Synthesis and characterization of two novel red-shifted isothiocyanate BODIPYs and their application in protein conjugation

Fluorescent organic small molecules are very important tools for researchers in the fields of biochemistry and biotechnology, and boron-dipyrromethene (BODIPY) class of organic fluorophores gained much attention in recent years due to their remarkable photophysical properties and chemical versatility. Their application often involves conjugation with biomolecules, which can be accomplished by inserting a reactive functionality to the fluorescent dye. In this paper we present the preparation and characterization of two unpublished BODIPYs bearing the electrophilic isothiocyanate group, widely used for conjugation with proteins and biological amines. These dyes were prepared by inserting a nitrobenzene group to the BODIPY core via direct arylation, which was later converted to the isothiocyanate functionality. The arylated BODIPYs retained their fluorescence and showed red-shifted absorption and fluorescence spectra, when compared to previously published isothiocyanateBODIPYs. Their application in bioconjugation was tested with bovine serum albumin (BSA) and was confirmed from spectroscopic and electrophoretic analysis. (AU)