On Wednesday 15 September 2010 12:34:21 pm 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
>
> One can find other, earlier programs, but they are small molecule specific.
The full early history of TLS is deeper than that.
It is reviewed at least briefly in
Driessen et al (1989) J. Appl. Cryst (1989). 22, 510-516
As to applying TLS to macromolecules, RESTRAIN was pre-dated by CORELS
Sussman et al (1977) Acta Cryst. A33, 800-804
although the treatment of TLS was added some time in the early 80s;
I'm not sure exactly when.
And there is nothing in the original theoretical formulation of TLS by
Schomaker & Trueblood (1968) Acta Cryst B24, 63-76
"On the rigid-body motion of molecules in crystals"
that is small-molecule specific. In fact we went back to this as the
basis for TLSMD analysis (as distinct from refinement).
Note that George is pointing to implementation rather than to theory.
I think it's fair to say that the improvement of computer hardware
and the introduction of FFT-based refinement coincided to make application
of TLS to refining macromolecules really practical only after it was
introduced in refmac. I can't find the exact quote at the moment,
but I recall coming across an old meeting abstract announcing that recent
computer advances allowed the use of TLS to analyze structures as large
as 19 atoms!!! Computation had indeed advanced a bit by the time CORELS
and RESTRAIN were written, but still the contemporary state of both
hardware and software limited what could be done.
Ethan
--
Ethan A Merritt
Biomolecular Structure Center, K-428 Health Sciences Bldg
University of Washington, Seattle 98195-7742
