Fluorophores allow for the visualization of labeled proteins within complex systems such as living cells. In particular, near-infrared (NIR) fluorescent dyes are of interest for in vivo imaging because they absorb at long wavelengths (&gt;650 nm) that have improved tissue penetration depth, making them desirable for imaging biological processes. Additionally, longer wavelength excitation is less likely to cause background autofluorescence. Recently, we reported a series of NIR dyes that we termed the Nebraska Red (NR) series. NR dyes are based on the rhodamine scaffold and contain a phosphinate group at the bridging position. NR dyes demonstrate remarkable photostability and brightness under physiological conditions, making them especially promising for biological applications. Herein we present the synthesis and evaluation of NR derivatives for protein labeling. NHS ester as well as chloroalkane derivatives for the respective labeling of amines or HaloTag conjugates were obtained. In addition, we have synthesized a fluorogenic spirocyclic derivative for no-wash protein labeling applications. These reagents provide a basis for the analysis of protein localization using NIR fluorescence detection in cellular imaging experiments.

Synthesis and evaluation of Nebraska Red derivatives for protein labeling studies

255th National Meeting (2018)

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