Bioorthogonal fluorescent labels: a review on combined forces

This review ventures to summarize the latest developments in bioorthogonal fluorescent imaging labels with a special focus on bioimaging applications. We briefly summarize the most preferred means of bioorthogonal tagging schemes for the labeling of specific biomolecular structures. The review is structured by the type of the fluorescent labels that can address the problems that most commonly compromise fluorescent imaging techniques, i.e. the autofluorescence of biomolecules, the background fluorescence of unreacted reagents, and photobleaching. Thus, we present (i) far- red/near-infra-red emitting dyes, (ii) fluorogenic scaffolds, and (iii) nanoparticle-based signaling platforms

Tyrosine specific sequential labeling of proteins

We report (a) on the synthesis of a long-wavelength fluorescent coumarin containing an allyloxy acetate moiety, (b) the synthesis of two linkers containing an allyloxy acetate and an alkyne or azide function, respectively, and (c) the selective modification human serum albumin by a sequential method involving Pd(II) catalyzed modification of the phenolic side chain of tyrosine residues with an alkyne bearing linker and a subsequent azide-alkyne click reaction with an azide functionalized long-wavelength emitting coumarin dye. The method is likely to be applicable to various kinds of azido-modified fluorophores, and the Pd(II)-catalyzed modification of the tyrosines may also be used to introduce other kinds of tags. With these reagents, tyrosine specific modulation of proteins and peptides becomes possible either directly or in a sequential manner

Clickable fluorophores for biological labeling—with or without copper

The synthesis of a set of new clickable fluorophores that virtually cover the whole visible spectrum reaching the near infra-red regime is presented herein. Besides dyes that are capable of participating in classical copper catalyzed 1,3-dipolar cycloaddition reactions with the counterparting function we have also prepared dyes containing a cyclooctyne moiety, an alkyne derivative that enables copper free clicking to azides. The suitability of these dyes for fluorescent labeling of biomolecules is presented by examples on model frameworks representing major biopolymer building blocks. The versatility of these dyes is presented in cell labeling experiments as well as by labeling the azide modified surface glycans of CHO-cells either by copper catalyzed or copper-free click reaction. These dyes are expected to have a large variety of applications in (bio)orthogonal labeling schemes both in vivo and in vitro