IF Solutions

Blocking buffer for immunofluorescence of cultured or primary cells
(also used for primary and secondary antibody incubation steps)

1x PBS (1 mM Ca²⁺, 1 mM Mg²⁺), pH 7.4
+ 0.2% saponin
+5% normal donkey serum (or goat, depending on secondary antibody species)
+1% BSA

Dissolve by stirring or gentle vortexing.  Filter sterilize and store aliquots at -20°C.

For permeabilization step, supplement the above with 0.1-0.3% Triton X-100.


4% formaldehyde solution for fixing cells

1. Dissolve 4g paraformaldehyde in 80ml H2O in a fume hood
2. Heat to 60 °C (approximately) on a hot plate with stirring until mostly dissolved; add a few drops of NaOH to help dissolve
3. Cool to room temperature
4. Add 10 ml 10x PBS (no Ca²⁺, Mg²⁺) 
5. Filter with a 0.22 µM disposable syringe filter

Use within 1 week or store aliquots at -20°C for up to 3 months.