1
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Lehnert N, Kim E, Dong HT, Harland JB, Hunt AP, Manickas EC, Oakley KM, Pham J, Reed GC, Alfaro VS. The Biologically Relevant Coordination Chemistry of Iron and Nitric Oxide: Electronic Structure and Reactivity. Chem Rev 2021; 121:14682-14905. [PMID: 34902255 DOI: 10.1021/acs.chemrev.1c00253] [Citation(s) in RCA: 101] [Impact Index Per Article: 33.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/14/2023]
Abstract
Nitric oxide (NO) is an important signaling molecule that is involved in a wide range of physiological and pathological events in biology. Metal coordination chemistry, especially with iron, is at the heart of many biological transformations involving NO. A series of heme proteins, nitric oxide synthases (NOS), soluble guanylate cyclase (sGC), and nitrophorins, are responsible for the biosynthesis, sensing, and transport of NO. Alternatively, NO can be generated from nitrite by heme- and copper-containing nitrite reductases (NIRs). The NO-bearing small molecules such as nitrosothiols and dinitrosyl iron complexes (DNICs) can serve as an alternative vehicle for NO storage and transport. Once NO is formed, the rich reaction chemistry of NO leads to a wide variety of biological activities including reduction of NO by heme or non-heme iron-containing NO reductases and protein post-translational modifications by DNICs. Much of our understanding of the reactivity of metal sites in biology with NO and the mechanisms of these transformations has come from the elucidation of the geometric and electronic structures and chemical reactivity of synthetic model systems, in synergy with biochemical and biophysical studies on the relevant proteins themselves. This review focuses on recent advancements from studies on proteins and model complexes that not only have improved our understanding of the biological roles of NO but also have provided foundations for biomedical research and for bio-inspired catalyst design in energy science.
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Affiliation(s)
- Nicolai Lehnert
- Department of Chemistry and Department of Biophysics, University of Michigan, Ann Arbor, Michigan 48109-1055, United States
| | - Eunsuk Kim
- Department of Chemistry, Brown University, Providence, Rhode Island 02912, United States
| | - Hai T Dong
- Department of Chemistry and Department of Biophysics, University of Michigan, Ann Arbor, Michigan 48109-1055, United States
| | - Jill B Harland
- Department of Chemistry and Department of Biophysics, University of Michigan, Ann Arbor, Michigan 48109-1055, United States
| | - Andrew P Hunt
- Department of Chemistry and Department of Biophysics, University of Michigan, Ann Arbor, Michigan 48109-1055, United States
| | - Elizabeth C Manickas
- Department of Chemistry and Department of Biophysics, University of Michigan, Ann Arbor, Michigan 48109-1055, United States
| | - Kady M Oakley
- Department of Chemistry, Brown University, Providence, Rhode Island 02912, United States
| | - John Pham
- Department of Chemistry, Brown University, Providence, Rhode Island 02912, United States
| | - Garrett C Reed
- Department of Chemistry and Department of Biophysics, University of Michigan, Ann Arbor, Michigan 48109-1055, United States
| | - Victor Sosa Alfaro
- Department of Chemistry and Department of Biophysics, University of Michigan, Ann Arbor, Michigan 48109-1055, United States
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2
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Dauphas N, Hu MY, Baker EM, Hu J, Tissot FLH, Alp EE, Roskosz M, Zhao J, Bi W, Liu J, Lin JF, Nie NX, Heard A. SciPhon: a data analysis software for nuclear resonant inelastic X-ray scattering with applications to Fe, Kr, Sn, Eu and Dy. JOURNAL OF SYNCHROTRON RADIATION 2018; 25:1581-1599. [PMID: 30179200 PMCID: PMC6140397 DOI: 10.1107/s1600577518009487] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/15/2018] [Accepted: 07/02/2018] [Indexed: 06/01/2023]
Abstract
The synchrotron radiation technique of nuclear resonant inelastic X-ray scattering (NRIXS), also known as nuclear resonance vibrational spectroscopy or nuclear inelastic scattering, provides a wealth of information on the vibrational properties of solids. It has found applications in studies of lattice dynamics and elasticity, superconductivity, heme biochemistry, seismology, isotope geochemistry and many other fields. It involves probing the vibrational modes of solids by using the nuclear resonance of Mössbauer isotopes such as 57Fe, 83Kr, 119Sn, 151Eu and 161Dy. After data reduction, it provides the partial phonon density of states of the Mössbauer isotope that is investigated, as well as many other derived quantities such as the mean force constant of the chemical bonds and the Debye velocity. The data reduction is, however, not straightforward and involves removal of the elastic peak, normalization and Fourier-Log transformation. Furthermore, some of the quantities derived are highly sensitive to details in the baseline correction. A software package and several novel procedures to streamline and hopefully improve the reduction of the NRIXS data generated at sector 3ID of the Advanced Photon Source have been developed. The graphical user interface software is named SciPhon and runs as a Mathematica package. It is easily portable to other platforms and can be easily adapted for reducing data generated at other beamlines. Several tests and comparisons are presented that demonstrate the usefulness of this software, whose results have already been used in several publications. Here, the SciPhon software is used to reduce Kr, Sn, Eu and Dy NRIXS data, and potential implications for interpreting natural isotopic variations in those systems are discussed.
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Affiliation(s)
- Nicolas Dauphas
- Department of the Geophysical Sciences and Enrico Fermi Institute, The University of Chicago, 5734 South Ellis Avenue, Chicago, IL 60615, USA
| | - Michael Y. Hu
- Advanced Photon Source, Argonne National Laboratory, 9700 South Cass Avenue, Argonne, IL 60439, USA
| | - Erik M. Baker
- Department of the Geophysical Sciences and Enrico Fermi Institute, The University of Chicago, 5734 South Ellis Avenue, Chicago, IL 60615, USA
- Department of Earth and Planetary Sciences, Northwestern University, 2145 Sheridan Road, Evanston, IL 60208, USA
| | - Justin Hu
- Department of the Geophysical Sciences and Enrico Fermi Institute, The University of Chicago, 5734 South Ellis Avenue, Chicago, IL 60615, USA
| | - Francois L. H. Tissot
- Department of the Geophysical Sciences and Enrico Fermi Institute, The University of Chicago, 5734 South Ellis Avenue, Chicago, IL 60615, USA
| | - E. Ercan Alp
- Advanced Photon Source, Argonne National Laboratory, 9700 South Cass Avenue, Argonne, IL 60439, USA
| | - Mathieu Roskosz
- IMPMC-UMR CNRS 7590, Sorbonne Universités, UPMC, IRD, MNHN, Muséum National d’Histoire Naturelle, 61 Rue Buffon, 75005 Paris, France
| | - Jiyong Zhao
- Advanced Photon Source, Argonne National Laboratory, 9700 South Cass Avenue, Argonne, IL 60439, USA
| | - Wenli Bi
- Advanced Photon Source, Argonne National Laboratory, 9700 South Cass Avenue, Argonne, IL 60439, USA
| | - Jin Liu
- Department of Geological Sciences, Stanford University, Stanford, CA, USA
| | - Jung-Fu Lin
- Department of Geological Sciences, Jackson School of Geosciences, University of Texas at Austin, Austin, TX 78712, USA
| | - Nicole X. Nie
- Department of the Geophysical Sciences and Enrico Fermi Institute, The University of Chicago, 5734 South Ellis Avenue, Chicago, IL 60615, USA
| | - Andrew Heard
- Department of the Geophysical Sciences and Enrico Fermi Institute, The University of Chicago, 5734 South Ellis Avenue, Chicago, IL 60615, USA
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3
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Scheidt WR, Li J, Sage JT. What Can Be Learned from Nuclear Resonance Vibrational Spectroscopy: Vibrational Dynamics and Hemes. Chem Rev 2017; 117:12532-12563. [PMID: 28921972 PMCID: PMC5639469 DOI: 10.1021/acs.chemrev.7b00295] [Citation(s) in RCA: 27] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/14/2022]
Abstract
![]()
Nuclear resonance
vibrational spectroscopy (NRVS; also known as
nuclear inelastic scattering, NIS) is a synchrotron-based method that
reveals the full spectrum of vibrational dynamics for Mössbauer
nuclei. Another major advantage, in addition to its completeness (no
arbitrary optical selection rules), is the unique selectivity of NRVS.
The basics of this recently developed technique are first introduced
with descriptions of the experimental requirements and data analysis
including the details of mode assignments. We discuss the use of NRVS
to probe 57Fe at the center of heme and heme protein derivatives
yielding the vibrational density of states for the iron. The application
to derivatives with diatomic ligands (O2, NO, CO, CN–) shows the strong capabilities of identifying mode
character. The availability of the complete vibrational spectrum of
iron allows the identification of modes not available by other techniques.
This permits the correlation of frequency with other physical properties.
A significant example is the correlation we find between the Fe–Im
stretch in six-coordinate Fe(XO) hemes and the trans Fe–N(Im)
bond distance, not possible previously. NRVS also provides uniquely
quantitative insight into the dynamics of the iron. For example, it
provides a model-independent means of characterizing the strength
of iron coordination. Prediction of the temperature-dependent mean-squared
displacement from NRVS measurements yields a vibrational “baseline”
for Fe dynamics that can be compared with results from techniques
that probe longer time scales to yield quantitative insights into
additional dynamical processes.
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Affiliation(s)
- W Robert Scheidt
- Department of Chemistry and Biochemistry, University of Notre Dame , Notre Dame, Indiana 46556 United States
| | - Jianfeng Li
- College of Materials Science and Optoelectronic Technology, University of Chinese Academy of Sciences , YanQi Lake, HuaiRou District, Beijing 101408, China
| | - J Timothy Sage
- Department of Physics and Center for Interdisciplinary Research on Complex Systems, Northeastern University , 120 Forsyth Street, Boston, Massachusetts 02115, United States
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4
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Peng Q, Pavlik JW, Silvernail NJ, Alp EE, Hu MY, Zhao J, Sage JT, Scheidt WR. 3D Motions of Iron in Six-Coordinate {FeNO}(7) Hemes by Nuclear Resonance Vibration Spectroscopy. Chemistry 2016; 22:6323-6332. [PMID: 26999733 PMCID: PMC4999340 DOI: 10.1002/chem.201505155] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/24/2015] [Indexed: 11/08/2022]
Abstract
The vibrational spectrum of a six-coordinate nitrosyl iron porphyrinate, monoclinic [Fe(TpFPP)(1-MeIm)(NO)] (TpFPP=tetra-para-fluorophenylporphyrin; 1-MeIm=1-methylimidazole), has been studied by oriented single-crystal nuclear resonance vibrational spectroscopy (NRVS). The crystal was oriented to give spectra perpendicular to the porphyrin plane and two in-plane spectra perpendicular or parallel to the projection of the FeNO plane. These enable assignment of the FeNO bending and stretching modes. The measurements reveal that the two in-plane spectra have substantial differences that result from the strongly bonded axial NO ligand. The direction of the in-plane iron motion is found to be largely parallel and perpendicular to the projection of the bent FeNO on the porphyrin plane. The out-of-plane Fe-N-O stretching and bending modes are strongly mixed with each other, as well as with porphyrin ligand modes. The stretch is mixed with v50 as was also observed for dioxygen complexes. The frequency of the assigned stretching mode of eight Fe-X-O (X=N, C, and O) complexes is correlated with the Fe-XO bond lengths. The nature of highest frequency band at ≈560 cm(-1) has also been examined in two additional new derivatives. Previously assigned as the Fe-NO stretch (by resonance Raman), it is better described as the bend, as the motion of the central nitrogen atom of the FeNO group is very large. There is significant mixing of this mode. The results emphasize the importance of mode mixing; the extent of mixing must be related to the peripheral phenyl substituents.
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Affiliation(s)
- Qian Peng
- Contribution from Department of Chemistry and Biochemistry, University of Notre Dame, University of Notre Dame, Notre Dame, Indiana 46556 USA
| | - Jeffrey W. Pavlik
- Contribution from Department of Chemistry and Biochemistry, University of Notre Dame, University of Notre Dame, Notre Dame, Indiana 46556 USA
| | - Nathan J. Silvernail
- Contribution from Department of Chemistry and Biochemistry, University of Notre Dame, University of Notre Dame, Notre Dame, Indiana 46556 USA
| | - E. Ercan Alp
- Advanced Photon Source, Argonne National Laboratory, Argonne, IL 60439, USA
| | - Michael Y. Hu
- Advanced Photon Source, Argonne National Laboratory, Argonne, IL 60439, USA
| | - Jiyong Zhao
- Advanced Photon Source, Argonne National Laboratory, Argonne, IL 60439, USA
| | - J. Timothy Sage
- Department of Physics and Center for Interdisciplinary Research on Complex Systems, Northeastern University, 120 Forsyth Street, Boston, MA 02115, USA
| | - W. Robert Scheidt
- Contribution from Department of Chemistry and Biochemistry, University of Notre Dame, University of Notre Dame, Notre Dame, Indiana 46556 USA
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5
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Chakraborty S, Reed J, Sage JT, Branagan NC, Petrik ID, Miner KD, Hu MY, Zhao J, Alp EE, Lu Y. Recent advances in biosynthetic modeling of nitric oxide reductases and insights gained from nuclear resonance vibrational and other spectroscopic studies. Inorg Chem 2015; 54:9317-29. [PMID: 26274098 PMCID: PMC4677664 DOI: 10.1021/acs.inorgchem.5b01105] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
![]()
This Forum Article focuses on recent
advances in structural and spectroscopic studies of biosynthetic models
of nitric oxide reductases (NORs). NORs are complex metalloenzymes
found in the denitrification pathway of Earth’s nitrogen cycle
where they catalyze the proton-dependent two-electron reduction of
nitric oxide (NO) to nitrous oxide (N2O). While much progress
has been made in biochemical and biophysical studies of native NORs
and their variants, a clear mechanistic understanding of this important
metalloenzyme related to its function is still elusive. We report
herein UV–vis and nuclear resonance vibrational spectroscopy
(NRVS) studies of mononitrosylated intermediates of the NOR reaction
of a biosynthetic model. The ability to selectively substitute metals
at either heme or nonheme metal sites allows the introduction of independent 57Fe probe atoms at either site, as well as allowing the preparation
of analogues of stable reaction intermediates by replacing either
metal with a redox inactive metal. Together with previous structural
and spectroscopic results, we summarize insights gained from studying
these biosynthetic models toward understanding structural features
responsible for the NOR activity and its mechanism. The outlook on
NOR modeling is also discussed, with an emphasis on the design of
models capable of catalytic turnovers designed based on close mimics
of the secondary coordination sphere of native NORs. New insights into nitric oxide reductases (NORs) are obtained. Using
nuclear resonance vibrational spectroscopy, we probe both iron atoms
in mononitrosylated intermediates of the NOR reaction in a biosynthetic
protein model that reveal new insights into the structural and electronic
features responsible for the NOR activity and its likely mechanism.
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Affiliation(s)
| | | | - J Timothy Sage
- Department of Physics, Northeastern University , Boston, Massachusetts 02115, United States
| | - Nicole C Branagan
- Department of Physics, Northeastern University , Boston, Massachusetts 02115, United States
| | | | | | - Michael Y Hu
- Advanced Photon Source, Argonne National Laboratory , Argonne, Illinois 60439, United States
| | - Jiyong Zhao
- Advanced Photon Source, Argonne National Laboratory , Argonne, Illinois 60439, United States
| | - E Ercan Alp
- Advanced Photon Source, Argonne National Laboratory , Argonne, Illinois 60439, United States
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6
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Li J, Peng Q, Oliver A, Alp EE, Hu MY, Zhao J, Sage JT, Scheidt WR. Comprehensive Fe-ligand vibration identification in {FeNO}6 hemes. J Am Chem Soc 2014; 136:18100-10. [PMID: 25490350 PMCID: PMC4295236 DOI: 10.1021/ja5105766] [Citation(s) in RCA: 22] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/14/2014] [Indexed: 01/06/2023]
Abstract
Oriented single-crystal nuclear resonance vibrational spectroscopy (NRVS) has been used to obtain all iron vibrations in two {FeNO}(6) porphyrinate complexes, five-coordinate [Fe(OEP)(NO)]ClO4 and six-coordinate [Fe(OEP)(2-MeHIm)(NO)]ClO4. A new crystal structure was required for measurements of [Fe(OEP)(2-MeHIm)(NO)]ClO4, and the new structure is reported herein. Single crystals of both complexes were oriented to be either parallel or perpendicular to the porphyrin plane and/or axial imidazole ligand plane. Thus, the FeNO bending and stretching modes can now be unambiguously assigned; the pattern of shifts in frequency as a function of coordination number can also be determined. The pattern is quite distinct from those found for CO or {FeNO}(7) heme species. This is the result of unchanging Fe-N(NO) bonding interactions in the {FeNO}(6) species, in distinct contrast to the other diatomic ligand species. DFT calculations were also used to obtain detailed predictions of vibrational modes. Predictions were consistent with the intensity and character found in the experimental spectra. The NRVS data allow the assignment and observation of the challenging to obtain Fe-Im stretch in six-coordinate heme derivatives. NRVS data for this and related six-coordinate hemes with the diatomic ligands CO, NO, and O2 reveal a strong correlation between the Fe-Im stretch and Fe-N(Im) bond distance that is detailed for the first time.
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Affiliation(s)
- Jianfeng Li
- College
of Materials Science and Optoelectronic Technology, University of Chinese Academy of Sciences, YanQi Lake, HuaiRou District, Beijing 101408, China
- Department
of Chemistry and Biochemistry, University
of Notre Dame, Notre Dame, Indiana 46556, United States
| | - Qian Peng
- Department
of Chemistry and Biochemistry, University
of Notre Dame, Notre Dame, Indiana 46556, United States
| | - Allen
G. Oliver
- Department
of Chemistry and Biochemistry, University
of Notre Dame, Notre Dame, Indiana 46556, United States
| | - E. Ercan Alp
- Advanced
Photon Source, Argonne National Laboratory, Argonne, Illinois 60439, United States
| | - Michael Y. Hu
- Advanced
Photon Source, Argonne National Laboratory, Argonne, Illinois 60439, United States
| | - Jiyong Zhao
- Advanced
Photon Source, Argonne National Laboratory, Argonne, Illinois 60439, United States
| | - J. Timothy Sage
- Department
of Physics and Center for Interdisciplinary Research on Complex Systems, Northeastern University, 120 Forsyth Street, Boston, Massachusetts 02115, United States
| | - W. Robert Scheidt
- Department
of Chemistry and Biochemistry, University
of Notre Dame, Notre Dame, Indiana 46556, United States
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7
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Linder D, Silvernail NJ, Barabanschikov A, Zhao J, Alp EE, Sturhahn W, Sage JT, Scheidt WR, Rodgers KR. The diagnostic vibrational signature of pentacoordination in heme carbonyls. J Am Chem Soc 2014; 136:9818-21. [PMID: 24950373 PMCID: PMC4120987 DOI: 10.1021/ja503191z] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/31/2014] [Indexed: 11/28/2022]
Abstract
Heme-carbonyl complexes are widely exploited for the insight they provide into the structural basis of function in heme-based proteins, by revealing the nature of their bonded and nonbonded interactions with the protein. This report presents two novel results which clearly establish a FeCO vibrational signature for crystallographically verified pentacoordination. First, anisotropy in the NRVS density of states for ν(Fe-C) and δ(FeCO) in oriented single crystals of [Fe(OEP)(CO)] clearly reveals that the Fe-C stretch occurs at higher frequency than the FeCO bend and considerably higher than any previously reported heme carbonyl. Second, DFT calculations on a series of heme carbonyls reveal that the frequency crossover occurs near the weak trans O atom donor, furan. As ν(Fe-C) occurs at lower frequencies than δ(FeCO) in all heme protein carbonyls reported to date, the results reported herein suggest that they are all hexacoordinate.
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Affiliation(s)
- Douglas
P. Linder
- Department
of Chemistry and Biochemistry, North Dakota
State University, Fargo, North Dakota 58105, United States
| | - Nathan J. Silvernail
- Department
of Chemistry and Biochemistry, University
of Notre Dame, Notre Dame, Indiana 46556, United States
| | | | - Jiyong Zhao
- Advanced
Photon Source, Argonne National Laboratory, Argonne, Illinois 60439, United States
| | - E. Ercan Alp
- Advanced
Photon Source, Argonne National Laboratory, Argonne, Illinois 60439, United States
| | - Wolfgang Sturhahn
- Advanced
Photon Source, Argonne National Laboratory, Argonne, Illinois 60439, United States
| | - J. Timothy Sage
- Department
of Physics, Northeastern University, Boston, Massachusetts 02115, United States
| | - W. Robert Scheidt
- Department
of Chemistry and Biochemistry, University
of Notre Dame, Notre Dame, Indiana 46556, United States
| | - Kenton R. Rodgers
- Department
of Chemistry and Biochemistry, North Dakota
State University, Fargo, North Dakota 58105, United States
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8
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Leu BM, Zgierski MZ, Bischoff C, Li M, Hu MY, Zhao J, Martin SW, Alp EE, Scheidt WR. Quantitative vibrational dynamics of the metal site in a tin porphyrin: an IR, NRVS, and DFT study. Inorg Chem 2013; 52:9948-53. [PMID: 23962374 PMCID: PMC3787516 DOI: 10.1021/ic401152b] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
We used a newer, synchrotron-based, spectroscopic technique (nuclear resonance vibrational spectroscopy, NRVS) in combination with a more traditional one (infrared absorption, IR) to obtain a complete, quantitative picture of the metal center vibrational dynamics in a six-coordinated tin porphyrin. From the NRVS (119)Sn site-selectivity and the sensitivity of the IR signal to (112)Sn/(119)Sn isotope substitution, we identified the frequency of the antisymmetric stretching of the axial bonds (290 cm(-1)) and all the other vibrations involving Sn. Experimentally authenticated density functional theory (DFT) calculations aid the data interpretation by providing detailed normal mode descriptions for each observed vibration. These results may represent a starting point toward the characterization of the local vibrational dynamics of the metallic site in tin porphyrins and compounds with related structures. The quantitative complementariness between IR, NRVS, and DFT is emphasized.
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Affiliation(s)
- Bogdan M Leu
- Advanced Photon Source, Argonne National Laboratory, Argonne, Illinois 60439, United States.
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9
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Goodrich LE, Roy S, Alp EE, Zhao J, Hu MY, Lehnert N. Electronic Structure and Biologically Relevant Reactivity of Low-Spin {FeNO}8 Porphyrin Model Complexes: New Insight from a Bis-Picket Fence Porphyrin. Inorg Chem 2013; 52:7766-80. [DOI: 10.1021/ic400977h] [Citation(s) in RCA: 94] [Impact Index Per Article: 8.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Affiliation(s)
- Lauren E. Goodrich
- Department of Chemistry, University of Michigan, Ann Arbor, Michigan 48109,
United States
| | - Saikat Roy
- Department of Chemistry, University of Michigan, Ann Arbor, Michigan 48109,
United States
| | - E. Ercan Alp
- Advanced
Photon Source, Argonne National Laboratory, Argonne, Illinois 60439,
United States
| | - Jiyong Zhao
- Advanced
Photon Source, Argonne National Laboratory, Argonne, Illinois 60439,
United States
| | - Michael Y. Hu
- Advanced
Photon Source, Argonne National Laboratory, Argonne, Illinois 60439,
United States
| | - Nicolai Lehnert
- Department of Chemistry, University of Michigan, Ann Arbor, Michigan 48109,
United States
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10
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Kamali S, Wang H, Mitra D, Ogata H, Lubitz W, Manor BC, Rauchfuss TB, Byrne D, Bonnefoy V, Jenney FE, Adams MWW, Yoda Y, Alp E, Zhao J, Cramer SP. Observation of the Fe-CN and Fe-CO vibrations in the active site of [NiFe] hydrogenase by nuclear resonance vibrational spectroscopy. Angew Chem Int Ed Engl 2013; 52:724-8. [PMID: 23136119 PMCID: PMC3535562 DOI: 10.1002/anie.201204616] [Citation(s) in RCA: 53] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/13/2012] [Revised: 08/09/2012] [Indexed: 11/06/2022]
Abstract
Nuclear inelastic scattering of (57)Fe labeled [NiFe] hydrogenase is shown to give information on different states of the enzyme. It was thus possible to detect and assign Fe-CO and Fe-CN bending and stretching vibrations of the active site outside the spectral range of the Fe-S cluster normal modes.
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Affiliation(s)
- Saeed Kamali
- Department of Chemistry, University of California Davis, CA 95616 (USA)
| | - Hongxin Wang
- Physical Biosciences Division, Lawrence Berkeley National Laboratory, Berkeley, CA 94720 (USA)
- Department of Chemistry, University of California Davis, CA 95616 (USA)
| | - Devrani Mitra
- Department of Chemistry, University of California Davis, CA 95616 (USA)
| | - Hideaki Ogata
- Max-Planck-Institut für Chemische Energiekonversion 45470 Mülheim an der Ruhr (Germany)
| | - Wolfgang Lubitz
- Max-Planck-Institut für Chemische Energiekonversion 45470 Mülheim an der Ruhr (Germany)
| | - Brian C. Manor
- Department of Chemistry, University of Illinois Champaign-Urbana, IL 61801 (USA)
| | - Thomas B. Rauchfuss
- Department of Chemistry, University of Illinois Champaign-Urbana, IL 61801 (USA)
| | - Deborah Byrne
- Institut de Microbiologie de la Méditerranée Aix-Marseille-Universit , Marseille 13009 (France)
| | - Violaine Bonnefoy
- CNRS, IMM, Laboratoire de Chimie Bactérienne Marseille Cedex 20 (France)
| | - Francis E. Jenney
- Georgia Campus, Philadelphia College of Osteopathic Medicine Suwanee, GA 30024 (USA)
| | - Michael W. W. Adams
- Department of Biochemistry & Molecular Biology University of Georgia, Athens, GA 30602 (USA)
| | - Yoshitaka Yoda
- JASRI, SPring-8 1-1-1 Kouto, Sayo-cho, Sayo-gun, Hyogo 679-5198 (Japan)
| | - Ercan Alp
- Advanced Photon Source, Argonne National Laboratory Argonne, IL 60439 (USA)
| | - Jiyong Zhao
- Advanced Photon Source, Argonne National Laboratory Argonne, IL 60439 (USA)
| | - Stephen P. Cramer
- Physical Biosciences Division, Lawrence Berkeley National Laboratory, Berkeley, CA 94720 (USA)
- Department of Chemistry, University of California Davis, CA 95616 (USA)
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11
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Goodrich LE, Lehnert N. The trans effect of nitroxyl (HNO) in ferrous heme systems: Implications for soluble guanylate cyclase activation by HNO. J Inorg Biochem 2013; 118:179-86. [DOI: 10.1016/j.jinorgbio.2012.07.024] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/30/2012] [Revised: 07/19/2012] [Accepted: 07/31/2012] [Indexed: 10/27/2022]
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12
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Lehnert N, Scheidt WR, Wolf MW. Structure and Bonding in Heme–Nitrosyl Complexes and Implications for Biology. NITROSYL COMPLEXES IN INORGANIC CHEMISTRY, BIOCHEMISTRY AND MEDICINE II 2013. [DOI: 10.1007/430_2013_92] [Citation(s) in RCA: 43] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/12/2022]
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13
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Ohta T, Liu JG, Saito M, Kobayashi Y, Yoda Y, Seto M, Naruta Y. Axial Ligand Effects on Vibrational Dynamics of Iron in Heme Carbonyl Studied by Nuclear Resonance Vibrational Spectroscopy. J Phys Chem B 2012; 116:13831-8. [DOI: 10.1021/jp304398g] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Affiliation(s)
- Takehiro Ohta
- Institute
for Materials Chemistry
and Engineering and International Institute for Carbon-Neutral Energy
Research (WPI-I2CNER), Kyushu University, Fukuoka 812-8581, Japan
- JST, ACT-C, Saitama 332-0012,
Japan
| | - Jin-Gang Liu
- Institute
for Materials Chemistry
and Engineering and International Institute for Carbon-Neutral Energy
Research (WPI-I2CNER), Kyushu University, Fukuoka 812-8581, Japan
- Department of Chemistry, East China University of Science and Technology, 130
Meilong Rd, 200237, Shanghai, P. R. China
| | - Makina Saito
- Research Reactor Institute, Kyoto University, Osaka 590-0494, Japan
| | - Yasuhiro Kobayashi
- Research Reactor Institute, Kyoto University, Osaka 590-0494, Japan
- CREST, Japan Science and Technology Agency, Saitama 332-0012, Japan
| | - Yoshitaka Yoda
- Japan Synchrotron Radiation Research Institute, Hyogo 679-5198, Japan
- CREST, Japan Science and Technology Agency, Saitama 332-0012, Japan
| | - Makoto Seto
- Research Reactor Institute, Kyoto University, Osaka 590-0494, Japan
- Japan Atomic Energy Agency, Hyogo 679-5148, Japan
- CREST, Japan Science and Technology Agency, Saitama 332-0012, Japan
| | - Yoshinori Naruta
- Institute
for Materials Chemistry
and Engineering and International Institute for Carbon-Neutral Energy
Research (WPI-I2CNER), Kyushu University, Fukuoka 812-8581, Japan
- JST, ACT-C, Saitama 332-0012,
Japan
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14
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Kamali S, Wang H, Mitra D, Ogata H, Lubitz W, Manor BC, Rauchfuss TB, Byrne D, Bonnefoy V, Jenney FE, Adams MWW, Yoda Y, Alp E, Zhao J, Cramer SP. Detektion von Fe-CN- und Fe-CO-Schwingungen im aktiven Zentrum der [NiFe]-Hydrogenase durch inelastische kernresonante Streuung. Angew Chem Int Ed Engl 2012. [DOI: 10.1002/ange.201204616] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/10/2022]
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15
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Li J, Peng Q, Barabanschikov A, Pavlik JW, Alp EE, Sturhahn W, Zhao J, Sage JT, Scheidt WR. Vibrational probes and determinants of the S = 0 ⇌ S = 2 spin crossover in five-coordinate [Fe(TPP)(CN)]-. Inorg Chem 2012; 51:11769-78. [PMID: 23082814 PMCID: PMC3498855 DOI: 10.1021/ic301719v] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
The low-frequency vibrational characterization of the spin-crossover complex, five-coordinate cyano(tetraphenylporphyrinato)iron(II), [Fe(TPP)(CN)](-), is reported. Nuclear resonance vibrational spectroscopy has been used to measure all low-frequency vibrations involving iron at several temperatures; this yields vibrational spectra of both the low- (S = 0) and high-spin (S = 2) states. Multitemperature oriented single-crystal measurements facilitate assignments of the vibrational character of all modes and are consistent with the DFT-predicted spectra. The availability of the entire iron vibrational spectrum allows for the complete correlation of the modes between the two spin states. These data demonstrate that not only do the frequencies of the vibrations shift to lower values for the high-spin species as would be expected owing to the weaker bonds in the high-spin state, but also the mixing of iron modes with ligand modes changes substantially. Diagrams illustrating the changing character of the modes and their correlation are given. The reduced iron-ligand frequencies are the primary factor in the entropic stabilization of the high-spin state responsible for the spin crossover.
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Affiliation(s)
- Jianfeng Li
- To whom correspondence should be addressed. JL: , JTS: , WRS:
| | | | | | | | | | | | | | - J. Timothy Sage
- To whom correspondence should be addressed. JL: , JTS: , WRS:
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16
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Guo Y, Brecht E, Aznavour K, Nix JC, Xiao Y, Wang H, George SJ, Bau R, Keable S, Peters JW, Adams MWW, Jenney F, Sturhahn W, Alp EE, Zhao J, Yoda Y, Cramer SP. Nuclear resonance vibrational spectroscopy (NRVS) of rubredoxin and MoFe protein crystals. ACTA ACUST UNITED AC 2012; 222:77-90. [PMID: 26052177 DOI: 10.1007/s10751-012-0643-2] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/27/2022]
Abstract
We have applied 57Fe nuclear resonance vibrational spectroscopy (NRVS) for the first time to study the dynamics of Fe centers in Fe-S protein crystals, including oxidized wild type rubredoxin crystals from Pyrococcus furiosus, and the MoFe protein of nitrogenase from Azotobacter vinelandii. Thanks to the NRVS selection rule, selectively probed vibrational modes have been observed in both oriented rubredoxin and MoFe protein crystals. The NRVS work was complemented by extended X-ray absorption fine structure spectroscopy (EXAFS) measurements on oxidized wild type rubredoxin crystals from Pyrococcus furiosus. The EXAFS spectra revealed the Fe-S bond length difference in oxidized Pf Rd protein, which is qualitatively consistent with the X-ray crystal structure.
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Affiliation(s)
- Yisong Guo
- Department of Applied Science, University of California, Davis, CA 95616
| | - Eric Brecht
- Department of Chemistry and Biochemistry, Montana State University, Bozeman, MT 59717
| | - Kristen Aznavour
- Department of Chemistry, University of Southern California, Los Angeles, CA 90033
| | - Jay C Nix
- Physical Biosciences Division, Lawrence Berkeley National Laboratory, Berkeley, CA 94720
| | - Yuming Xiao
- Department of Applied Science, University of California, Davis, CA 95616
| | - Hongxin Wang
- Department of Applied Science, University of California, Davis, CA 95616 ; Physical Biosciences Division, Lawrence Berkeley National Laboratory, Berkeley, CA 94720
| | - Simon J George
- Physical Biosciences Division, Lawrence Berkeley National Laboratory, Berkeley, CA 94720
| | - Robert Bau
- Department of Chemistry, University of Southern California, Los Angeles, CA 90033
| | - Stephen Keable
- Department of Chemistry and Biochemistry, Montana State University, Bozeman, MT 59717
| | - John W Peters
- Department of Chemistry and Biochemistry, Montana State University, Bozeman, MT 59717
| | | | - Francis Jenney
- Georgia Campus, Philadelphia College of Osteopathic Medicine, Suwanee, GA 30024
| | - Wolfgang Sturhahn
- Advanced Photon Source, Argonne National Laboratory, Argonne, IL 60439
| | - Ercan E Alp
- Advanced Photon Source, Argonne National Laboratory, Argonne, IL 60439
| | - Jiyong Zhao
- Advanced Photon Source, Argonne National Laboratory, Argonne, IL 60439
| | - Yoshitaka Yoda
- JASRI, SPring-8, 1-1-1 Kouto, Mikazuki-cho, Sayo-gun, Hyogo 679-5198, Japan
| | - Stephen P Cramer
- Department of Applied Science, University of California, Davis, CA 95616 ; Physical Biosciences Division, Lawrence Berkeley National Laboratory, Berkeley, CA 94720 ; Department of Chemistry, University of California, Davis, CA 95616
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17
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Hu C, Barabanschikov A, Ellison MK, Zhao J, Alp EE, Sturhahn W, Zgierski MZ, Sage JT, Scheidt WR. Nuclear resonance vibrational spectra of five-coordinate imidazole-ligated iron(II) porphyrinates. Inorg Chem 2012; 51:1359-70. [PMID: 22243131 PMCID: PMC3273671 DOI: 10.1021/ic201580v] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
Nuclear resonance vibrational spectra have been obtained for six five-coordinate imidazole-ligated iron(II) porphyrinates, [Fe(Por)(L)] (Por = tetraphenylporphyrinate, octaethylporphyrinate, tetratolylporphyrinate, or protoporphyrinate IX and L = 2-methylimidazole or 1,2-dimethylimidazole). Measurements have been made on both powder and oriented crystal samples. The spectra are dominated by strong signals around 200-300 cm(-1). Although the in-plane and out-of-plane vibrations are seriously overlapped, oriented crystal spectra allow their deconvolution. Thus, oriented crystal experimental data, along with density functional theory (DFT) calculations, enable the assignment of key vibrations in the spectra. Molecular dynamics are also discussed. The nature of the Fe-N(Im) vibrations has been elaborated further than was possible from resonance Raman studies. Our study suggests that the Fe motions are coupled with the porphyrin core and peripheral groups motions. Both peripheral groups and their conformations have significant influence on the vibrational spectra (position and shape).
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Affiliation(s)
- Chuanjiang Hu
- Contribution from Key Laboratory of Organic Synthesis of Jiangsu Province, College of Chemistry, Chemical Engineering and Materials Science, Soochow University, Suzhou 215123, P.R. China
- Department of Chemistry and Biochemistry, University of Notre Dame, Notre Dame, Indiana 46556
| | - Alexander Barabanschikov
- Department of Physics and Center for Interdisciplinary Research on Complex Systems, Northeastern University, Boston, Massachusetts 02115
| | - Mary K. Ellison
- Department of Chemistry and Biochemistry, University of Notre Dame, Notre Dame, Indiana 46556
| | - Jiyong Zhao
- Advanced Photon Source, Argonne National Laboratory, Argonne, Illinois 60439
| | - E. Ercan Alp
- Advanced Photon Source, Argonne National Laboratory, Argonne, Illinois 60439
| | - Wolfgang Sturhahn
- Advanced Photon Source, Argonne National Laboratory, Argonne, Illinois 60439
| | - Marek Z. Zgierski
- Steacie Institute for Molecular Science, National Research Council of Canada, Ottawa, Ontario, Canada KIA OR6
| | - J. Timothy Sage
- Department of Physics and Center for Interdisciplinary Research on Complex Systems, Northeastern University, Boston, Massachusetts 02115
| | - W. Robert Scheidt
- Department of Chemistry and Biochemistry, University of Notre Dame, Notre Dame, Indiana 46556
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18
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Rokob TA, Srnec M, Rulíšek L. Theoretical calculations of physico-chemical and spectroscopic properties of bioinorganic systems: current limits and perspectives. Dalton Trans 2012; 41:5754-68. [DOI: 10.1039/c2dt12423h] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/16/2022]
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19
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Paulsen H, Trautwein AX, Wegner P, Schmidt C, Chumakov AI, Schünemann V. Interpretation of Nuclear Resonant Vibrational Spectra of Rubredoxin Using a Combined Quantum Mechanics and Molecular Mechanics Approach. Chemphyschem 2011; 12:3434-41. [DOI: 10.1002/cphc.201100595] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/01/2011] [Indexed: 11/06/2022]
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20
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Li J, Peng Q, Barabanschikov A, Pavlik JW, Alp EE, Sturhahn W, Zhao J, Schulz CE, Sage JT, Scheidt WR. New perspectives on iron-ligand vibrations of oxyheme complexes. Chemistry 2011; 17:11178-85. [PMID: 21922552 PMCID: PMC3234299 DOI: 10.1002/chem.201101352] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/03/2011] [Indexed: 11/12/2022]
Abstract
We report our studies of the vibrational dynamics of iron for three imidazole-ligated oxyheme derivatives that mimic the active sites of histidine-ligated heme proteins complexed with dioxygen. The experimental vibrational data are obtained from nuclear resonance vibrational spectroscopy (NRVS) measurements conducted on both powder samples and oriented single crystals, and which includes several in-plane (ip) and out-of-plane (oop) measurements. Vibrational spectral assignments have been made through a combination of the oriented sample spectra and predictions based on density functional theory (DFT) calculations. The two Fe-O(2) modes that have been previously observed by resonance Raman spectroscopy in heme proteins are clearly shown to be very strongly mixed and are not simply either a bending or stretching mode. In addition, a third Fe-O(2) mode, not previously reported, has been identified. The long-sought Fe-Im stretch, not observed in resonance Raman spectra, has been identified and compared with the frequencies observed for the analogous CO and NO species. The studies also suggest that the in-plane iron motion is anisotropic and is controlled by the orientation of the Fe-O(2) group and not sensitive to the in-plane Fe-N(p) bonds and/or imidazole orientations.
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Affiliation(s)
- Jianfeng Li
- Department of Chemistry and Biochemistry, University of Notre Dame, Notre Dame, Indiana 46556 (USA), Fax (574) 631-6652
| | - Qian Peng
- Department of Chemistry and Biochemistry, University of Notre Dame, Notre Dame, Indiana 46556 (USA), Fax (574) 631-6652
| | - Alexander Barabanschikov
- Department of Physics and Center for Interdisciplinary Research on Complex Systems, Northeastern University, Boston, Massachusetts 02115 (USA)
| | - Jeffrey W. Pavlik
- Department of Chemistry and Biochemistry, University of Notre Dame, Notre Dame, Indiana 46556 (USA), Fax (574) 631-6652
| | - E. Ercan Alp
- Advanced Photon Source, Argonne National Laboratory, Argonne, Illinois 60439 (USA)
| | - Wolfgang Sturhahn
- Advanced Photon Source, Argonne National Laboratory, Argonne, Illinois 60439 (USA)
| | - Jiyong Zhao
- Advanced Photon Source, Argonne National Laboratory, Argonne, Illinois 60439 (USA)
| | - Charles E. Schulz
- Department of Physics, Knox College, Galesburg, Illinois 61401 (USA)
| | - J. Timothy Sage
- Department of Physics and Center for Interdisciplinary Research on Complex Systems, Northeastern University, Boston, Massachusetts 02115 (USA)
| | - W. Robert Scheidt
- Department of Chemistry and Biochemistry, University of Notre Dame, Notre Dame, Indiana 46556 (USA), Fax (574) 631-6652
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21
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Barabanschikov A, Demidov A, Kubo M, Champion PM, Sage JT, Zhao J, Sturhahn W, Alp EE. Spectroscopic identification of reactive porphyrin motions. J Chem Phys 2011; 135:015101. [PMID: 21744919 PMCID: PMC3144962 DOI: 10.1063/1.3598473] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/06/2011] [Accepted: 05/18/2011] [Indexed: 11/14/2022] Open
Abstract
Nuclear resonance vibrational spectroscopy (NRVS) reveals the vibrational dynamics of a Mössbauer probe nucleus. Here, (57)Fe NRVS measurements yield the complete spectrum of Fe vibrations in halide complexes of iron porphyrins. Iron porphine serves as a useful symmetric model for the more complex spectrum of asymmetric heme molecules that contribute to numerous essential biological processes. Quantitative comparison with the vibrational density of states (VDOS) predicted for the Fe atom by density functional theory calculations unambiguously identifies the correct sextet ground state in each case. These experimentally authenticated calculations then provide detailed normal mode descriptions for each observed vibration. All Fe-ligand vibrations are clearly identified despite the high symmetry of the Fe environment. Low frequency molecular distortions and acoustic lattice modes also contribute to the experimental signal. Correlation matrices compare vibrations between different molecules and yield a detailed picture of how heme vibrations evolve in response to (a) halide binding and (b) asymmetric placement of porphyrin side chains. The side chains strongly influence the energetics of heme doming motions that control Fe reactivity, which are easily observed in the experimental signal.
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Affiliation(s)
- Alexander Barabanschikov
- Department of Physics and Center for Interdisciplinary Research on Complex Systems, Northeastern University, Boston, Massachusetts 02115, USA
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22
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Seufert K, Bocquet ML, Auwärter W, Weber-Bargioni A, Reichert J, Lorente N, Barth JV. Cis-dicarbonyl binding at cobalt and iron porphyrins with saddle-shape conformation. Nat Chem 2011; 3:114-9. [PMID: 21258383 DOI: 10.1038/nchem.956] [Citation(s) in RCA: 85] [Impact Index Per Article: 6.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/19/2010] [Accepted: 11/25/2010] [Indexed: 11/09/2022]
Abstract
Diatomic molecules attached to complexed iron or cobalt centres are important in many biological processes. In natural systems, metallotetrapyrrole units carry respiratory gases or provide sensing and catalytic functions. Conceiving synthetic model systems strongly helps to determine the pertinent chemical foundations for such processes, with recent work highlighting the importance of the prosthetic groups' conformational flexibility as an intricate variable affecting their functional properties. Here, we present simple model systems to investigate, at the single molecule level, the interaction of carbon monoxide with saddle-shaped iron- and cobalt-porphyrin conformers, which have been stabilized as two-dimensional arrays on well-defined surfaces. Using scanning tunnelling microscopy we identified a novel bonding scheme expressed in tilted monocarbonyl and cis-dicarbonyl configurations at the functional metal-macrocycle unit. Modelling with density functional theory revealed that the weakly bonded diatomic carbonyl adduct can effectively bridge specific pyrrole groups with the metal atom as a result of the pronounced saddle-shape conformation of the porphyrin cage.
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Affiliation(s)
- Knud Seufert
- Physik Department E20, TU München, James-Franck Strasse, D-85748 Garching, Germany
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23
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Pavlik JW, Barabanschikov A, Oliver AG, Alp EE, Sturhahn W, Zhao J, Sage JT, Scheidt WR. Probing vibrational anisotropy with nuclear resonance vibrational spectroscopy. Angew Chem Int Ed Engl 2010; 49:4400-4. [PMID: 20422668 DOI: 10.1002/anie.201000928] [Citation(s) in RCA: 29] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Affiliation(s)
- Jeffrey W Pavlik
- Department of Chemistry and Biochemistry, University of Notre Dame, Notre Dame, IN 46556, USA
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24
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Lehnert N, Sage JT, Silvernail N, Scheidt WR, Alp EE, Sturhahn W, Zhao J. Oriented single-crystal nuclear resonance vibrational spectroscopy of [Fe(TPP)(MI)(NO)]: quantitative assessment of the trans effect of NO. Inorg Chem 2010; 49:7197-215. [PMID: 20586416 PMCID: PMC2917100 DOI: 10.1021/ic1010677] [Citation(s) in RCA: 63] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
This paper presents oriented single-crystal Nuclear Resonance Vibrational Spectroscopy (NRVS) data for the six-coordinate (6C) ferrous heme-nitrosyl model complex [(57)Fe(TPP)(MI)(NO)] (1; TPP(2-) = tetraphenylporphyrin dianion; MI = 1-methylimidazole). The availability of these data enables for the first time the detailed simulation of the complete NRVS data, including the porphyrin-based vibrations, of a 6C ferrous heme-nitrosyl, using our quantum chemistry centered normal coordinate analysis (QCC-NCA). Importantly, the Fe-NO stretch is split by interaction with a porphyrin-based vibration into two features, observed at 437 and 472 cm(-1). The 437 cm(-1) feature is strongly out-of-plane (oop) polarized and shows a (15)N(18)O isotope shift of 8 cm(-1) and is therefore assigned to nu(Fe-NO). The admixture of Fe-N-O bending character is small. Main contributions to the Fe-N-O bend are observed in the 520-580 cm(-1) region, distributed over a number of in-plane (ip) polarized porphyrin-based vibrations. The main component, assigned to delta(ip)(Fe-N-O), is identified with the feature at 563 cm(-1). The Fe-N-O bend also shows strong mixing with the Fe-NO stretching internal coordinate, as evidenced by the oop NRVS intensity in the 520-580 cm(-1) region. Very accurate normal mode descriptions of nu(Fe-NO) and delta(ip)(Fe-N-O) have been obtained in this study. These results contradict previous interpretations of the vibrational spectra of 6C ferrous heme-nitrosyls where the higher energy feature at approximately 550 cm(-1) had usually been associated with nu(Fe-NO). Furthermore, these results provide key insight into NO binding to ferrous heme active sites in globins and other heme proteins, in particular with respect to (a) the effect of hydrogen bonding to the coordinated NO and (b) changes in heme dynamics upon NO coordination. [Fe(TPP)(MI)(NO)] constitutes an excellent model system for ferrous NO adducts of myoglobin (Mb) mutants where the distal histidine (His64) has been removed. Comparison to the reported vibrational data for wild-type (wt) Mb-NO then shows that the effect of H bonding to the coordinated NO is weak and mostly leads to a polarization of the pi/pi* orbitals of bound NO. In addition, the observation that delta(ip)(Fe-N-O) does not correlate well with nu(N-O) can be traced back to the very mixed nature of this mode. The Fe-N(imidazole) stretching frequency is observed at 149 cm(-1) in [Fe(TPP)(MI)(NO)], and spectral changes upon NO binding to five-coordinate ferrous heme active sites are discussed. The obtained high-quality force constants for the Fe-NO and N-O bonds of 2.57 and 11.55 mdyn/A can further be compared to those of corresponding 5C species, which allows for a quantitative analysis of the sigma trans interaction between the proximal imidazole (His) ligand and NO. This is key for the activation of the NO sensor soluble guanylate cyclase. Finally, DFT methods are calibrated against the experimentally determined vibrational properties of the Fe-N-O subunit in 1. DFT is in fact incapable of reproducing the vibrational energies and normal mode descriptions of the Fe-N-O unit well, and thus, DFT-based predictions of changes in vibrational properties upon heme modification or other perturbations of these 6C complexes have to be treated with caution.
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Affiliation(s)
- Nicolai Lehnert
- Department of Chemistry, University of Michigan, Ann Arbor, MI 48109, USA
| | - J. Timothy Sage
- Department of Physics and Center for Interdisciplinary Research on Complex Systems, Northeastern University, Boston, MA 02115, USA
| | - Nathan Silvernail
- Department of Chemistry and Biochemistry, 251 Nieuwland Science Hall, University of Notre Dame, Notre Dame, IN 46556, USA
| | - W. Robert Scheidt
- Department of Chemistry and Biochemistry, 251 Nieuwland Science Hall, University of Notre Dame, Notre Dame, IN 46556, USA
| | - E. Ercan Alp
- Argonne National Laboratory, APS/XFD, 431/D003, Argonne, IL 60439, USA
| | - Wolfgang Sturhahn
- Argonne National Laboratory, APS/XFD, 431/D003, Argonne, IL 60439, USA
| | - Jiyong Zhao
- Argonne National Laboratory, APS/XFD, 431/D003, Argonne, IL 60439, USA
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25
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Scheidt WR, Barabanschikov A, Pavlik JW, Silvernail NJ, Sage JT. Electronic structure and dynamics of nitrosyl porphyrins. Inorg Chem 2010; 49:6240-52. [PMID: 20666384 PMCID: PMC2919577 DOI: 10.1021/ic100261b] [Citation(s) in RCA: 37] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
Nitric oxide (NO) is a signaling molecule employed to regulate essential physiological processes. Thus, there is great interest in understanding the interaction of NO with heme, which is found at the active site of many proteins that recognize NO, as well as those involved in its creation and elimination. We summarize what we have learned from investigations of the structure, vibrational properties, and conformational dynamics of NO complexes with ferrous porphyrins, as well as computational investigations in support of these experimental studies. Multitemperature crystallographic data reveal variations in the orientational disorder of the nitrosyl ligand. In some cases, equilibria among NO orientations can be analyzed using the van't Hoff relationship and the free energy and enthalpy of the solid-state transitions evaluated experimentally. Density functional theory (DFT) calculations predict that intrinsic barriers to torsional rotation are smaller than thermal energies at physiological temperatures, and the coincidence of observed NO orientations with minima in molecular mechanics potentials indicates that nonbonded interactions with other chemical groups control the conformational freedom of the bound NO. In favorable cases, reduced disorder at low temperatures exposes subtle structural features including off-axis tilting of the Fe-NO bond and anisotropy of the equatorial Fe-N bonds. We also present the results of nuclear resonance vibrational spectroscopy measurements on oriented single crystals of [Fe(TPP)(NO)] and [Fe(TPP)(1-MeIm)(NO)]. These describe the anisotropic vibrational motion of iron in five- and six-coordinate heme-NO complexes and reveal vibrations of all Fe-ligand bonds as well as low-frequency molecular distortions associated with the doming of the heme upon ligand binding. A quantitative comparison with predicted frequencies, amplitudes, and directions facilitates identification of the vibrational modes but also suggests that commonly used DFT functionals are not fully successful at capturing the trans interaction between the axial NO and imidazole ligands. This supports previous conclusions that heme-NO complexes exhibit an unusual degree of variability with respect to the computational method, and we speculate that this variability hints at a genuine electronic instability that a protein can exploit to tune its reactivity. We anticipate that ongoing characterization of heme-NO complexes will deepen our understanding of their structure, dynamics, and reactivity.
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Affiliation(s)
- W. Robert Scheidt
- To whom correspondence should be addressed: WRS: , Fax (574) 631-6652; JTS , FAX (617)-373-2943
| | | | | | | | - J. Timothy Sage
- To whom correspondence should be addressed: WRS: , Fax (574) 631-6652; JTS , FAX (617)-373-2943
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26
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Lehnert N, Galinato MGI, Paulat F, Richter-Addo GB, Sturhahn W, Xu N, Zhao J. Nuclear resonance vibrational spectroscopy applied to [Fe(OEP)(NO)]: the vibrational assignments of five-coordinate ferrous heme-nitrosyls and implications for electronic structure. Inorg Chem 2010; 49:4133-48. [PMID: 20345089 DOI: 10.1021/ic902181e] [Citation(s) in RCA: 41] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/05/2023]
Abstract
This study presents Nuclear Resonance Vibrational Spectroscopy (NRVS) data on the five-coordinate (5C) ferrous heme-nitrosyl complex [Fe(OEP)(NO)] (1, OEP(2-) = octaethylporphyrinato dianion) and the corresponding (15)N(18)O labeled complex. The obtained spectra identify two isotope sensitive features at 522 and 388 cm(-1), which shift to 508 and 381 cm(-1), respectively, upon isotope labeling. These features are assigned to the Fe-NO stretch nu(Fe-NO) and the in-plane Fe-N-O bending mode delta(ip)(Fe-N-O), the latter has been unambiguously assigned for the first time for 1. The obtained NRVS data were simulated using our quantum chemistry centered normal coordinate analysis (QCC-NCA). Since complex 1 can potentially exist in 12 different conformations involving the FeNO and peripheral ethyl orientations, extended density functional theory (DFT) calculations and QCC-NCA simulations were performed to determine how these conformations affect the NRVS properties of [Fe(OEP)NO]. These results show that the properties and force constants of the FeNO unit are hardly affected by the conformational changes involving the ethyl substituents. On the other hand, the NRVS-active porphyrin-based vibrations around 340-360, 300-320, and 250-270 cm(-1) are sensitive to the conformational changes. The spectroscopic changes observed in these regions are due to selective mechanical couplings of one component of E(u)-type (in ideal D(4h) symmetry) porphyrin-based vibrations with the in-plane Fe-N-O bending mode. This leads to the observed variations in Fe(OEP) core mode energies and NRVS intensities without affecting the properties of the FeNO unit. The QCC-NCA simulated NRVS spectra of 1 show excellent agreement with experiment, and indicate that conformer F is likely present in the samples of this complex investigated here. The observed porphyrin-based vibrations in the NRVS spectra of 1 are also assigned based on the QCC-NCA results. The obtained force constants of the Fe-NO and N-O bonds are 2.83-2.94 (based on the DFT functional applied) and about 12.15 mdyn/A, respectively. The electronic structures of 5C ferrous heme-nitrosyls in different model complexes are then analyzed, and variations in their properties based on different porphyrin substituents are explained. Finally, the shortcomings of different DFT functionals in describing the axial FeNO subunit in heme-nitrosyls are elucidated.
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Affiliation(s)
- Nicolai Lehnert
- Department of Chemistry, University of Michigan, Ann Arbor, Michigan 48109, USA.
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27
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Pavlik J, Barabanschikov A, Oliver A, Alp E, Sturhahn W, Zhao J, Sage J, Scheidt W. Probing Vibrational Anisotropy with Nuclear Resonance Vibrational Spectroscopy. Angew Chem Int Ed Engl 2010. [DOI: 10.1002/ange.201000928] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022]
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28
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Devereux M, Meuwly M. Force Field Optimization using Dynamics and Ensemble Averaged Data: Vibrational Spectra and Relaxation in Bound MbCO. J Chem Inf Model 2010; 50:349-57. [DOI: 10.1021/ci9004404] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022]
Affiliation(s)
- Michael Devereux
- Department of Chemistry, University of Basel, Klingelbergstrasse 80, 4056 Basel, Switzerland
| | - Markus Meuwly
- Department of Chemistry, University of Basel, Klingelbergstrasse 80, 4056 Basel, Switzerland
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Devereux M, Meuwly M. Anharmonic Coupling in Molecular Dynamics Simulations of Ligand Vibrational Relaxation in Bound Carbonmonoxy Myoglobin. J Phys Chem B 2009; 113:13061-70. [DOI: 10.1021/jp903741v] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/23/2023]
Affiliation(s)
- Michael Devereux
- Department of Chemistry, University of Basel, Klingelbergstrasse 80, 4056 Basel, Switzerland
| | - Markus Meuwly
- Department of Chemistry, University of Basel, Klingelbergstrasse 80, 4056 Basel, Switzerland
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30
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Leu BM, Ching TH, Zhao J, Sturhahn W, Alp EE, Sage JT. Vibrational dynamics of iron in cytochrome C. J Phys Chem B 2009; 113:2193-200. [PMID: 19173569 DOI: 10.1021/jp806574t] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
Nuclear resonance vibrational spectroscopy (NRVS) and Raman spectroscopy on (54)Fe- and (57)Fe-enriched cytochrome c (cyt c) identify multiple bands involving vibrations of the heme Fe. Comparison with predictions from Fe isotope shifts reveals that 70% of the NRVS signal in the 300-450 cm(-1) frequency range corresponds to vibrations resolved in Soret-enhanced Raman spectra. This frequency range dominates the "stiffness", an effective force constant determined by the Fe vibrational density of states (VDOS), which measures the strength of nearest-neighbor interactions with Fe. The stiffness of the low-spin Fe environment in both oxidation states of cyt c significantly exceeds that for the high-spin Fe in deoxymyoglobin, where the 200-300 cm(-1) frequency range dominates the VDOS. This situation is reflected in the shorter Fe-ligand bond lengths in the former with respect to the latter. The longer Fe-S(Met80) in oxidized cyt c with respect to reduced cyt c leads to a decrease in the stiffness of the iron environment upon oxidation. Comparison with NRVS measurements allows us to assess assignments for vibrational modes resolved in this region of the heme Raman spectrum. We consider the possibility that the 372 cm(-1) band in reduced cyt c involves the Fe-S(Met80) bond.
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Affiliation(s)
- Bogdan M Leu
- Department of Physics and Center for Interdisciplinary Research on Complex Systems, Northeastern University, Boston, Massachusetts 02115, USA
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31
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Salazar-Salinas K, Jauregui LA, Kubli-Garfias C, Seminario JM. Molecular biosensor based on a coordinated iron complex. J Chem Phys 2009; 130:105101. [DOI: 10.1063/1.3070235] [Citation(s) in RCA: 27] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
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32
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Mitin AV, Kubicki JD. Quantum mechanical investigations of heme structure and vibrational spectra: effects of conformation, oxidation state, and electric field. LANGMUIR : THE ACS JOURNAL OF SURFACES AND COLLOIDS 2009; 25:548-554. [PMID: 19063621 DOI: 10.1021/la802647c] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/27/2023]
Abstract
Three conformers of a complex consisting of a Fe-porphyrin ring with axial imidazole groups FeP(Im)(2) that differed by orientation of axial imidazole groups were studied with quantum mechanical calculations in both reduced (neutral) and oxidized (cationic) states. In the reduced state, all three conformers correspond to local minima. On the other hand, in the oxidized state the conformer with the imidazole groups perpendicular to one another does not have a local minimum, which suggests that there could be changes in the structure of heme groups depending on oxidation state. The relative energy differences between conformers are small as well the differences of orbital energies. However, the populations of Fe 3d orbitals, and hence charge distributions, are predicted to change significantly between conformations. The orientation of heme groups can affect the kinetics of interheme electron transfer, so this electronic population redistribution will affect electron transfer kinetics. A comparison of calculated Raman spectra with measured surface-enhanced Raman spectra (Biju et al. Langmuir 2007, 23, 1333) shows excellent agreement for frequencies, but correlations of Raman intensities are less satisfactory. Possible explanations of the observed discrepancies could arise due to a problem in assignments of vibration bands in the experiment, a dependence of Raman spectra on heme complex on oxidation state, long-range protein structure, or membrane electric field are discussed. In particular, it was shown that the oxidation state does not dramatically alter the calculated Raman spectrum. However, the cell membrane electric field can significantly modify Raman spectra. An interpretation of the experimental oxidized cytochrome surface-enhanced Raman spectra is discussed.
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Affiliation(s)
- Alexander V Mitin
- The Center for Environmental Kinetics Analysis, The Pennsylvania State University, University Park, Pennsylvania 16802, USA
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33
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Praneeth VKK, Paulat F, Berto TC, George SD, Näther C, Sulok CD, Lehnert N. Electronic Structure of Six-Coordinate Iron(III)−Porphyrin NO Adducts: The Elusive Iron(III)−NO(radical) State and Its Influence on the Properties of These Complexes. J Am Chem Soc 2008; 130:15288-303. [PMID: 18942830 DOI: 10.1021/ja801860u] [Citation(s) in RCA: 128] [Impact Index Per Article: 8.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Affiliation(s)
- V. K. K. Praneeth
- Department of Chemistry, University of Michigan, Ann Arbor, Michigan 48109, Stanford Synchrotron Radiation Laboratory, SLAC, Stanford University, Stanford, California 94309, and Institut für Anorganische Chemie, Christian-Albrechts-Universität Kiel, Olshausenstrasse 40, D-24098 Kiel, Germany
| | - Florian Paulat
- Department of Chemistry, University of Michigan, Ann Arbor, Michigan 48109, Stanford Synchrotron Radiation Laboratory, SLAC, Stanford University, Stanford, California 94309, and Institut für Anorganische Chemie, Christian-Albrechts-Universität Kiel, Olshausenstrasse 40, D-24098 Kiel, Germany
| | - Timothy C. Berto
- Department of Chemistry, University of Michigan, Ann Arbor, Michigan 48109, Stanford Synchrotron Radiation Laboratory, SLAC, Stanford University, Stanford, California 94309, and Institut für Anorganische Chemie, Christian-Albrechts-Universität Kiel, Olshausenstrasse 40, D-24098 Kiel, Germany
| | - Serena DeBeer George
- Department of Chemistry, University of Michigan, Ann Arbor, Michigan 48109, Stanford Synchrotron Radiation Laboratory, SLAC, Stanford University, Stanford, California 94309, and Institut für Anorganische Chemie, Christian-Albrechts-Universität Kiel, Olshausenstrasse 40, D-24098 Kiel, Germany
| | - Christian Näther
- Department of Chemistry, University of Michigan, Ann Arbor, Michigan 48109, Stanford Synchrotron Radiation Laboratory, SLAC, Stanford University, Stanford, California 94309, and Institut für Anorganische Chemie, Christian-Albrechts-Universität Kiel, Olshausenstrasse 40, D-24098 Kiel, Germany
| | - Corinne D. Sulok
- Department of Chemistry, University of Michigan, Ann Arbor, Michigan 48109, Stanford Synchrotron Radiation Laboratory, SLAC, Stanford University, Stanford, California 94309, and Institut für Anorganische Chemie, Christian-Albrechts-Universität Kiel, Olshausenstrasse 40, D-24098 Kiel, Germany
| | - Nicolai Lehnert
- Department of Chemistry, University of Michigan, Ann Arbor, Michigan 48109, Stanford Synchrotron Radiation Laboratory, SLAC, Stanford University, Stanford, California 94309, and Institut für Anorganische Chemie, Christian-Albrechts-Universität Kiel, Olshausenstrasse 40, D-24098 Kiel, Germany
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34
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Starovoitova V, Wyllie GRA, Scheidt WR, Sturhahn W, Alp EE, Durbin SM. Intermolecular dynamics in crystalline iron octaethylporphyrin (FeOEP). J Phys Chem B 2008; 112:12656-61. [PMID: 18793016 DOI: 10.1021/jp806215r] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
The new technique of nuclear resonance vibrational spectroscopy (NRVS) has increased the range and quality of dynamical data from Fe-containing molecules that when combined with Raman and infrared spectroscopies impose stricter constraints on normal mode simulations, especially at lower frequencies. Going beyond the usual single molecule approximation, a classical normal-mode analysis that includes intermolecular coupling and the full crystalline symmetry is found to produce a better fit with fewer free parameters for the heme compound iron octaethylporphyrin (FeOEP), using NRVS data from polycrystalline material. Off-diagonal force constants were completely unnecessary, indicating that their role in previous single molecule fits was just to emulate intermolecular coupling. Sound velocities deduced from the calculated phonon dispersion curves are compared to NRVS measurements to further constrain the intermolecular force constants. The NRVS data by themselves are insufficient to rigorously determine all unknown force constants for molecules of this size, but the improved crystal model fit indicates the necessity of including intermolecular interactions for normal-mode analyses.
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36
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Silvernail NJ, Pavlik JW, Noll BC, Schulz CE, Scheidt WR. Reversible NO motion in crystalline [Fe(Porph)(1-MeIm)(NO)] derivatives. Inorg Chem 2008; 47:912-20. [PMID: 18173262 DOI: 10.1021/ic701700p] [Citation(s) in RCA: 29] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
The synthesis, characterization, and X-ray structures of three low-spin (nitrosyl)iron(II) tetraarylporphyrinates, [Fe(TpXPP)(NO)(1-MeIm)], where X = F (in a triclinic and a monoclinic form) and OCH(3) are reported. All three molecules, at 100 K, have a single orientation of NO. These structures are the first examples of ordered NO's in [Fe(Porph)(NO)(1-MeIm)] complexes. The three new derivatives have similar structural features including a previously unnoted "bowing" of the N(NO)-Fe-N(Im) angle caused by a concerted tilting of the axial Fe-N(NO) and Fe-N(Im) bonds. Structural features such as the displacement of Fe out of the mean porphyrin plane toward NO, tilting of the Fe-N(NO) bond off the heme normal, and the asymmetry of the Fe-N(por) bonds further strengthen and confirm observations from earlier studies. The [Fe(TpXPP)(NO)(1-MeIm)] complexes were also studied at temperatures between 125 and 350 K to investigate temperature-dependent variations and trends in the coordination group geometry. At varying temperatures (above 150 K), all three derivatives display a second orientation of the NO ligand. The population and depopulation of this second orientation are thermally driven, with no apparent hysteresis. Crystal packing appears to be the significant feature in defining the order/disorder of the NO ligand. The length of the bond trans to NO, Fe-N(Im), was also found to be sensitive to temperature variation. The Fe-N(Im) bond length increases with increased temperature, whereas no other bonds change appreciably. The temperature-dependent Fe-N(Im) bond length change and cell volume changes are consistent with a "soft" Fe-N(Im) bond. Variable-temperature measurements show that the N-O stretching frequency changes with the Fe-N(Im) bond length. Temperature-dependent changes in the Fe-NIm bond length and N-O stretching frequency were also found to be completely reversible with no apparent hysteresis.
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Affiliation(s)
- Nathan J Silvernail
- Contribution from the Department of Chemistry and Biochemistry, University of Notre Dame, Notre Dame, Indiana 46556, USA
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Scheidt WR. Explorations in metalloporphyrin stereochemistry, physical properties and beyond. J PORPHYR PHTHALOCYA 2008; 12:979-992. [PMID: 20198111 PMCID: PMC2829777 DOI: 10.1142/s1088424608000364] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022]
Abstract
A review of selected portions of our work in the area of porphyrin structure and physical characterization is presented. Topics covered include early work on periodic trends in first row transtion metalloporphyrins, a survey of electronic structure of iron derivatives including spin-state trends, ligand orientation effects and the elucidtion of unusual low-spin states for iron(II). A discussion of the different tlypes of high-spin iron(II) complexes and the effects of hydrogen bonding is given. A survey of nitric oxide (NO) derivatives is presented as well as a brief introduction into the use of nuclear resonance vibrational spectroscopy for the study of iron porphyrins and heme proteins.
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Affiliation(s)
- W Robert Scheidt
- Department of Chemistry and Biochemistry, 251 Nieuwland Science Hall, University of Notre Dame, Notre Dame, Indiana 46556, USA
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