Fibrous structure in a flavin monolayer observed by dark-field electron microscopy

A microscopic study on a monolayer of flavin ((7,8-dimethyl-3,10-dinonylisoalloxazine) (DNI)), which is typical of functional groups of redox proteins, has been performed using dark-field electron microscopy. It was found that the flavin monolayer has a fibrous structure with good crystallinity and no holes over the region of a few micrometers squared. From the electron diffraction pattern, it was also found that the orientation of the fiber axis is virtually {pi}/6 off the lifting direction during preparation of the monolayer. For molecular orientation, it was clarified from the FT-IR measurement that the long axis of the isoalloxazine ring is oriented perpendicularly to the lifting direction of the substrate.