red
ucti
on
po
ten
tial (V
)
Mn
center
H2O
P680
Photon 1
P680*
Ph
QA
QBCytochrome
bf complexP700
P700*
Pc
Photon 2
A0
A1
4Fe-4S
Fd-NADP+
reductase
NADPH
Photosystem II
Photosystem I
O2
PQ
Lumen4 H+
Localization of N-methylflindersin sites of
interaction on PSI
We analyzed the effect of N-methylflindersine
on electron transport from Cy bf complex using
DCPIPred to MV; then to 4Fe-4S.
2 H+
OH
ClCl
OH
N H
O
N
ClCl
OH
- e-
Dichlorophenol-
indophenol
DCPIPred
DCPIPredMV
DCMU
N
Cl
Cl
N
O
H
Localization of N-methylflindersin sites of
interaction on PSI
2 Conc. M
0
100
200
300
400
500
PSII
DCPIPred to MV (%)
100
-
100
100
-
-
N-methylflindersine did
not inhibit electron transport
from DCPIPred to MV.
Veiga, da Silva et al, Allelopathy J. 21, 133-144, 2008
1.0
0.0
- 1.0
Re
du
cti
on
po
ten
tial (V
)
Mn
center
H2O
P680
Photon 1
P680*
Ph
QA
QBCytochrome
bf complexP700
P700*
Pc
Photon 2
A0
A1
4Fe-4S
Fd-NADP+
reductase
NADPH
Photosystem II
Photosystem I
O2
PQ
Lumen4 H+
1.0
0.0
- 1.0
Re
du
cti
on
po
ten
tial (V
)
Mn
center
H2O
P680
Photon 1
P680*
Ph
QA
QBCytochrome
bf complexP700
P700*
Pc
Photon 2
A0
A1
4Fe-4S
Fd-NADP+
reductase
NADPH
Photosystem II
Photosystem I
O2
PQ
1.0
0.0
- 1.0
Re
du
cti
on
po
ten
tial (V
)
Mn
center
H2O
P680
Photon 1
P680*
Ph
QA
QBCytochrome
bf complexP700
P700*
Pc
Photon 2
A0
A1
4Fe-4S
Fd-NADP+
reductase
NADPH
Photosystem II
Photosystem I
O2
PQ
Lumen4 H+
DCPIPredMV
DCMU
N
Cl
Cl
N
O
H
*
*
Thus N-methylflindersine has two sites of
interaction and inhibition, one where QB interacts
and the second one is at PQH2 oxidation site.
Localization of N-methylflindersin sites of
interaction on PSI
1.0
0.0
- 1.0
Re
du
cti
on
po
ten
tial (V
)
Mn
center
H2O
P680
Photon 1
P680*
Ph
QA
QBCytochrome
bf complexP700
P700*
Pc
Photon 2
A0
A1
4Fe-4S
Fd-NADP+
reductase
NADPH
Photosystem II
Photosystem I
O2
PQ
Lumen4 H+
1.0
0.0
- 1.0
Re
du
cti
on
po
ten
tial (V
)
Mn
center
H2O
P680
Photon 1
P680*
Ph
QA
QBCytochrome
bf complexP700
P700*
Pc
Photon 2
A0
A1
4Fe-4S
Fd-NADP+
reductase
NADPH
Photosystem II
Photosystem I
O2
PQ
1.0
0.0
- 1.0
Re
du
cti
on
po
ten
tial (V
)
Mn
center
H2O
P680
Photon 1
P680*
Ph
QA
QBCytochrome
bf complexP700
P700*
Pc
Photon 2
A0
A1
4Fe-4S
Fd-NADP+
reductase
NADPH
Photosystem II
Photosystem I
O2
PQ
Lumen4 H+
Several natural products isolated for our group have
been evaluated as inhibitor of photophosphorylation
and electron transport chain in thylakoids.
Among the 200 compounds evaluated, only 16 were the
most active:
Veiga, PhD Thesis, UFSCar, Brazil, 2008
ATP synthesis inhibition by:
I50 26.0 M
N
O
O
H
I50 48.0 M I50 46.0 M
I50 61.5 M
I50 82.0 M
N O
OMe
MeO
OMe
N O
OMe
MeO
MeO
N O
OMe
MeO
N O
OMe
OMe
MeO
ATP synthesis inhibition by:
N
O
OH
OH
OMe
O
OH
Me N
O
OH
OOH
OH
OMeMe
N
O
OH
OH
OH
Me
N
O
OH
OH
OH
OMeMe
N
O
OH
OH
OH
Me
I50 3.3 M I50 6.5 M
I50 33.0 M
I50 24.0 MI50 43.4 M
ATP synthesis inhibition by:
AcO
O
H
OH O
H
OH
O
O
O
OH
H
HO
H
OH
O
O
HO
OH
I50 6.8 M I50 16.7 M
I50 13.1 MI50 22.7 M
Veiga, PhD Thesis, UFSCar, Brazil, 2008
N
O
OH
OH
OH
Me
N
O
OH
OH
OH
OMeMe
Localization of compounds sites of interaction on PSII
I50 33.0 MI50 24.0 M
The results indicated that the targets of
these compounds are located at the donor and
acceptor sides of PSII, between P680 to QA.
O
H
OH
O
I50 16.7 MO
O
HO
OH
I50 22.7 M
1.0
0.0
- 1.0
Red
ucti
on
po
ten
tial (V
)
Mn
center
H2O
P680
Photon 1
P680*
Ph
QA
QBCytochrome
bf complexP700
P700*
Pc
Photon 2
A0
A1
4Fe-4S
Fd-NADP+
reductase
NADPH
Photosystem II
Photosystem I
O2
PQ
Lumen4 H+
1.0
0.0
- 1.0
Red
ucti
on
po
ten
tial (V
)
Mn
center
H2O
P680
Photon 1
P680*
Ph
QA
QBCytochrome
bf complexP700
P700*
Pc
Photon 2
A0
A1
4Fe-4S
Fd-NADP+
reductase
NADPH
Photosystem II
Photosystem I
O2
PQ
1.0
0.0
- 1.0
Red
ucti
on
po
ten
tial (V
)
Mn
center
H2O
P680
Photon 1
P680*
Ph
QA
QBCytochrome
bf complexP700
P700*
Pc
Photon 2
A0
A1
4Fe-4S
Fd-NADP+
reductase
NADPH
Photosystem II
Photosystem I
O2
PQ
Lumen4 H+
1.0
0.0
- 1.0
Red
ucti
on
po
ten
tial (V
)
Mn
center
H2O
P680
Photon 1
P680*
Ph
QA
QBCytochrome
bf complexP700
P700*
Pc
Photon 2
A0
A1
4Fe-4S
Fd-NADP+
reductase
NADPH
Photosystem II
Photosystem I
O2
PQ
Lumen4 H+
1.0
0.0
- 1.0
Red
ucti
on
po
ten
tial (V
)
Mn
center
H2O
P680
Photon 1
P680*
Ph
QA
QBCytochrome
bf complexP700
P700*
Pc
Photon 2
A0
A1
4Fe-4S
Fd-NADP+
reductase
NADPH
Photosystem II
Photosystem I
O2
PQ
1.0
0.0
- 1.0
Red
ucti
on
po
ten
tial (V
)
Mn
center
H2O
P680
Photon 1
P680*
Ph
QA
QBCytochrome
bf complexP700
P700*
Pc
Photon 2
A0
A1
4Fe-4S
Fd-NADP+
reductase
NADPH
Photosystem II
Photosystem I
O2
PQ
Lumen4 H+
The results
indicated that the
actions of these
compounds are
located at the
acceptor side of
PSII, between QA
and QB.
Localization of
compounds sites of
interaction on PSII
I50 26.0 M
N
O
O
HI50 48.0 M
I50 46.0 M
N O
OMe
MeO
OMe
N O
OMe
OMe
MeO
I50 61.5 M
N O
OMe
MeO
MeO
I50 82.0 M
N O
OMe
MeO
In contrast, dihydropyranoacridones and
dihydrofuroacridones have the site of
interaction and inhibition at Cy bf complex.
Localization of
compounds sites of
interaction on PSI
N
O
OH
OH
OMe
O
OH
MeN
O
OH
OOH
OH
OMeMeI50 3.3 M
I50 6.5 MVeiga, PhD Thesis, UFSCar, Brazil, 2008
1.0
0.0
- 1.0
Red
ucti
on
po
ten
tial (V
)
Mn
center
H2O
P680
Photon 1
P680*
Ph
QA
QBCytochrome
bf complexP700
P700*
Pc
Photon 2
A0
A1
4Fe-4S
Fd-NADP+
reductase
NADPH
Photosystem II
Photosystem I
O2
PQ
Lumen4 H+
1.0
0.0
- 1.0
Red
ucti
on
po
ten
tial (V
)
Mn
center
H2O
P680
Photon 1
P680*
Ph
QA
QBCytochrome
bf complexP700
P700*
Pc
Photon 2
A0
A1
4Fe-4S
Fd-NADP+
reductase
NADPH
Photosystem II
Photosystem I
O2
PQ
1.0
0.0
- 1.0
Red
ucti
on
po
ten
tial (V
)
Mn
center
H2O
P680
Photon 1
P680*
Ph
QA
QBCytochrome
bf complexP700
P700*
Pc
Photon 2
A0
A1
4Fe-4S
Fd-NADP+
reductase
NADPH
Photosystem II
Photosystem I
O2
PQ
Lumen4 H+
DCMU
N
Cl
Cl
N
O
H
Many commercial
herbicides kill weeds by
interfering with the
action of PSII or PSI.
PSII inhibitors include
urea derivatives, such as
diuron (DCMU), one of
the most sold herbicides.
The mechanism of action
of these compounds were
similar to DCMU.
O OMeO
OMe
N
O
OH
OH
OH
Me
N
O
OH
OH
OH
OMeMe
I50 27.0 MI50 33.0 MI50 24.0 M
O
H
OH
O O
O
HO
OH
I50 22.7 MI50 16.7 M
1.0
0.0
- 1.0
Red
uctio
n po
tent
ial (
V)
Mn
center
H2O
P680
Photon 1
P680*
Ph
QA
QBCytochrome
bf complexP700
P700*
Pc
Photon 2
A0
A1
4Fe-4S
Fd-NADP+
reductase
NADPH
Photosystem II
Photosystem I
O2
PQ
Thylakoid lumen
4 H+
1.0
0.0
- 1.0
Red
uctio
n po
tent
ial (
V)
Mn
center
H2O
P680
Photon 1
P680*
Ph
QA
QBCytochrome
bf complexP700
P700*
Pc
Photon 2
A0
A1
4Fe-4S
Fd-NADP+
reductase
NADPH
Photosystem II
Photosystem I
O2
PQ
1.0
0.0
- 1.0
Red
uctio
n po
tent
ial (
V)
Mn
center
H2O
P680
Photon 1
P680*
Ph
QA
QBCytochrome
bf complexP700
P700*
Pc
Photon 2
A0
A1
4Fe-4S
Fd-NADP+
reductase
NADPH
Photosystem II
Photosystem I
O2
PQ
Thylakoid lumen
4 H+
Concluding Remarks
DCMU
N
Cl
Cl
N
O
H
O OMeO
OMe
N
O
OH
OH
OH
Me
N
O
OH
OH
OH
OMeMe
I50 27.0 MI50 33.0 MI50 24.0 M
O
H
OH
O O
O
HO
OH
I50 22.7 MI50 16.7 M
1.0
0.0
- 1.0
Red
uctio
n po
tent
ial (
V)
Mn
center
H2O
P680
Photon 1
P680*
Ph
QA
QBCytochrome
bf complexP700
P700*
Pc
Photon 2
A0
A1
4Fe-4S
Fd-NADP+
reductase
NADPH
Photosystem II
Photosystem I
O2
PQ
Thylakoid lumen
4 H+
1.0
0.0
- 1.0
Red
uctio
n po
tent
ial (
V)
Mn
center
H2O
P680
Photon 1
P680*
Ph
QA
QBCytochrome
bf complexP700
P700*
Pc
Photon 2
A0
A1
4Fe-4S
Fd-NADP+
reductase
NADPH
Photosystem II
Photosystem I
O2
PQ
1.0
0.0
- 1.0
Red
uctio
n po
tent
ial (
V)
Mn
center
H2O
P680
Photon 1
P680*
Ph
QA
QBCytochrome
bf complexP700
P700*
Pc
Photon 2
A0
A1
4Fe-4S
Fd-NADP+
reductase
NADPH
Photosystem II
Photosystem I
O2
PQ
Thylakoid lumen
4 H+
Concluding Remarks
If its assumed that it
is possible to modify the
chemical structure of
compounds to improve
activity, our results are
so good.
Experiments in vivo are
in progress.
OUR STUDENTS
FINALLY WE ARE GRATEFUL TO
FINANCIAL
AGENCY
BLAS LOTINA-
HENNSEN
UNVERSIDAD
NACIONAL
AUTONOMA DE
MÉXICO, MÉXICO