Hi Julia,
For a table 1 you should make a sensible split of the atoms over which you
calculate the mean. You might need to pool certain chains. There is not really
convenient tool for that because the choice depends on the biology/biochemistry
of your system. In practice, the easiest way is using the command line on just
the ATOM/HETATM records (atom_site in mmCIF format) in which you are
interested. Calculating the mean of a column of values is pretty
straightforward in awk.
Example for all atoms in a PDB file:
grep ^[HA][TE][OT][MA] 100d_final.pdb | cut -c 61-66 | awk '{sum = sum + $1}
END {print sum/NR}'
Or mmCIF:
grep [HA][TE][OT][MA] /DATA/pdb_redo/00/100d/100d_final.cif | awk '{sum = sum
+ $16} END {print sum/NR}'
HTH,
Robbie
From: CCP4 bulletin board <[email protected]> On Behalf Of Julia Griese
Sent: Thursday, November 26, 2020 15:11
To: [email protected]
Subject: [ccp4bb] Mean B factors and number of atoms (Refmac/baverage)
Hi all,
I’m writing a Table 1 and getting a bit confused when it comes to number of
atoms and average B factors. Refmac has these in the table in the GUI, but the
atom numbers in that table seem to include H, and I’m only interested in non-H
atoms.
As an example, the PDB file says:
REMARK 3 NUMBER OF NON-HYDROGEN ATOMS USED IN REFINEMENT.
REMARK 3 ALL ATOMS : 8351
Which agrees with the total count minus TER cards, so that seems to be correct.
However, the table in the GUI for this refinement run looks like this:
Chain mean B<br/>(No. atoms)
AAA
41.4( 2193 )
BBB
57.7( 3499 )
CCC
57.7( 3499 )
DDD
41.7( 2212 )
EEE
60.3( 923 )
FFF
60.6( 920 )
aaa
55.4( 1323 )
ddd
56.0( 1346 )
GGG
34.3( 1 )
GaG
42.7( 1 )
GbG
34.3( 1 )
GcG
40.1( 1 )
GdG
40.6( 1 )
GeG
35.8( 1 )
GfG
34.2( 1 )
GgG
43.2( 1 )
HHH
40.6( 136 )
You can easily see that this adds up to a lot more than 8351 atoms. The numbers
for the G chain (metal ions) and the H chain (water) are correct, whereas the
numbers for the macromolecule chains appear to include H. (If I run a
refinement with H output to the final file, I get approximately the same number
of atoms in total, though not quite.) But what I’m really interested in is of
course the number of non-H atoms per chain. I don’t want to count all the atoms
by hand…
I used to use baverage to calculate average B factors (and that would also give
me the number of non-H atoms per chain), but can’t get that to work on the
command line and can’t find it in the i2 GUI. I don’t have the old ccp4i
anymore.
So if anyone could either tell me how to get baverage to work, or if there is
another way to extract these numbers, I would much appreciate it!
Best,
Julia
--
Dr. Julia Griese
Assistant Professor
Department of Cell and Molecular Biology
Uppsala University
BMC, Box 596
SE-75124 Uppsala
Sweden
email: [email protected]<mailto:[email protected]>
phone: +46-(0)18-471 4043
http://www.icm.uu.se/structural-biology/griese-lab/
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