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Star Republic: Guide for Biologists

Fixation solutions

Fixation

Mechanism

Advantages/Disadvantages

Examples

Acetone

Precipitation

Excellent preservative of immnuoreactive sites, poor penetrator. Used only for cells and sections. May cause protein loss, shrinkage and artifacts.

100% acetone (4 or –20 ˚C)

Ethanol

Precipitation

Good antibody penetration, don't block immunoreactive site. Conformational change may occur. Preferred for preserve DNA and RNA. May cause protein loss, shrinkage and artifacts.

70% cold ethanol

Methanol

Precipitation

100% methanol (-20 ˚C)

Glutaraldehyde

Cross-linking

Glutaraldehyde provides the best morphological preservation but causes high background fluorescence. Difficult for macromolecules to penetrate. Cross-links DNA and RNA.

0.4% Glutaraldehyde, 4% Paraformaldehyde, 0.1 M Phosphate buffer, pH 7.4

Formaldehyde

Cross-linking

Well tolerated by tissue and have good penetration. Cross-linking slower than Glutaraldehyde. Optimal fixation condition variable. Difficult for macromolecules to penetrate. Cross-links DNA and RNA.

10% formaline or 1-5% formaldehyde in PBS

Neutral buffered formalin

Bouin’s solution (0.9% picric acid,5% acetic acid, 1% formaldehyde)

Zinc chloride (2.5%ZnCl2,6%formaldehye,0.95%acetic acid)

 

Note: see Formaldehyde/paraformaldehyde/formalin for relationships between these reagents.