Unveiling the Neutral Forms of Glutamine

Abstract

Neutral glutamine has been evaporated by laserablation of its solid sample to seed a rare gas carrier prior toa supersonic expansion and proved by Fourier transformmicrowave techniques. We report on three distinct neutralconformers that show a singular non-interacting and flexibleamide sidechain in contrast with the other proteinogenicaliphatic amino acids. It could explain the essential biologicalrole of glutamine as a nitrogen source, and its unique ability toform a variety of hydrogen bonds with peptide backbones.Common computational methods fail to predict the delicatebalance of intramolecular interactions controlling the geome-try of the most stable conformer. The spectroscopic data herereported can be used to benchmark novel computationalmethods in quantum chemistry.