Self-Assembly Propensity Dictates Lifetimes in Transient Naphthalimide-Dipeptide Nanofibers.

Transient self-assembly of dipeptide nanofibers with lifetimes that are predictably variable through dipeptide sequence design are presented. This was achieved using 1,8-naphthalimide (NI) amino acid methyl-esters (Phe, Tyr, Leu) that are biocatalytically coupled to amino acid-amides (Phe, Tyr, Leu, Val, Ala, Ser) to form self-assembling NI-dipeptides. However, competing hydrolysis of the dipeptides results in disassembly. It was demonstrated that the kinetic parameters like lifetimes of these nanofibers can be predictably regulated by the thermodynamic parameter, namely the self-assembly propensity of the constituent dipeptide sequence. These lifetimes could vary from minutes, to hours, to permanent gels that do not degrade. Moreover, the in-built NI fluorophore was utilized to image the transient nanostructures in solution with stimulated emission depletion (STED) based super-resolution fluorescence microscopy.