Biomedical Engineering Reference
In-Depth Information
Figure 8.1
Angular dependence of a static RDC in the PAS. Upper part: orientation
of a internuclear vector in the PAS. Lower part: angular dependence of a
static RDC. The value is encoded from blue (negative) to red (positive).
From left to right: the used tensor is axially symmetric (left) or presents
increasing rhombicity (middle, right). A
xx
, A
yy
and A
zz
represent the
directions of the alignment tensor axes.
respect to the axes of an alignment frame that is attached to the molecule
(Figure 8.1).
8.3 Residual Dipolar Couplings for Structure
Determination
Most publications using RDCs measured in biomolecules have exploited their
power as structural constraints, implicitly assuming a so-called static
description that supposes the absence of differential dynamics within the
framework of the molecular or alignment frame (the angular terms in eqn (8.2)
are interpreted in terms of a single average orientation). While this assumption
ignores the averaging over the population of conformational sub-states that
one would expect to be sampled on timescales up to the millisecond, early data
from diverse proteins indicated that a very good reproduction of experimental
data could be found by comparison with a known high-resolution static
structure.
9
Such observations implied that the level of dynamics in these
proteins in solution is either minimal, or averaged in such a way as to be in
