Fig. 7
From: Crystal structures of increasingly large molecules: meeting the challenges with CRYSTALS software
The structure of potassium phenoxymethylpenicillin viewed down the b-axis. The asymmetric unit consists of four potassium ions (shown in purple) and four phenoxymethylpenicillin molecules (shown in red, green, blue and yellow). The red and green pair of equivallents of phenoxymethylpenicillin are related by a pseudo 21 screw axis and the red and yellow pair by an approximate translation; the blue and yellow pair and blue and green pair exhibit similar relationships