Redetermined structure of β-dl-me-thio-nine at 105 K: an example of the importance of freely refining the positions of the amino-group H atoms

Diffraction data were taken from the contribution named 'β-dl-Me-thio-nine at 105 K' by Alagar et al. [Acta Cryst. (2005 ▶). E61, o1165-o1167]. Refinement of the coordinates of the three amino H atoms, previously constrained to an idealized geometry, shows that the amino group is in fact rotated 13.5° from the perfectly staggered orientation. This apparently modest change has a profound impact on the calculated hydrogen-bond geometries.