Comprehensive computational study of gas-phase conformations of neutral, protonated and deprotonated glutamic acids

► Thorough conformational search for glutamic acid and related ions. ► Important new conformations of neutral and deprotonated glutamic acids are found. ► Protonation and deprotonation energetics examined by various computational methods. ► The best agreement with the experiments is obtained by the BHandHLYP method. ► The MP2 method underestimates the proton detachment energy of glutamic acid.