Related Experiment Video
Updated: Jun 30, 2026
09:25
NMR 15N Relaxation Experiments for the Investigation of Picosecond to Nanoseconds Structural Dynamics of Proteins
Published on: November 1, 2024
Transverse NMR relaxation in magnetically heterogeneous media
1Department of Physics, Yale University, New Haven, CT 06520, USA. dima@alum.mit.edu
Journal of Magnetic Resonance (San Diego, Calif. : 1997)
|October 1, 2008
Summary
This study analyzes Nuclear Magnetic Resonance (NMR) signals in heterogeneous media. We show how NMR spectra can quantify Larmor frequency variations and correlation lengths in materials like human blood.
Area of Science:
- Physics
- Materials Science
- Biophysics
Background:
- Nuclear Magnetic Resonance (NMR) is sensitive to molecular motion and local environment.
- Heterogeneous Larmor frequencies in permeable media complicate NMR signal interpretation.
- Understanding mesoscopic relaxation is key for material characterization.
Purpose of the Study:
- To develop a method for quantifying Larmor frequency heterogeneity in permeable media using NMR.
- To relate NMR spectral lineshape to spin-carrier diffusion and Larmor frequency correlations.
- To apply this method to analyze human blood spectra.
Main Methods:
- Analysis of transverse relaxation in heterogeneous Larmor frequency fields.
- Relating NMR spectral lineshape to correlation functions of spatially varying Larmor frequency.
- Numerical simulations to validate theoretical predictions.
- Application to quantify human blood NMR spectra.
Main Results:
- Demonstrated a method to determine correlation length and Larmor frequency variance from NMR spectra.
- Showed that mesoscopic transverse relaxation is influenced by diffusive spin motion.
- Successfully applied the method to quantify human blood spectra.
Conclusions:
- NMR spectroscopy can effectively characterize Larmor frequency distributions in heterogeneous media.
- The developed approach provides insights into spin dynamics and material properties.
- This method offers a new tool for analyzing complex biological fluids like blood.
![Measuring the Spin-Lattice Relaxation Magnetic Field Dependence of Hyperpolarized [1-13C]pyruvate](/_next/image?url=https%3A%2F%2Fcloudfront.jove.com%2FCDNSource%2Fteasers%2F59399.jpg&w=3840&q=50)
Related Concept Videos
01:23Atomic Nuclei: Nuclear Relaxation Processes
In the absence of an external magnetic field, nuclear spin states are degenerate and randomly oriented. When a magnetic field is applied, the spins begin to precess and orient themselves along (lower energy) or against (higher energy) the direction of the field. At equilibrium, a slight excess population of spins exists in the lower energy state. Because the direction of the magnetic field is fixed as the z-axis, the precessing magnetic moments are randomly oriented around the z-axis. This...
01:28Atomic Nuclei: Types of Nuclear Relaxation
Nuclear relaxation restores the equilibrium population imbalance and can occur via spin–lattice or spin–spin mechanisms, which are first-order exponential decay processes.
In spin–lattice or longitudinal relaxation, the excited spins exchange energy with the surrounding lattice as they return to the lower energy level. Among several mechanisms that contribute to spin–lattice relaxation, magnetic dipolar interactions are significant. Here, the excited nucleus transfers energy to a nearby...
In spin–lattice or longitudinal relaxation, the excited spins exchange energy with the surrounding lattice as they return to the lower energy level. Among several mechanisms that contribute to spin–lattice relaxation, magnetic dipolar interactions are significant. Here, the excited nucleus transfers energy to a nearby...
01:05Atomic Nuclei: Magnetic Resonance
The number of nuclear spins aligned in the lower energy state is slightly greater than those in the higher energy state. In the presence of an external magnetic field, as the spins precess at the Larmor frequency, the excess population results in a net magnetization oriented along the z axis. When a pulse or a short burst of radio waves at the Larmor frequency is applied along the x axis, the coupling of frequencies causes resonance and flips the nuclear spins of the excess population from the...
01:14NMR Spectrometers: Resolution and Error Correction
When magnetic nuclei in a sample achieve resonance and undergo relaxation, the signal detected in NMR is an approximately exponential free induction decay. Fourier transform of an exponential decay yields a Lorentzian peak in the frequency domain. Lorentzian peaks in an NMR spectrum are defined by their amplitude, full width at half maximum, and position, where the peak width is governed by the spin-spin relaxation time alone. In real experiments, however, the applied magnetic field is rendered...
01:02¹H NMR: Interpreting Distorted and Overlapping Signals
Spin systems where the difference in chemical shifts of the coupled nuclei is greater than ten times J are called first-order spin systems. These nuclei are weakly coupled, and their chemical shifts and coupling constant can generally be estimated from the well-separated signals in the spectrum.
As Δν decreases and the signals move closer, the doublets appear increasingly distorted. The intensities of the inner lines increase at the cost of those of the outer lines as the signals are slanted or...
As Δν decreases and the signals move closer, the doublets appear increasingly distorted. The intensities of the inner lines increase at the cost of those of the outer lines as the signals are slanted or...
01:17NMR Spectrometers: Radiofrequency Pulses and Pulse Sequences
A pulse is a short burst of radio waves distributed over a range of frequencies that simultaneously excites all the nuclei in the sample. Upon passing a radio frequency pulse along the x-axis, the nuclei absorb energy corresponding to their Larmor frequencies and achieve resonance. This shifts the net magnetization vector from the z-axis toward the transverse plane. This angle of rotation of the magnetization vector, or the flip angle, is proportional to the duration and intensity of the pulse.