Topological analysis of DL-arginine monohydrate at 100 K

The charge density of DL-arginine monohydrate has been extracted from a synchrotron data set of 212121 reflections collected at 100 K with a Bruker CCD area detector up to a resolution of sin θ/λ = 1.40 Å^-1 (d = 0.36 Å). DL-arginine monohydrate is characterised by a neutral α-amino group and a notable different hydrogen bond pattern compared to previously examined free arginine structures. All bond critical points of the electron density at the covalent and hydrogen bonds were located. We compare the local topological indices of p(r) with other amino acids. The conformation obtained from the experimental structure is found to be different from the Hartree-Fock (HF) optimization for the isolated molecule, thus the topology obtained from the static experimental charge density is compared to that derived from calculations at experimental and optimized geometry at HF and B3LYP levels of theory.