Journal of Fluorescence

, Volume 3, Issue 3, pp 153–155

An investigation of squaraines as a new class of fluorophores with long-wavelength excitation and emission

  • Ewald Terpetschnig
  • Henryk Szmacinski
  • Joseph R. Lakowicz
Probe Development

DOI: 10.1007/BF00862734

Cite this article as:
Terpetschnig, E., Szmacinski, H. & Lakowicz, J.R. J Fluoresc (1993) 3: 153. doi:10.1007/BF00862734

Abstract

We present an overview of our investigation of the spectral properties and photostabilities of squaraine derivatives. The objective was to identify long-wavelength probes with reasonable quantum yields, reasonably long lifetimes, and good photostabilities for use in fluorescence-based assays and/or imaging. Both symmetrical and unsymmetrical squaraines were studied. Based on this investigation the most suitable probes for use in a biological application were found to be the symmetrical indolenine derivatives of the squaraines, which display the highest photostability. Importantly, their quantum yields and lifetimes increase significantly upon covalent and noncovalent binding to proteins (bovine serum albumin, antibodies), demonstrating the usefulness of the squaraines as long wavelength probes. The squaraine absorbance maxima between 630 and 650 nm allows the use of the new commercially available 635- and 650-nm diode lasers.

Key Words

Fluorescence sensing squaraines phase-modulation fluorometry red fluorescence near-infrared fluorescence 

Copyright information

© Plenum Publishing Corporation 1993

Authors and Affiliations

  • Ewald Terpetschnig
    • 1
  • Henryk Szmacinski
    • 1
  • Joseph R. Lakowicz
    • 1
  1. 1.Center for Fluorescence Spectroscopy, Department of Biological ChemistryUniversity of Maryland-School of MedicineBaltimore

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