A back of the envellope calculation shows that your asymmetric unit
contains most likely 4 molecules with Vm = 2.16 A3/Da, corresponding to
43% solvent. Searching for 16 molecules is thus nonsense.
Remy Loris
Vrije Universiteit Brussel
On 17/08/14 08:54, Avisek Mondal wrote:
Hello everyone, i am struggling with a problem.. My crystal was
diffracted at 1.9A in P21 spacegoup with unit cell parameter a=87.7
b=93.9, c=111.78 ,beta=94.98 which contains 16 molecules per
assymmetric unit (Molecular weight of the Protein+DNA =56 KDa.
actually it is a complex of 40Kda tetramer and 23bpDNA ) .In solution,
it shows tetrameric in nature The crystal structure of its
homologous structure has been reported earlier (50%identical in amino
acid seq.) and it was also a tetramer and its unit cell (also P21)
was approximately 4 times less than mine. It showed 4 molecules per
assymmetric unit. I didn't get any molecular replacement. All
the programms are takings very long time to do it. Although the single
crystal is untwinned i think it is a case of pseudosymmetry.
Please help me if you have any good suggestion regarding molecular
replacement other than experimental phasing.
