Spin Exchange in Chemistry and Biology

Molin, Yuri N.; Salikhov, K. M.; Zamaraev, K. I.

doi:10.1007/978-3-642-67666-6_4

Cited by 100 publications

(364 citation statements)

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“…Typically, spin-spin interactions between nitroxide labels in proteins are dominated by dipolar effects that result in a broadening of EPR spectra, providing distance information in the range of Ϸ8-25 Å (23,24). A second type of interaction, spin exchange, occurs at much smaller distances, when on the EPR time scale (Ͻ10 Ϫ7 s) multiple nitroxide labels are in sufficient proximity to allow orbital overlap (25)(26)(27). This type of interaction strikingly reduces classical three-line EPR spectra to a single feature.…”

Section: Resultsmentioning

confidence: 99%

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Molecular architecture of human prion protein amyloid: A parallel, in-register β-structure

Cobb

Sönnichsen

Mchaourab³

et al. 2007

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

303

342

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Transmissible spongiform encephalopathies (TSEs) represent a group of fatal neurodegenerative diseases that are associated with conformational conversion of the normally monomeric and ␣-helical prion protein, PrP C , to the ␤-sheet-rich PrP Sc . This latter conformer is believed to constitute the main component of the infectious TSE agent. In contrast to high-resolution data for the PrP C monomer, structures of the pathogenic PrP Sc or synthetic PrP Sc -like aggregates remain elusive. Here we have used sitedirected spin labeling and EPR spectroscopy to probe the molecular architecture of the recombinant PrP amyloid, a misfolded form recently reported to induce transmissible disease in mice overexpressing an N-terminally truncated form of PrP C . Our data show that, in contrast to earlier, largely theoretical models, the conformational conversion of PrP C involves major refolding of the C-terminal ␣-helical region. The core of the amyloid maps to C-terminal residues from Ϸ160 -220, and these residues form single-molecule layers that stack on top of one another with parallel, in-register alignment of ␤-strands. This structural insight has important implications for understanding the molecular basis of prion propagation, as well as hereditary prion diseases, most of which are associated with point mutations in the region found to undergo a refolding to ␤-structure.EPR ͉ spin labeling ͉ transmissible spongiform encephalopathy

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Section: Resultsmentioning

confidence: 99%

“…Single-line EPR signals are commonly associated with crystals or highly concentrated solutions of nitroxide radicals, where the frequent interaction of paramagnetic centers is due to either tight packing or transient collisions (25). To probe the nature of these interactions in PrP amyloid fibrils, we measured EPR spectra at low temperatures.…”

Section: Resultsmentioning

confidence: 99%

Molecular architecture of human prion protein amyloid: A parallel, in-register β-structure

Cobb

Sönnichsen

Mchaourab³

et al. 2007

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

303

342

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“…1, Eq. 2), is diffusion-controlled with k e = k 1 ≈ 3.6 MHz/mM for PRAs in water at 25°C, p154 in (49). For real PRAs, k e is less than k 1 , due to dependence on electronic, steric, and magnetic factors (49).…”

Section: Spin Exchange As a Bimolecular Chemical Reactionmentioning

confidence: 98%

“…2), is diffusion-controlled with k e = k 1 ≈ 3.6 MHz/mM for PRAs in water at 25°C, p154 in (49). For real PRAs, k e is less than k 1 , due to dependence on electronic, steric, and magnetic factors (49). For example k e ≈ 0.2 k 1 was measured for Fe(CN) 6 3-in aqueous solution with a nitroxide spin label (50).…”

Section: Spin Exchange As a Bimolecular Chemical Reactionmentioning

confidence: 99%

“…By choosing small PRAs of the same diameter, the ratios between k e values remain constant for a spin label in a tight protein crevice. Nitroxyl group hydration has been hypothesized to explain nitroxidenitroxide k e values that are half as large in aqueous compared to organic solutions (49). We later account for this water by defining the nitroxyl oxygen surface from which position r in Eq.…”

Section: Calculating Voltage From Relaxation Enhancementmentioning

confidence: 99%

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A paramagnetic molecular voltmeter

Surek

Thomas

2008

Journal of Magnetic Resonance

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We have developed a general electron paramagnetic resonance (EPR) method to measure electrostatic potential at spin labels on proteins to millivolt accuracy. Electrostatic potential is fundamental to energy-transducing proteins like myosin, because molecular energy storage and retrieval is primarily electrostatic. Quantitative analysis of protein electrostatics demands a sitespecific spectroscopic method sensitive to millivolt changes. Previous electrostatic potential studies on macromolecules fell short in sensitivity, accuracy and/or specificity. Our approach uses fastrelaxing charged and neutral paramagnetic relaxation agents (PRAs) to increase nitroxide spin label relaxation rate solely through collisional spin exchange. These PRAs were calibrated in experiments on small nitroxides of known structure and charge to account for differences in their relaxation efficiency. Nitroxide longitudinal (R 1 ) and transverse (R 2 ) relaxation rates were separated by applying lineshape analysis to progressive saturation spectra. The ratio of measured R 1 increases for each pair of charged and neutral PRAs measures the shift in local PRA concentration due to electrostatic potential. Voltage at the spin label is then calculated using the Boltzmann equation. Measured voltages for two small charged nitroxides agree with Debye-Hückel calculations. Voltage for spin-labeled myosin fragment S1 also agrees with calculation based on the pK shift of the reacted cysteine.

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Functional in vivo EPR Spectroscopy and Imaging Using Nitroxide and Trityl Radicals

Khramtsov¹,

Zweíer²

2010

Stable Radicals

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Spin Exchange in Chemistry and Biology

Cited by 100 publications

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Molecular architecture of human prion protein amyloid: A parallel, in-register β-structure

Molecular architecture of human prion protein amyloid: A parallel, in-register β-structure

A paramagnetic molecular voltmeter

Functional in vivo EPR Spectroscopy and Imaging Using Nitroxide and Trityl Radicals

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