Molecular Patterning of a Guanidinium/Orotate Mixed Monolayer through Molecular Recognition with Flavin Adenine Dinucleotide

Flavin adenine dinucleotide (FAD) undergoes multisite molecular recognition at the air-water interface with mixed monolayers that are capable of complementary hydrogen bonding. Molecular images were obtained with an atomic force microscope (AFM) for mixed monolayers of guanidinium (<BO>G</BO>) and orotate (<BO>O</BO>) amphiphiles transferred from pure water and from aqueous FAD. The AFM image of the <BO>G</BO>/<BO>O</BO> mixed monolayer on FAD showed a periodic oblique pattern composed of two kinds of methyl peaks with different heights, whereas that on pure water showed a periodic hexagonal pattern of only one kind of methyl peak. The two-dimensional molecular patterning as height difference is conceivably caused by rearrangement of monolayer components based on specific recognition by the FAD template molecule.