Immunolabeling for correlative light and electron microscopy on ultrathin cryosections

Area of Science:

• Biophysics
• Molecular Biology
• Microscopy Techniques

Background:

• Correlative light and electron microscopy (CLEM) enables simultaneous observation of molecular species.
• Accurate colocalization requires robust labeling strategies for both imaging modalities.
• Existing methods may face challenges with signal interference and spatial resolution.

Purpose of the Study:

• To develop and validate a correlative labeling technique for simultaneous light microscopy (LM) and transmission electron microscopy (TEM).
• To optimize labeling protocols to prevent fluorescence quenching while maintaining high spatial resolution.
• To enable rapid evaluation of labeling efficiency using LM before extensive TEM analysis.

Main Methods:

• Utilized ultrathin cryosections labeled with myosin bands.
• Employed fluorophore-conjugated secondary antibodies for LM and colloidal gold (cAu)-conjugated primary antibodies for TEM.
• Investigated the effect of fluorophore-cAu particle distance and size on fluorescence signal intensity.

Main Results:

• Fluorescence quenching was inversely related to the distance between fluorophore and cAu particles.
• Using secondary antibodies for fluorophore attachment significantly reduced quenching compared to direct labeling.
• The technique allowed rapid LM assessment and yielded complementary LM/TEM data sets.

Conclusions:

• Correlative labeling with fluorescent secondary antibodies and cAu-conjugated primary antibodies is effective for molecular colocalization.
• This method provides efficient sample evaluation and high-resolution imaging in CLEM.
• The strategy minimizes fluorescence quenching, enhancing the utility of CLEM for biological research.