Development of a 1,3a,6a-triazapentalene derivative as a compact and thiol-specific fluorescent labeling reagent

Atsushi Nakayama,Daisuke Tsuji,Akira Nakayama,Tsubasa Inokuma,Akira Otani,Kosuke Namba,Akira Otaka,Kohji Itoh,Haruka Mukaiyama,Keiji Tanino

doi:10.1038/s42004-019-0250-0

Atsushi Nakayama, Daisuke Tsuji + Show 8 more

Open Access

https://doi.org/10.1038/s42004-019-0250-0

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Abstract

For the fluorescence imaging of biologically active small compounds, the development of compact fluorophores that do not perturb bioactivity is required. Here we report a compact derivative of fluorescent 1,3a,6a-triazapentalenes, 2-isobutenylcarbonyl-1,3a,6a-triazapentalene (TAP-VK1), as a fluorescent labeling reagent. The reaction of TAP-VK1 with various aliphatic thiols proceeds smoothly to afford the corresponding 1,4-adducts in high yields, and nucleophiles other than thiols do not react. After the addition of thiol groups in dichloromethane, the emission maximum of TAP-VK1 shifts to a shorter wavelength and the fluorescence intensity is substantially increased. The utility of TAP-VK1 as a compact fluorescent labeling reagent is clearly demonstrated by the labeling of Captopril, which is a small molecular drug for hypertension. The successful imaging of Captopril, one of the most compact drugs, in this study demonstrates the usefulness of compact fluorophores for mechanistic studies.

Highlights

For the fluorescence imaging of biologically active small compounds, the development of compact fluorophores that do not perturb bioactivity is required
We report the successful development of a compact fluorescent labeling reagent that reacts with aliphatic thiols based on the 1,3a,6a-triazapentalene (TAP) skeleton, in which the usefulness of the compact fluorophore is clearly demonstrated by the fluorescence imaging of small-molecule drug in living cells
We recently discovered that a 1,3a,6a-triazapentalene (TAP) (1) skeleton is a compact and highly fluorescent chromophore with the potential to overcome the molecular size problem (Fig. 2)[15], and it has been applied to various fluorescent probes[16,17,18,19]

Summary

Introduction

For the fluorescence imaging of biologically active small compounds, the development of compact fluorophores that do not perturb bioactivity is required. The utility of TAP-VK1 as a compact fluorescent labeling reagent is clearly demonstrated by the labeling of Captopril, which is a small molecular drug for hypertension. The successful imaging of Captopril, one of the most compact drugs, in this study demonstrates the usefulness of compact fluorophores for mechanistic studies. Most highly fluorescent molecules are large in relation to bioactive organic compounds, and fluorescence-labeled compounds sometimes lose their biological activities as a result of the structural modifications. We report the successful development of a compact fluorescent labeling reagent that reacts with aliphatic thiols based on the 1,3a,6a-triazapentalene (TAP) skeleton, in which the usefulness of the compact fluorophore is clearly demonstrated by the fluorescence imaging of small-molecule drug in living cells

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