PMSF solution

Jim Owens jow at
Mon May 22 10:35:15 EST 1995

In article <vuilleumier.140.0009F1D8 at> Stephane
Vuilleumier, vuilleumier at writes:
>We were having a discussion about PMSF stability in solution in the lab. 
>Some claim that PMSF is only stable for minutes in solution
>(ie you only dissolve what you need, no stock solutions). 
>Does anybody have a reference handy?

According to the 1994 Boehringer-Mannheim catalog, American edition, on
page 194:

"...Solubility: Soluble to > 10 mg/ml in isopropanol, ethanol, methanol,
and 1,2-propanediol.  Unstable in aqueous solution.  Suggested working
concentration: 17-174 ug/ml (100-1000uM).  Stability: Dry crystals are
stable at room temperature.  Stable at least nine months at +25 degC in
100% isopropanol."

Also from Boerhinger-Mannheim in the 1987 edition of Biochemica
Information is the following information derived from journal references:

"...Stability and solubility in organic solvents: PMSF is soluble (>= 1M)
in polar organic solvents such as isopropanol, methanol, ethanol, and 1,2
propanediol.  A stock solution of PMSF in 100% isopropanol is stable at
least 9 months at 25degC.  Stability and solubility in aqueous solution: 
PMSF is sparingly soluble (slightly greater than 1mM, 25degC) in aqueous
buffers.  It is also _very_  unstable.  Aqueous solutions of PMSF are
inactivated rapidly (hydrolyzed), an effect accelerated by rising pHG and
temperature.  The half-life of 100uM PMSF at 25degC (measured as ability
to inhibit chymotrypsin) is 110 min. at pH 7.0 (phosphate buffer), 55
min. at pH 7.5 (Hepes), and 35 minutes at pH 8.0 (Tris).  At 4degC, 100uM
PMSF is completely inactivated in 30h at pH 7.6 (Hepes), 22h at pH 8.0
(Tris), and 10h at pH 8.6 (Tris).  Presence of EDTA and other metal
chelators, DTT or 2-mercaptoethanol does not interfere with the action of
The references are:
1) Fahrney and Gold, J Am Chem Soc 85: 997-100 (1963)
2) Gold and Fahrney, Biochemistry 3: 783-791 (1964)
3) Turini, et al., J Pharmacol Exp Ther 167: 98-104 (1969)
4) Gold, Methods Enzymol 11: 706-711 (1967)
5) James. Anal Biochem 86: 574-579 (1978)

I also have the Promega Protein Guide: Tips and Techniques (1993) that
cites Beynon and Bond (1989) in Proteolytic Enzymes: A Practical Approach
for the claim that  a stock solution of PMSF of 200uM in ethanol is
stable for months at 4degC.

Good luck,

Jim Owens

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