On the Hydration State of Amino Acids and Their Derivatives at Different Ionization States: A Comparative Multinuclear NMR and Crystallographic Investigation
Figure 7
(a) Cambridge Crystallographic Database (CSD) search queries for intramolecular hydrogen bond in the presence and in the absence of two water molecules bound to the carboxylate and carboxylic groups, respectively. C (gray), N (blue), any group (cyan), H (light-yellow), and O (red). (b) Plot of the number of structures versus the distances (N⋯O−) and (N⋯O=C) in the absence of a water molecule. (c) Plot of the number of structures versus the distances (N⋯O−) and (N⋯O=C) in the presence of two water molecules bound to the carboxylate and the carboxylic groups, respectively.
