In this work, the thermotropic liquid crystals (LCs) composed of a biological molecule, guanosine 5'-monophosphate disodium salt (GMP), with different cationic surfactants were reported. When GMP interacted with the surfactants, the length of the surfactant alkyl chains was found to be of great importance in modulating the LC phase. The smectic A (SmA) phase and columnar rectangular (Col(r)) phase were formed upon increasing the length of the aliphatic chains due to the enlargement of the steric hindrance. Interestingly, K+ ions were observed to cause the phase transition of LCs from the SmA or Col(r) mesophase to a columnar hexagonal (Col(h)) mesophase in the GMP-surfactant complexes, which was attributed to the formation of G-quadruplexes. Accordingly, the chirality and fluorescence properties of the complexes also exhibited K+-responsive characters as the phase transition of the LCs emerged. Compared with the reported LCs containing guanosine groups, the thermotropic LCs with high elasticity and tunable mesophase structures in this study are easy to be prepared and are hopeful to provide potential applications for constructing stimuli-responsive luminescent materials, biocatalysis and biosensor devices. (C) 2019 Elsevier Inc. All rights reserved.