A new type of fluorescent molecular architecture is described that can be used to prepare fluorescent lasso peptide probes with high stability and brightness. The probe contains three components: a deep-red squaraine fluorophore, macrocycle which surrounds the squaraine, and two bioactive peptide loops that form the lasso architecture. The dye has narrow and deep-red absorption and emission bands. The synthesis of these probes starts by attaching the peptides to a central squaraine rotaxane core and then forms the loop(s) by conducting an intramolecular copper(I)-catalyzed azide-alkyne cycloaddition. The final step is global deprotection to produce the fluorescent lasso peptide probes. The structure of an organic lasso molecule was characterized by dynamic <sup>1</sup>H NMR and X-ray crystallography. A fluorescent cancer imaging lasso probe containing integrin binding motif Arg-Gly-Asp (RGD) was synthesized and cancer cell targeting was demonstrated using cell microscopy.

Squaraine lasso peptides: New family of self-threaded fluorescent molecular probes

2019 Fall National Meeting

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