Two questions.
What is the resolution of your data? what is the percentage sequence identity?

even if you are confident of C2, try using PHASER with all space groups and searching for 2-4 monomers.


Ivan

On Mon, Sep 13, 2010 at 7:52 AM, Paul Holland <[log in to unmask]> wrote:
Hello fellow crystallographers,

I am trying molecular replacement for a protein crystal dataset that has very high sequence similarity to the search model with several predicted flexible loop regions; however, all attempts at finding a solution have not produce very ideal starting solutions using Phaser and Molrep (CC = 0.3 and Z-score = 5).  I am very confident that the unit cell parameters are C2 84.027  120.565  108.272  90.00 104.71  90.00, and there appears to be no evidence of twinning.  The Matthews calculation predicts from anywhere from 2-4 monomers in the ASU, and calculation of the SRF in Molrep does not identify any peaks in higher order symmetry except for the expected crystallographic two-fold for C2.  Below is the table from the calculated SRF in molrep.  Any advice would be greatly appreciated.

#                    theta    phi    chi     alpha   beta  gamma         Rf             Rf/sigma
Sol_RF   1     0.00    0.00    0.00    0.00    0.00    0.00     870.5              21.59
Sol_RF   2    58.61  -10.17  180.00  169.83 -117.23   10.17     162.5      4.03
Sol_RF   3    66.02   -0.00  180.00  180.00 -132.03    0.00     161.1      4.00
Sol_RF   4    58.42   -9.54  180.00  170.46 -116.85    9.54     159.8      3.96
Sol_RF   5   149.84    0.00  180.00 -180.00   60.32    0.00     156.0      3.87
Sol_RF   6    58.96   -5.52  180.00  174.48 -117.91    5.52     151.5      3.76
Sol_RF   7    65.59   20.95  180.00   20.95  131.18  159.05     143.9      3.57
Sol_RF   8    90.00  -98.96  180.00    0.00  180.00   17.92     142.9      3.55
Sol_RF   9    56.53   15.78  180.00   15.78  113.07  164.22     142.0      3.52
Sol_RF  10    71.10  -19.94  180.00  160.06 -142.20   19.94     141.6      3.51
Sol_RF  11    71.28   29.78  180.00   29.78  142.55  150.22     140.4      3.48
Sol_RF  12    65.22  -15.88  180.00  164.12 -130.44   15.88     139.2      3.45
Sol_RF  13    68.84   -0.00  180.00  180.00 -137.67    0.00     138.0      3.42
Sol_RF  14    32.51 -180.00  180.00 -180.00   65.02   -0.00     137.9      3.42
Sol_RF  15    75.02  -28.84  180.00  151.16 -150.04   28.84     134.7      3.34
Sol_RF  16    71.69  -20.99  180.00  159.01 -143.37   20.99     133.0      3.30
Sol_RF  17    92.13  101.46  179.93  102.35 -175.74   79.42     130.9      3.25
Sol_RF  18   107.89  144.73  179.79  145.06 -144.22   35.61     128.8      3.19
Sol_RF  19    87.45  -78.19  180.00  101.81 -174.90   78.19     128.1      3.18
Sol_RF  20    38.57    0.69   30.36  102.66  -18.79  -78.71     122.4      3.04
Sol_RF  21    26.77  174.59  176.58  172.68   53.52    3.49     120.5      2.99
Sol_RF  22   116.66  178.08  175.14    3.49  126.48  187.32     120.5      2.99
Sol_RF  23    75.56  -41.35  180.00  138.65 -151.12   41.35     119.8      2.97
Sol_RF  24    66.12   36.35  180.00   36.35  132.24  143.65     116.6      2.89
Sol_RF  25    83.87   71.62  180.00   71.62  167.74  108.38     114.7      2.85
Sol_RF  26    69.24  -12.37  180.00  167.63 -138.48   12.37     112.3      2.79
Sol_RF  27    59.75   15.26  172.29    7.64  119.07  157.12     112.2      2.78
Sol_RF  28   120.25 -164.74  172.29   22.88  119.07  172.36     112.2      2.78
Sol_RF  29    96.68  -70.99  180.00  109.01 -166.63   70.99     110.9      2.75
Sol_RF  30    63.23  -44.73  180.00  135.27 -126.47   44.73     108.9      2.70

Cheers,

Paul Holland