Nitric oxide myoglobin: Crystal structure and analysis of ligand geometry

Brucker, E.A.; Olson, John S.; Ikeda‐Saito, Masao; Phillips, George N.

doi:10.1002/(sici)1097-0134(19980301)30:4<352::aid-prot2>3.3.co;2-g

Cited by 57 publications

(113 citation statements)

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“…Crystallographic investigations on ferrous Mb-NO57 in fact implicate the presence of a hydrogen bond between the distal His and NO, but the strength of this interaction, and correspondingly, its effect on the properties of the bound NO are not clear. Vibrational spectroscopy is a great method to gain further insight into this issue, since metal-NO stretching frequencies are very sensitive reporters of changes in the metal-NO bond as described above.…”

Section: Discussionmentioning

confidence: 99%

Oriented Single-Crystal Nuclear Resonance Vibrational Spectroscopy of [Fe(TPP)(MI)(NO)]: Quantitative Assessment of the trans Effect of NO

et al. 2010

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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 an 15 N 18 O isotope shift of 8 cm −1 , and is therefore assigned to ν(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 δ 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 ν(Fe-NO) and δ 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 ~550 cm −1 had usually been associated with ν(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 coordinated NO is weak, and mostly leads to a polarization of the π/π* orbitals of Correspondence to: Nicolai Lehnert, lehnertn@umich.edu; J. Timothy Sage, jtsage@neu.edu; W. Robert Scheidt, Scheidt.1@nd.edu. Supporting Information Complete ref. 39 , DFT-calculated NRVS spectra, complete list of force constants altered in the fit of the NRVS data of 1, vibrational assignments for the adjusted BP86/TZVP result, cartesian coordinates of the DFT-optimized structures, definition of the force field of 1 used in the QCC-NCA simulation, and complete list of force constants from the QCC-NCA fit.

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Section: Discussionmentioning

confidence: 99%

Oriented Single-Crystal Nuclear Resonance Vibrational Spectroscopy of [Fe(TPP)(MI)(NO)]: Quantitative Assessment of the trans Effect of NO

et al. 2010

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“…18). In Mb, unlike NIR, the N δ H of the distal histidine is closer to N NO than to O NO [143-145]. The νFeN/νNO point for wild-type Mb falls far from the backbonding line, but when the distal histidine is replaced by a weaker H-bonding residue, glutamine (H64Q), the point moves toward the line, along the positive correlation, and when it is replaced by hydrophobic residues (H64V,I,A) the point falls close to the backbonding line.…”

Section: Fe(ii)no Adductsmentioning

confidence: 99%

CO, NO and O2 as vibrational probes of heme protein interactions

Spiro

Soldatova

Balakrishnan

2013

Coordination Chemistry Reviews

133

216

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The gaseous XO molecules (X = C, N or O) bind to the heme prosthetic group of heme proteins, and thereby activate or inhibit key biological processes. These events depend on interactions of the surrounding protein with the FeXO adduct, interactions that can be monitored via the frequencies of the Fe-X and X-O bond stretching modes, νFeX and νXO. The frequencies can be determined by vibrational spectroscopy, especially resonance Raman spectroscopy. Backbonding, the donation of Fe dπ electrons to the XO π* orbitals, is a major bonding feature in all the FeXO adducts. Variations in backbonding produce negative νFeX/νXO correlations, which can be used to gauge electrostatic and H-bonding effects in the protein binding pocket. Backbonding correlations have been established for all the FeXO adducts, using porphyrins with electron donating and withdrawing substituents. However the adducts differ in their response to variations in the nature of the axial ligand, and to specific distal interactions. These variations provide differing vantages for evaluating the nature of protein-heme interactions. We review experimental studies that explore these variations, and DFT computational studies that illuminate the underlying physical mechanisms.

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“…[33–35] They all show distinctly shorter distances from the nearest N atom of the distal histidine to N NO than to O NO (Table 1). Interestingly, two of the reported Fe-N-O angles, 121° [35] and 112° [34] are much smaller than the other two, 147° [33] and 144°[35], and they are associated with significantly shorter (His64)N ··· N NO distances. This trend is as expected from the DFT computations.…”

Section: H-bonding Effectsmentioning

confidence: 99%

Ambidentate H-bonding of NO and O2 in heme proteins

Spiro

Soldatova

2012

Journal of Inorganic Biochemistry

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The affinity and reactivity of the gaseous molecules CO, NO and O2 (XO) in heme protein adducts are controlled by secondary interactions, especially by H-bonds donated from distal protein residues. Vibrational spectroscopy, supported by DFT modeling, has revealed that for NO and O2, but not for CO, a critical issue is whether the H-bond is donated to the outer or inner atom of the bound diatomic ligand. DFT modeling shows that bound NO and O2 are ambidentate, both atoms separately acting as H-bond acceptors. This is not the case for CO, whose π* orbital acts as a delocalized H-bond acceptor. Vibrational spectra of heme-XO adducts reveal a general pattern of backbonding variations, marked by families of negative correlations between frequencies associated with Fe-X and X-O bond stretches. For heme-CO adducts, H-bonding increases backbonding, the νFeX/νXO points moving up the backbonding correlation established with model compounds. For NO and O2 adducts, however, increased backbonding is only observed when the outer atom is the H-bond acceptor. H-bonding to the inner (X) atom instead produces a positive νFeX/νXO correlation. This effect can be reproduced by DFT modeling. Its mechanism is polarization of the sp2 orbital on the X atom, on the back side of the bent FeXO unit, drawing electrons from both the Fe-X and X-O bonds and weakening them together. Thus, the positioning of H-bond donors in the protein differentially affects bonding and reactivity in heme adducts of NO and O2.

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Nitric oxide myoglobin: Crystal structure and analysis of ligand geometry

Cited by 57 publications

References 0 publications

Oriented Single-Crystal Nuclear Resonance Vibrational Spectroscopy of [Fe(TPP)(MI)(NO)]: Quantitative Assessment of the trans Effect of NO

Oriented Single-Crystal Nuclear Resonance Vibrational Spectroscopy of [Fe(TPP)(MI)(NO)]: Quantitative Assessment of the trans Effect of NO

CO, NO and O2 as vibrational probes of heme protein interactions

Ambidentate H-bonding of NO and O2 in heme proteins

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