Abstract Extensive conformational searches have been performed in order to more fully characterize the potential energy surfaces of the neutral, protonated and deprotonated glutamic acids in gas phase. A large number of trial structures were generated by combinations of all internal single-bond rotamers of these species. Based on the final geometry optimization at the B3LYP/6-311++G(d,p) level, a total of 385, 80, and 77 conformers are found respectively for the neutral, protonated, and deprotonated species. Hydrogen bonding configurations and IR spectra are characterized. The proton affinity, gas phase basicity, proton detachment energy and gas phase acidity are calculated by the methods of CCSD, BHandHLYP, B3LYP, MP2 and G3MP2. The theoretical results are compared with the experiments. The BHandHLYP results are in accord with the recent experiments, while the MP2 method is inadequate for providing reliable results for the proton dissociation reaction.