Artifact-Free Pure Absorption PFG-Enhanced DQF-COSY Spectra Including a Gradient Pulse in the Evolution Period

Ancian, Bernard; Bourgeois, Isabelle; Dauphin, Jean-François; Shaw, Anthony A.

doi:10.1006/jmre.1997.1112

Cited by 53 publications

(38 citation statements)

References 13 publications

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“…Two-dimensional homonuclear experiments were used to assist the assignment of the peaks that appeared during the progress of the melanogenesis reaction. DQF-COSY spectra were acquired with gradient coherence selection (33,34) and Clean-TOCSY spectra were recorded in the phase-sensitive manner using the TPPI method (35, 36) with 100 ms of mixing time. All two-dimensional exper-FIGURE 1.…”

Section: Methodsmentioning

confidence: 99%

Kinetic and Structural Analysis of the Early Oxidation Products of Dopamine

Bisaglia

Mammi

Bubacco

2007

Journal of Biological Chemistry

271

257

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Oxidative stress appears to be directly involved in the pathogenesis of several neurodegenerative disorders, including Alzheimer and Parkinson diseases. Nigral dopaminergic neurons are particularly exposed to oxidative stress because a pathological accumulation of cytosolic dopamine gives rise to various toxic molecules, including free radicals and reactive quinones. These latter species can react with proteins preventing them from exerting their physiological functions. Among the possible targets of quinones, ␣-synuclein is of primary interest because of its direct involvement in dopamine metabolism. Contrary to the neurotoxic processes, neuromelanin synthesis seems to play a protective role by its ability to sequester a variety of potentially damaging substances. In this study, we carried out a kinetic and structural analysis of the early oxidation products of dopamine. Specifically, considering the potential high toxicity of aminochrome for both cells and mitochondria, we focused our attention on its rearrangement to 5,6-dihydroxyindole. After the spectroscopic characterization of the products derived from the oxidation of dopamine, the structural information obtained was used to analyze the reactivity of quinones toward ␣-synuclein. Our results suggest that indole-5,6-quinone, rather than dopamine-o-quinone or aminochrome, is the reactive species. We propose that the observed reactivity could represent a general reaction pathway whenever cysteinyl residues are absent in proteins or if they are sterically protected.Parkinson disease, the second most common neurodegenerative disorder, is a chronic and progressive disease characterized by degeneration of dopaminergic neuromelanin-containing neurons in the substantia nigra pars compacta (1) and by the presence of cytoplasmic inclusions that are mainly composed of fibrillar ␣-synuclein (␣syn) 2 (2). Postmortem studies support the involvement of oxidative stress and the production of reactive oxygen species in Parkinson disease (3, 4). A possible source of oxidative stress is the redox reactions that specifically involve dopamine (DA). A critical aspect is the amount of DA present in the cytoplasm, outside the synaptic vesicles where the neurotransmitter is confined under physiological conditions. Spontaneous oxidation of DA in the presence of molecular oxygen leads to the formation of several cytotoxic molecules, including superoxide anions (O 2 . ), hydroxyl radicals (OH ⅐ ), and reactive quinones (DAQs) (5). Reactive oxygen species derived from the oxidation of DA can damage cellular components such as lipids, proteins, and DNA (6). The electrondeficient quinones can also react with cellular nucleophiles, leading to further cytotoxicity. DAQs have been shown to bind covalently to cysteinyl residues of proteins both in vitro and in vivo (7-12). Because these residues are often located at the active site of a protein, it has been proposed that covalent modifications result in an impairment of protein function with potentially deleterious effects on the cell (10...

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Section: Methodsmentioning

confidence: 99%

Kinetic and Structural Analysis of the Early Oxidation Products of Dopamine

Bisaglia

Mammi

Bubacco

2007

Journal of Biological Chemistry

271

257

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“…A key feature of DQDiff is the asymmetric amplitudes of the gradient pulses. This, in turn, is similar to another DQF COSY experiment where asymmetric gradient values are used to filter out longitudinal interference [23,24]. The selection of a single CTP is inherent in the DQDiff experiment and required by its (CTP-specific) convection compensation [4,25].…”

Section: The Dqdiff Schemementioning

confidence: 97%

Convection-compensating diffusion experiments with phase-sensitive double-quantum filtering

Momot

Kuchel

2005

Journal of Magnetic Resonance

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We present a design scheme for phase-sensitive, convection-compensating diffusion experiments with gradient-selected homonuclear double-quantum filtering. The scheme consists of three blocks: a 1/2J evolution period during which antiphase single-quantum coherences are created; a period of double-quantum evolution; and another 1/2J period, during which antiphase single-quantum coherences are converted back into an in-phase state. A single coherence transfer pathway is selected using an asymmetric set of gradient pulses, and both diffusion sensitization and convection compensation are built into the gradient coherence transfer pathway selection. Double-quantum filtering can be used either for solvent suppression or spectral editing, and we demonstrate examples of both applications. The new experiment performs well in the absence of a field-frequency lock and does not require magnitude Fourier transformation. The proposed scheme may offer advantages in diffusion measurements of spectrally crowded systems, particularly small molecules solubilized in colloidal solutions or bound to macromolecules.

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“…All experiments were performed at 75°C using a pulse sequence (zgcppr) by which the water resonance is pre-saturated before a composite 90-degree pulse is applied (Bax, 1985). All spectra were acquired using a recycle delay of 4 s, 64 scans, a spin-rate of 7 kHz and a dwell time of 60.4 μs for acquisition of 32 k data points resulting in a total acquisition time of 1.979 s. In addition, a series of 2D experiments were recorded ( 1 H-1 H COSY (Ancian, Bourgeois, Dauphin, & Shaw, 1997), 1 H-1 H TOCSY (Bax & Davis, 1985), and 1 H-13 C HSQC (Bodenhausen & Ruben, 1980)) in order to perform spectral assignments.…”

Section: H Hr-mas Nmr Spectroscopymentioning

confidence: 99%