[buster-discuss] rhofit, use maps instead mtz, or specify map coefficients?

[BUSTER Developers]

Dear Guenter,

On Mon, Oct 17, 2022 at 09:17:59AM +0200, Guenter Fritz wrote:
> I was wondering whether one could use directly maps for rhofit or whether it
> is possible to specify the map coefficients of the mtz to be used by rhofit.

It is possible in a maybe slightly round-about way ...

Rhofit can also start from a set of already defined so-called
"clusters" - which would be the result of internally running
"prep_rhofit" on the given MTZ file and some default map
coefficients. What you need is a simple text file with a list of
cluster PDB files (one per line, i.e. several lines if you have
several binding sites you want Rhofit to analyse). Each cluster PDB
file contains a set of grid points with an associated map score
(usually: mFo-DFc map value) that is generated e.g. by prep_rhofit,
which has more control about the coefficients to use for map
calculation (see "prep_rhofit -h" for details).

Of course, you could always rename the map coefficients of your input
MTZ file e.g. via

  mtzutils hklin my.mtz hklout tmp.mtz <<e
  COLU MY_F=2FOFCWT MY_P=PH2FOFCWT
  e

If you have only one set of map coefficients: you need to give them as
both (2mFo-DFc and mFo-DFc) to prep_rhofit.

In principle one can prepare such cluster files also directly from
maps: if you could give a bit more background information maybe we can
provide further information for you here?

Cheers

Clemens & Andrew