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Re: AMORE

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> while the xtal structure of the wild type is already solved in
> spacegroup of p212121. 

If you are working on a mutant then chances are that you have the same
P212121 crystal form as native. Are the unit cell paramaters close to
those of the wild type crystal? If so you can skip molecular replacement.
Just take the wild type structure as the starting model, run a few cycles
of rigid body refinement against your mutant data and make a difference
electron density map. Hopefully the mutation will be clearly visible in
the density.

If it does turn out to be a different orthorhombic crystal form then, as
suggested by others, do try to find out the systematic absences. One other
trick to do this is, if you used SCALA to scale your data, to look near
the end of its log file where it lists the I/SigI values along the h, k
and l axes. In my case it looks like:

     h         I      sigI    I/sigI

     3      443.       80.     5.530
     4    48836.     3793.    12.877
     5      152.       86.     1.759
     6    18208.      988.    18.428
     7      172.      146.     1.184
     8   118772.     6728.    17.654
     9     2188.      270.     8.111     <<<
    10   148297.     8439.    17.572
    11      568.      340.     1.669
    12   578948.    33628.    17.216
    13     2149.      457.     4.698
    14   102346.     6310.    16.221
    15     1161.      553.     2.101
    16   109650.     6638.    16.520
    17     -151.      600.    -0.252
    18   108251.     6674.    16.221
    19     1189.      651.     1.826
    20    19826.     1431.    13.857
    21       61.      581.     0.105
    22     2770.      621.     4.459
    23      857.      605.     1.417

You can see that all even reflections are strong and most odd ones are
weak. The one outlier h=9 is due to Kbeta radiation, but in general the
trend is clear and this is indeed a 2(1) screw axis.

Bart