Electronic states of the O
            <sub>2</sub>
            -tolerant [NiFe] hydrogenase proximal cluster

Mouesca, Jean‐Marie; Amara, Patricia; Fontecilla‐Camps, J.C.

doi:10.1073/pnas.1302304110

Cited by 7 publications

(10 citation statements)

References 4 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…Mouesca et al (1) argue that OX2_24 emerges from unrecognized, unwanted charge migration, which leads to "local spin state 3/2, instead of 5/2, for Fe2," and therefore is an "artificially trapped electronic state." We note that: (i) the magnetic properties are well explained by OX2_24; (ii) the reactivity argument is invalid; and (iii) the local spin is not an observable and BS-DFT does not conserve the total spin but only its projection onto the z axis.…”

Section: Mouesca Et Al (1) Criticize Our Analysis (2) Of the Superoxmentioning

confidence: 99%

“…3. Because our quantum mechanical model was not inferior to that of Volbeda et al (3), we have no reason to revoke deprotonation of GLU82. Our choice was derived from a comprehensive comparison of a wide range of spectroscopic parameters, and no conclusive evidence against it was presented in Mouesca et al (1).…”

Section: Mouesca Et Al (1) Criticize Our Analysis (2) Of the Superoxmentioning

confidence: 99%

See 1 more Smart Citation

Reply to Mouesca et al.: Electronic structure of the proximal [4Fe-3S] cluster of O ₂ -tolerant [NiFe] hydrogenases

Pandelia

Bykov

Infossi

et al. 2013

Proc. Natl. Acad. Sci. U.S.A.

View full text Add to dashboard Cite

Mouesca et al.(1) criticize our analysis (2) of the superoxidized proximal 5+ cluster in O 2 -tolerant hydrogenases (A) that was also studied in Volbeda et al. (3), albeit from a different organism. Both analyses were based on broken-symmetry (BS) density functional theory (DFT) calculations (2, 3), which presently is the only feasible alternative for the treatment of complex systems like A. However, BS-DFT is a crude approach and we regard the differences in refs. 2 and 3 as subtle rather than major.The critique raised in Mouesca et al.(1) that our cluster model was too small and incorporated spurious constraints is unfounded. In Volbeda et al. (3), only three additional amino acid residues in the third coordination sphere were included, but their importance was not demonstrated. Furthermore, our constraints allowed for sufficient structural relaxation and the link atoms used in the quantum mechanical/molecular mechanical investigation (3) imposed almost identical constraints.The allegation that our selection of BS solution Ox2_24 over OX2_14 (favored in ref.3) on the basis of "chemical intuition" and "weak isomer shift considerations" is factually wrong. Instead, we analyzed relative energies and four Mössbauer parameters (δ, ΔE Q , η, A) for each iron site, whereas in Volbeda et al. (3) only energetics and unsigned ΔE Q values were used. The energy difference in favor of OX2_14 (3) is below 2 kcal/mol, which is well within the uncertainty of BS-DFT. Thus, we have presented more solid evidence for our choice than the authors of ref. 3.Because our quantum mechanical model was not inferior to that of Volbeda et al. (3), we have no reason to revoke deprotonation of GLU82. Our choice was derived from a comprehensive comparison of a wide range of spectroscopic parameters, and no conclusive evidence against it was presented in Mouesca et al. (1).The authors of refs. 1 and 3 argue in favor of OX2_14 as leading to an explanation of the cluster's reactivity. However, no sound conclusions on transition states or mechanisms can be drawn from the analysis of the magnetic properties of one reactant only. Thus, the argument is invalid.Mouesca et al. (1) argue that OX2_24 emerges from unrecognized, unwanted charge migration, which leads to "local spin state 3/2, instead of 5/2, for Fe2," and therefore is an "artificially trapped electronic state." We note that: (i) the magnetic properties are well explained by OX2_24; (ii) the reactivity argument is invalid; and (iii) the local spin is not an observable and BS-DFT does not conserve the total spin but only its projection onto the z axis. The assignment of oxidation states and local spins in refs. 1 and 3 relies on differences as small as 0.1 electrons in Mulliken spin populations. In our experience, differences of this order are not conclusive. Importantly, the lower spin population on Fe2 in OX2_24 is simply a result of spin-canting, as well as (partial) formation of covalent chemical bonds between spin-carrying fragments. Related effects are predominant in BS-DFT calculati...

show abstract

Section: Mouesca Et Al (1) Criticize Our Analysis (2) Of the Superoxmentioning

confidence: 99%

Section: Mouesca Et Al (1) Criticize Our Analysis (2) Of the Superoxmentioning

confidence: 99%

Reply to Mouesca et al.: Electronic structure of the proximal [4Fe-3S] cluster of O ₂ -tolerant [NiFe] hydrogenases

Pandelia

Bykov

Infossi

et al. 2013

Proc. Natl. Acad. Sci. U.S.A.

View full text Add to dashboard Cite

show abstract

“… 5 , 7 Interpreting spin populations in BS24 in terms of a ferrous Fe4 contradicts this expectation: all three BS24 S-OX candidates are (at PBE/lacv3p** level) at most 3.1 kcal/mol (for S-OX P 5+ ) above the lowest BS12 state with an undisputedly ferric Fe4. Mouesca et al have claimed 21 that the Ox2_24 state (spin-alignment corresponding to our BS34, i.e., Fe1 and Fe2 are ‘↑’ and Fe3 and Fe4 are ‘↓’ in the present numbering of Fe sites) favored by Pandelia et al for S-OX has a ferrous Fe1 and a ferric Fe4, the latter with a local spin quantum number of S 4 = 3/2. Indeed, a diverse set of computational data supports this notion.…”

Section: Results and Discussionmentioning

confidence: 54%

“…The local spin state of ferric Fe4 in model Ox2_24 (spin coupling corresponding to our BS34, see section 3.2 ) favored by Pandelia et al was controversial, and a discussion on the best-suited broken-symmetry state for S-OX and the probable protonation state and conformation of the glutamate residue binding to (proximal) or in the vicinity of (distal) Fe4 ensued. 21 , 22 …”

Section: Brief Summary Of Previous Experimental/computational Studiesmentioning

confidence: 99%

“…Two previous combined experimental/DFT studies by Volbeda et al and Pandelia et al have tackled the problem of establishing a correlation between Fe sites from Mössbauer spectroscopy , and the S-OX proximal cluster molecular structure. The cited works disagree on the electronic structure of S-OX, and consequently, there is no consensus on the identity of 57 Fe Mössbauer centers with respect to Fe centers in the molecular structure. , The identity of Fe sites and spin coupling has also been addressed for the reduced-state [4Fe-3S] 3+ cluster . However, severe doubts are in order regarding the DFT-optimized reduced-state structure proposed in ref on account of calculated Mössbauer parameters: the computational model differs fundamentally from available X-ray crystal structures as the bond between Fe3 (in the present Re - and Ec -MBH numbering), one of the supernumerary cysteinates, Cys120, is ruptured, and the Fe3–Fe4 distance is contracted from 3.98 to 2.81 Å.…”

Section: Introductionmentioning

confidence: 99%

See 1 more Smart Citation

The Mössbauer Parameters of the Proximal Cluster of Membrane-Bound Hydrogenase Revisited: A Density Functional Theory Study

Tabrizi

Pelmenschikov

Noodleman

et al. 2015

J. Chem. Theory Comput.

View full text Add to dashboard Cite

An unprecedented [4Fe-3S] cluster proximal to the regular [NiFe] active site has recently been found to be responsible for the ability of membrane-bound hydrogenases (MBHs) to oxidize dihydrogen in the presence of ambient levels of oxygen. Starting from proximal cluster models of a recent DFT study on the redox-dependent structural transformation of the [4Fe-3S] cluster, 57Fe Mössbauer parameters (electric field gradients, isomer shifts, and nuclear hyperfine couplings) were calculated using DFT. Our results revise the previously reported correspondence of Mössbauer signals and iron centers in the [4Fe-3S]3+ reduced-state proximal cluster. Similar conflicting assignments are also resolved for the [4Fe-3S]5+ superoxidized state with particular regard to spin-coupling in the broken-symmetry DFT calculations. Calculated 57Fe hyperfine coupling (HFC) tensors expose discrepancies in the experimental set of HFC tensors and substantiate the need for additional experimental work on the magnetic properties of the MBH proximal cluster in its reduced and superoxidized redox states.

show abstract

Electronic Structure, Bonding, Spin Coupling, and Energetics of Polynuclear Iron–Sulfur Clusters – A Broken Symmetry Density Functional Theory Perspective

Hopmann

Pelmenschikov

et al. 2015

Spin States in Biochemistry and Inorganic Chemistry

View full text Add to dashboard Cite

Electronic states of the O ₂ -tolerant [NiFe] hydrogenase proximal cluster

Cited by 7 publications

References 4 publications

Reply to Mouesca et al.: Electronic structure of the proximal [4Fe-3S] cluster of O ₂ -tolerant [NiFe] hydrogenases

Reply to Mouesca et al.: Electronic structure of the proximal [4Fe-3S] cluster of O ₂ -tolerant [NiFe] hydrogenases

The Mössbauer Parameters of the Proximal Cluster of Membrane-Bound Hydrogenase Revisited: A Density Functional Theory Study

Electronic Structure, Bonding, Spin Coupling, and Energetics of Polynuclear Iron–Sulfur Clusters – A Broken Symmetry Density Functional Theory Perspective

Contact Info

Product

Resources

About

Electronic states of the O 2 -tolerant [NiFe] hydrogenase proximal cluster

Cited by 7 publications

References 4 publications

Reply to Mouesca et al.: Electronic structure of the proximal [4Fe-3S] cluster of O 2 -tolerant [NiFe] hydrogenases

Reply to Mouesca et al.: Electronic structure of the proximal [4Fe-3S] cluster of O 2 -tolerant [NiFe] hydrogenases

The Mössbauer Parameters of the Proximal Cluster of Membrane-Bound Hydrogenase Revisited: A Density Functional Theory Study

Electronic Structure, Bonding, Spin Coupling, and Energetics of Polynuclear Iron–Sulfur Clusters – A Broken Symmetry Density Functional Theory Perspective

Contact Info

Product

Resources

About

Electronic states of the O ₂ -tolerant [NiFe] hydrogenase proximal cluster

Reply to Mouesca et al.: Electronic structure of the proximal [4Fe-3S] cluster of O ₂ -tolerant [NiFe] hydrogenases

Reply to Mouesca et al.: Electronic structure of the proximal [4Fe-3S] cluster of O ₂ -tolerant [NiFe] hydrogenases