Local diffusion in paramagnetic solutions by NMR relaxometry at one frequency.

Area of Science:

• Nuclear Magnetic Resonance (NMR) Spectroscopy
• Chemical Physics
• Materials Science

Background:

• Diffusion coefficients are crucial for understanding molecular interactions and dynamics.
• Measuring diffusion coefficients noninvasively can be challenging, especially for paramagnetic species.
• Existing methods may require specialized equipment or complex procedures.

Purpose of the Study:

• To develop a straightforward, noninvasive method for determining the relative diffusion coefficient (D) of paramagnetic and diamagnetic molecules.
• To utilize standard NMR relaxation times (T1 and T2) for diffusion coefficient calculation.
• To validate the proposed method using a gadolinium(III)-based contrast agent.

Main Methods:

• Introduced longitudinal relaxivity (r1) and mixed relaxivity (rmix) derived from T1 and T2 relaxation times.
• Established a relationship between the diffusion coefficient (D) and the derived relaxivities: D is proportional to (rmix - r1)^(-2/3) and rmix^(-1).
• Employed standard NMR spectrometers and imagers for measurements.

Main Results:

• Demonstrated that the relative diffusion coefficient (D) can be accurately determined from relaxivity values.
• The proportionality factors in the derived equations are easily determinable.
• The method proved effective and was validated with a Gd(III) contrast agent.

Conclusions:

• The developed NMR-based method provides a simple and noninvasive approach to measure relative diffusion coefficients.
• This technique is applicable to standard NMR instrumentation, enhancing accessibility.
• The findings have implications for studying molecular diffusion in various chemical and biological systems.