NMR Reference and Calculators
Dipolar Couplings
The static dipolar couping constants are calculated as follows1:
\( D_{ij} = - \frac{\mu_0 \gamma_i \gamma_j \hbar}{4 \pi r_{ij}^3} \) in rad/s
Isotopes | Distance (Å) | Dipolar Coupling (Hz) |
---|---|---|
1H-1H | ||
1H-13C | ||
1H-15N | ||
13C-13C |
NOE
The nuclear Overhauser effect (NOE) rates are calculated as follows:1
\( \sigma_{ij} = \frac{1}{10} \left( \frac{\mu_0 \gamma_i \gamma_j \hbar^2}{4 \pi r_{ij}^3} \right) \tau_c \) in s-1
Isotopes | Distance (Å) | τc (ns) | σi,j (s-1) | R2 (s-1) |
---|---|---|---|---|
1H-1H |
Tensors
The chemical shift tensors are defined as follows:2,3
Spin | δ (ppm)a | ηb | δiso (ppm)e | β (deg)c | Δδ / Δσ (ppm)d | δ11 / σzz (ppm)e | δ22 / σxx (ppm)e | δ33 / σyy (ppm)e |
---|---|---|---|---|---|---|---|---|
13C' (ave carbonyl) | 38 | |||||||
15N (ave backbone) | 19 | |||||||
1HN (ave backbone) | 8 |
J-couplings
The 3JHN-HA couplings in proteins can be calculated from the backbone φ angle as follows:4
\( ^3J_{HNHA} = A \cos^2(\phi - 60) + B \cos(\phi - 60) + C \) in Hz where A=6.51, B=-1.76 and C=1.60
φ (deg) | 3JHNHA (Hz) |
---|---|
Pulse Widths
The following are pulse calculations for a null at ν1 (ppm) when the pulse is applied at ν2
ν0H (MHz) | Channel | ν1 (ppm) | ν2 (ppm) | p90 (μs) | 0.5·p180 / p180 (μs) |
---|---|---|---|---|---|
References
- Cavanagh J, Fairbrother W, Palmer A, Skelton N. Protein NMR Spectroscopy: Principles and Practice. 2nd ed. Burlington, MA: Academic Press; 2007.
- Cornilescu G, Bax A. J Am Chem Soc. 2000 Oct;122(41):10143–10154.
- Saitô H, Ando I, Ramamoorthy A. Prog Nucl Magn Reson Spectrosc. 2010 Aug;57(2):181–228.
- Vuister G, Bax A. J Am Chem Soc. 1993;115:7772–7777.