Recognition of aqueous flavin mononucleotide (FMN) on the surface of binary monolayers of guanidinium amphiphiles (monoalkyl derivative, C18Gua, or dialkyl derivative, 2C18Gua) and the melamine amphiphile (2C18mela-NN) has been investigated by π-A isotherms, FTIR spectroscopy, and XPS measurements. π-A Isotherms and FTIR spectra of C18Gua-2C18mela-NN (1:1) monolayers show that there is no direct hydrogen bonding and/or coulombic interactions between C18Gua and 2C18mela-NN on pure water and that the C18Gua component is dissolved into the subphase upon compression. In contrast, the presence of aqueous FMN prevented C18Gua molecules from dissolving into the subphase. Maximum condensation was observed at a 1:1 ratio in C18Gua-2C18mela-NN mixed monolayers on aqueous FMN. XPS analyses revealed that one FMN molecule was bound to one C18Gua-2C18mela-NN (1:1) unit and binding was saturated at 5 × 10-6 mol dm-3FMN. Peak shifts observed in FTIR spectra indicated that the isoalloxiazine ring in FMN formed hydrogen bonds with 2C18mela-NN. These results support a model that the isoalloxazine and phosphate functions in FMN are bound via hydrogen bonding to melamine in 2C18mela-NN and guanidinium in C18Gua, respectively. Similar binding behaviour of FMN was observed for mixed monolayers of 2C18Gua-2C18mela-NN.
All Science Journal Classification (ASJC) codes
- Materials Chemistry