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Re: [ccp4bb] Characterization of common salt crystal forms?
 

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CCP4bb <-- 2008 <-- January 2008 <-- 23 January 2008
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From: mb1pja P {- dot -} Artymiuk {- at -} SHEFFIELD {- dot -} AC {- dot -} UK
Date: 2008-01-23 		Next message:
Subject: Re: Why there are difference density when occupancy is 1.00
From: Eleanor Dodson ccp4 {- at -} YSBL {- dot -} YORK {- dot -} AC {- dot -} UK
Date: 2008-01-23


Subject: Re: Characterization of common salt crystal forms?
From: "R {- dot -} M {- dot -} Garavito" garavito {- at -} MSU {- dot -} EDU
Date: 2008-01-23
Joe,


As David said many different types of salt crystals can grow in the
presence of phosphate, even when the concentrations of PO4 or many
divalent cations are VERY low (10s of micromolar or less). Struvite
is common (NH4MgPO4) when ammonium sulfate is the precipitant, mM
magnesium is present, and the pH is >7; struvite is a common mineral
in kidney stones. If we have removed phosphate just before
crystallization, as with a spin desalting column (best way) or by
repeated spin concentration (poorer way), we always redouble check
"hits" in divalent cation containing conditions with a variety of
controls (e.g., keep the filtrate fraction from the last spin
concentration step).

Michael



****************************************************************
R. Michael Garavito, Ph.D.
Professor of Biochemistry & Molecular Biology
513 Biochemistry Bldg.
Michigan State University
East Lansing, MI 48824-1319
Office: (517) 355-9724 Lab: (517) 353-9125
FAX: (517) 353-9334 Email: garavito@msu.edu
****************************************************************


On Jan 23, 2008, at 4:06 AM, David Briggs wrote:

> Hi Joe,
>
> I've known most salt crystals in Phosphate - and I think most people
> are weary of phosphate.
>
> Also, Calcium Sulphate is a fairly common one, esp if your buffers are
> titrated with sulphuric acid. Fluoride Ions are also prone to form
> salt crystals with transition metal ions.
>
> HTH,
>
> Dave
>
>
> On 22/01/2008, Joe Krahn wrote:
>> Salt crystals are common in macromolecular crystallography. Has
>> anyone
>> tried to tabulate salt crystal forms that commonly occur?
>>
>> I just identified a salt crystal as Mirabilite, made of Na2SO4·10H2O.
>> The high water content makes them rather soft, and may not be
>> recognized
>> as salt right away. In this case, it probably happened because the
>> buffer was made with Na·Citrate + HCl instead of citric acid, while
>> trying to optimize conditions. So, characterization of salt
>> crystals can
>> help to avoid the conditions that cause them.
>>
>> There is probably a reasonably small number of salt crystal forms
>> that
>> are very common in crystallization trials. Maybe it would be
>> useful to
>> tabulate common salt crystals to help guide optimization experiments.
>> Has anyone else tried to use salt crystal information beyond ensuring
>> that it is not protein?
>>
>> Joe Krahn
>>
>
>
> --
> ============================
> David C. Briggs PhD
> Father & Crystallographer
> http://www.dbriggs.talktalk.net
> AIM ID: dbassophile
> ============================
>


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CCP4bb <-- 2008 <-- January 2008 <-- 23 January 2008
Previous message:
Subject: Re: microsoft 3-button wheel mouse with OS X 10.5
From: mb1pja P {- dot -} Artymiuk {- at -} SHEFFIELD {- dot -} AC {- dot -} UK
Date: 2008-01-23 		Next message:
Subject: Re: Why there are difference density when occupancy is 1.00
From: Eleanor Dodson ccp4 {- at -} YSBL {- dot -} YORK {- dot -} AC {- dot -} UK
Date: 2008-01-23


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