Effects of Diffusion on Free Precession in Nuclear Magnetic Resonance Experiments

Carr, H. Y.; Purcell, Edward M.

doi:10.1103/physrev.94.630

Cited by 5,921 publications

(3,603 citation statements)

References 7 publications

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“…2͑neϩ1͒ 180/⌬t ␥⌬B͑r͑k͒͒ ⅐ ⌬t, [20] taking the refocusing interval 180 to be 6 ms and n e as the index for the even echoes, for a total of 20 echoes. The time evolution of transverse magnetization in the presence of CPMG refocusing was formed from these echoes by applying Eq.…”

Section: Simulation Methodsmentioning

confidence: 99%

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On the parameters affecting the sensitivity of MR measures of pressure with microbubbles

Dharmakumar

Plewes

Wright

2002

Magnetic Resonance in Med

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Recently, it has been suggested that gas encapsulated distensible microbubbles may serve as pressure probes in the MR field through the relationship between bubble size and 1/T 2 or 1/T* 2 . Currently, in vivo application of this technique is hindered by the ability of T 2 or T * 2 to detect pressure changes that are clinically relevant. This work identifies and characterizes, through numerical simulations, the set of parameters which optimize the ability of this technique to detect small pressure changes. Results show that when the bubbles do not interact magnetically, the T 2 -and T * 2 -based measurements of pressure are strongly influenced by the bubble size at atmospheric pressure, static magnetic field strength, magnitude of the susceptibility difference between the encapsulated gas and plasma, bubble volume fraction, and the refocusing interval.

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Section: Simulation Methodsmentioning

confidence: 99%

“…The time evolution of transverse magnetization in the presence of CPMG refocusing was formed from these echoes by applying Eq. [20] into Eq. [19] at the 21 points of M(2n e 180 ),…”

Section: Simulation Methodsmentioning

confidence: 99%

On the parameters affecting the sensitivity of MR measures of pressure with microbubbles

Dharmakumar

Plewes

Wright

2002

Magnetic Resonance in Med

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“…The first example addresses the application of the quadrupolar Carr-Purcell-Meiboom-Gill (QCPMG) [85,86] pulse sequence in combination with MAS to improve the sensitivity of quadrupolar-echo spectra for half-integer quadrupolar nuclei [34]. Calculation of QCPMG-MAS NMR experiments based on the pulse sequence in Fig.…”

Section: Fig 13mentioning

confidence: 99%

SIMPSON: A general simulation program for solid-state NMR spectroscopy

Bak

Rasmussen

Nielsen

2011

Journal of Magnetic Resonance

1,361

308

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A computer program for fast and accurate numerical simulation of solid-state NMR experiments is described. The program is designed to emulate a NMR spectrometer by letting the user specify high-level NMR concepts such as spin systems, nuclear spin interactions, rf irradiation, free precession, phase cycling, coherence-order filtering, and implicit/explicit acquisition. These elements are implemented using the Tcl scripting language to ensure a minimum of programming overhead and direct interpretation without the need for compilation, while maintaining the flexibility of a fullfeatured programming language. Basicly, there are no intrinsic limitations to the number of spins, types of interactions, sample conditions (static or spinning, powders, uniaxially oriented molecules, single crystals, or solutions), and the complexity or number of spectral dimensions for the pulse sequence. The applicability ranges from simple 1D experiments to advanced multiple-pulse and multiple-dimensional experiments, series of simulations, parameter scans, complex data manipulation/visualization, and iterative fitting of simulated to experimental spectra. A major effort has been devoted to optimize the computation speed using state-of-the-art algorithms for the timeconsuming parts of the calculations implemented in the core of the program using the C programming language. Modification and maintenance of the program are facilitated by releasing the program as open source software (General Public License) currently at http://nmr.imsb.au.dk. The general features of the program are demonstrated

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“…37,38 Examples of typical decay curves used to measure heteronuclear 13 C relaxation rates in RNA are shown in Figure 3. The relaxation times T 1 and T 2 directly related to spectral densities J(!)…”

Section: Nmr Studies Of Fast Molecular Motions By Relaxation Rate Meamentioning

confidence: 99%

NMR studies of dynamics in RNA and DNA by ¹³C relaxation

Shajani

Varani

2006

Biopolymers

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T he many functions of RNA in biology very often require this molecule to change its conformation in response to biological signals in the form of small molecules, proteins, or other nucleic acids. 1,2 Although structurally more conservative and therefore dynamically less diverse, local motions in DNA may facilitate protein recognition and allow enzymes acting on DNA to access functional groups on the bases that would otherwise be buried in Watson-Crick base pairs. 3 These statements make a compelling case to study the sequence dependent dynamics in nucleic acids; yet, residue-specific studies of nucleic acid dynamics are relatively few. Fortunately, NMR studies of dynamics of nucleic acids and nucleic acids-protein complexes are gaining increased attention, this spectroscopy being the only way to access information on a residue-by-residue basis. The questions that are being asked are how motion contributes to the affinity and specificity of biological interactions and what trajectories lead to the remarkably large conformational changes that are sometimes observed.RNA and DNA molecules experience motions on a wide range of time scales, ranging from rapid localized motions to much slower collective motions of entire helical domains. Figure 1 summarizes the NMR spectroscopic techniques commonly used to obtain information in each motional regime. Dynamics occurring on time scales that are considered ''fast'' in NMR spectroscopic studies (ps-ns) largely reflects bond librations associated with small amplitude and localized motions.

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Effects of Diffusion on Free Precession in Nuclear Magnetic Resonance Experiments

Cited by 5,921 publications

References 7 publications

On the parameters affecting the sensitivity of MR measures of pressure with microbubbles

On the parameters affecting the sensitivity of MR measures of pressure with microbubbles

SIMPSON: A general simulation program for solid-state NMR spectroscopy

NMR studies of dynamics in RNA and DNA by ¹³C relaxation

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Effects of Diffusion on Free Precession in Nuclear Magnetic Resonance Experiments

Cited by 5,921 publications

References 7 publications

On the parameters affecting the sensitivity of MR measures of pressure with microbubbles

On the parameters affecting the sensitivity of MR measures of pressure with microbubbles

SIMPSON: A general simulation program for solid-state NMR spectroscopy

NMR studies of dynamics in RNA and DNA by 13C relaxation

Contact Info

Product

Resources

About

NMR studies of dynamics in RNA and DNA by ¹³C relaxation