TAPSO at low temperature

The crystal structure of TAPSO, 2-hydroxy-3-[tris-(hydroxymethyl)methylamino]propane-1-sulfonic acid, C₇H₁₇NO₇S, was determined at 153 K. This widely used buffer crystallizes as a zwitterion, 2-hydroxy-3-[tris(hydroxymethyl)methylammonio]propane-l-sulfonate, and crystal cohesion is provided by a dense network of hydrogen bonds. The molecular conformation of TAPSO is compared with the structure of TRIS (or TRIZMA), another commonly used buffering agent in protein crystallization. Cell parameters reported in the literature for a series of biological buffers used in protein crystallography are also provided.