Revisiting spin–lattice relaxation time measurements for dilute spins in high-resolution solid-state NMR spectroscopy
| Autor: | Jun Li, Riqiang Fu, Jingyu Cui, Xinhua Peng |
|---|---|
| Rok vydání: | 2016 |
| Předmět: |
Nuclear and High Energy Physics
Biophysics 02 engineering and technology 010402 general chemistry Sensitivity and Specificity 01 natural sciences Biochemistry Molecular physics Solomon equations Spin–spin relaxation Magnetization Carbon-13 Magnetic Resonance Spectroscopy Isoleucine Condensed matter physics Spins Chemistry Relaxation (NMR) Spin–lattice relaxation Reproducibility of Results Signal Processing Computer-Assisted 021001 nanoscience & nanotechnology Condensed Matter Physics 0104 chemical sciences Solid-state nuclear magnetic resonance Heteronuclear molecule Spin Labels Powders 0210 nano-technology Algorithms |
| Zdroj: | Journal of Magnetic Resonance. 268:107-113 |
| ISSN: | 1090-7807 |
| DOI: | 10.1016/j.jmr.2016.05.004 |
| Popis: | Numerous nuclear magnetic resonance (NMR) measurements of spin-lattice relaxation times (T1S) for dilute spins such as (13)C have led to investigations of the motional dynamics of individual functional groups in solid materials. In this work, we revisit the Solomon equations and analyze how the heteronuclear cross relaxation between the dilute S (e.g. (13)C) and abundant I (e.g. (1)H) spins affects the measured T1S values in solid-state NMR in the absence of (1)H saturation during the recovery time. It is found theoretically that at the beginning of the S spin magnetization recovery, the existence of non-equilibrium I magnetization introduces the heteronuclear cross relaxation effect onto the recovery of the S spin magnetization and confirmed experimentally that such a heteronuclear cross relaxation effect results in the recovery overshoot phenomena for the dilute spins when T1S is on the same order of T1H, leading to inaccurate measurements of the T1S values. Even when T1S is ten times larger than T1H, the heteronuclear cross relaxation effect on the measured T1S values is still noticeable. Furthermore, this cross relaxation effect on recovery trajectory of the S spins can be manipulated and even suppressed by preparing the initial I and S magnetization, so as to obtain the accurate T1S values. A sample of natural abundance l-isoleucine powder has been used to demonstrate the T1S measurements and their corresponding measured T1C values under various experimental conditions. |
| Databáze: | OpenAIRE |
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