BCMB/CHEM 8190
Answers, Problem Set 7
1a) B is appears to be on the midpoint of the A-C line +/- 0.05 Å
1b) A 50% occupied site 2.5 Å away gives the same NOE as a fully occupied site at 2.8 Å. The RMSD is
likely to be meaningless as it over constraints the postion of B
2)
C5
A2
T7
G4
C1
G8
A6
T3
3) Scaling in solids NMR is by a factor of (1-3cos2θ)/2 . This factor is zero at 54.7°, but 0.12 at
50°. The line would be 24 ppms wide or 24 X 500 X 0.25 or 3000 Hz at 125 MHz for 13C.
4) The magnitude is simply 94-73 = 11 Hz. The sign is positive. This is because one bond 1H15
N couplings are negative because of the negative gamma for 15N. A decrease in splitting must
come from a positive RDC (we assume all RDCs would be less than 94 Hz).