Molecular dynamics of solid cortisol studied by NMR
| Autor: | E.R. ANDREW, M. KEMPKA, A. SZYCZEWSKI |
|---|---|
| Rok vydání: | 1996 |
| Předmět: |
Chemistry
Pulse (signal processing) media_common.quotation_subject Relaxation (NMR) Biophysics Analytical chemistry Second moment of area Condensed Matter Physics Asymmetry Molecular dynamics Proton NMR Asymmetric distribution Crystallite Physical and Theoretical Chemistry Molecular Biology media_common |
| Zdroj: | Molecular Physics. 88:605-610 |
| ISSN: | 0026-8976 |
| DOI: | 10.1080/00268979609482440 |
| Popis: | Polycrystalline cortisol (hydrocortisone; 11β,17α,21-trihydroxy-4-preg- nene-3,20-dione; C21H30O5) has been investigated by continuous and pulse proton NMR methods between 78 and 400 K at Larmor frequencies of 7, 25 and 60 MHz. A reduced value of second moment was found above 90 K and is ascribed to reorientation of two methyl groups. A single asymmetric minimum was found in the temperature dependence of the spin–lattice relaxation times and this also is attributed to reorientation of two methyl groups. The asymmetry suggests an asymmetric distribution of correlation times of the motion. Using the Cole–Davidson distribution, the best computer fit yields the following parameters characterizing the motion: E a = 11·8 ± 0·1 kJ mol-1, τ0 = 4·6 ±0·4) x 10-13s, distribution parameter δ = 0·62. |
| Databáze: | OpenAIRE |
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