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Time-resolved polarization imaging by pump-probe (stimulated emission) fluorescence microscopy.
1Novartis Pharma AG, Pharma Research, CTA, LFU/NAT S-360.4.16, CH-4002 Basel, Switzerland.
Biophysical Journal
|June 27, 2000
Summary
Pump-probe fluorescence microscopy enables time-resolved polarization imaging of fluorophores within cells. This novel method reveals cellular microenvironment viscosity and molecular interactions with high resolution.
Area of Science:
- Biophysics
- Cell Biology
- Microscopy
Background:
- Time-resolved polarization imaging offers insights into molecular dynamics.
- Existing methods may lack the resolution or speed for cellular-level analysis.
Purpose of the Study:
- To apply pump-probe fluorescence microscopy for time-resolved polarization imaging.
- To characterize the pump-probe stimulated emission process for cellular imaging.
- To image polarization properties of fluorophores across entire cells.
Main Methods:
- Developed equations for pump-probe stimulated emission.
- Characterized laser power levels for signal saturation.
- Applied pump-probe fluorescence microscopy to image latex spheres and labeled cells.
Main Results:
- Observed depolarization in an orange latex sphere, potentially due to energy transfer.
- Measured fast rotation of CellTracker Orange CMTMR in mouse fibroblasts (30-150 ps rotational correlation time).
- Demonstrated high-resolution, time-resolved polarization imaging across entire cells.
Conclusions:
- Pump-probe stimulated emission is effective for acquiring detailed polarization information.
- The technique reveals microenvironmental viscosity and molecular dynamics within cells.
- This method provides a novel approach for studying cellular structures and functions.