Searching for the Optimal Fluorophore to Label Antimicrobial Peptides.

With the advent of antimicrobial resistance, there is an urgent need for new strategies to treat infectious diseases. Antimicrobial peptides are considered as promising candidates, and therefore there is a need to understand their mechanism of action in order to exploit their therapeutic potential. To this end, fluorescent analogs are powerful tools to analyze their behavior and subcellular localization in cells and in vivo. However, the conjugation of fluorophores to antimicrobial peptides, especially in short sequences, can impair their biological activity, making the selection of the fluorescent label an essential step in these studies. In the present work, we have systematically modified a model antifungal hexapeptide with a collection of fluorophores covering broad physicochemical and spectral properties. The resulting conjugates have been examined in two different fungal species, in terms of their activity and intracellular localization. The biological results confirm the influence of the different fluorescent moieties on the subcellular localization of antimicrobial sequences, and provides an insight on the optimal fluorophores to be used in the preparation of fluorescent peptides for different bioimaging assays.