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Cryptolepine and quindoline: understanding their photophysics.

Inês F A Mariz1, Sandra Pinto, João Lavrado

  • 1Centro de Química-Física Molecular (CQFM) and Institute of Nanoscience and Nanotechnology (IN), Instituto Superior Técnico, University of Lisbon, Av. Rovisco Pais, 1,1049-001 Lisboa, Portugal. ermelinda.macoas@tecnico.ulisboa.pt ines.mariz@tecnico.ulisboa.pt.

Physical Chemistry Chemical Physics : PCCP
|March 8, 2017
PubMed
Summary

Quindoline (QUIND) and cryptolepine (CRYPT) photophysics were studied across various pH and solvent conditions. Both compounds exhibit two-photon absorption, enabling cellular imaging with CRYPT localizing in the nucleus and QUIND in the cytoplasm.

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Area of Science:

  • Photophysics and photobiology
  • Medicinal chemistry
  • Cellular imaging

Background:

  • Quindoline (QUIND) and cryptolepine (CRYPT) derivatives have demonstrated significant biological activity, particularly against malaria.
  • Fluorescence-based methods are standard for assessing drug efficacy, but the photophysical properties of CRYPT and its analogs remain unclear.
  • Understanding photophysics is crucial for developing novel fluorescence-based diagnostic and therapeutic applications.

Purpose of the Study:

  • To investigate the photophysical properties of QUIND and CRYPT in aqueous solutions across varying pH.
  • To examine the influence of protic and aprotic solvents with different polarities on CRYPT and QUIND.
  • To determine the two-photon absorption (TPA) characteristics and cellular localization of these compounds.

Main Methods:

  • Spectroscopic analysis of QUIND and CRYPT in aqueous solutions at different pH values.
  • Solvent-dependent photophysical studies in protic and aprotic solvents.
  • Measurement of two-photon absorption (TPA) cross-sections in the 710-960 nm range.
  • Cellular imaging in HEK 293 T cells to determine subcellular localization.

Main Results:

  • QUIND and CRYPT exist in multiple prototropic forms influenced by pH and solvent polarity.
  • CRYPT exhibits greater sensitivity to solvent environment compared to QUIND.
  • Both compounds display two-photon stimulated emission with measurable TPA cross-sections.
  • Low TPA cross-sections allowed for cellular observation, revealing CRYPT predominantly in the nucleus and QUIND in the cytoplasm of HEK 293 T cells.

Conclusions:

  • The photophysical behavior of QUIND and CRYPT is significantly affected by pH and solvent polarity.
  • Their two-photon absorption properties enable their visualization within cells.
  • Differential cellular localization (nucleus for CRYPT, cytoplasm for QUIND) suggests distinct biological interactions and potential applications.