D1-S169A Substitution of Photosystem II Perturbs Water Oxidation
Abstract
In photosystem II (PSII), photosynthetic water oxidation occurs at the tetramanganese–calcium cluster that cycles through light-induced intermediates (S0–S4) to produce oxygen from two substrate waters. The surrounding hydrogen-bonded amino acid residues and waters form channels that facilitate proton transfer and substrate water delivery, thereby ensuring efficient water oxidation. The residue D1-S169 lies in the “narrow” channel and forms hydrogen bonds with the Mn4CaO5 cluster via waters W1 and Wx. To probe the role of the narrow channel in substrate-water binding, we studied the D1-S169A mutation. PSII core complexes isolated from mutant cells exhibit inefficient S-state cycling and delayed oxygen evolution. The S2-state multiline EPR spectrum of D1-S169A PSII core complexes differed significantly from that of wild-type, and FTIR difference spectra showed that the mutation strongly perturbs the extensive network of hydrogen bonds that extends at least from D1-Y161 (YZ) to D1-D61. Finally, these results imply a possible role of D1-S169 in proton egress or substrate water delivery.
- Authors:
-
- Yale Univ., New Haven, CT (United States). Dept. of Chemistry
- Univ. of California, Riverside, CA (United States). Dept. of Biochemistry
- Publication Date:
- Research Org.:
- Lawrence Berkeley National Lab. (LBNL), Berkeley, CA (United States). National Energy Research Scientific Computing Center (NERSC)
- Sponsoring Org.:
- USDOE Office of Science (SC), Basic Energy Sciences (BES)
- OSTI Identifier:
- 1530435
- Grant/Contract Number:
- FG02-05ER15646; SC0005291; SC0001423
- Resource Type:
- Accepted Manuscript
- Journal Name:
- Biochemistry
- Additional Journal Information:
- Journal Volume: 58; Journal Issue: 10; Journal ID: ISSN 0006-2960
- Publisher:
- American Chemical Society (ACS)
- Country of Publication:
- United States
- Language:
- English
- Subject:
- 37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CHEMISTRY; cyanobacteria; mutation; oxygen evolution; photosystem II; structure; substrate water
Citation Formats
Ghosh, Ipsita, Banerjee, Gourab, Kim, Christopher J., Reiss, Krystle, Batista, Victor S., Debus, Richard J., and Brudvig, Gary W. D1-S169A Substitution of Photosystem II Perturbs Water Oxidation. United States: N. p., 2019.
Web. doi:10.1021/acs.biochem.8b01184.
Ghosh, Ipsita, Banerjee, Gourab, Kim, Christopher J., Reiss, Krystle, Batista, Victor S., Debus, Richard J., & Brudvig, Gary W. D1-S169A Substitution of Photosystem II Perturbs Water Oxidation. United States. https://doi.org/10.1021/acs.biochem.8b01184
Ghosh, Ipsita, Banerjee, Gourab, Kim, Christopher J., Reiss, Krystle, Batista, Victor S., Debus, Richard J., and Brudvig, Gary W. Fri .
"D1-S169A Substitution of Photosystem II Perturbs Water Oxidation". United States. https://doi.org/10.1021/acs.biochem.8b01184. https://www.osti.gov/servlets/purl/1530435.
@article{osti_1530435,
title = {D1-S169A Substitution of Photosystem II Perturbs Water Oxidation},
author = {Ghosh, Ipsita and Banerjee, Gourab and Kim, Christopher J. and Reiss, Krystle and Batista, Victor S. and Debus, Richard J. and Brudvig, Gary W.},
abstractNote = {In photosystem II (PSII), photosynthetic water oxidation occurs at the tetramanganese–calcium cluster that cycles through light-induced intermediates (S0–S4) to produce oxygen from two substrate waters. The surrounding hydrogen-bonded amino acid residues and waters form channels that facilitate proton transfer and substrate water delivery, thereby ensuring efficient water oxidation. The residue D1-S169 lies in the “narrow” channel and forms hydrogen bonds with the Mn4CaO5 cluster via waters W1 and Wx. To probe the role of the narrow channel in substrate-water binding, we studied the D1-S169A mutation. PSII core complexes isolated from mutant cells exhibit inefficient S-state cycling and delayed oxygen evolution. The S2-state multiline EPR spectrum of D1-S169A PSII core complexes differed significantly from that of wild-type, and FTIR difference spectra showed that the mutation strongly perturbs the extensive network of hydrogen bonds that extends at least from D1-Y161 (YZ) to D1-D61. Finally, these results imply a possible role of D1-S169 in proton egress or substrate water delivery.},
doi = {10.1021/acs.biochem.8b01184},
journal = {Biochemistry},
number = 10,
volume = 58,
place = {United States},
year = {Fri Feb 01 00:00:00 EST 2019},
month = {Fri Feb 01 00:00:00 EST 2019}
}
Web of Science
Works referenced in this record:
Photosystem II: The Reaction Center of Oxygenic Photosynthesis
journal, June 2013
- Vinyard, David J.; Ananyev, Gennady M.; Charles Dismukes, G.
- Annual Review of Biochemistry, Vol. 82, Issue 1
Oxygen-evolving complex of Photosystem II: an analysis of second-shell residues and hydrogen-bonding networks
journal, April 2015
- Vogt, Leslie; Vinyard, David J.; Khan, Sahr
- Current Opinion in Chemical Biology, Vol. 25
Progress Toward a Molecular Mechanism of Water Oxidation in Photosystem II
journal, May 2017
- Vinyard, David J.; Brudvig, Gary W.
- Annual Review of Physical Chemistry, Vol. 68, Issue 1
Reflections on substrate water and dioxygen formation
journal, August 2013
- Cox, Nicholas; Messinger, Johannes
- Biochimica et Biophysica Acta (BBA) - Bioenergetics, Vol. 1827, Issue 8-9
Recent developments in biological water oxidation
journal, April 2016
- Pérez-Navarro, Montserrat; Neese, Frank; Lubitz, Wolfgang
- Current Opinion in Chemical Biology, Vol. 31
Missing Pieces in the Puzzle of Biological Water Oxidation
journal, September 2018
- Pantazis, Dimitrios A.
- ACS Catalysis, Vol. 8, Issue 10
Crystal structure of oxygen-evolving photosystem II at a resolution of 1.9 Å
journal, April 2011
- Umena, Yasufumi; Kawakami, Keisuke; Shen, Jian-Ren
- Nature, Vol. 473, Issue 7345
Two Interconvertible Structures that Explain the Spectroscopic Properties of the Oxygen-Evolving Complex of Photosystem II in the S 2 State
journal, August 2012
- Pantazis, Dimitrios A.; Ames, William; Cox, Nicholas
- Angewandte Chemie International Edition, Vol. 51, Issue 39
Oxygen-evolving complex of photosystem II: correlating structure with spectroscopy
journal, January 2014
- Pokhrel, Ravi; Brudvig, Gary W.
- Physical Chemistry Chemical Physics, Vol. 16, Issue 24
Substrate water exchange in photosystem II core complexes of the extremophilic red alga Cyanidioschyzon merolae
journal, August 2014
- Nilsson, Håkan; Krupnik, Tomasz; Kargul, Joanna
- Biochimica et Biophysica Acta (BBA) - Bioenergetics, Vol. 1837, Issue 8
Perturbing the Water Cavity Surrounding the Manganese Cluster by Mutating the Residue D1-Valine 185 Has a Strong Effect on the Water Oxidation Mechanism of Photosystem II
journal, September 2013
- Dilbeck, Preston L.; Bao, Han; Neveu, Curtis L.
- Biochemistry, Vol. 52, Issue 39
Water oxidation chemistry of photosystem II
journal, October 2007
- Brudvig, Gary W.
- Philosophical Transactions of the Royal Society B: Biological Sciences, Vol. 363, Issue 1494
Structures and Energetics for O 2 Formation in Photosystem II
journal, December 2009
- Siegbahn, Per E. M.
- Accounts of Chemical Research, Vol. 42, Issue 12
Extended protein/water H-bond networks in photosynthetic water oxidation
journal, August 2012
- Bondar, Ana-Nicoleta; Dau, Holger
- Biochimica et Biophysica Acta (BBA) - Bioenergetics, Vol. 1817, Issue 8
Water in Photosystem II: Structural, functional and mechanistic considerations
journal, January 2014
- Linke, Katrin; Ho, Felix M.
- Biochimica et Biophysica Acta (BBA) - Bioenergetics, Vol. 1837, Issue 1
Mutation of Lysine 317 in the D2 Subunit of Photosystem II Alters Chloride Binding and Proton Transport
journal, July 2013
- Pokhrel, Ravi; Service, Rachel J.; Debus, Richard J.
- Biochemistry, Vol. 52, Issue 28
Oxygenic Photosystem II: The Mutation D1−D61N in Synechocystis sp. PCC 6803 Retards S-State Transitions without Affecting Electron Transfer from Y Z to P 680 + †
journal, October 1998
- Hundelt, Monika; Hays, Anna-Maria A.; Debus, Richard J.
- Biochemistry, Vol. 37, Issue 41
Probing the Effect of Mutations of Asparagine 181 in the D1 Subunit of Photosystem II
journal, February 2015
- Pokhrel, Ravi; Debus, Richard J.; Brudvig, Gary W.
- Biochemistry, Vol. 54, Issue 8
Evidence from FTIR Difference Spectroscopy of an Extensive Network of Hydrogen Bonds near the Oxygen-Evolving Mn 4 Ca Cluster of Photosystem II Involving D1-Glu65, D2-Glu312, and D1-Glu329
journal, August 2010
- Service, Rachel J.; Hillier, Warwick; Debus, Richard J.
- Biochemistry, Vol. 49, Issue 31
Network of Hydrogen Bonds near the Oxygen-Evolving Mn 4 CaO 5 Cluster of Photosystem II Probed with FTIR Difference Spectroscopy
journal, February 2014
- Service, Rachel J.; Hillier, Warwick; Debus, Richard J.
- Biochemistry, Vol. 53, Issue 6
Evidence from FTIR Difference Spectroscopy That D1-Asp61 Influences the Water Reactions of the Oxygen-Evolving Mn 4 CaO 5 Cluster of Photosystem II
journal, April 2014
- Debus, Richard J.
- Biochemistry, Vol. 53, Issue 18
FTIR studies of metal ligands, networks of hydrogen bonds, and water molecules near the active site Mn4CaO5 cluster in Photosystem II
journal, January 2015
- Debus, Richard J.
- Biochimica et Biophysica Acta (BBA) - Bioenergetics, Vol. 1847, Issue 1
Exploring the energetics of water permeation in photosystem II by multiple steered molecular dynamics simulations
journal, September 2012
- Vassiliev, Sergey; Zaraiskaya, Tatiana; Bruce, Doug
- Biochimica et Biophysica Acta (BBA) - Bioenergetics, Vol. 1817, Issue 9
Substitution of the D1-Asn87 site in photosystem II of cyanobacteria mimics the chloride-binding characteristics of spinach photosystem II
journal, February 2018
- Banerjee, Gourab; Ghosh, Ipsita; Kim, Christopher J.
- Journal of Biological Chemistry, Vol. 293, Issue 7
p K a of a Proton-Conducting Water Chain in Photosystem II
journal, May 2016
- Takaoka, Tomohiro; Sakashita, Naoki; Saito, Keisuke
- The Journal of Physical Chemistry Letters, Vol. 7, Issue 10
Ammonia Binds to the Dangler Manganese of the Photosystem II Oxygen-Evolving Complex
journal, July 2015
- Oyala, Paul H.; Stich, Troy A.; Debus, Richard J.
- Journal of the American Chemical Society, Vol. 137, Issue 27
Ammonia binding to the oxygen-evolving complex of photosystem II identifies the solvent-exchangeable oxygen bridge ( -oxo) of the manganese tetramer
journal, September 2013
- Perez Navarro, M.; Ames, W. M.; Nilsson, H.
- Proceedings of the National Academy of Sciences, Vol. 110, Issue 39
Structural Effects of Ammonia Binding to the Mn 4 CaO 5 Cluster of Photosystem II
journal, January 2018
- Marchiori, David A.; Oyala, Paul H.; Debus, Richard J.
- The Journal of Physical Chemistry B, Vol. 122, Issue 5
Interaction of methanol with the oxygen-evolving complex: atomistic models, channel identification, species dependence, and mechanistic implications
journal, January 2016
- Retegan, Marius; Pantazis, Dimitrios A.
- Chemical Science, Vol. 7, Issue 10
Pulse Electron Paramagnetic Resonance Studies of the Interaction of Methanol with the S 2 State of the Mn 4 O 5 Ca Cluster of Photosystem II
journal, December 2014
- Oyala, Paul H.; Stich, Troy A.; Stull, Jamie A.
- Biochemistry, Vol. 53, Issue 50
Location of Methanol on the S 2 State Mn Cluster in Photosystem II Studied by Proton Matrix Electron Nuclear Double Resonance
journal, January 2017
- Nagashima, Hiroki; Mino, Hiroyuki
- The Journal of Physical Chemistry Letters, Vol. 8, Issue 3
Mechanism of Methanol Inhibition of Photosynthetic Water Oxidation As Studied by Fourier Transform Infrared Difference and Time-Resolved Infrared Spectroscopies
journal, July 2018
- Yata, Haruna; Noguchi, Takumi
- Biochemistry, Vol. 57, Issue 32
Impact of D1-V185 on the Water Molecules That Facilitate O 2 Formation by the Catalytic Mn 4 CaO 5 Cluster in Photosystem II
journal, June 2018
- Kim, Christopher J.; Bao, Han; Burnap, Robert L.
- Biochemistry, Vol. 57, Issue 29
Evidence from FTIR Difference Spectroscopy That a Substrate H 2 O Molecule for O 2 Formation in Photosystem II Is Provided by the Ca Ion of the Catalytic Mn 4 CaO 5 Cluster
journal, May 2017
- Kim, Christopher J.; Debus, Richard J.
- Biochemistry, Vol. 56, Issue 20
QM/MM study of the S2 to S3 transition reaction in the oxygen-evolving complex of photosystem II
journal, September 2015
- Shoji, Mitsuo; Isobe, Hiroshi; Yamaguchi, Kizashi
- Chemical Physics Letters, Vol. 636
Redox-coupled substrate water reorganization in the active site of Photosystem II—The role of calcium in substrate water delivery
journal, June 2016
- Ugur, Ilke; Rutherford, A. William; Kaila, Ville R. I.
- Biochimica et Biophysica Acta (BBA) - Bioenergetics, Vol. 1857, Issue 6
Strong Coupling between the Hydrogen Bonding Environment and Redox Chemistry during the S 2 to S 3 Transition in the Oxygen-Evolving Complex of Photosystem II
journal, April 2015
- Isobe, Hiroshi; Shoji, Mitsuo; Shen, Jian-Ren
- The Journal of Physical Chemistry B, Vol. 119, Issue 43
Does Histidine 332 of the D1 Polypeptide Ligate the Manganese Cluster in Photosystem II? An Electron Spin Echo Envelope Modulation Study †
journal, March 2001
- Debus, Richard J.; Campbell, Kristy A.; Gregor, Wolfgang
- Biochemistry, Vol. 40, Issue 12
Evidence from Biosynthetically Incorporated Strontium and FTIR Difference Spectroscopy that the C-Terminus of the D1 Polypeptide of Photosystem II Does Not Ligate Calcium †
journal, June 2005
- Strickler, Melodie A.; Walker, Lee M.; Hillier, Warwick
- Biochemistry, Vol. 44, Issue 24
Insights into Substrate Binding to the Oxygen-Evolving Complex of Photosystem II from Ammonia Inhibition Studies
journal, December 2014
- Vinyard, David J.; Brudvig, Gary W.
- Biochemistry, Vol. 54, Issue 2
Thermodynamically accurate modeling of the catalytic cycle of photosynthetic oxygen evolution: A mathematical solution to asymmetric Markov chains
journal, July 2013
- Vinyard, David J.; Zachary, Chase E.; Ananyev, Gennady
- Biochimica et Biophysica Acta (BBA) - Bioenergetics, Vol. 1827, Issue 7
S 0 -State Model of the Oxygen-Evolving Complex of Photosystem II
journal, October 2013
- Pal, Rhitankar; Negre, Christian F. A.; Vogt, Leslie
- Biochemistry, Vol. 52, Issue 44
Structural Changes in the Oxygen-Evolving Complex of Photosystem II Induced by the S 1 to S 2 Transition: A Combined XRD and QM/MM Study
journal, October 2014
- Askerka, Mikhail; Wang, Jimin; Brudvig, Gary W.
- Biochemistry, Vol. 53, Issue 44
The ONIOM (our own N-layered integrated molecular orbital + molecular mechanics) method for the first singlet excited (S1) state photoisomerization path of a retinal protonated Schiff base
journal, August 2000
- Vreven, Thom; Morokuma, Keiji
- The Journal of Chemical Physics, Vol. 113, Issue 8
Density-functional exchange-energy approximation with correct asymptotic behavior
journal, September 1988
- Becke, A. D.
- Physical Review A, Vol. 38, Issue 6
Density‐functional thermochemistry. III. The role of exact exchange
journal, April 1993
- Becke, Axel D.
- The Journal of Chemical Physics, Vol. 98, Issue 7, p. 5648-5652
Ab initio effective core potentials for molecular calculations. Potentials for K to Au including the outermost core orbitals
journal, January 1985
- Hay, P. Jeffrey; Wadt, Willard R.
- The Journal of Chemical Physics, Vol. 82, Issue 1, p. 299-310
Self‐Consistent Molecular‐Orbital Methods. IX. An Extended Gaussian‐Type Basis for Molecular‐Orbital Studies of Organic Molecules
journal, January 1971
- Ditchfield, R.; Hehre, W. J.; Pople, J. A.
- The Journal of Chemical Physics, Vol. 54, Issue 2
The influence of polarization functions on molecular orbital hydrogenation energies
journal, January 1973
- Hariharan, P. C.; Pople, J. A.
- Theoretica Chimica Acta, Vol. 28, Issue 3
Fourier transform infrared analysis of the photosynthetic oxygen-evolving center
journal, February 2008
- Noguchi, T.
- Coordination Chemistry Reviews, Vol. 252, Issue 3-4
Monitoring the reactions of photosynthetic water oxidation using infrared spectroscopy
journal, January 2013
- Noguchi, Takumi
- Biomedical Spectroscopy and Imaging, Vol. 2, Issue 2
Changes of Low-Frequency Vibrational Modes Induced by Universal 15 N- and 13 C-Isotope Labeling in S 2 /S 1 FTIR Difference Spectrum of Oxygen-Evolving Complex †
journal, November 2003
- Kimura, Yukihiro; Mizusawa, Naoki; Ishii, Asako
- Biochemistry, Vol. 42, Issue 45
Changes in the Functional and Structural Properties of the Mn Cluster Induced by Replacing the Side Group of the C-Terminus of the D1 Protein of Photosystem II
journal, October 2004
- Mizusawa, Naoki; Yamanari, Toshihiro; Kimura, Yukihiro
- Biochemistry, Vol. 43, Issue 46
Mid- to Low-Frequency Fourier Transform Infrared Spectra of S-State Cycle for Photosynthetic Water Oxidation in Synechocystis sp. PCC 6803 †
journal, June 2004
- Yamanari, Toshihiro; Kimura, Yukihiro; Mizusawa, Naoki
- Biochemistry, Vol. 43, Issue 23
Analysis of Flash-Induced FTIR Difference Spectra of the S-State Cycle in the Photosynthetic Water-Oxidizing Complex by Uniform 15 N and 13 C Isotope Labeling †
journal, May 2003
- Noguchi, Takumi; Sugiura, Miwa
- Biochemistry, Vol. 42, Issue 20
Participation of Glutamate-354 of the CP43 Polypeptide in the Ligation of Manganese and the Binding of Substrate Water in Photosystem II
journal, January 2011
- Service, Rachel J.; Yano, Junko; McConnell, Iain
- Biochemistry, Vol. 50, Issue 1
FTIR Detection of Water Reactions during the Flash-Induced S-State Cycle of the Photosynthetic Water-Oxidizing Complex †
journal, December 2002
- Noguchi, Takumi; Sugiura, Miwa
- Biochemistry, Vol. 41, Issue 52
Role of a Water Network around the Mn 4 CaO 5 Cluster in Photosynthetic Water Oxidation: A Fourier Transform Infrared Spectroscopy and Quantum Mechanics/Molecular Mechanics Calculation Study
journal, January 2016
- Nakamura, Shin; Ota, Kai; Shibuya, Yuichi
- Biochemistry, Vol. 55, Issue 3
Infrared Determination of the Protonation State of a Key Histidine Residue in the Photosynthetic Water Oxidizing Center
journal, June 2017
- Nakamura, Shin; Noguchi, Takumi
- Journal of the American Chemical Society, Vol. 139, Issue 27
A guide to electron paramagnetic resonance spectroscopy of Photosystem II membranes
journal, January 1991
- Miller, Anne-Frances; Brudvig, Gary W.
- Biochimica et Biophysica Acta (BBA) - Bioenergetics, Vol. 1056, Issue 1
Mutation of Arginine 357 of the CP43 Protein of Photosystem II Severely Impairs the Catalytic S-State Cycle of the H 2 O Oxidation Complex †
journal, October 2007
- Hwang, Hong Jin; Dilbeck, Preston; Debus, Richard J.
- Biochemistry, Vol. 46, Issue 43
D1-Asn-298 in photosystem II is involved in a hydrogen-bond network near the redox-active tyrosine Y Z for proton exit during water oxidation
journal, October 2017
- Nagao, Ryo; Ueoka-Nakanishi, Hanayo; Noguchi, Takumi
- Journal of Biological Chemistry, Vol. 292, Issue 49
The O 2 -Evolving Complex of Photosystem II: Recent Insights from Quantum Mechanics/Molecular Mechanics (QM/MM), Extended X-ray Absorption Fine Structure (EXAFS), and Femtosecond X-ray Crystallography Data
journal, December 2016
- Askerka, Mikhail; Brudvig, Gary W.; Batista, Victor S.
- Accounts of Chemical Research, Vol. 50, Issue 1
Native structure of photosystem II at 1.95 Å resolution viewed by femtosecond X-ray pulses
journal, November 2014
- Suga, Michihiro; Akita, Fusamichi; Hirata, Kunio
- Nature, Vol. 517, Issue 7532
Participation of Glutamate-333 of the D1 Polypeptide in the Ligation of the Mn 4 CaO 5 Cluster in Photosystem II
journal, November 2013
- Service, Rachel J.; Yano, Junko; Dilbeck, Preston L.
- Biochemistry, Vol. 52, Issue 47
The Basic Properties of the Electronic Structure of the Oxygen-evolving Complex of Photosystem II Are Not Perturbed by Ca 2+ Removal
journal, May 2012
- Lohmiller, Thomas; Cox, Nicholas; Su, Ji-Hu
- Journal of Biological Chemistry, Vol. 287, Issue 29
Influence of the PsbA1/PsbA3, Ca2+/Sr2+ and Cl−/Br− exchanges on the redox potential of the primary quinone QA in Photosystem II from Thermosynechococcus elongatus as revealed by spectroelectrochemistry
journal, November 2012
- Kato, Yuki; Shibamoto, Tadao; Yamamoto, Shoichi
- Biochimica et Biophysica Acta (BBA) - Bioenergetics, Vol. 1817, Issue 11
Effect of Ca 2+ /Sr 2+ Substitution on the Electronic Structure of the Oxygen-Evolving Complex of Photosystem II: A Combined Multifrequency EPR, 55 Mn-ENDOR, and DFT Study of the S 2 State
journal, March 2011
- Cox, Nicholas; Rapatskiy, Leonid; Su, Ji-Hu
- Journal of the American Chemical Society, Vol. 133, Issue 10
Ammonia binds to the manganese site of the oxygen-evolving complex of photosystem II in the S2 state
journal, July 1986
- Beck, Warren F.; De Paula, Julio C.; Brudvig, Gary W.
- Journal of the American Chemical Society, Vol. 108, Issue 14
Ligation of D1-His332 and D1-Asp170 to the Manganese Cluster of Photosystem II from Synechocystis Assessed by Multifrequency Pulse EPR Spectroscopy †
journal, August 2011
- Stich, Troy A.; Yeagle, Gregory J.; Service, Rachel J.
- Biochemistry, Vol. 50, Issue 34
Structures of the intermediates of Kok’s photosynthetic water oxidation clock
journal, November 2018
- Kern, Jan; Chatterjee, Ruchira; Young, Iris D.
- Nature, Vol. 563, Issue 7731
Works referencing / citing this record:
Study of the role of Mg2+ in dsRNA processing mechanism by bacterial RNase III through QM/MM simulations
journal, November 2019
- Drusin, Salvador I.; Rasia, Rodolfo M.; Moreno, Diego M.
- JBIC Journal of Biological Inorganic Chemistry, Vol. 25, Issue 1