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I have interests in several areas of protein dynamics, particularly
with respect to the interpretation of X-ray diffraction data.
- TLS refinement
- Normal modes
- Analysis of anisotropic U factors
See developing pages
on TLS refinement.
TLS parameters describe the translation, libration and screw-rotation of
a rigid body, and represent the simplest collective motion of groups
of atoms. This motion is anisotropic, but is described by far fewer
parameters than treating individual atoms anisotropically. Thus, refining
TLS parameters against X-ray data rather than individual anisotropic displacement
parameters (U's) requires fewer refinement parameters, and is feasible at
Refinement of TLS parameters has been implemented in the refinement program
REFMAC, and is available in the current release. REFMAC documentation
can be found
here. There is also some background
information on TLS.
Normal modes represent another type of collective motion. Refinement of
parameters modelling such collective motions is planned.
Analysis of anisotropic U factors
At high enough resolution, individual anisotropic displacement parameters (U's)
can be refined. The result of such refinement is typically a large quantity of
numbers plus some ORTEP figures! The CCP4 program
ANISOANL provides a number of utilities for interpreting the results of
individual U factor refinement:
- Attempt to fit TLS parameters to refined U values, for given rigid
groups, as is done routinely for small molecules.
- Assess Rosenfield's rigid-body postulate, which states that for
two atoms belonging to the same rigid-body (not
necessarily bonded), the projections of the anisotropic displacement
parameters along the interatomic vector should be equal.
- Produce plots of equivalent isotropic B values, anisotropy,
and radial and tangential projections of U.
The following references give examples of the use of ANISOANL:
Last modified: Fri May 26 16:17:00 BST 2000