DL-3-Aminoisobutyric Acid

A zwitterionic dimer model constructed of inter-molecular -N-H⋯O bonding has been proposed for the solid sample of DL-3-Aminoisobutyric acid consistent with IR absorption and Raman spectral features measured in the 3500-400/50 cm-1. This zwitterionic dimer model in water as solvent has been computed at B3LYP/6-311++G(d,p) and B3LYP-D3/6-311++G(d,p) levels including Grimme's dispersion correction associated with the -N-H⋯O interaction and SCRF-SMD method. Of the several possible monomer and dimer conformational structures, the most stable dimer constructed of two zwitterion monomer units has produced vibrational modes due to the -NH3 + cation and -CO2‾ anion involved in the -N-H⋯O bonding in fair agreement with the observed broad but composite IR modal features near the 3500-2000 cm-1. Except for the frequency of asymmetric stretching mode of the -NH3 + cation, its symmetric and bending modes agree with the observed values. As for the -CO2‾ anion, the frequencies of all of its modes are in good agreement with the experiment. Natural bond orbital (NBO), molecular electrostatic potential (MEP), atoms-in-molecules (AIM) and non-covalent interaction (NCI) analyses have been used to understand electronic characterization of the -N-H⋯O bonding.

The title acid, 3-amino-2-methylpropanoic acid monohydrate, C4H9NO2.H2O, crystallized in the centrosymmetric space group Pbca in the zwitterionic form. The three H atoms on N, which are involved in hydrogen bonding, are ordered. The three intermolecular N-H...O hydrogen bonds have N...O distances ranging from 2.758 (2) to 2.809 (2) A and N-H...O angles ranging from 149 (2) to 171 (1) degrees. The two intermolecular O-H...O hydrogen bonds have O...O distances 2.739 (2) and 2.755 (2) A, and O-H...O angles 170 (2) and 175 (2) degrees. Each acid molecule and its associated water molecule are directly hydrogen bonded to five acid molecules and two water molecules; the structure comprises two subsets of molecules which are not cross-linked by these hydrogen bonds. Through basic second-level graphs, approximately two-thirds of the hydrogen-bonding patterns are finite and one-third are chains; there is a single ring pattern, which occurs about a center of symmetry.

The etiology of dry mouth conditions is multi-faceted. Patients radiated after head and neck cancer (HNC) and those with primary Sjögren's syndrome (pSS) share many of the same symptoms despite different causes. With the aim of better understanding the pathophysiology and biochemical processes behind dry mouth with different etiologies, we investigated the metabolic profile of 10 HNC patients, 9 pSS patients and 10 healthy controls using high-performance liquid chromatography-high resolution mass spectrometry (HPLC-MS) metabolomics. Principal component analysis (PCA) revealed different metabolic profiles when comparing all subjects included in the study. Both patient groups showed higher ratios of several pyrimidine nucleotides and nucleosides when compared to controls. This finding may indicate that purinergic signaling plays a role in dry mouth conditions. Moreover, significantly increased levels of DL-3-aminoisobutyric acid were found in HNC patients when compared to controls, and a similar tendency was observed in the pSS patients. Furthermore, a dysregulation in amino acid metabolism was observed in both patient groups. In conclusion, metabolomics analysis showed separate metabolic profiles for HNC and pSS patients as compared to controls that could be useful in diagnostics and for elucidating the different pathophysiologies. The demonstrated dysregulation of pyrimidine nucleotides and levels of metabolites derived from amino acids in the patient groups should be studied further.