Clarification about symmetry of the GroEL simulated data

The authors of the GroEL simulated dataset have asked us to let all map challenge participants know that 4HEL, the model from which the images were generated, is non-symmetrical, owing to unmatched crystallographic symmetry (P2₁2₁2₁).   They have just become aware of this issue following discussion with two challenge participants.

To try to reach high resolution it will therefore more appropriate to perform reconstructions assuming C1 symmetry instead of D7 symmetry.  (D7 resolution limit is  ~ 4 angstrom).  The full hemisphere of projections were generated by the authors, so in principle enough information exists to reconstruct in the lower symmetry. However, since there are only 10K particles it will be very interesting to see if it is possible.

Thanks for Steve Ludtke and Sjors Scheres for initiating the discussion, and Fei Sun for the clarification.