Dear Pavel,
Stressing Ethan's point about TLS refinement becoming practical with
Refmac implementation, Winn et al. (2001) Acta D, 57, 122-133 (I know
you like references) states:
Derivatives of the residual with respect to the TLS parameters are
expanded in terms of the derivatives with respect to individual
anisotropic U values, which in turn are calculated using a fast
Fourier transform technique. TLS refinement is therefore fast and can
be used routinely.
Best wishes
Roberto
On 15 Sep 2010, at 19:34, Pavel Afonine wrote:
Dear George,
a small correction if I may:
However
you will not find TLS in the index, because the credit for
implementing this very useful concept should be given to
Martin Winn, Garib and Ethan, long after the current version
of SHELXL (and its manual) were released in 1997.
Acta Cryst. (1985). A41, 426-433
Restrained structure-factor least-squares refinement of protein
structures using a vector processing computer
I. Haneef, D. S. Moss, M. J. Stanford and N. Borkakoti
Abstract: A least-squares refinement program RESTRAIN has been
developed, which is capable of refining macromolecular structures
using structure amplitudes, phases from isomorphous replacement
or anomalous scattering and pseudo-energy restraints. In addition to
positional parameters and isotropic temperature factors, anisotropic
mean-square displacements may be refined either as individual atomic
U tensors or as TLS tensors applied to groups of atoms. Anharmonic
effects may be handled by coupling together occupancies to enable
the electron density of an atomic group to be distributed over more
than one subsite. A novel way of restraining groups of atoms to be
planar has been developed that does not require dummy atoms and does
not restrain the plane to lie in its current orientation.
One can find other, earlier programs, but they are small molecule
specific.
Regards,
Pavel.
---
Dr. Roberto Steiner
Randall Division of Cell and Molecular Biophysics
New Hunt's House
King's College London
Guy's Campus
London, SE1 1UL
Phone +44 (0)20-7848-8216
Fax +44 (0)20-7848-6435
e-mail [email protected]
