Related Experiment Video
Updated: Jun 20, 2026
10:23
Time-Resolved Fluorescence Anisotropy from Single Molecules for Characterizing Local Flexibility in Biomolecules
Published on: April 25, 2025
Reducing background contributions in fluorescence fluctuation time-traces for single-molecule measurements in
Zeno Földes-Papp1, Shih-Chu Jeff Liao, Tiefeng You
1ISS, Champaign-Urbana, IL 61822, USA. Zeno.Foldes-Papp@medunigraz.at
Current Pharmaceutical Biotechnology
|August 20, 2009
Summary
New microscopy techniques significantly reduce background noise, enabling sensitive detection of molecules at picomolar concentrations. This breakthrough enhances signal-to-background ratios for single-molecule analysis in solutions and live cells.
Area of Science:
- Optical microscopy
- Biophysical chemistry
- Analytical chemistry
Background:
- Fluorescence fluctuation methods are powerful for studying molecular dynamics.
- High background noise limits sensitivity, especially at low analyte concentrations.
- Current methods often require sample immobilization or complex focusing techniques.
Purpose of the Study:
- To develop novel microscopy techniques for reducing background noise in fluorescence fluctuation measurements.
- To enhance the sensitivity of detecting molecules at low concentrations.
- To enable single-molecule detection in solution and live cells without prior manipulation.
Main Methods:
- Implementation of an excitation shutter to minimize background light.
- Utilization of electronic switches for precise control of illumination.
- Application of early and late time-gating with time-correlated single-photon counting.
- Optimization of optical setup for diffraction-limited resolution.
Main Results:
- Achieved a significant reduction in background contributions.
- Demonstrated a 140-fold increase in fluorescence fluctuation amplitude at 15 pM analyte concentration.
- Obtained a signal-to-background advantage exceeding two orders of magnitude.
- Validated the effectiveness of time-gating strategies for signal enhancement.
Conclusions:
- The developed microscopy methods substantially improve signal-to-background ratios.
- Enables sensitive single-molecule detection in solution and live cells.
- Eliminates the need for immobilization or hydrodynamic/electrokinetic focusing.
- Extends observation times for dynamic molecular studies.
Related Concept Videos
01:37Super-resolution Fluorescence Microscopy
Super-resolution fluorescence microscopy (SRFM) provides a better resolution than conventional fluorescence microscopy by reducing the point spread function (PSF). PSF is the light intensity distribution from a point that causes it to appear blurred. Due to PSF, each fluorescing point appears bigger than its actual size, and it is the PSF interference of nearby fluorophores that causes the blurred image. Various approaches to achieving higher resolution through SRFM have recently been developed.
01:19Protein Dynamics in Living Cells
Different fluorescence-based techniques are used to study the protein dynamics in living cells. These techniques include FRAP, FRET, and PET.
Fluorescent recovery after photobleaching (FRAP) is a fluorescent-protein-based detection technique used to quantify protein movement rates within the cell. This method exposes a small portion of the cell to an intense laser beam. The laser beam causes permanent photobleaching of the fluorophore-tagged proteins in the exposed region. As the bleached...
Fluorescent recovery after photobleaching (FRAP) is a fluorescent-protein-based detection technique used to quantify protein movement rates within the cell. This method exposes a small portion of the cell to an intense laser beam. The laser beam causes permanent photobleaching of the fluorophore-tagged proteins in the exposed region. As the bleached...