Water admixture triggers the self-assembly of the glycyl-glycine thin film at the presence of organic vapors

The formation of dipeptide micro- and nanostructures in the solid state or in solutions usually occurs in the presence of water in the ambient air or in the organic media used. This factor should be taken into account since the results of the self-assembly of dipeptides are very sensitive to external conditions and may depend on the water content. In this work, the study of the mutual effect of water and organic vapors on the self-assembly of the glycyl-glycine (GlyGly) dipeptide in the solid state was carried out for the first time using atomic force microscopy. The crystallization of an amorphous GlyGly film upon interaction with vapors of organic compounds such as dichloromethane, chloroform, tetrachloromethane, and benzene occurs only in the presence of water vapors. The rate of dipeptide crystallization was found also depends on the organic compound used. The solubility of GlyGly in organic media and the solubility of organic solvent in water are the main factors that affect the dipeptide self-assembly. Using the Raman spectroscopy and quantum chemical calculations a possible mechanism of the combined effect of water and organic compounds on the GlyGly self-assembly has been proposed. • The mechanism of glycyl-glycine self-assembly in thin film under organic and water vapors was studied by AFM technique. • The key role of water in self-assembly of glycyl-glycine in the solid state revealed. • The amorphous film consists mostly of a molecular form of dipeptide. • The dualism of water effect on the glycyl-glycine self-assembly was demonstrated. • The atomic force microscopy technique was used for qualitative estimation of dipeptide solubility for the first time.