L-Lysine: Exploiting Powder X-ray Diffraction to Complete the Set of Crystal Structures of the 20 Directly Encoded Proteinogenic Amino Acids

• Published in: Angewandte Chemie International Edition 2015-03, Vol.54 (13), p.3973-3977
• Main Authors: Williams, P. Andrew, Hughes, Colan E., Harris, Kenneth D. M.
• Format: Article
• Language: English
• Subjects: Algorithms; Amino acids; Amino Acids - chemistry; Atmospherics; Crystal structure; Crystallization; Diffraction; Glycine; Hydrates; Hydrogen Bonding; L-lysine; Lysine - chemistry; Models, Molecular; Molecular Conformation; powder x-ray diffraction; Powders; Single crystals; structure determination; Structure-Activity Relationship; X-Ray Diffraction; X-rays
• ISSN: 1433-7851; 1521-3773
• DOI: 10.1002/anie.201411520

During the last 75 years, crystal structures have been reported for 19 of the 20 directly encoded proteinogenic amino acids in their natural (enantiomerically pure) form. The crystal structure is now reported for the final member of this set: L‐lysine. As crystalline L‐lysine has a strong propensity to incorporate water under ambient atmospheric conditions to form a hydrate phase, the pure (non‐hydrate) crystalline phase can be obtained only by dehydration under rigorously anhydrous conditions, resulting in a microcrystalline powder sample. For this reason, modern powder X‐ray diffraction methods have been exploited to determine the crystal structure in this final, elusive case. Completing the set: L‐lysine is the final member of the set of 20 directly encoded proteinogenic amino acids to have its crystal structure determined, 75 years after glycine became the first member of this set to have a crystal structure reported. With good‐quality single crystals of L‐lysine unavailable, modern powder X‐ray diffraction methods were exploited for the structure determination.