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Choosing the appropriate section thickness in the melamine embedding technique.
Journal of Microscopy
|February 1, 1985
Summary
Biological materials hardened with resin allow for extreme thin-sectioning. While larger structures like ferritin and microtubules show damage at 10 nm, DNA molecules are preserved, indicating resin infiltration is key for preserving fine biological structures.
Area of Science:
- Biophysics
- Materials Science
- Electron Microscopy
Background:
- Extreme thin-sectioning is crucial for high-resolution structural analysis of biological materials.
- Conventional sectioning methods can introduce mechanical damage, compromising structural integrity.
- Melamine resin infiltration offers a novel approach to harden biological samples for ultra-thin sectioning.
Purpose of the Study:
- To evaluate the effectiveness of water-soluble melamine resin infiltration for preserving structural information in ultra-thin biological sections.
- To compare the structural integrity of various biological macromolecules and cellular components after extreme thin-sectioning using resin infiltration.
- To determine the minimum section thickness required for electron phase contrast imaging of unstained insect muscle.
Main Methods:
- Biological samples (beef liver catalase, calf thymus DNA, horse spleen ferritin, insect muscle, rat microtubules) were infiltrated with water-soluble melamine resin and hardened.
- Unsupported transparent thin sections of varying thicknesses were prepared.
- Structural information from resin-infiltrated sections was compared to that of normal thin sections using electron microscopy.
- Mechanical damage was assessed by resectioning.
- Minimum section thickness for imaging was determined for insect muscle.
Main Results:
- Resin infiltration enabled extreme thin-sectioning of biological materials.
- Larger structures (ferritin, microtubule subunits, catalase crystals) showed mechanical damage in 10 nm sections.
- Smaller structures (DNA molecules, 3 nm diameter) were satisfactorily preserved in 10 nm sections.
- A minimum section thickness of 30-40 nm was required for electron phase contrast imaging of unstained insect muscle.
Conclusions:
- Water-soluble melamine resin infiltration is a viable method for preparing biological samples for extreme thin-sectioning, preserving fine structural details.
- The effectiveness of preservation is dependent on the size and nature of the biological material.
- This technique advances the capability for high-resolution structural analysis of delicate biological specimens.