TCEP is often sold as hydrochloride salt and therefore reacts highly
acidic. We usually titrate the concentrated solution *before* we add
it to our proteins. This can be done within small volumes by dropwise
addition of a saturated TRIS solution, check pH by pipetting a drop on
a pH test strip.
Clemens
Zitat von "John A. Newitt" <[log in to unmask]>:
> At 5:04 PM -0600 11/25/08, Jacob Keller wrote:
>
>> Sorry for this very prosaic question:
>>
>> does anybody have a reference describing the mechanisms of reducing
>> agents (TCEP, DTT, BME, etc.), and in particular the effects of the
>> reactions on pH? I think I can draw a convincing reaction mechanism
>> for myself, but I am not sure theoretically why (or even whether)
>> the pH drops in the presence of reducing agents (although I am
>> pretty sure empirically that it does.) I have looked around a bit,
>> but perhaps have not hit on the right google search terms...
>
> This doesn't directly address the question I think you are asking,
> but one obvious way that adding reducing agents could affect the pH
> is if they contain significant amounts of strong acids. One vendor
> of TCEP that we used in the past presumably had so much residual HCl
> in the solid reagent that even when TCEP was added at 1 mM it caused
> a significant decrease in pH of a buffered solution. It taught us to
> check the pH after adding reducing agents and also to find another
> vendor.
>
> - John
>
>
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