The Measurement of Diffusion Using Pulsed Nmr
نویسنده
چکیده
Pulsed NMR is the most convenient and powerful technique for measuring diffusion, when it is applicable. Hahn (1) in a seminal paper laid the foundations of the technique. He showed that for a nuclear spin system that obeyed the Bloch equations (taking small liberties with exact details), a 9O.y T 180, RF pulse sequence produced a free induction decay (FID) and an echo, as pictured in Figure 1. The FID had an initial amplitude A> and a shape f (t) that was the Fourier transform of the frequency distribution function g(Aa>) that described the magnetic field distribution over the sample [f(0) = 1]. The echo had a shape A, (2r)f(t-2T), and peaked at t = 2T with a value
منابع مشابه
Pulsed-field-gradient measurements of time-dependent gas diffusion.
Pulsed-field-gradient NMR techniques are demonstrated for measurements of time-dependent gas diffusion. The standard PGSE technique and variants, applied to a free gas mixture of thermally polarized xenon and O2, are found to provide a reproducible measure of the xenon diffusion coefficient (5.71 x 10(-6) m2 s-1 for 1 atm of pure xenon), in excellent agreement with previous, non-NMR measurement...
متن کاملMeasurement of diffusion constants for nucleic acids by NMR.
Pulsed field-gradient NMR experiments can be used to measure the diffusion constants of nucleic acids. The diffusion constants measured in this way for double-helical DNAs of defined length agree well both with theory and with measurements done using other techniques. When applied to RNAs, this experiment easily distinguishes duplex RNAs from RNA hairpins and thus it can solve one of the perenn...
متن کاملNMR measurement of small-molecule diffusion in PVA hydrogels: a comparison of CONVEX and standard PGSE methods
Hydrogels are biocompatible polymeric materials that are becoming increasingly important in biomedical applications, such as drug delivery and tissue engineering. Understanding of small-molecule diffusion in these systems is important in the contexts of controlled drug release; transport of nutrients (e.g., O2 and growth factors) into the gel; and transport of cellular waste out of the gel. In ...
متن کاملRapid measurement of three-dimensional diffusion tensor.
In this article, the authors demonstrate a rapid NMR method to measure a full three-dimensional diffusion tensor. This method is based on a multiple modulation multiple echo sequence and utilizes static and pulsed magnetic field gradients to measure diffusion along multiple directions simultaneously. The pulse sequence was optimized using a well-known linear inversion metric (condition number) ...
متن کاملNMR Chromatography: Molecular Diffusion in the Presence of Pulsed Field Gradients in Analytical Chemistry Applications
Nuclear magnetic resonance (NMR) spectroscopy is an excellent analytical tool for precise structural characterization of organic and bio-molecules. Though NMR is often used to characterize a single compound in solution, emerging experimental methods using pulsed-field-gradients (PFGs) allow structural dynamic characterization of several compounds, simultaneously in the same solution. NMR as a c...
متن کامل