Synthesis of squaraine-N-hydroxysuccinimide esters and their biological application as long-wavelength fluorescent labels

Ewald A. Terpetschnig; Henryk Szmacinski; Joseph R. Lakowicz

doi:10.1117/12.182771

17 August 1994 Synthesis of squaraine-N-hydroxysuccinimide esters and their biological application as long-wavelength fluorescent labels

Ewald A. Terpetschnig, Henryk Szmacinski, Joseph R. Lakowicz

Author Affiliations +

Proceedings Volume 2137, Time-Resolved Laser Spectroscopy in Biochemistry IV; (1994) https://doi.org/10.1117/12.182771
Event: OE/LASE '94, 1994, Los Angeles, CA, United States

Abstract

We synthesized two conjugatable long-wavelength fluorescence probes. They consist of a squaraine moiety, which is a cyanine- type chromophore with a central squarate bridge and a reactive N- hydroxysuccinimide group for coupling with amino functions. One form is water soluble due to the presence of a sulfobutyl group, the other is water insoluble. The water insoluble form was reacted with taurine to achieve water solubility and this squaraine-taurine conjugate displayed a very high binding affinity to BSA. The squaraines exhibit desirable properties of short lifetimes and low quantum yields in water, with a significant increase of lifetime and quantum yields when bound to proteins. Their absorption maxima around 635 nm in water and 640 nm when bound to proteins allow excitation with the newly commercially available diode lasers sources at 635, 645, and 650 nm. The spectral properties and photostabilities of the water soluble squaraine probes are compared with those of the commercially available CY5-NHS-ester.

Citation Download Citation

Ewald A. Terpetschnig, Henryk Szmacinski, and Joseph R. Lakowicz "Synthesis of squaraine-N-hydroxysuccinimide esters and their biological application as long-wavelength fluorescent labels", Proc. SPIE 2137, Time-Resolved Laser Spectroscopy in Biochemistry IV, (17 August 1994); https://doi.org/10.1117/12.182771

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