Nuclear Magnetic Resonance Shifts in Paramagnetic Metalloporphyrins and Metalloproteins

Mao, Junhong; Zhang, Yong; Oldfield, Eric

doi:10.1021/ja020297w

Cited by 99 publications

(109 citation statements)

References 57 publications

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“…As shown in Figure 3A, with these geometry-optimized large models of Az, Pc, Pa, St, Am, and Rc, the predictions of all 53 experimental shifts (using only the average shifts for the nonstereospecifically assigned protons) have a very good correlation with experiment, R 2 = 0.94, slope = 1.01 (to be compared with the ideal value of 1.00), and a SD = 40.5 ppm or 4.7% of the whole 862.5 ppm shift range seen experimentally. These results also fit the same correlation line ( Figure S1) seen previously with heme proteins and model systems, 7 indicating the good overall accuracy of the methods employed.…”

Section: Hyperfine Shift Calculationssupporting

confidence: 84%

“…However, the slope is 1.20 (to be compared with an ideal value of 1.00) in both cases, and some δ hf predictions for Cys-C β hydrogen atoms have large errors (e.g., in Pc), as shown in Table 1. Because using eq 4 previously enabled accurate predictions of experimental shifts over a 6000 ppm range 7 with R 2 = 0.99 and slope = 1.05, the errors here may be (at least partly) associated with the uncertainties in the X-ray geometries of these proteins, 46 and indeed, in previous work, we found that ab initio calculations of NMR (and other spectroscopic) properties facilitated protein structure refinement. 22,[47][48][49][50] We thus next began to use geometry optimization to see to what extent the shift predictions might be improved.…”

Section: Hyperfine Shift Calculationsmentioning

confidence: 59%

“…21 This is basically the approach that we used previously to evaluate both solution and solid-state NMR hyperfine shifts, as well as other hyperfine (ESR, ENDOR) properties. 7,16,17,22 Spin densities were converted to hyperfine shifts by using the relation obtained previously: 7…”

Section: Computational Detailsmentioning

confidence: 99%

“…3,4 For example, the iron centers in paramagnetic proteins (and model systems) have a >5000 ppm range of 13 C NMR shifts 5,6 and are well-correlated with electronic structure. 7 While 1 H NMR shifts are typically smaller, recent studies on several blue copper proteins (BCPs), amicyanin (Am), 8 azurin (Az), 9 plastocyanin (Pc), 10 pseudoazurin (Pa), 11 stellacyanin (St), 9 and rusticyanin (Rc), 11 revealed that the Cys-C β H 2 shifts are in the range of ~240-850 ppm, 9-11 since they are only three bonds removed from the paramagnetic (Cu II ) center. Such a large shift range strongly suggests that 1 H NMR spectroscopy should be a useful technique with which to probe the active site structures of these and other copper-containing proteins.…”

Section: Introductionmentioning

confidence: 99%

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NMR Hyperfine Shifts in Blue Copper Proteins: A Quantum Chemical Investigation

Zhang

Oldfield

2008

J. Am. Chem. Soc.

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We present the results of the first quantum chemical investigations of 1 H NMR hyperfine shifts in the blue copper proteins (BCPs): amicyanin, azurin, pseudoazurin, plastocyanin, stellacyanin, and rusticyanin. We find that very large structural models that incorporate extensive hydrogen bond networks, as well as geometry optimization, are required to reproduce the experimental NMR hyperfine shift results, the best theory vs experiment predictions having R 2 = 0.94, a slope = 1.01, and a SD = 40.5 ppm (or ~4.7% of the overall ~860 ppm shift range). We also find interesting correlations between the hyperfine shifts and the bond and ring critical point properties computed using atoms-in-molecules theory, in addition to finding that hyperfine shifts can be well-predicted by using an empirical model, based on the geometry-optimized structures, which in the future should be of use in structure refinement.

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Section: Hyperfine Shift Calculationssupporting

confidence: 84%

Section: Hyperfine Shift Calculationsmentioning

confidence: 59%

Section: Computational Detailsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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NMR Hyperfine Shifts in Blue Copper Proteins: A Quantum Chemical Investigation

Zhang

Oldfield

2008

J. Am. Chem. Soc.

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“…In addition, they give added confidence in the use of the MO results to describe details of structure and bonding. For example, the spin density in a ferric myoglobin model is found to have the distribution shown in figure 3b, in sharp contrast to that found in the more unusual Fe(III) species, shown in figure 3c (Mao et al 2002), while in an NO-haem system the unpaired electron is localized primarily in a d z 2 orbital (figure 3d ). These representations also help visualize the associated contact shifts, which depend on r ab .…”

Section: Spin Densities and Hyperfine Shiftsmentioning

confidence: 75%

Quantum chemical studies of protein structure

Oldfield

2004

Phil. Trans. R. Soc. B

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Quantum chemical methods now permit the prediction of many spectroscopic observables in proteins and related model systems, in addition to electrostatic properties, which are found to be in excellent accord with those determined from experiment. I discuss the developments over the past decade in these areas, including predictions of nuclear magnetic resonance chemical shifts, chemical shielding tensors, scalar couplings and hyperfine (contact) shifts, the isomer shifts and quadrupole splittings in Mö ssbauer spectroscopy, molecular energies and conformations, as well as a range of electrostatic properties, such as charge densities, the curvatures, Laplacians and Hessians of the charge density, electrostatic potentials, electric field gradients and electrostatic field effects. The availability of structure/spectroscopic correlations from quantum chemistry provides a basis for using numerous spectroscopic observables in determining aspects of protein structure, in determining electrostatic properties which are not readily accessible from experiment, as well as giving additional confidence in the use of these techniques to investigate questions about chemical bonding and chemical reactions.

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Iron Porphyrin Chemistry

Walker¹,

Simonis²

2005

Encyclopedia of Inorganic Chemistry

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This article reviews most aspects of the chemistry of iron porphyrins, from Fe(0) to Fe(V), including occurrence and roles of natural iron porphyrins (hemes) and their synthetic analogs, structures and electron configurations of iron porphyrins of all oxidation and spin states, π electron configuration of the porphyrin ring, synthesis of metal‐free porphyrins and other related macrocycles, insertion of iron into free‐base porphyrins and related macrocycles, the properties, reactions, uses and biological relevance of iron(0), ‐(I), ‐(II) porphyrins (the latter with S = 0, 1, and 2 spin state possibilities), of iron(II) porphyrin π‐cation radicals, of iron(III) porphyrins (with S = 1/2, 3/2, and 5/2 spin state possibilities), of iron(III) porphyrin and corrole π‐cation radicals, of iron(IV) porphyrins (including five‐ and six‐coordinate ferryl (FeO) 2+ , iron(IV) phenyl, carbene and hydrazine complexes, and the bis‐methoxide complex) and a comparison of iron(IV) porphyrins to iron(III) porphyrin π‐cation radicals, of iron(IV) porphyrin π‐cation radicals, and of the possible existence of iron(V) porphyrins. Included in the Fe(II) part are sections on addition of ligands to four‐coordinate iron(II) porphyrins, including equilibrium binding constants, photodissociation of ligands from PFeL 2 complexes, binding of small molecules (O 2 , CO, NO, HNO) to 5‐coordinate iron(II) porphyrins and design of porphyrin ligands that will mimic the active sites of heme proteins such as myoglobin and hemoglobin, the cytochromes P450 and nitric oxide synthases, and the nitrophorins and guanylyl cyclases. Included in the iron(III) part are sections on both 5‐ and 6‐coordinate high‐spin complexes and their similarities and differences, bridged or through‐space magnetically coupled complexes of high‐spin iron(III) porphyrins with other metal complexes as possible models for cytochrome oxidase and the assimilatory sulfite reductases, coupled oxidation of hemes by hydrogen peroxide or its equivalent, and the relationship of this reactivity to the reactions of heme oxygenase, iron(III) porphyrins as reduction catalysts, and photochemistry of iron(III) porphyrins, possible electron configurations of low‐spin iron(III) porphyrins, the phenomenon and possible electronic consequences of ruffling of the porphinato core in iron(III) porphyrins, the preferred orientation of planar axial ligands bound to low‐spin iron(III) porphyrins, NO complexes of iron(III) porphyrins, reduction potentials, equilibrium constants and rates of axial‐ligand addition and exchange, kinetics of axial‐ligand rotation and porphyrin ring inversion, kinetics of reduction and autoreduction of iron(III) porphyrins, electron self‐exchange between low‐spin iron(III) and iron(II) porphyrins, synthetic ferriheme proteins, and synthesis of five‐coordinate low‐spin iron(III) porphyrins having σ‐alkyl or σ‐aryl groups as axial ligands. The iron(IV) and iron(IV) cation radical sections discuss the high‐valent states of cytochromes P450 and related enzymes.

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Nuclear Magnetic Resonance Shifts in Paramagnetic Metalloporphyrins and Metalloproteins

Cited by 99 publications

References 57 publications

NMR Hyperfine Shifts in Blue Copper Proteins: A Quantum Chemical Investigation

NMR Hyperfine Shifts in Blue Copper Proteins: A Quantum Chemical Investigation

Quantum chemical studies of protein structure

Iron Porphyrin Chemistry

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