Nitroolefin functionalized bodipy dyes for protein labeling

Abstract

Protein labeling has significant importance in terms of visualizing dynamics of proteins, cell-cell interactions, mechanisms of life cycles of proteins, etc. Proteins are labeled by either synthetic or natural molecules with purposes such as analysis of 3D structures, determination of turnover number, covalent modifications and tracking protein-protein interactions. In addition to this, sensing and signalling thiol groups have gained popularity recently. Nitroolefin groups on dyes are good Micheal acceptors which undergo fast and selective reaction with thiol moieties. With this knowledge, in this study, we aimed to obtain derivatives of BODIPY dyes having nitroolefin substituents on its different positions. Nitroolefin functionalization of BODIPY dyes was targeted to result in conjugation of nitroolefins with thiol groups such as those belonging to cysteine residues on proteins. Three different nitroolefin functionalized BODIPY dyes have been designed, synthesized and characterized successfully. Incorporating triethylene glycol (TEG) units onto BODIPYs increased water-solubility of the molecules. To prove bioconjugation of the dyes with proteins, absorbance and emission changes were recorded after reaction with both L-cysteine and Bovine Serum Albumin (BSA) and large spectral changes were obtained. The result suggests that nitroolefin functionalization of BODIPY dyes is a promising way to sense biological thiols and hence labeling proteins having thiol groups.