hi Alex,
a few points:
we used this approach to enforce our confidence in predicting of a 6 res
segment and explore the possible uncertainty in the environment. I.e.
the analysis was aiming to explore the question, how far one can extend
selecting the loop environment and still predicting a similar
conformation? since the conclusion was, that the shorter loops (6, 7N,
7C, 8N 8C .. )are returning the same conformation and at some loop
length it got drastically worse (random) any of those shorter
consistent loops will be suitable for a final model.
Unfortunately the details of this extensive study are not published,
just a short report about reinforcing our prediction with NMR data and
vice versa for this special case.
More importantly: Modeller scores are -essentially- a cumulative summary
of the restraints deviations in a probabilistic form. Conversely the
scores depend on the set of restraints selected, which is directly
correlated with the number of atoms involved. It means that scores can
be compared if you select the same loop to optimize but not among
different loops. I.e. the scores from separate modeling of 6,7,8.. res
long loops are not comparable.
Once the best loop or a couple of best loops are selected energetically
(i.e. modeller score-wise) from each loop prediction (same loop selected
for optimization), these "best" loops from different sets of loop
prediction (involving different loop lengths) were compared
geometrically, (RMS-wise) for consistency.
another note: 6-10 hour sounds slow even if you use one computer only.
We used SGI unix and red hat linux on pc, maybe the MAC OS is not
optimal for this. Normally one loop optimization is around 1 minute or
so, i.e. 200 runs is ~2+ hours. But it maybe normal given the compiler
and code optimization differences among various platforms. However I
would expect that a computational lab has more than 1 processor: if you
submit them in parallel to several machine you can drastically reduce
the time required for these calculation. E.g. in our case we can
conduct a calculation like this in 1 minute. The only parameter you need
to set differently in each loop top file is the random number seed
RAND_SEED.
Andras
--
,
Andras Fiser, PhD # phone: (212) 327 7216
The Rockefeller University # fax: (212) 327 7540
Box 270, 1230 York Avenue # e-mail:fisera AT rockefeller.edu
New York, NY 10021-6399, USA # http://salilab.org/~andras