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Guendouz L.,Mesures et Architectures Electroniques IJL | Aissani S.,Methodologie RMN CRM2 | Mareche J.-F.,Materiaux Carbones IJL | Retournard A.,Methodologie RMN CRM2 | And 2 more authors.
Solid State Nuclear Magnetic Resonance | Year: 2013

The application of a weak static B0 magnetic field (less than 1 mT) may produce a well-defined splitting of the 14N Quadrupole Resonance line when the electric field gradient tensor at the nitrogen nucleus level is of axial symmetry. It is theoretically shown and experimentally confirmed that the actual splitting (when it exists) as well as the line-shape and the signal intensity depends on three factors: (i) the amplitude of B 0, (ii) the amplitude and pulse duration of the radio-frequency field, B1, used for detecting the NQR signal, and (iii) the relative orientation of B0 and B1. For instance, when B0 is parallel to B1 and regardless of the B0 value, the signal intensity is three times larger than when B0 is perpendicular to B1. This point is of some importance in practice since NQR measurements are almost always performed in the earth field. Moreover, in the course of this study, it has been recognized that important pieces of information regarding line-shape are contained in data points at the beginning of the free induction decay (fid) which, in practice, are eliminated for avoiding spurious signals due to probe ringing. It has been found that these data points can generally be retrieved by linear prediction (LP) procedures. As a further LP benefit, the signal intensity loss (by about a factor of three) is regained. © 2013 Elsevier Inc. Source


Jover J.,Methodologie RMN CRM2 | Aissani S.,Methodologie RMN CRM2 | Guendouz L.,CNRS Jean Lamour Institute | Thomas A.,University of Lorraine | Canet D.,Methodologie RMN CRM2
NATO Science for Peace and Security Series B: Physics and Biophysics | Year: 2014

Cylindrical pieces of wood which can be placed in 10 mm o.d. NMR sample tubes have been impregnated by an aqueous solution of sodium nitrite (NaNO2). They were subsequently dried and examined by 14N quadrupole resonance. To our surprise, we were able to observe a signal at the right frequency (4.64 MHz, the highest frequency NaNO2 line). This implies that the material has been properly embedded but also that sodium nitrite was properly recrystallized. This latter point was more than speculative. Anyway, we could observe that it works for spruce, beech, ash, maritime pine, but not for oak (which is known to be difficult to impregnate). Instrumental parameters have been optimized for reducing the duration of the experiment. If the first measurements required around 4 h, we obtain at the present time acceptable results in about 2 min or less. In addition, we have designed a simple NLLS (Non Linear Least Squares) algorithm by which the spectral parameters of the NQR signal can be retrieved even if the peak is hardly visible in the frequency domain. Extensive measurements have been performed on NaNO2 recrystallized in spruce. They show, among other things, that the totality of NaNO2 which has penetrated the material has actually recrystallized and seemingly forever. Various assays have been carried out as a function of impregnation and drying conditions. The evolution of the width of the NaNO 2 line reflects defects in the crystal lattice of NaNO2 due probably to alteration of the wood structure upon drying. © Springer Science+Business Media Dordrecht 2014. Source


Canet D.,Methodologie RMN CRM2 | Bouguet-Bonnet S.,Methodologie RMN CRM2 | Leclerc S.,CNRS Mechanical Energy, Theories, and Applications Laboratory | Yemloul M.,Methodologie RMN CRM2
Annual Reports on NMR Spectroscopy | Year: 2011

Owing to an extremely abundant literature making use of spin relaxation for structural studies, this review is limited to carbon-13 spectroscopy, to small or medium size molecules, to stereochemical and preferably geometrical determinations. The parameter of choice is evidently the Nuclear Overhauser effect (NOE) because it depends exclusively on the dipolar interaction mechanism, thus on 1/r 6, where r is the distance between the two interacting spins. However, it depends also on the dynamical features of the system under investigation which must be characterized prior to any attempt for obtaining geometrical or stereochemical information. Therefore, this review is devoted not only to 1H- 13C NOE but, more generally, to 13C longitudinal relaxation. After comprehensive theoretical developments, experimental methods presently available will be presented. The latter include the usual gated decoupling experiment and pulse experiments of the HOESY (Heteronuclear Overhauser Effect SpectroscopY) family. These pulse experiments, which imply carbon-13 observation, can be one-dimensional, selective one-dimensional or two-dimensional. The emphasis will be put on the interpretation which is different according to the occurrence or not of extreme narrowing conditions. Along with a literature survey, some selected examples will be presented in detail in order to illustrate the potentiality of the method. © 2011 Elsevier Ltd. Source


Zhang L.,Case Western Reserve University | Bouguet-Bonnet S.,Methodologie RMN CRM2 | Buck M.,Case Western Reserve University
Methods in Molecular Biology | Year: 2012

Combinations of experimentally derived data from nuclear magnetic resonance spectroscopy and analyses of molecular dynamics trajectories increasingly allow us to obtain a detailed description of the molecular mechanisms by which proteins function in signal transduction. This chapter provides an introduction into these two methodologies, illustrated by example of a small GTPase-effector interaction. It is increasingly becoming clear that new insights are provided by the combination of experimental and computational methods. Understanding the structural and protein dynamical contributions to allostery will be useful for the engineering of new binding interfaces and protein functions, as well as for the design/in silico screening of chemical agents that can manipulate the function of small GTPase-protein interactions in diseases such as cancer. © 2012 Springer Science+Business Media, LLC. Source

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