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