conformation about an N-glycosylic bond is synor anti(Figure 11.9). This information lends support to
the quantitative analysis of three-bond (or vicinal) scalar coupling constants,^3 J.
Inter-strand hydrogen bonding may be detected indirectly by the observation of nOes among imino,
amino and adenine H2 protons. If^15 N-labelled bases are present, then the hydrogen bond can be detected
directly through measurement of one-bond and two-bond inter-residue^1 H–^15 N couplings.^12
436 Chapter 11
Figure 11.9 An illustration of the through-space connections sought to confirm: (a) the sugar pucker of the furanose
ring or (b) the arrangement of the N-glycosylic bond. The numbers shown on the arrows are in Å.
A short distance leads to a large NOESY cross-peak
Figure 11.8 An example of a ‘nOe-walk’ for the sequential assignment of^1 H resonances. (a) The red arrows indicate
key nOe connections. (b) The CH 3 (Me) to H6/H8 region of the (A) TOCSY and (B) NOESY spectrum for
the 16 base pair DNA/RNA hybrid (Figure 11.6). The ‘walk’ A 6 H8 to T 7 Me to T 7 H6 to T 8 Me to T 8 H6 to
T 9 Me is shown