Technical Aspects of Fast Field Cycling

Ferrante, Gianni; Sýkora, S.

doi:10.1016/s0898-8838(05)57009-0

Cited by 118 publications

(116 citation statements)

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“…FT-IR and CPMAS 13C NMR) provided a good basis for the comprehension of DOM relaxograms, much more must still be done to retrieve additional and more detailed relaxometric information. In fact, field cycling NMR relaxometry can be used to investigate the underlying correlation functions (Kimmich and Anoardo, 2004;Ferrante and Sykora, 2005;Conte et al, 2009a,b;Pohlmeier et al, 2009;Pru˚ šova et al, 2010) which in turn contain the physical information needed for the understanding of the nature of the interactions involved in the complexation of natural organic matter (such as DOM) and the organic and inorganic components of the environmental compartments.…”

Section: Discussionmentioning

confidence: 99%

“…To the best of our knowledge, low field 1H T1 NMR relaxometry with fast field cycling (FFC) has never been applied to the identification of DOM conformational properties. The technique is based on the cycling of the Zeeman magnetic field (B0) through three different values traditionally indicated as polarization (Bpol), relaxation (Brelax) and acquisition (Bacq) fields (Kimmich and Anoardo, 2004;Ferrante and Sykora, 2005). Bpol is applied for a limited and ixed period of time in order to obtain magnetization saturation and sensitivity enhancement (Kimmich and Anoardo, 2004).…”

Section: Introductionmentioning

confidence: 99%

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Adsorption of dissolved organic matter on clay minerals as assessed by infra-red, CPMAS 13C NMR spectroscopy and low field T1 NMR relaxometry

Conte

Abbate

Baglieri

et al. 2011

Organic Geochemistry

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This is an author version of the contribution published on:Questa è la versione dell 'autore dell'opera: Organic Geochemistry 42 (2011) 972-977 2011,http://dx.doi.org/10.1016/j.orggeochem.2011 ABSTRACTDissolved organic matter (DOM) is a very important environmental constituent due to its role in controlling factors for soil formation, mineral weathering and pollutant transport in the environment. Prediction of DOM physical-chemical properties is achieved by studying its chemical structure and spatial conformation. In the present study, dissolved organic matter extracted from compost obtained from the organic fraction of urban wastes (DOM-P) has been analysed by FT-IR, CPMAS 13C NMR spectroscopy and 1H T1 NMR relaxometry with fast field cycling (FFC) setup. While the first two spectroscopic techniques revealed the chemical changes of dissolved organic matter after adsorption either on kaolinite (DOMK) or montmorillonite (DOM-S), the latter permitted the evaluation of the conformational variations as assessed by longitudinal relaxation time (T1) distribution at the fixed magnetic field of 500 mT. Alterations of T1 distributions from DOM-P to DOM-K and DOM-S were attributed to a decreasing molecular complexity following DOM-P adsorption on the clay minerals. This study applied for the first time solid state 1H T1 NMR relaxometry to dissolved organic matter from compost obtained from the organic fraction of urban wastes and revealed that this technique is very promising for studying environmentally relevant natural organic systems.

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Section: Discussionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Adsorption of dissolved organic matter on clay minerals as assessed by infra-red, CPMAS 13C NMR spectroscopy and low field T1 NMR relaxometry

Conte

Abbate

Baglieri

et al. 2011

Organic Geochemistry

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“…The FC technique overcomes the sensitivity problem of conventional fixed-field experiments in weak magnetic fields (33,34). The prepolarized sequence (PP/S) was used with polarization and detection at 20 and 9.1 MHz, respectively, and a 90°pulse length of 4.5 s. In the non-FC experiments (with variable detection field), R 1 was measured with the 180°--90°inversion recovery sequence.…”

Section: Mrd Experimentsmentioning

confidence: 99%

Molecular basis of water proton relaxation in gels and tissue

Chávez

Halle

2006

Magnetic Resonance in Med

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An extensive set of water-1 H magnetic relaxation dispersion (MRD) data are presented for aqueous agarose and gelatin gels. It is demonstrated that the EMOR model, which was developed in a companion paper to this study (see Halle, this issue), accounts for the dependence of the water-1 H spin-lattice relaxation rate on resonance frequency over more than four decades and on pH. The parameter values deduced from analysis of the 1 H MRD data are consistent with values derived from 2 H MRD profiles from the same gels and with small-molecule reference data. This agreement indicates that the water-1 H relaxation dispersion in aqueous biopolymer gels is produced directly by exchange-mediated orientational randomization of internal water molecules or labile biopolymer protons, with little or no role played by collective biopolymer vibrations or coherent spin diffusion. This ubiquitous mechanism is proposed to be the principal source of water-1 H spin-lattice relaxation at low magnetic fields in all aqueous systems with rotationally immobile biopolymers, including biological tissue. The same mechanism also contributes to transverse and rotating-frame relaxation and magnetization transfer at high fields. Intrinsic contrast in magnetic resonance images of soft tissue is generated largely by spatial variations in spin relaxation rates. Whereas the phenomenology of water-1 H relaxation in tissue is well documented (1-3), the underlying molecular mechanism remains controversial (4 -9). The task of elucidating the relaxation mechanism is complicated by incomplete knowledge about the chemical composition and supramolecular structure of most tissues. In addition, it is usually not possible to vary biopolymer composition, pH, or temperature in a controlled way while maintaining the integrity of the tissue. For these reasons, most mechanistic studies have been carried out on model systems, such as aqueous biopolymer gels, with relaxation characteristics similar to those of tissue. Here we report an extensive set of water-1 H relaxation data from two widely used tissue models: aqueous gels of agarose and gelatin.Detailed information about relaxation mechanisms in complex systems can be obtained from the magnetic relaxation dispersion (MRD) profile, that is, the field/frequency dependence of the spin-lattice relaxation rate, R 1 ϭ 1/T 1 . Ideally, the dispersion profile should be recorded from typical MRI frequencies of order 100 MHz down to the kHz range. The water-1 H MRD profiles reported here cover more than four frequency decades. The strong frequency dependence of R 1 at low fields, which is the focus of the present study, can be used to enhance image contrast in prepolarized MRI experiments (10). The low-field R 1 dispersion also yields information about the zero-frequency dipolar contributions to transverse relaxation and steadystate magnetization transfer and to the low-frequency dipolar contribution to rotating-frame spin-lattice relaxation.Agarose is a linear polysaccharide with a disaccharide repeat (agarobiose) composed...

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“…35 % by mass, [7,8] far from physiological conditions. Improvements in field-cycling technology [9][10][11][12] have led to the production of instrumentation [13] with a % 10-fold increase in the signal-to-noise ratio, [14] with which direct protein 1 H detection can be attempted for protein concen- Figure 1. Protein 1 H relaxation dispersions for lysozyme solutions (2.8 mm in D 2 O) at a) pH* 3.5, and b) pH* 9.0 (pH=pH-meter reading in D20 solution).…”

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confidence: 99%

NMR Spectroscopic Detection of Protein Protons and Longitudinal Relaxation Rates between 0.01 and 50 MHz

et al. 2005

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Nuclear magnetic relaxation data of water nuclei at variable fields provide valuable information on the dynamics of watersolute interactions. [1][2][3] However, information can be collected only within certain field ranges in which the nuclear relaxation rates are field-dependent owing to the dispersion of the spectral density, J(w,t). The dispersion depends on the type of motion and on the observed nucleus. The most informative 1 H NMR spectroscopic frequency range for rotational motions is centered around 10 MHz for small proteins (M W % 10 4 Da) and smaller frequencies for larger proteins and protein aggregates. Of course, resolution is low at these fields and in practice only one signal (or an unresolved signal envelope) can be detected. Furthermore, only the abundant water protons can be conveniently studied under such low sensitivity.Relaxation of the isotopes 17 O and 2 H in enriched water can also be studied; [1] in these cases the centers of the informative field ranges increase by a factor % 7 with respect to 1 H as a result of the magnetogyric ratios of 17 O and 2 H. Because water interacts with proteins, such relaxation studies provide direct information on the nature of water-protein dynamics, but give only indirect information on the protein itself.[4-6] It would be highly desirable to have complementary information directly from the protons of the protein, but this has been impractical so far owing to the low sensitivity of the available instrumentation. Protein 1 H relaxation data have been reported only on protein solutions of concentrations ! 35 % by mass, [7,8] far from physiological conditions. Improvements in field-cycling technology [9][10][11][12] have led to the production of instrumentation [13] with a % 10-fold increase in the signal-to-noise ratio, [14] with which direct protein 1 H detection can be attempted for protein concen- Figure 1. Protein 1 H relaxation dispersions for lysozyme solutions (2.8 mm in D 2 O) at a) pH* 3.5, and b) pH* 9.0 (pH=pH-meter reading in D20 solution). The time decay of the collective protein 1 H magnetization at 0.1 MHz and its single-exponential fit are shown in the inset of part a). Theoretical relaxation rates were obtained through singleexponential fits of time decays of collective protein 1 H magnetization calculated from the known protein structure of lysozyme [17] and a complete relaxation matrix (CORMA) analysis.[18] Only exchangeable NH protons from secondary structure elements ( % 50 % of total) were included, whereas all other exchangeable proton positions were assumed to be deuterated. Inclusion of either all or none of the NH protons affected the calculated rates by AE 2 %. The theoretical lowfield hE 2 i values obtained in this way were used to fit Equation (1) to the data (solid lines). The dotted lines represent data fits with two J-(w,t) terms in Equation (1) ( Table 1). Panel c) shows the protein 1 H relaxation dispersion for a solution of a-synuclein in D 2 O (1.4 mm, pH* 7.1). The solid and dotted lines represent fits with one or two J-(...

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Technical Aspects of Fast Field Cycling

Cited by 118 publications

References 113 publications

Adsorption of dissolved organic matter on clay minerals as assessed by infra-red, CPMAS 13C NMR spectroscopy and low field T1 NMR relaxometry

Adsorption of dissolved organic matter on clay minerals as assessed by infra-red, CPMAS 13C NMR spectroscopy and low field T1 NMR relaxometry

Molecular basis of water proton relaxation in gels and tissue

NMR Spectroscopic Detection of Protein Protons and Longitudinal Relaxation Rates between 0.01 and 50 MHz

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