Table 3. Measured NMR and MD-Predicted 3J Couplings (hertz) at 278 K for Each Force Field with the A-Form (C3′-endo/anti) Starting Structure.
| torsion | NMR scalar couplinga | parm99b | parm99χb | parm99TORb,c | A-formd | angle (deg)e |
|---|---|---|---|---|---|---|
| C1 H1′–H2′ | ≤1.0 | 5.6 | 0.7 | 0.5 (0.6) | 0.0–1.0 | 91–104 |
| C2 H1′–H2′ | ≤1.0 | 4.6 | 0.5 | 0.5 (0.7) | 0.0–1.0 | 91–104 |
| C3 H1′–H2′ | ≤1.0 | 3.6 | 0.6 | 0.5 (0.6) | 0.0–1.0 | 91–104 |
| C4 H1′–H2′ | 2.6 | 6.7 | 1.5 | 1.8 (1.9) | 0.0–1.0 | 116 |
| C1 H2′–H3′ | 3.6 | 5.1 | 4.4 | 4.3 (4.3) | 3.8–4.8 | 50 |
| C2 H2′–H3′ | 4.3 | 5.0 | 4.4 | 4.4 (4.3) | 3.8–4.8 | 42 |
| C3 H2′–H3′ | 4.7 | 5.1 | 4.5 | 4.4 (4.4) | 3.8–4.8 | 38 |
| C4 H2′–H3′ | 4.9 | 5.1 | 4.7 | 4.9 (4.8) | 3.8–4.8 | 36 |
| C1 H3′–H4′ | 8.7 | 5.2 | 7.7 | 7.8 (7.8) | 7.6–8.6 | f |
| C3 H3′–H4′ | 8.8 | 5.8 | 7.7 | 7.9 (7.9) | 7.6–8.6 | f |
| C4 H3′–H4′ | 7.2 | 3.6 | 7.1 | 6.7 (7.0) | 7.6–8.6 | 205 |
| C2 H4′–H5′ | ≤1.0 | 2.5 | 2.6 | 2.8 (3.0) | 1.6–2.6 | f |
| C3 H4′–H5′ | 2.1 | 2.3 | 2.5 | 2.8 (2.8) | 1.6–2.6 | 63 |
| C4 H4′–H5′ | 2.0 | 2.3 | 2.5 | 3.7 (2.9) | 1.6–2.6 | 62 |
| C2 H4′–H5″ | ≤1.0 | 4.9 | 3.9 | 3.2 (3.1) | 2.9–4.4 | f |
| C3 H4′–H5″ | ≤1.0 | 3.8 | 3.5 | 3.1 (3.2) | 2.9–4.4 | f |
| C4 H4′–H5″ | 1.4 | 4.3 | 3.8 | 3.4 (3.5) | 2.9–4.4 | 292 |
| C1 H3′–C2 P | 8.8 | 5.1 | 8.7 | 7.1 (8.3) | 6.9–9.4 | 1 |
| C2 H3′–C3 P | 9.3 | 5.6 | 9.0 | 3.8 (5.2) | 6.9–9.4 | 3 |
| C3 H3′–C4 P | 9.3 | 5.8 | 8.6 | 4.7 (5.0) | 6.9–9.4 | 3 |
| C2 P–C2 H5′ | 3.8 | 3.1 | 3.8 | 4.2 (5.0) | 3.4–6.6 | 309 |
| C3 P–C3 H5′ | 3.9 | 3.8 | 3.8 | 3.7 (4.1) | 3.4–6.6 | 309 |
| C4 P–C4 H5′ | 3.8 | 2.7 | 3.6 | 6.2 (4.3) | 3.4–6.6 | 309 |
| C2 P–C2 H5″ | 1.2 | 3.0 | 2.3 | 2.6 (2.4) | 0.9–1.9 | 72 |
| C3 P–C3 H5″ | 0.5 | 2.4 | 2.2 | 2.5 (2.2) | 0.9–1.9 | f |
| C4 P–C4 H5″ | 1.1 | 3.3 | 2.4 | 4.2 (3.7) | 0.9–1.9 | 74 |
a
The error limit is ±0.5 Hz for scalar couplings of >1.0 Hz.
b
Marino et al.54 equations (Table S13 of the Supporting Information) were used to calculate 3J couplings for each time point of the MD trajectory, and then the couplings were averaged.
c
Parentheses indicate MD predicted 3J scalar coupling values calculated from 0 to 770 ns. After 770 ns, C1 intercalates between C3 and C4.
d
Range of values measured from four CC doublets in PDB entry 1QC0.57
e
Torsion angles determined via NMR (Table S13 of the Supporting Information). For scalar couplings of <1.0 Hz, an angle range covering 0–1 Hz is shown.
f
Could not be calculated with Marino et al.54 equations (Table S13 of the Supporting Information).