Thesis Title: Subtitle - NMR Spectroscopy Research Group

1.2 Paramagnetic NMR. 7
lead to large deviations between measurement and prediction. PCSs are less sensitive to the
difference between the crystal model and the solution structure. The focus in my PhD has been on
using PCS to study proteins and their interactions.
Figure 1.4 The PCS is less sensitive than RDC to small discrepancies
between X-ray and solution structure. A large change in the orientation
of the N-H vector will considerably affect the calculation of the RDC
(equation (1.2) and Figure 1.2.b). On the other hand, the PCS will be
less affected as the relative position of the hydrogen with respect to the
tensor frame is almost unchanged when PCS are measurable (d > 10 Å).
1.2.2 The pseudocontact shift as a restraint
PCSs can be calculated using equation (1.1) if the magnitude (two parameters: Δχax and
Δχrh, Figure 1.5.a), location (three Cartesian coordinates x, y and z, Figure 1.5.b) and orientation
(three Euler angles α, β and γ, Figure 1.5.c) of the Δχ-tensor are known, and if a structure is
available. The paramagnetic chemical shift of a spin located close to the paramagnetic center is
broadened beyond detection due to PRE, and consequently, its PCS cannot be observed. The cutoff
radius is typically about 10 Å.
The NMR resonances have first to be assigned in order to measure PCSs. Three kinds of
assignment have to be distinguished (Figure 1.6):
(i) The assignment of the diamagnetic NMR spectrum: it is routinely performed with
conventional sequential assignment methods using one or a combination of COSY,
TOCSY, NOESY NMR and triple resonance experiments.