You are correct. My Friday frazzled brain is stuck in pharmacology mode so
I was thinking not of free hydroxide concentration but in terms of
potential exchangable groups being sequestered by the buffer. No more
posting on Friday. My apologies.

Katherine

On Fri, May 11, 2012 at 12:23 PM, Jacob Keller <
[email protected]> wrote:

> Just to make sure I understand pH correctly: isn't it true that the [OH-]
> should always be the same at a given pH (by definition)?
>
> JPK
>
> On Fri, May 11, 2012 at 11:48 AM, Katherine Sippel <
> [email protected]> wrote:
>
>> That is probably because you pH Tris with HCl rather than HEPES with
>> NaOH. The Ksp for Zn(OH)2 is 3x10^17 so the excess hydroxides are probably
>> what are killing your solution.
>>
>> Cheers,
>>
>> Katherine
>>
>>
>> On Fri, May 11, 2012 at 11:43 AM, Rajesh Kumar <[email protected]>wrote:
>>
>>>  If there is no cure , then fine.
>>> pH may not be the answer as it doesn't Happen with TRIS buffer pH 7.6.
>>> Thanks to every one
>>> Rajesh
>>>
>>>
>>> ------------------------------
>>> Date: Fri, 11 May 2012 12:35:45 -0400
>>> From: [email protected]
>>>
>>> Subject: Re: [ccp4bb] zinc with HEPES
>>> To: [email protected]
>>>
>>>
>>>
>>>  There is no cure for HEPES.
>>>
>>>
>>>
>>>
>>> --
>>> =======================================================================
>>> All Things Serve the Beam
>>> =======================================================================
>>>                                David J. Schuller
>>>                                modern man in a post-modern world
>>>                                MacCHESS, Cornell University
>>>                                [email protected]
>>>
>>>
>>
>
>
> --
> *******************************************
> Jacob Pearson Keller
> Northwestern University
> Medical Scientist Training Program
> email: [email protected]
> *******************************************
>

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