Multi-purpose embryo extracts- Freon Free protocol

Multi-purpose embryo extracts- a freon-free protocol to remove yolk from oocyte extracts.

Source: Veenstra Lab, Radboud Centre for Molecular Life Sciences, the Netherlands

Diluted yolk-depleted embryo extracts:

Yolk can be depleted from whole-embryo lysates by simple centrifugation.
Please note that high salt or ionic detergents (SDS) partially solubilize yolk, which interferes with clearing the extract.


  • Collect staged embryos (up to 50 / tube)

  • Remove excess buffer / water

  • Snap freeze in liquid nitrogen / dry ice

  • Store at -80°C

  • Add 4 volume equivalents of room temperature WCE-LS buffer to frozen embryos

NB One embryo corresponds to approx. 1 μl

Final concentration 0.2 embryo equivalent / μl (X. laevis)

  • Quick-thaw and homogenize embryos by pipetting up and down (yellow tip), then keep on ice
  • Spin in eppendorf centrifuge for 5 mins at max speed at 4ºC
  • Quick-freeze (aliquots of) supernatant in liquid nitrogen / dry ice, store at -80°C

Low-salt whole cell extract (WCE-LS) buffer

20 mM Tris pH 7.5

70 mM KCl


10 % Glycerol

5 mM DTT

0.125 % Nonidet P40 / IGEPAL CA-630

Add “Complete” protease inhibitor, or cocktail of leupeptin, pepstatin A aprotinin 1 μg/μl each

Example: Veenstra GJ, Destrée OH, Wolffe AP. Translation of maternal TATA-binding protein mRNA potentiates basal but not activated transcription in Xenopus embryos at the midblastula transition. Mol Cell Biol. 1999 Dec;19(12):7972-82. doi: 10.1128/MCB.19.12.7972. PMID: 10567523; PMCID: PMC84882.