A photostable, pH-invariant fluorescein derivative for single-molecule microscopy

Area of Science:

• Biochemistry and Biophysics
• Organic Chemistry
• Analytical Chemistry

Background:

• Fluorescein isothiocyanate (FITC) is a widely used fluorescent label but suffers from limited photostability and pH sensitivity.
• Development of novel fluorophores with improved properties is crucial for advanced biological imaging and sensing.
• Biotinylated probes are essential tools for molecular biology, enabling specific detection and purification of biomolecules.

Purpose of the Study:

• To characterize the spectral and single-photon fluorescence properties of a novel fluorescein derivative and its biotinylated analog.
• To evaluate the photostability and pH independence of the new fluorescein variant compared to FITC.
• To assess the suitability of the new fluorophore for single-molecule studies and as a fluorescent bridge.

Main Methods:

• Spectroscopic analysis (absorption and emission spectra).
• Single-photon fluorescence measurements.
• Photostability and pH stability assays.
• Characterization of functional groups for conjugation.

Main Results:

• The novel fluorescein derivative exhibits significantly enhanced photostability over FITC.
• The fluorophore demonstrates excellent pH independence across a wide range.
• Two independent functional groups (aniline NH2 and phenol OH) allow for versatile chemical modification.
• High-quality single-photon counting data confirms its suitability for single-molecule applications.

Conclusions:

• The new fluorescein derivative represents a significant advancement over traditional fluorescein labels.
• Its robust photophysical properties and versatile conjugation capabilities make it a valuable tool for various biological applications, including single-molecule detection.
• The biotinylated analog provides a specific and sensitive probe for biomolecular interactions.