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[ccp4bb]: twinning detection (II)



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Dear all,

Thank you for your kind suggetions. I've check my data and I am sure that I 
have not made a mistake in I or F's. And the reflection images do not show 
the existence of ice or salt crystals. But my data really has a pseudo 
translational vector.
	 
The spacegroup is P4(3), a=b=109A, c=284A. 4 molecules in ASU.
The 4 moleclues are related by a pseudo 4-fold screw axis at c direction 
(a=0, b=0.5, fractional) with a tranlation of 11A. However, it seems that 
the screw axis dot not extend to the whole unit cell.
	
More than half of the reflections are very weak ( < 2 sigma).
	
Here is the result from scalepack:
	
     Shell            I/Sigma in resolution shells:
  Lower Upper      No. of reflections with I / Sigma less than
  limit limit     0     1     2     3     5    10    20   >20  total
  20.00  6.82  1682  2193  2550  2740  2963  3198  3520  1947   5467
   6.82  5.45  1794  2445  2778  2955  3138  3416  3831  1596   5427
   5.45  4.77  1919  2441  2721  2876  3072  3344  3781  1628   5409
   4.77  4.34  1870  2329  2594  2774  2980  3275  3713  1599   5312
   4.34  4.03  1909  2400  2684  2846  3032  3386  3855  1497   5352
   4.03  3.79  1916  2473  2799  2994  3226  3560  4039  1341   5380
   3.79  3.61  1803  2380  2807  3043  3307  3667  4205  1184   5389
   3.61  3.45  1749  2447  2904  3149  3456  3919  4437   955   5392
   3.45  3.32  1802  2585  3071  3356  3675  4094  4692   702   5394
   3.32  3.20  1733  2607  3196  3488  3835  4327  4899   530   5429
   3.20  3.10  1712  2646  3285  3585  3963  4517  4988   411   5399
   3.10  3.02  1762  2744  3371  3737  4102  4659  5096   306   5402
   3.02  2.94  1802  2807  3489  3897  4276  4756  5172   226   5398
   2.94  2.86  1786  2850  3609  3996  4416  4878  5222   165   5387
   2.86  2.80  1823  2971  3772  4156  4546  4965  5240   127   5367
 All hkl      27062 38318 45630 49592 53987 59961 66690 14214  80904


     Shell            I/Sigma in resolution shells:
  Lower Upper      % of of reflections with I / Sigma less than
  limit limit     0     1     2     3     5    10    20   >20  total
  20.00  6.82  30.7  40.0  46.5  50.0  54.1  58.4  64.3  35.5   99.8
   6.82  5.45  33.0  45.0  51.2  54.4  57.8  62.9  70.5  29.4   99.9
   5.45  4.77  35.3  44.9  50.1  52.9  56.5  61.5  69.6  30.0   99.5
   4.77  4.34  34.6  43.0  47.9  51.3  55.1  60.5  68.6  29.6   98.2
   4.34  4.03  35.3  44.4  49.6  52.6  56.0  62.6  71.3  27.7   98.9
   4.03  3.79  35.3  45.6  51.6  55.2  59.5  65.6  74.5  24.7   99.2
   3.79  3.61  33.4  44.0  51.9  56.3  61.2  67.8  77.8  21.9   99.7
   3.61  3.45  32.4  45.3  53.7  58.3  63.9  72.5  82.1  17.7   99.7
   3.45  3.32  33.4  47.9  56.9  62.2  68.1  75.9  87.0  13.0  100.0
   3.32  3.20  31.9  48.0  58.8  64.2  70.6  79.7  90.2   9.8  100.0
   3.20  3.10  31.7  49.0  60.8  66.4  73.3  83.6  92.3   7.6   99.9
   3.10  3.02  32.6  50.8  62.4  69.2  75.9  86.2  94.3   5.7  100.0
   3.02  2.94  33.3  51.9  64.6  72.1  79.1  88.0  95.7   4.2   99.9
   2.94  2.86  33.1  52.8  66.9  74.1  81.9  90.4  96.8   3.1   99.9
   2.86  2.80  33.9  55.3  70.2  77.3  84.5  92.3  97.5   2.4   99.8
 All hkl       33.3  47.2  56.2  61.1  66.5  73.8  82.1  17.5   99.6
 
In such case how can I know whether the data is twinned?
	
Thanks in advance.

Best,

Fan
	


		
PS: CNS gave the check statistics in resolution shells:
                       testing for perfect twinning

 column  1:     bin number
 columns 2:     upper resolution limit
 columns 3:     lower resolution limit
 column  4:     number of reflections in bin
 column  5:     average resolution in bin
 column  6:      <|I|^2>/(<|I|>)^2
 column  7:     (<|F|>)^2/<|F|^2>
 column  8:     fraction of theoretically complete data

  <|I|^2>/(<|I|>)^2 is 2.0 for untwinned data, 1.5 for twinned data
 (<|F|>)^2/<|F|^2> is 0.785 for untwinned data, 0.865 for twinned data
	
 #bin | resolution range | #refl | 
    1   9.89   20.00       1153     12.7730    5.7333    0.3819    0.7039
    2   8.02    9.89       1077      8.8411    5.6025    0.4368    0.6508
    3   7.05    8.02       1051      7.4933    5.0372    0.4497    0.6480
    4   6.43    7.05       1045      6.7285    5.0025    0.4757    0.6564
    5   5.98    6.43       1069      6.2047    4.5450    0.4813    0.6459
    6   5.64    5.98       1078      5.8062    4.4521    0.4831    0.6622
    7   5.36    5.64       1035      5.4972    4.7670    0.5170    0.6369
    8   5.13    5.36       1003      5.2427    4.3709    0.5089    0.6249
    9   4.94    5.13       1050      5.0341    3.8806    0.5257    0.6454
   10   4.77    4.94       1023      4.8524    4.0424    0.5212    0.6288
   11   4.62    4.77       1000      4.6940    4.1963    0.5173    0.6200
   12   4.49    4.62        999      4.5566    3.9060    0.5320    0.6159
   13   4.38    4.49        997      4.4342    3.9939    0.5333    0.6227
   14   4.27    4.38       1045      4.3229    4.2874    0.5135    0.6423
   15   4.17    4.27        988      4.2200    3.4972    0.5732    0.6133
   16   4.09    4.17       1047      4.1287    3.9929    0.5382    0.6392
   17   4.00    4.09        979      4.0440    4.3740    0.5380    0.6153
   18   3.93    4.00       1055      3.9672    4.4091    0.5318    0.6537
   19   3.86    3.93       1014      3.8934    3.9353    0.5396    0.6225
   20   3.79    3.86       1012      3.8271    3.7867    0.5612    0.6305
   21   3.73    3.79       1022      3.7634    4.3050    0.5472    0.6262
   22   3.68    3.73       1100      3.7054    4.0124    0.5552    0.6782
   23   3.62    3.68       1037      3.6493    4.2247    0.5479    0.6469
   24   3.57    3.62       1054      3.5976    4.3048    0.5420    0.6583
   25   3.52    3.57       1057      3.5494    4.7428    0.5344    0.6660
   26   3.48    3.52       1100      3.5014    3.9066    0.5636    0.6517
   27   3.44    3.48       1057      3.4572    3.9779    0.5829    0.6741
   28   3.39    3.44       1055      3.4147    4.8184    0.5663    0.6549
   29   3.36    3.39       1052      3.3751    4.1344    0.5767    0.6454
   30   3.32    3.36       1084      3.3366    3.8702    0.5756    0.6716
   31   3.28    3.32       1073      3.2995    4.0869    0.5795    0.6673
   32   3.25    3.28       1121      3.2646    3.7595    0.5871    0.6903
   33   3.21    3.25       1048      3.2307    3.7332    0.5978    0.6620
   34   3.18    3.21       1108      3.1984    4.0920    0.6012    0.6667
   35   3.15    3.18       1086      3.1675    3.5534    0.6152    0.6852
   36   3.12    3.15       1036      3.1378    3.4910    0.6218    0.6549
   37   3.09    3.12       1110      3.1091    3.8727    0.6165    0.6760
   38   3.07    3.09       1122      3.0813    3.7887    0.6116    0.6841
   39   3.04    3.07       1070      3.0542    3.7695    0.6283    0.6687
   40   3.02    3.04       1039      3.0277    3.0640    0.6531    0.6465
   41   2.99    3.02       1109      3.0033    4.1035    0.6325    0.6754
   42   2.97    2.99       1060      2.9788    3.6140    0.6404    0.6709
   43   2.94    2.97       1044      2.9552    3.8177    0.6344    0.6476
   44   2.92    2.94       1082      2.9325    3.3001    0.6495    0.6594
   45   2.90    2.92       1048      2.9105    3.3628    0.6731    0.6591
   46   2.88    2.90       1043      2.8895    3.4731    0.6449    0.6580
   47   2.86    2.88       1075      2.8684    3.5207    0.6660    0.6595
   48   2.84    2.86       1104      2.8481    3.2404    0.6683    0.6651
   49   2.82    2.84       1020      2.8286    4.1193    0.6408    0.6468
   50   2.80    2.82       1033      2.8092    3.2242    0.6880    0.6432







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