DFT characterization of isomers (IMAGE) Science China Press Caption (a) Chemical structure and electrostatic potential (ESP) of s-HATBAQ and a-HATBAQ, (b) HOMO/LUMO energy levels and energy gaps (ΔEH-L) of s-HATBAQ and a-HATBAQ, and (c) The Gibbs free energy change (ΔG) upon the complexation with H+ at different binding sites of s-HATBAQ and a-HATBAQ. The blue, red, black and gray balls represent the N, O, C and H atoms, respectively, and M1 and M2 stand for s-HATBAQ and a-HATBAQ, respectively. Credit ©Science China Press Usage Restrictions Use with credit. License Original content Disclaimer: AAAS and EurekAlert! are not responsible for the accuracy of news releases posted to EurekAlert! by contributing institutions or for the use of any information through the EurekAlert system.