Water-soluble norsquaraine dyes for protein labeling and pH-sensing applications

Iryna V. Hovor, Olga S. Kolosova, Edward V. Sanin, Olena M. Obukhova, Anatoliy L. Tatarets, Ewald A. Terpetschnig, Leonid D. Patsenker

Research output: Contribution to journalArticlepeer-review

15 Scopus citations


Novel pH-sensitive, water-soluble, long-wavelength fluorescent norsquaraine dyes and their barbituric and dicyanomethylene derivatives were synthesized and investigated. Some of these dyes contain a carboxylic functionality that was converted into an NHS ester to facilitate bio-conjugation. The absorption and emission spectra, fluorescence quantum yields, lifetimes, polarization, and photostabilities were measured free in solution and after binding to bovine serum albumin (BSA) and compared to those of conventional squaraines and the norcyanine dye CypHer5. Contrary to squaraines, norsquaraines are pH-sensitive but almost unaffected by the interaction with proteins. These dyes can potentially be used as fluorescent labels for biomedical applications, in particular for protein labeling, polarization-based assays, cell-based and pH-sensing measurements.

Original languageEnglish
Article number107567
JournalDyes and Pigments
StatePublished - Nov 2019


  • BSA conjugates
  • Fluorescence lifetimes
  • Fluorescent pH-sensors
  • Norsquaraines
  • Quantum yields
  • Squaraines


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