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Published on: September 15, 2016
Site-Specific Labeling of Proteins with Near-IR Heptamethine Cyanine Dyes
Chen-Ming Lin1, Syed Muhammad Usama2, Kevin Burgess3
1Department of Chemistry, Texas A & M University, Box 30012, College Station, TX 77842, USA. chen-ming_lin@tamu.edu.
Abstract:
Convenient labeling of proteins is important for observing its function under physiological conditions. In tissues particularly, heptamethine cyanine dyes (Cy-7) are valuable because they absorb in the near-infrared (NIR) region (750⁻900 nm) where light penetration is maximal. In this work, we found Cy-7 dyes with a meso-Cl functionality covalently binding to proteins with free Cys residues under physiological conditions (aqueous environments, at near neutral pH, and 37 °C). It transpired that the meso-Cl of the dye was displaced by free thiols in protein, while nucleophilic side-chains from amino acids like Tyr, Lys, and Ser did not react. This finding shows a new possibility for convenient and selective labeling of proteins with NIR fluorescent probes.
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