Check out the letters in the Dec 2007 edition of Acta D. There is
lively discussion even among the experts (and while I recall no
mention of angels in this discussion, there IS a reference to Winnie
the Pooh).
Acta Cryst. (2007). D63, 1274-1281
Acta Cryst. (2007). D63, 1282-1283
Some people believe 0.02 Å deviation from ideality is reasonable,
based on
the accuracy of the dictionary values of bond lengths and angles;
others
consider that to be "too sloppy" and a way to artificially deflate
Rfactors.
I seem to have detected a tendency in the literature to aim for
about 0.01
Å deviation. The new refinement program phenix.refine, which is
supposed
to optimize weighting between X-ray terms and stereochemical
constraints
automatically, seems to settle in at quite conservative values,
such as
0.005 Å, whereas with refmac, I can't seem to get the geometry any
more
ideal than 0.005 Å even if I try to idealize a structure in the
absence of
X-ray data.
So, like you, I am a bit confused, and wouldn't mind hearing more
from the
experts.
All the best,
Bill
yang li wrote:
Dear All,
I am very sorry to involve you into such insignificance
discussion,
I
have reached agreement
with Prof Gerard, please stop talking about things beyond science,
thanks!
I read a book today, which said "A refined model should
exhibit rms
deviations of no more
than 0.02A for bond length and 4 for bond angels", I just wonder
about the
standard of the
bond length and the bond angel. I think most of you have read similar
words!
But maybe I
didnot express clearly and made some phrasal mistakes.
At last, happy new year to you all--though very late!
Sincerely!
Yang Li
------------------------------------------------------------------------
---------------
Patrick J. Loll, Ph. D. (215) 762-7706
Associate Professor FAX: (215) 762-4452
Department of Biochemistry & Molecular Biology
Director, Biochemistry Graduate Program
Drexel University College of Medicine
Room 10-102 New College Building
245 N. 15th St., Mailstop 497
Philadelphia, PA 19102-1192 USA
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