prefixation

Prefixation is the first-step fixation technique of chemical fixation for biological specimens observed with a TEM.  This technique aims at inactivation and preservation of proteins.  In the preparation of a biological specimen for TEM observation, dehydration and resin embedding are applied.  Under these procedures, a robust fixation of the fine structures of biological tissues is required.  For such a fixation, it is effective to use strong oxidizing reagents (osmium tetroxide, potassium permanganate, etc.).  However, these reagents have disadvantages that include slow permeation into the specimen and destruction of proteins in the specimen.  To avoid these disadvantageous phenomena, the specimen is pre-fixed with paraformaldehyde or glutaraldehyde, which permeate quickly the specimen and cross-links the proteins to preserve the original morphologies.

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