Molecular Structures of Nitroxides

Lajzérowicz-Bonneteau, J.

doi:10.1016/b978-0-12-092350-2.50011-4

Cited by 39 publications

(25 citation statements)

References 16 publications

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“…This means that collisional effects as seen in solution systems are not required for spin exchange. The arrangement of spin labels in tau filaments is thus more similar to solid͞crystal systems in which arrays of spin labels are in orbital overlap (29). As a control, we also confirmed that crystals of our spin label indeed show spin exchange (Fig.…”

Section: Spin Exchange Reveals Crystal-like Order In the Core Of Tau supporting

confidence: 73%

“…In other systems, however, where spin labels come together by frequent collision as is the case of spin-labeled lipids in membranes or free spin labels at high concentration in solution, spin exchange is a well established phenomenon (20). Furthermore, single-peak EPR spectra are observed in systems where spin labels are fixed at Van der Waals distance as for example in crystals (29).…”

Section: Spin Exchange Reveals Crystal-like Order In the Core Of Tau mentioning

confidence: 99%

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Template-assisted filament growth by parallel stacking of tau

Margittai

Langen

2004

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

249

264

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Tau Filaments are found in >20 neurodegenerative diseases. Yet, because of their enormous molecular weights and poor tendency to form highly ordered 3D crystal lattices, they have evaded high-resolution structure determination. Here, we studied 25 derivatized tau mutants by using electron paramagnetic resonance and fluorescence spectroscopy to report structural details of tau filaments. Based on strong spin exchange and pyrene excimer formation of core residues, we find that individual tau proteins form single molecule layers along the fiber axis that perfectly stack on top of each other by in-register, parallel alignment of ␤-strands. We suggest a model of filament growth wherein the existing filament serves as a template for the incoming, unfolded tau molecule, resulting in a new structured layer with maximized hydrogen-bonded contact surface and side-chain stacking. In addition to its role in stabilizing microtubules in neuritic extensions, tau has gained prominence as the protein constituent of filamentous inclusions in numerous neurodegenerative diseases (1). These inclusions, together with extracellular fibril deposits of the amyloid-␤ (A␤)-peptide, constitute the pathological hallmarks of Alzheimer's disease.In the adult human CNS, six different tau isoforms, ranging in size from 352 to 441 aa, are produced by alternative mRNA splicing. These isoforms vary by the absence or presence of the second of four microtubule-binding repeats in the C-terminal half and two inserts in the near N-terminal half of the protein (Fig. 1). The tau inclusions in Alzheimer's disease contain all six isoforms (2) and consist of paired helical and straight filaments (3, 4). Viewed under an electron microscope, tau filaments have a fuzzy coat that can be cleaved off by pronase (5). Cleavage leaves a core that is comprised of three microtubule-binding repeats (6). The importance of these repeats in filament formation was underscored by the finding that tau fragments comprising only the repeat region aggregate in vitro (7). In contrast, recombinant full-length tau is remarkably unreactive and aggregates only when anionic cofactors such as heparin are present (8,9).A recent study involving x-ray and selected area electron diffraction of both straight and paired helical filaments (10) revealed a common cross-␤ structure, with ␤-strands running perpendicular to the fiber axis. These data agreed with earlier findings of diffraction patterns from filaments obtained from shorter tau fragments (11,12). Importantly, they resolved some controversy concerning the filament structure of full-length tau (12)(13)(14). Thus, with respect to the cross-␤ structure and a seeded growth mechanism (15), tau filaments share similarities with a whole range of amyloidogenic protein aggregates (16). Beyond this, however, little is known about the structure of tau filaments. For example, it is not known how individual ␤-strands are arranged with each other and whether tau molecules align along or across the fiber axis, (i.e., whether hydrogen bonding among...

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Section: Spin Exchange Reveals Crystal-like Order In the Core Of Tau supporting

confidence: 73%

Section: Spin Exchange Reveals Crystal-like Order In the Core Of Tau mentioning

confidence: 99%

Template-assisted filament growth by parallel stacking of tau

Margittai

Langen

2004

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

249

264

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show abstract

“…Furthermore, studies in which three (51) or four (50) spin labels came into close contact did not reveal any significant exchange narrowing. In crystals of spin labels, however, wherein an indefinite number of nitroxides are stacked on top of each other, such exchange narrowing is commonly observed (62). The distance between the spin labels in such crystals as well as in ␣-synuclein must be close enough to allow averaging of the hyperfine interaction.…”

Section: Discussionmentioning

confidence: 99%

Investigation of α-Synuclein Fibril Structure by Site-directed Spin Labeling

Chen

Margittai

Chen

et al. 2007

Journal of Biological Chemistry

223

254

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The misfolding and fibril formation of ␣-synuclein plays an important role in neurodegenerative diseases such as Parkinson disease. Here we used electron paramagnetic resonance spectroscopy, together with site-directed spin labeling, to investigate the structural features of ␣-synuclein fibrils. We generated fibrils from a total of 83 different spin-labeled derivatives and observed single-line, exchange-narrowed EPR spectra for the majority of all sites located within the core region of ␣-synuclein fibrils. Such exchange narrowing requires the orbital overlap between multiple spin labels in close contact. The core region of ␣-synuclein fibrils must therefore be arranged in a parallel, inregister structure wherein same residues from different molecules are stacked on top of each other. This parallel, in-register core region extends from residue 36 to residue 98 and is tightly packed. Only a few sites within the core region, such as residues 62-67 located at the beginning of the NAC region, as well as the N-and C-terminal regions outside the core region, are significantly less ordered. Together with the accessibility measurements that suggest the location of potential ␤-sheet regions within the fibril, the data provide significant structural constraints for generating three-dimensional models. Furthermore, the data support the emerging view that parallel, in-register structure is a common feature shared by a number of naturally occurring amyloid fibrils.

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“…For some of the combinations of nitroxyl and solvent the spectra could not be fitted with isotropic rotation, but could be fitted with axial rotation. The x-axis and z-axis are along the direction of the N-O bond and along the π orbital of nitrogen, respectively, and these were defined as the axes for R ⊥ [30]. The tumbling correlation times for these cases were calculated as .…”

Section: Determination Of Nitroxyl Tumbling Correlation Timesmentioning

confidence: 99%

Electron spin–lattice relaxation of nitroxyl radicals in temperature ranges that span glassy solutions to low-viscosity liquids

Sato

Bottle

Blinco

et al. 2008

Journal of Magnetic Resonance

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Electron spin-lattice relaxation rates, 1/T 1 , at X-band of nitroxyl radicals (4-hydroxy-2,2,6,6-tetramethylpiperidin-1-oxyl, 4-oxo-2,2,6,6-tetramethylpiperidin-1-oxyl, 3-carbamoyl-2,2,5,5-tetramethylpyrrolidin-1-oxyl and 3-carbamoyl-2,2,5,5-tetramethylpyrrolin-1-oxyl) in glass-forming solvents (decalin, glycerol, 3-methylpentane, o-terphenyl, 1-propanol, sorbitol, sucrose octaacetate, and 1:1 water:glycerol) at temperatures between 100 K and 300 K were measured by long-pulse saturation recovery to investigate the relaxation processes in slow-to-fast tumbling regimes. A subset of samples was also studied at lower temperatures or at Q-band. Tumbling correlation times were calculated from continuous wave lineshapes. Temperature dependence and isotope substitution ( 2 H and 15 N) were used to distinguish the contributions of various processes. Below about 100 K relaxation is dominated by the Raman process. At higher temperatures, but below the glass transition temperature, a local mode process makes significant contributions. Above the glass transition temperature, increased rates of molecular tumbling modulate nuclear hyperfine and g anisotropy. The contribution from spin rotation is very small. Relaxation rates at X-band and Q-band are similar. The dependence of 1/T 1 on tumbling correlation times fits better with the Cole-Davidson spectral density function than with the Bloembergen-Purcell-Pound model.

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Molecular Structures of Nitroxides

Cited by 39 publications

References 16 publications

Template-assisted filament growth by parallel stacking of tau

Template-assisted filament growth by parallel stacking of tau

Investigation of α-Synuclein Fibril Structure by Site-directed Spin Labeling

Electron spin–lattice relaxation of nitroxyl radicals in temperature ranges that span glassy solutions to low-viscosity liquids

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