Photosynthesis
Transition Metal Clusters in Biology
(Manganese Cluster in Oxygen Evolving Center) Water as Reductant?
Main Elements in Biology
H N O P
Biology
CH4 H2
NO3-
Recuded Form
Oxidized Form
CO2
(CO32-) H2O
N2 H2O
PO43- (Pi)
C
O2
Carbon Dioxide Cycle
Tha carbon dioxide cycle, showing the reserviors (in GtC) and fluxes (GtC/y) in 1980-1989.
(In "Understandinh Our Environment" Ed. R. M. Harrison, RCS, 1999).
Carbon Cycle v ia Photosynthesis
hν
plants bacteria
animals CO2
food
O2
(CO2 fixiation)
Photosynthesis
1x1011 t/y
carbohydrates
biomolecules
H2O
petroleum coal natural gas fossil
resources
industry chemicals
energy
3x109 t/y
(from petrol.)
What is Photosynthesis
6CO2 + 6H2O Ch! 6H12O6 + 6O2
Cox reductant Cred
? oxidant
photosynthetic cells (plants, algae,
bacteria)
heterotrophic cells (plants, algae,
bacteria)
SUN
O2 Glucose
H2O CO2 h!
Photosynthesis
Cred
Cox reductant oxidant
Photosynthesis Two Phases and Takes Place in Chloroplast (Plant)
Light Reactions!"#$%
Dark Reactions!&#$%
SUN
O2 H2O
CO2 NADP+
ADP + Pi
NADPH ATP
(CH2O)n
Chloroplast
!'()%
Chloroplast from Corn
granum
intergranal lamella intergranal lamella
Light Reactions
Photosynthetic Electron Transfer making Charge (H+) Separation
Light Harvesting Complex (LHC) Reaction Center (RC)
Photosynthetic Electron Transfer forming NADHP and ATP Light Harvesting Complex (LHC)
Photosystem II (PSII) Photosystem I (PSI)
Bacteria Bacteria
Plants Plants
Light Harvesting Complex
Light Harvesting Complex (LHC) Reaction Center (RC)
Bacteria
antenna molecule photon
reaction center photon
photon
photon
photon energy transfer
membrane
LHC Diagram
Light harvesting complex involves hundreds of antenna molecules (pigments);
chlorophyll and carotenoid.
.
excited state
antenna molecule ground state
reaction center h!
excited energy transfer
energy
Antenna Molecules (Pigments)
Light Harvesting Complex (LHC) Reaction Center (RC)
Bacteria
Antenna Molecules (Pigments)
Light Harvesting Complex (LHC) Reaction Center (RC)
Bacteria
Light Harvesting Protein
Light Harvesting Complex (LHC) Reaction Center (RC)
Bacteria
Photosynthesis Reaction Center (R hodospseudomonas viridis )
Light Harvesting Complex (LHC) Reaction Center (RC)
Bacteria
Photosynthesis Reaction Center (R hodospseudomonas viridis )
Light Harvesting Complex (LHC) Reaction Center (RC)
Bacteria
Photosynthesis Reaction Center -Electron Transfer-
Light Harvesting Complex (LHC) Reaction Center (RC)
Bacteria
Photosynthetic Electron Transfer System
(Rhodospseudomonas viridis)
Light Harvesting Complex (LHC) Reaction Center (RC)
Bacteria
Photosynthetic Electron Transfer (Plant)
Plants
Light Harvesting Complex (LHC) Photosystem II (PSII)
Photosystem I (PSI)
hν
LHC
hν
LHC
Photosystem I complex (PS I)
Photosystem II complex (PS II)
ATP Syntase Fd-NADP+
Reductase
Photosynthetic Electron Transfer (Plant)
Plants
Light Harvesting Complex (LHC) Photosystem II (PSII) Photosystem I (PSI)
Photosystem II (PS II)
Plants
Light Harvesting Complex (LHC) Photosystem II (PSII)
Photosystem I (PSI)
LHC
PSII
P680*
Chl a
Pheo a QA
QB
P680 h!
Fe(II) e-
thylakoid membrane
H3C H3C
H CH2 C
H C C H2 H CH3
n O
O
plastquinoneQ
cyt b6
cyt f [4Fe-4S]
Cy b6f
Q pool
8H+
thylakoid stroma
Q QH2
8H+
-2 •H 2 •H
H3C H CH2 C
H C C H2 H CH3
n OH
OH
QH2 plastquinol
H3C
plastcyanin
PC
PS I
Oxygen Evolving Center (OEC)
2H2O O2 + 4H+
thylakoid
Z Mn4
Crystal Structure of PS II from Synechococcus elongatus
at 3.8 Å Resolution
A. Zouni et al. Nature 2001, 409, 739-743
Plants
Light Harvesting Complex (LHC) Photosystem II (PSII) Photosystem I (PSI)
D1 D2
CP47 CP43
28
cyt b-559
PsbO(33)
PsbV (24) cyt c-550 17
OEC
lumen stroma
thylakoid membrane
Crystal Structure of PS II from Synechococcus elongatus
at 3.8 Å Resolution
Plants
Light Harvesting Complex (LHC) Photosystem II (PSII)
Photosystem I (PSI)
Chl a
Chl a plast
quinone
Fe
10.7 Å 10.6 Å
9.8 Å
Mg Mg
Mg 11 Å 11 Å Mg 10.0 Å 10 Å
P680
h!
Tyr
H2 H2
Mg Mg
22.8 Å
12.4 Å
7.0 Å
Chl a Pheo
QA QB
Fe Cyt c-550
Cyt b-559
25.8 Å
~28 Å
27 Å 10.5 Å ~10 Å
Fe(II)
Mn4
24.5 Å
23.9 Å 23.7 Å
24.6 Å 12.0 Å
Crystal Structure of PS II
from Synechococcus elongatus at 3.8 Å Resolution
Plants
Light Harvesting Complex (LHC) Photosystem II (PSII) Photosystem I (PSI)
Oxygen Evolving Center Still Not Clear
thylakoid membrane
h!
PSI
P700 P700*
A0 A1
X A
B e-
LHC
(Chl a)
(Chl a)
(quinone)
[Fe4S4]
Plants
Light Harvesting Complex (LHC) Photosystem II (PSII) Photosystem I (PSI)
Photosystem I (PS I)
CH3
CH2 C
H C CH2 CH3 O
O
H2C C H2 C
H C H2 CH3
H
phylloquinone 3
Fd
[Fe4S4]
2NADP+
2NADPH 2H++
FAD
Fd-NADP+
Reductase
cyt b6
cyt f [4Fe-4S]
Cy b6f
plastcyanin
PC
shunt
Photosystem I (PS I)
Plants
Light Harvesting Complex (LHC) Photosystem II (PSII) Photosystem I (PSI)
Ferredoxin-NADP+ Reductase
Plants
Light Harvesting Complex (LHC) Photosystem II (PSII) Photosystem I (PSI)
(FRN)
FAD
NADP+
N N N
N
NH2
O
OH OH H O
P OH O HO P O
O O
CH2 CH(OH) CH2
3
N N
NH N H3C
H3C
O O
N N N
N
NH2
O
O OH O
P OH O HO P O
O O
O N
OH OH H CH2
CONH2 P O
OH OH
Ferredoxin PS I
e-
H+
Ferredoxin-NADP+ Reductase
Plants
Light Harvesting Complex (LHC) Photosystem II (PSII)
Photosystem I (PSI)
ATP Synthase
Plants
Light Harvesting Complex (LHC) Photosystem II (PSII) Photosystem I (PSI)
ATP Synthase
Plants
Light Harvesting Complex (LHC) Photosystem II (PSII) Photosystem I (PSI)
ADP + Pi energy ATP + H2O
H+ pump
Summary of Light Reactions in Chloroplast
Plants
Light Harvesting Complex (LHC) Photosystem II (PSII) Photosystem I (PSI)
2H2O + 2NADP+ 2NADP + O2 + 2H+ (!Go = 438 kJ·mol-1) 4ADP + 4Pi 4ATP + 4H2O (!Go = 122 kJmol-1)
h"
h"
Manganese Cluster Chemistry in Relation to
Oxygen Evolving Center in PS II
Oxygen Evolving Mechanism
2H2O Ohν 2 + 4e- + 4H+
Normalized O 2 Yield
Flash Number
6 12 18 24 30
2.4
1.6 0.8
0
Dioxygen Evolution in Flashing Light 1971 by P. Joliet & B. Kok
So S1
S2 S3
S4
hν
hν
hν hν
e-
e-
e- e-
2H2O
O2 (resting)
OEC Involves Four Mn Ions (4Mn) -H+
-H+ -2H+
A Proposed Mechanism of OEC
A Proposed Mechanism of OEC
cubane-type [Mn4O4]
Mn Mn
Mn
O Mn
O
O Mn Mn
Mn
O Mn
O
HO O2
2H2O
e- H+
e-
e- e-
3H+
Mn Mn
Mn
O Mn
O
Mn Mn
Mn
O Mn
O
OH2 H2O O
Mn Mn
Mn
O Mn
O
O
So
S1
S2 S3
S4
h!
h!
h! h!
J. B. Vincent, G. Christou, Inorg. Chim. Acta 1987, 136, L41
butterfly-type [Mn4O2]
Modified Proposed Mechanism of OEC
O Mn Mn
Mn
O Mn
O O
Mn Mn
Mn
O Mn
O
O H O H H
O Mn Mn
Mn
O Mn
O
O H O H
O Mn Mn
Mn
O Mn
O
O H O H O
Mn Mn
Mn
O Mn
O
O O
O2
2H2O
e- H+
e-
H+
e- e-
2H+
S1
S2 S3
S4
h!
h!
h!
h!
So
J. B. Vincent, R. H. Christou, Adv. Inorg. Chem., 1989, 33, 197
D. N. Hendrickson, G. Christou, J. Am. Chem. Soc., 1994, 116, 8376
O Mn Mn
Mn
O Mn
O
O C O
model compound
EPE Studies Revealed
the Oxidation States of Mn 4 Cluster in OEC
V. K. Yachandra, C hem. Rev., 1 996, 9 6, 2927
C-shape Dimer-to-Dimer Structure
was Proposed from Detailed EXAFS Studies
V. K. Yachandra, S cience, 1 993, 260, 675
C-shape Dimer-to-Dimer Structure
was Proposed from Detailed EXAFS Studies
Mn HO Mn O Mn
Mn
Mn O
Mn O
Mn HO
Mn O
Mn HO
Mn OH
Mn O O Mn O
Mn O O Mn O O
Mn O
Mn O Mn
Mn
Mn O
Mn O
Mn O
Mn O
RO OR
~3.2 Å ~3.4 Å
~2.7 Å ~2.8 Å ~2.9 Å
~2.4 Å ~2.5 Å
~3.3-3.5 Å
~4.0 Å
Structural Parameters
from Synthetic Compounds
EXAFS
O Mn
O Mn Mn
O Mn O
Mn O O Mn
O
Mn O
Mn O
Mn O
Mn O
Mn O
Mn O
Mn O
Mn O
Mn O
Mn O Mn
O Mn O
Mn O
Mn O
O Mn O
O Mn
O Ca
O
O O
O Mn Mn O
Mn
O Mn O O
O
Mn
O Mn O
O O Mn O Mn
Mn
O Mn
O O
Mn
Mn Mn O
O Mn
Mn O
O O Mn
Mn O
O Mn
Mn O
Mn O
Mn O
Mn O O
Structural Candidates for OEC
A Proposed Mechanism of OEC
V. K. Yachandra, C hem. Rev., 1 996, 9 6, 2927
2H2O
2H+ e-
O
MnIII
HO MnII O OH
O
MnIV
O MnIV O O
O
O
MnIII
O MnIII O O
O
MnIV
O MnIV O O
O
O
MnIII
O MnIV O O
O
MnIV
O MnIV O O
O
O
MnIII
O MnIV O O
O
MnIV
O MnIV O O
O O
MnIII
O MnIV O O
O
MnIV
O MnIV O O
O O
MnIII
O MnIV O O
O
MnIV
O MnIV O O
O
e-
e-
e- O2
So S1 S2
S3 S4
h!
h!
h! h!
Mn(II) Mn(III) Mn(IV)
2.7 Å 2.7 Å
3.3 Å
2.7 Å 3.3 Å
2.8 Å 2.9-3.0 Å
3.4 Å
>2.7 Å
Recently Proposed Structure of OEC Active Site
C. Tommos, G. T. Babcock, A cc . Chem. Res. , 1 998, 31, 18
Proposed Cycle for OEC in PSII
by G. T. Babcock 1998
Two Proposed Mechnisms with C-Shape Mn 4 Center
MnIII HO
OH
MnII MnIII O
O MnIII MnIII O
O MnIV
MnIII O
O MnIV MnIII O
O MnIV MnIII O
O MnIV -2H+
-O2 -2H+
-e- -e-
-e- -e-
2H2O
Yachandra 2.7 Å
MnIII OH2
MnII OH2
MnIII O
MnIII
-H+ H H OH
MnIII O
MnIV -H+ H H O
MnIII O
MnIV O H H MnIV
O
MnIV O
H -H+ MnIII
O
MnIV
O -H+ -O2
MnIII O
MnIV O
H -H+
-e- -e-
-e- -e-
2H2O
-e- Babcock
5.5 Å
Functional Model System of OEC Center by Dinuclear Mn Complex R. H. Crabtree et al.
Science, 1 999, 2 83, 1524
Functional Model System of OEC Center by Tetranuclear Mn Complex
Mn O O
P O
Mn O
P O
O O P
O O
P O OO Mn
P
O Mn O
O O
P
Mn O O
P O
Mn O
O P
O O
P O Mn O
P
Mn O
O O
P Mn O
O P
O Mn O
O P
O O
P O Mn O
P
Mn O
O O
P P O
O 4e- + 4H+
2H2O O2
Ph2PO2-
Ph2PO2H
+ -
Mn(II)2Mn(III)2 Mn(II)2Mn(III)2
Mn(III)2Mn(IV)2
Cubane
Butterfly
POP = Ph2PO2-
h!
G. C. Dismukes et al.
J. Am. Chem. Soc., 2000, in press
Dark Reactions of Photosynthesis
Dark Reactions (Calvin Cycle)
Dark Reactions (plants)
CH2OPO32- C O C OH C OH CH2OPO32- H
H
RuBP
CH2OH C O C OH C OH CH2OPO32- H
H
Ru5P
CHO C OH C OH C OH CH2OPO32- H
H
R5P
CH2OH C O C HO
C OH CH2OPO32-
H H
Xu5P H
CH2OH C O C HO
C OH
CH2OPO32- H H
F6P C OH H
CH2OPO32- C O C HO
C OH
CH2OPO32- H H
FBP C OH H
CH2OPO32- C
HO
CO2- C OH CH2OPO32- H
CO2- H
C C OH CH2OPO32- H
O OPO32-
C C OH CH2OPO32- H
O H
CH2OH C O CH2OPO32- DHAP
CH2OH C O C HO
C OH
CH2OPO32- H H
C OH H
C OH H
CH2OPO32- C O C HO
C OH
CH2OPO32- H H
C OH H
C OH H
SBP CHO C OH C OH CH2OPO32- H
H ATP
ADP
CO2
ATP ADP NADPH NADP+
(ribulose 1,5-bisphosphate)
(ribulose 5-phosphate)
(ribose 5-phosphate) (xylulose 5-phosphate) (fructose 6-phosphate) (fructose 1,6-bisphosphate)
3PG
(3-phosphoglycerate)
BPG
(1,3-bisphosphoglycerate)
GAP
(glyceraldehyde 3-phosphate)
(dihydroxyacetone phosphate)
S7P
E4P
(erythrose 4-phosphate)
(sedoheptulose 7-phosphate)
(sedoheptulose 1,7-bisphosphate)
Calvin Cycle
* ★ * * *
3CO2 + 9ATP + 6NADPH + 5H2O + 6H+ GAP + 9ADP + 6NADP+ 8Pi
Dark Reactions (Calvin Cycle)
Dark Reactions (plants)
Dark Reactions (Calvin Cycle)
Dark Reactions (plants)
CH2OPO32- C
O
C OH C OH CH2OPO32- H
H
RuBP B:
CH2OPO32- C
O
C O C OH CH2OPO32- H
CH2OPO32- C
HO
C O C OH CH2OPO32- H
CO2- C
O
H O
O
H -H+
CH2OPO32- C
HO
CO2- C OH CH2OPO32- H
CO2-
3PG
(3-phosphoglycerate)
CH2OPO32- C
HO
C O C OH CH2OPO32- H
CO2- HO
CH2OPO32- C
HO
CO2-
2 H H
+
(ribulose bisphosphate) H
* *
*
*
*
* *
Dark Reactions (plants)
Dark Reactions (Calvin Cycle)
Route from 3PG to GAP
Dark Reactions (from GAP)
Dark Reactions (plants)
glycogen
peptideglycan cellulose
starch
oligosaccharide
* *CH2OH
C O CH2OPO32-
DHAP
(dihydroxyacetone phosphate)
C
C OH CH2OPO32- H
O H
GAP
(glyceraldehyde 3-phosphate)
CH2OH C O C HO
C OH
CH2OPO32- H
H
F6P C OH H
CH2OPO32- C O
C HO
C OH
CH2OPO32- H
H
FBP C OH H
(fructose 1,6-bisphosphate) (fructose 6-phosphate)
C C C HO
C OH
CH2OPO32- H
H
G6P C OH H
(glucose 6-phosphate) OH H
O H O
OPO32- HO
OH HO HO
G1P
(glucose 1-phosphate)
*
*
aldolase
fructose
bisphasphatase (Mn2+, Mg+)
glucose 6-phosphate isomerase (Mg+)
phosphogluco mutase (Mg+)
Summary of Photosynthesi in Chloroplast
thylakoid membrane
thylakoid stroma PSII
OEC h!
P680
2H2O
PSI
P700 h!
Q cycle
4e-
8H+
8H+
low pH high pH
FNR 4e-
ATP synthase
12H+
12H+
4ADP
4Pi 4ATP
4H+ +O2
2H+
2NADP+ 2NADPH
8 photon CO2
+ H2O
C
C OH CH2OPO32- H
O H
GAP
Light Reactions Dark Reactions
Calvin Cycle
stroma
Concepts of Artificial Photosynthesis
O2
HC
Artificial Photosynthesis
Thanks a lot!
