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Dear Marilyn,
If you place 10 numbers after the decimal, the CRYST record will be more
precise but not necessarily more accurate. The accuracy of the value
51.1 is 0.05/51.1=0.1%. On a synchrotron beamline the accuracy in the
a,b,c parameters is mostly affected by the accuracy in the mean value of
the wavelength used. The latter can be around 0.01% but you should
probably check it with the beamlime responsible. Another factor
affecting a,b,c could be the distance to the detector (e.g. large
crystal of irregular shape and a short distance). There are many other
factors of hopefully lower significance.
With best regards,
Victor
Hi all,
I have a reviewer challenging the number of digits to the right of the
decimal point that I have reported in a submitted manuscript. I had
reported 3 digits to the right, frankly because that is what most of
the programs I use report and the PDB coordinate file reports 3 digits
to the right of the decimal in the CRYST1 record. The reviewer doubts
that the value is accurate to that many digits, and suggested
reporting to the tenth of an Angstrom. In corresponding with the PDB,
they allow 3 digits to the right of the decimal, but even if one gives
the PDB, say 51.1 A as an axis, the CRYST1 record will be padded and
will appear as 51.100A.
So my question is .... how does one determine what is a valid accuracy
or precision in unit cell axes? To be honest, I'm not sure what all
the numbers are, and how many significant digits they have, that are
used in calculating unit cell axes.
In my particular case, I have data to 1.73 A, synchrotron radiation,
0.41 degree mosacity. All unit cells are less than 115 A.
Thanks for any insight.
Regards,
Marilyn
Marilyn D. Yoder
Division of Cell Biology & Biophysics
School of Biological Sciences
University of Missouri-Kansas City
5007 Rockhill Rd.
Kansas City, MO 64110-2499
phone 816-235-1503
fax 816-235-1503
