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[ccp4bb]: Problems with C2 (fwd)

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Hi All

We are experiencing some weird problems with MR and subsequent building
in C2. MR (with different programs) gives clear solutions (R~45%,
CC~35%) that make good sense from packing considerations. Since we have
high resolution data (1.9 A for apo, 0.95 A for complex) we feed this
straight into warpNtrace which builds only about 15% of the structure with
some good looking secondary structure elements. Further refinement, or
refinement starting straight from the MR solutions halts with R-factors >
40%.

Some vital stats:

- UNIT CELL

    85.533 34.317 43.796 90.000 112.664 90.000 c2

    ( notice c = approximately 0.5*a )

    1 mol/a.s.u. ( Mw=14800 kD, matt.coef. = 1.99 )


- SCALEPACK output

 Shell Lower Upper Average Average Norm.  Linear Square
 limit Angstrom I error stat. Chi**2 R-fac R-fac
      20.00 4.08 28474.2 1046.9 729.8 0.693 0.025 0.030
       4.08 3.25 22524.7  750.7 507.8 0.857 0.026 0.027
       3.25 2.84  9597.1  374.8 278.9 0.958 0.038 0.038
       2.84 2.58  5174.4  236.1 188.7 1.090 0.053 0.050
       2.58 2.39  2923.4  179.9 158.3 1.077 0.079 0.072
       2.39 2.25  2395.0  181.4 164.3 1.171 0.111 0.156
       2.25 2.14  1921.2  189.7 178.6 1.388 0.152 0.159
       2.14 2.05  1500.2  189.2 181.8 1.210 0.183 0.163
       2.05 1.97  1125.4  187.9 183.4 1.115 0.242 0.203
       1.97 1.90   697.1  192.2 190.1 1.155 0.377 0.318

- TRUNCATE output :
 :Cumulative intensity distribution (Acentric and centric)
 :N:1,2,3,4,5:
 $$
         Z   N(Z)Atheor  N(Z)Acen  N(Z)Ctheor  N(Z)Cen    $$
 $$

        0.0       0.0       0.0       0.0       0.0
        0.1       9.5      11.9      24.8      21.0
        0.2      18.1      20.8      34.5      28.7
        0.3      25.9      29.4      41.6      35.5
        0.4      33.0      36.8      47.3      40.7
        0.5      39.3      43.3      52.1      45.8
        0.6      45.1      48.9      56.1      49.4
        0.7      50.3      54.1      59.7      53.2
        0.8      55.1      58.6      62.9      56.4
        0.9      59.3      62.5      65.7      60.3
        1.0      63.2      66.2      68.3      62.0

The CCP4 Twinning page suggests twinning in C2 can be solved by
re-indexing the data with different unit cell settings, but it's not clear
how this should be done.

Thanks in advance for any help!

cheers

Daan


##############################################################################
 
Dr. Daan van Aalten                    Wellcome Trust RCD Fellow 
Wellcome Trust Biocentre, Dow Street   TEL: ++ 44 1382 344979 
Div. of Biol.Chem. & Mol.Microbiology  FAX: ++ 44 1382 345764 
School of Life Sciences                E-mail: dava@davapc1.bioch.dundee.ac.uk
Univ. of Dundee, Dundee DD1 5EH, UK    WWW: http://davapc1.bioch.dundee.ac.uk 

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