The Secret of the Crystal Structure of Ribose is Revealed

D-ribose is only a small molecule but of great importance for living organisms. Although ribose is a fundamental building block of ribosome (the "protein factory" of cells), until now the crystal structure of ribose was not amongst the 500.000 decoded structures. In 2009, the analysis of the structure and function of the ribosome was awarded the Nobel Prize.
A German-Swiss team has now succeeded in decoding the crystal structure of ribose.

Ribose belongs to the chemical group of sugars. Its spine is a chain of five carbon atoms, of which four contain an OH group and one is connected to an oxygen atom via a double bond. In most up-to-date textbooks, ribose is depicted as β-furanose: four carbon atoms form a five membered ring together with the oxygen atom. However, for more than 40 years, it is known that ribose in solution is present in four different structures: α- or β-furanose and α- or β-pyranose (six membered ring of five carbon atoms and one oxygen atom).

Decoding the structure of ribose has been a hard task as the crystallization of the compound is extremely difficult to carry out. Despite of these difficult conditions, the team of researchers has now - after countless failures - succeeded in elucidating the crystal structure. Using sophisticated computer calculations, significant results could be gained from X-ray crystallography of powder samples. Afterwards, the researchers succeeded in producing monocrystals using zone refining. In this process, a small zone of the material is heated and then moved forward. After cooling, the melting zone solidifies into a monocrystal in a uniform crystal structure that can be examined using X-ray structure analysis. Further information was given by solid state NMR-spectroscopy.

The results show that d-ribose crystallizes as pyranose. Two variations of crystals exist that contain the α- and β-pyranose at different rates. 

Source: Society of German Chemists