Dear Jademilson,
At a CCP4 APS workshop a few years ago, one of the
students solved a molecular replacement problem where I think there were close
to 40 copies in the asu. I have to say that many people were surprised by this,
but I think the protein was smaller and they had a very good search model - I
can’t remember the resolution of the data. The job certainly ran for a long
time (overnight I think), but it does show that in some circumstances this can
work. Possibly Randy Ready can remember the details better than I do. However
in your case you may need to resort to experimental phasing.
Good luck!
Andrew
> On 26 Apr 2017, at 20:34, Jademilson Santos <[email protected]>
> wrote:
>
> Greetings all,
>
> I am having trouble with a data set and would like to know if somebody can
> help. I'm working with a protein of approximately 50 kDa, which I have
> successfully crystallized. The crystals diffracted at a resolution of 3,65
> angstroms and upon initial processing using XDS i obtained the following
> information:
>
> space group: P21
> ISA = 33.3
> cell unit: a=285.2, b=135.9, c= 287.5, α=90, β=117.5, γ=90
>
> Matthews coefficient indicates that there are 40 molecules in the asymmetric
> unit
>
> I am currently running the program Phaser (Phenix) to determine the phase via
> molecular replacement with a model that has 49% homology and query coverage
> of 94% and the program is taking extremly long to finish. In this case in
> which there is an extremly high number of molecules in the asymmetric unit,
> is this actually possible? Does someone know how to work with these values
> and is there a specific strategy which i must follow?
>
> Regards
>
> Jademilson Celestino dos Santos
>
> Laboratory of Applied Structural Biology
> Department of Microbiology
> Institute of Biomedical Sciences
> University of São Paulo- USP
