Site-Specific Labeling of Proteins with Near-IR Heptamethine Cyanine Dyes

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.

Explorations into the Effect of meso‐Substituents in Tricarbocyanine Dyes: A Path to Diverse Biomolecular Probes and Materials

“…Such reactions probably proceed following an S RN 1 mechanism. Due to their simplicity, and the often excellent yields, numerous studies using this pathway have been published [11b, 17] . The observed changes in photophysical properties are remarkable and stretch from increased photostability over direct labeling of proteins to increased Stokes shifts and new functionalities [11b, 18] .…”

“…Due to their simplicity, and the often excellent yields, numerous studies using this pathway have been published [11b, 17] . The observed changes in photophysical properties are remarkable and stretch from increased photostability over direct labeling of proteins to increased Stokes shifts and new functionalities [11b, 18] . While most of the work has been focusing on the synthesis of meso ‐nitrogen, ‐oxygen, and ‐sulfur derivatives, the reaction of cyanine dyes with carbon nucleophiles is, so far, rarely found in the literature.…”

“…Like the meso ‐arylethers, meso ‐Cl dyes were found to undergo nucleophilic substitution with a range of endogenous thiol‐based nucleophiles [11b, 18b, 27b, 61] . This reactivity may be used to directly label peptides and proteins and could, by extension, be used to directly label monoclonal antibodies, or fragments thereof.…”

Research progress of near-infrared fluorescence probes based on indole heptamethine cyanine dyes in vivo and in vitro

“…Lin et al [101] observed that Cy-7 dyes contain meso-Cl and can covalently bind to free Cys residues under physiological conditions (water environment, near-neutral pH, and 37 °C). The results showed that the meso-Cl of the dye was replaced by free thiols in the protein.…”

Bioinspired Heterocyclic Partnership in a Cyanine-Type Acidichromic Chromophore

“…The design and build-up of organic-based chromophores exhibiting tailored electronic and optical features has become an active research field over the past decade. Among different applications, particular interest has been focused on optoelectronics (e.g., dye sensitized solar cells, photo- and chemical-switching systems, organic light emitting devices) [ 1 , 2 , 3 , 4 , 5 ], organic electronics, such as organic semiconductors [ 6 , 7 , 8 , 9 ], imaging technologies (e.g., electrophotography, thermal printing, and ink-jet printing) [ 10 ], and biomedicine (e.g., fluorescent sensors and anticancer treatments or photodynamic therapy) [ 11 , 12 , 13 , 14 , 15 , 16 , 17 ].…”