Re: [ccp4bb]: Structure Resolution!

[Bart Hazes <bhazes@ualberta.ca>]

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On Sat, 7 Sep 2002, Rajeswari Edayathumangalam wrote:

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> Hi Everyone,
> I followed a discussion a while ago as to whether (and at what
> resolution) should one cut off their data. I am still somewhat confused.
> Following the discussion, I revisited some of my data and I find that
> the data is good to almost 2.6 A, while I am using 2.8 A as my cut-off
> based on the criteria of I/sigma > 2.0 and R-symm < 40.0 % , the
> standards used in our lab.
> I am already past 3 rounds of refinement and manual rebuilding using
> data to 2.8A. Can I, at this point, suddenly take data all the way to
> 2.6 A and proceed with refinement ? Or, should I restart the entire
> refinement from the very beginning ?

You can just continue refinement but including all data to 2.6A. People used
to do it this way in the past all the time. Now it is considered more
efficient to use all data right from the start but you don't have to start
again from scratch.

> Is it legitimate to refine data to a higher resolution and finally report
> to a lower resolution ?

Why would you want to do that? If the data is there you want to use it. If it
isn't you shouldn't have been using it. If you write in your methods section
that the structure has been refined with all data to 2.6A but statistics are
reported to 2.8A I expect that referees are going to complain (if they
notice).

> Also, I am not clear as to what kind of differences I would see between
> maps calculated with data upto 2.6A and 2.8A.  Any suggestions would be of
> great help. Thanks, Raji

Neither do I, it depends on how much information there is in the 2.6-2.8A
range. The only easy way to find out is to do it.

Bart

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