Table 2.
Contribution of homonuclear F-F dipolar couplings to the experimental 19F MAS NMR lineshapes of crystalline 5F-DL-Trp (Lform), 5F-LTrpH2O, and 6F-DL-Trp.
| Compound | Closest F-F distance (Å) | F-F dipolar coupling (Hz) | δ11 (ppm) |
δ22 (ppm) |
δ33 (ppm) |
δσ (ppm) |
η |
|---|---|---|---|---|---|---|---|
| 5F-DL-Trp (L-form) | 4.5 | −1179.0 | −1.6±0.2 | −67.2±0.1 | −78.5±0.1 | 47.5±0.2 | 0.2±0.0 |
| - | −1.7±0.2 | −67.4±0.1 | −78.2±0.1 | 47.4±0.2 | 0.2±0.0 | ||
| 5F-L-Trp·H2O | 4.6 | −1082.4 | 6.9±0.1 | −60.0±0.1 | −87.1±0.1 | 53.6±0.1 | 0.5±0.0 |
| - | 6.9±0.1 | −60.0±0.1 | −87.0±0.1 | 53.6±0.1 | 0.5±0.0 | ||
| 6F-DL-Trp | 2.9 | −4134.8 | 11.8±0.3 | −45.1±0.2 | −96.6±0.2 | 55.1±0.3 | 0.9±0.0 |
| 10.8±0.1 | −45.2±0.1 | −95.6±0.1 | 54.2±0.1 | 0.9±0.0 |
*
Experimental chemical shift tensor components and F-F homonuclear dipolar coupling contributions were extracted using SIMPSON. 19F MAS NMR simulations for the 19F crystals were carried out at 14.1 T ( 19F Larmor frequency of 564.278 MHz) and a MAS frequency of 11 kHz. 19F MAS NMR simulations for the clusters generated from 19F- substituted on non-F Tryptophan crystals were carried out at 9.4 T (376.476 MHz 19F Larmor frequency) and a MAS frequency of 7 kHz.