Use of the ESR half-field transition to determine the interspin distance and the orientation of the interspin vector in systems with two unpaired electrons

Eaton, Sandra S.; More, Kundalika M.; Sawant, Bhimrao M.; Eaton, Gareth R.

doi:10.1021/ja00360a005

Cited by 283 publications

(230 citation statements)

References 7 publications

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“…51,52 Investigation of PrP(23−28, 57−91) in the vicinity of 1600 G indeed reveals a half field signal that is not observed in the monomeric octarepeats as shown in Figure 2.…”

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confidence: 87%

The Octarepeat Domain of the Prion Protein Binds Cu(II) with Three Distinct Coordination Modes at pH 7.4

et al. 2005

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“…51,52 Investigation of PrP(23−28, 57−91) in the vicinity of 1600 G indeed reveals a half field signal that is not observed in the monomeric octarepeats as shown in Figure 2.…”

mentioning

confidence: 87%

The Octarepeat Domain of the Prion Protein Binds Cu(II) with Three Distinct Coordination Modes at pH 7.4

et al. 2005

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“…However, with B 1 || B 0 , the half-field features at 160 mT were 70 times more intense relative to the features at 298, 336, and 362 mT and, thus, confirm their assignment to an S = 1 system. [41][42][43][44] The temperature dependencies of the signals were studied, and the data for the high pH B 1 ⊥ B 0 signal in the g ~2 region at 298 mT and for the B 1 || B 0 signal at 160 mT are presented in Figure 5. Figure 5A shows a region of the spectrum of Figure 3C with the low-field region multiplied by nine and shown above the main trace.…”

Section: Epr Studies On Cu(ii)-substituted Aapmentioning

confidence: 99%

Structurally Distinct Active Sites in the Copper(II)-Substituted Aminopeptidases from Aeromonas proteolytica and Escherichia coli

et al. 2002

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The aminopeptidase from Aeromonas proteolytica (AAP) was titrated with copper, which bound sequentially at two distinct sites. Both the mono-and disubstituted forms of AAP exhibited catalytic hyperactivity relative to the native dizinc enzyme. Monosubstituted AAP exhibited an axial Cu(II) EPR spectrum with slight pH dependence: at pH 6.0 g || =2.249, g ⊥ = 2.055, and A || ( 63/65 Cu) = 1.77 × 10 −2 cm −1 , whereas at pH 9.65 g || = 2.245, g ⊥ = 2.056, and A || ( 63/65 Cu) = 1.77 × 10 −2 cm −1 . These data indicate oxygen and nitrogen ligation of Cu. AAP further substituted with copper exhibited a complex signal with features around g ~2 and 4. The features at g ~4 were relatively weak in the B 0 ⊥ B 1 (perpendicular) mode EPR spectrum but were intense in the B 0 || B 1 (parallel) mode spectrum. The g ~2 region of the perpendicular mode spectrum exhibited two components, one corresponding to mononuclear Cu(II) with g || = 2.218, g ⊥ = 2.023, and A || ( 63/65 Cu) = 1.55 × 10 −2 cm −1 and likely due to adventitious binding of Cu(II) to a site distant from the active site. Excellent simulations were obtained for the second component of the spectrum assuming that two Cu(II) ions experience dipolar coupling corresponding to an inter-copper distance of 5 Å with the two Cu(II) g z directions parallel to each other and at an angle of ~17° to the inter-copper vector (ℋ= βB·g CuA ·S CuA + βB·g CuB ·S CuB + [S·A·I] CuA + [S·A·I] CuB + [S CuA ·J·S CuB ]; g ||(CuA,CuB) = 2.218, g ⊥(CuA,CuB) = 2.060; A ||(CuA,CuB) ( 63/65 Cu) = 1.59 × 10 −2 cm −1 , J isotropic = 50 cm −1 , r Cu-Cu = 4.93 Å, and χ=17°). The exchange coupling between the two copper ions was found to be ferromagnetic as the signals exhibited Curie law temperature dependence. The Cu-Cu distance of ~5 Å indicated by EPR was significantly higher than the inter-zinc distance of 3.5 Å in the native enzyme, and the dicopper species therefore represents a novel dinuclear site capable of catalysis of hydrolysis. In contrast to AAP, the related methionyl aminopeptidase from Escherichia coli (EcMetAP) was found to bind only one Cu(II) ion despite possessing a dinuclear binding site motif. A further difference was the marked pH dependence of the signal in EcMetAP, suggestive of a change in ligation. The structural motifs of these two Cu(II)-substituted aminopeptidases provide important insight into the observed catalytic activity.

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“…The relative intensity of the half-field transition increases at lower frequencies 17) . However, electron-nuclear modulation, which can complicate some of the pulse measurements, is deeper at lower frequencies, which makes pulse techniques more difficult to interpret at lower frequencies.…”

Section: Comparison Of Methods To Obtain Distances Between Pairs Of Smentioning

confidence: 94%

Measuring Distances between Sites in Biomolecules by Electron Paramagnetic Resonance

Eaton¹

2006

Biophysics

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Interpretation of the function of biomolecules at the molecular level requires knowledge of the threedimensional structure. Electron paramagnetic resonance methods can be used to determine the distance between paramagnetic sites that are intrinsic to a biomolecule or are added by attachment of stable nitroxyl radicals or paramagnetic metals. Techniques have been developed to measure distances ranging from about 5 to 70 Å (0.5 to 7.0 nm). This article provides an overview of techniques and examples of systems to which they have been applied. EPR / distances measurement / dipolar interaction / biomolecules / radicals / paramagnetic metals

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Use of the ESR half-field transition to determine the interspin distance and the orientation of the interspin vector in systems with two unpaired electrons

Cited by 283 publications

References 7 publications

The Octarepeat Domain of the Prion Protein Binds Cu(II) with Three Distinct Coordination Modes at pH 7.4

The Octarepeat Domain of the Prion Protein Binds Cu(II) with Three Distinct Coordination Modes at pH 7.4

Structurally Distinct Active Sites in the Copper(II)-Substituted Aminopeptidases from Aeromonas proteolytica and Escherichia coli

Measuring Distances between Sites in Biomolecules by Electron Paramagnetic Resonance

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