Dear Sangheon,
you don't say which cubic space group you tried, perhaps you tried the wrong one? Did Pointless indicate a clear preference?
Between P23 and P213 for instance you can tell by systematic absences along h (if they were collected ok), but between I23 and I213 the only option is to try both and see if one or the other leads to a good solution.
In any case, in principle having P21 with beta near 90 and a nearly equal to b and c is rare, but possible.
Greetings,
Mark
Mark J van Raaij
Lab 20B
Dpto de Estructura de Macromoleculas
Centro Nacional de Biotecnologia - CSIC
c/Darwin 3
E-28049 Madrid, Spain
tel. (+34) 91 585 4616
http://www.cnb.csic.es/~mjvanraaij
On 25 Oct 2013, at 02:55, À¯»óÇå wrote:
> Hi everyone,
>
> Recently I¡¯ve got a protein crystal and I did indexing and scaling with a cubic space group (unit cell 104.115 104.115 104.115 90.0 90.0 90.0). But a Rmerge value was too high (around 0.5-0.6). So, I tried lower symmetry space groups and I successfully solved the structure with a space group P21 (Rwork/Rfree: 0.22/0.27). However, there was one strange fact. The unit cell of the P21 was 104.209 104.225 104.254 90.000 89.967 90.000. I¡¯m confused with this fact that a, b, and c of the unit cell are almost same, and in addition, the beta angle is too close to 90. I didn¡¯t do refinement with a twin option. So, is the space group correct? Is there anyone who know this case?
>
> Thanks,
>
> Sangheon Yu
> Rm. 1053 Bldg. 200
> School of Agricultural Biotechnology
> College of Agriculture & Life Sciences
> Seoul National University
> Seoul 151-921, KOREA
>
>
|