Re: [ccp4bb] heavyatom soaking problem

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CCP4bb <-- 1999 <-- November 1999 <-- 30 November 1999

Previous message:
Subject: Re: packing
From: Wim Burmeister wpb {- at -} EMBL-GRENOBLE {- dot -} FR
Date: 2007-06-29

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Subject: Re: heavyatom soaking problem
From: "Sanishvili, Ruslan" rsanishvili {- at -} ANL {- dot -} GOV
Date: 2007-06-29

Subject: Re: heavyatom soaking problem
From: "Mark A {- dot -} White" white {- at -} XRAY {- dot -} UTMB {- dot -} EDU
Date: 2007-06-29

Priyank,

When yo add NaI or KI, is it in addition to the 0.75M NaCl or in place
of it? Try replacing the 0.75M NaCl with your halide salt, then your
buffers should be isoionic-strength. Also have you tried a CsCl soak?
Remember that with all heavy atoms, and halide soaks in particular, you
need to collect highly redundant data to get at the signal. If you have
access to a synchrotron, then you can use NaBr, for MAD and/or use
longer wavelength radiation to increase the anomalous signal from the I
or Cs atoms.

Best of luck,

Mark

On Thu, 2007-06-28 at 18:28 +0100, Priyank Maindola wrote:

> Hello all,
> I am struggling with getting the phases out for my protein. Heavyatom
> database shows that only mercury and samarium have the binding motifs in it.
>
> Sodium iodide soak is killing the crystal even as less as 0.2 Molar
> concentration for 30sec.
> With Potassium iodide crystal is okay upto 0.75M for 1 & a half min but the
> incorporation is not at relevent sites.(Iodide signal is not distinct and
> is weak)
> Hg & Au salts precipitate it.
> With Pt signal is weak.
> Somewhere I read that high salt causes problems for heavy atom to bind to
> protein.My protein needs high salt for stability (750mM NaCl)
>
> Please help with some suggestion!!

Sincerely yours,

Mark A. White, Ph.D.
Assistant Professor, Dept. Biochemistry and Molecular Biology,
Manager, Sealy Center for Structural Biology and Molecular Biophysics
X-ray Crystallography Laboratory,
Basic Science Building, Room 6.660 C
University of Texas Medical Branch
Galveston, TX 77555-0647
Tel. (409) 747-4747
Fax. (409) 747-4745
mailto://white@xray.utmb.edu
http://xray.utmb.edu
http://xray.utmb.edu/~white

CCP4bb navigation

CCP4bb <-- 1999 <-- November 1999 <-- 30 November 1999

Previous message:
Subject: Re: packing
From: Wim Burmeister wpb {- at -} EMBL-GRENOBLE {- dot -} FR
Date: 2007-06-29

Next message:
Subject: Re: heavyatom soaking problem
From: "Sanishvili, Ruslan" rsanishvili {- at -} ANL {- dot -} GOV
Date: 2007-06-29