EDTA

EDTA (ethylenediaminetetraacetic acid) is a synthetic amino acid and chelating agent for divalent metals. Usually sold as the disodium salt (CAS 6381-92-6) (Sigma E1644).

• Molecular Weight, disodium salt dihydrate: 372.24

• pK₁ = 1.99
• pK₂ = 2.67
• pK₃ = 6.16
• pK₄ = 10.26

• Most enzymes that synthesize or modify nucleic acids (e.g. polymerases, ligases, kinases, nucleases) are Mg²⁺-dependent. The addition of EDTA is a convenient way to stop these reactions.

• EDTA is a component of many buffers used to store DNA, such as TE buffer, where the EDTA removes the metal cofactors (typically Mg⁺⁺ required for activity of DNAses and other DNA damaging enzymes.

• EDTA is essentially insoluble in water, and will only dissolve when neutralized with sodium hydroxide to a pH = 8.0

• Standard stock solutions are 0.5M at pH 8.0. A 1M solution cannot be made. Autoclave.

• Making the standard solution from disodium EDTA (the typical form sold) requires approximately 1 molar equivalent of NaOH

• Here's a great page about EDTA, including formation constant (K_f) values for metal-EDTA complexes. Note that many heavy metal ions (like Fe³⁺, Co²⁺, and Zn²⁺) are chelated much more strongly than Mg²⁺. A little bit of EDTA in your reaction will go a long way to keep these evildoers out of trouble and away from your precious biomolecules without interfering with your Mg²⁺-dependent reactions.

• Here's another article that speaks of the wonders of EDTA and how it can help treat Aunt Edna's cardiovascular disease, enhance your enjoyment of the Friday night happy hour, and act as a "get out of jail free" card.

• EDTA can prolong the life of your motorcycle battery!

• EDTA helps you determine the hidden contents of your hard water.