Conformationally restrained pentamethine cyanines and use in reductive single molecule localization microscopy

Area of Science:

• Organic Chemistry
• Photophysics
• Biophysical Imaging

Background:

• Pentamethine cyanines are crucial far-red fluorophores used in advanced imaging techniques.
• Their application is limited by low quantum yields caused by photoisomerization.
• Improving photon output is essential for enhanced sensitivity in microscopy.

Purpose of the Study:

• To develop a synthetic strategy for enhancing the fluorescence properties of pentamethine cyanines.
• To create conformationally restrained analogs with improved quantum yields and fluorescence lifetimes.
• To enable a simplified single-molecule localization microscopy (SMLM) protocol.

Main Methods:

• A novel cascade reaction involving a protected dialdehyde precursor.
• Formation of a tetracyclic ring system to restrict molecular conformation.
• Characterization of fluorescence quantum yield and lifetimes of the new analogs.

Main Results:

• The synthetic strategy successfully produced conformationally restrained pentamethine cyanine analogs.
• These analogs exhibit significantly improved fluorescence quantum yields.
• Extended fluorescence lifetimes and efficient recovery from hydride reduction were observed.

Conclusions:

• The developed synthetic route effectively overcomes the limitations of traditional pentamethine cyanines.
• The new fluorophores demonstrate superior photophysical properties for imaging applications.
• These enhanced molecules facilitate a simplified and more efficient single-molecule localization microscopy (SMLM).