Issue 24, 2015

Site-specific conjugation of 8-ethynyl-BODIPY to a protein by [2 + 3] cycloaddition


We report a straightforward synthesis of 8-ethynyl-BODIPY derivatives and their potential as fluorescent labeling compounds using an alkyne–azide click chemistry approach. The ethynyl substituted BODIPY dyes at the meso-position were reacted under Cu+ catalysis and mild physiological conditions in organic and biological model systems using benzyl azide and a Barstar protein which was selectively modified by a single amino acid substituted methionine at the N-terminus (Met1) → azidohomoalanine (Aha). Conjugation with the protein and the model azide was indicated by a significant blue shift upon formation of the triazole moiety system, which allowed easy distinction between free and coupled dyes. This blue shift was rationalized by the perpendicular orientation of the triazole relative to the chromophore using time dependent density functional theory (TDDFT) calculations. A full spectroscopic and thermodynamic characterization of the protein revealed that a fluorophore was incorporated without the cross influence of protein stability and functional integrity. Furthermore, model reactions of 8-ethynyl-BODIPY derivatives with benzyl azide under copper-free conditions indicate second order kinetics with high rate constants comparable with those found for the strain-promoted azide–alkyne cycloaddition (SPAAC). In this way, we establish a unique and highly efficient method to introduce alkyne-BODIPY into a protein scaffold potentially useful for diverse applications in areas ranging from fundamental protein dynamics studies to biotechnology or cell biology.

Graphical abstract: Site-specific conjugation of 8-ethynyl-BODIPY to a protein by [2 + 3] cycloaddition

Supplementary files

Article information

Article type
13 Mar 2015
06 May 2015
First published
07 May 2015
This article is Open Access
Creative Commons BY license

Org. Biomol. Chem., 2015,13, 6728-6736

Author version available

Site-specific conjugation of 8-ethynyl-BODIPY to a protein by [2 + 3] cycloaddition

M. Albrecht, A. Lippach, M. P. Exner, J. Jerbi, M. Springborg, N. Budisa and G. Wenz, Org. Biomol. Chem., 2015, 13, 6728 DOI: 10.1039/C5OB00505A

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