E-64 (epoxide) & Propidium Iodide Compatibility

Uncle Al UncleAl0 at ix.netcom.com
Thu Nov 6 11:21:48 EST 1997


Louis Hom wrote:
> 
> I usually add E-64, an epoxide-based irreversible protease inhibitor, to
> my cells to, duh, block protease activity.  Anyway, today I needed to
> treat my cells with propidium iodide as a vital stain, but I still wanted
> to use the E-64.  I'm wondering, though, if the presence of all that
> iodide might be attacking the epoxide of E-64, inactivating it.  From what
> I recall, I- isn't a great nucleophile, but it *has* been awhile . . .

It will be pH dependent.  Alkyl epoxides are generally stable to bases
and very labile in acids.  Iodide is a soft Lewis base which must spring
open the epoxide to alkoxide, a very hard Lewis base.  In acid medium
the epoxide will first protonate, facilitating all nucleophilic attack.

It probably won't make much difference either way.  The product
iodohydrin will be hot to reclose to epoxide in the presence of base.

This is biology.  Theory is always after the fact.  Try it.

-- 
Uncle Al Schwartz
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