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Re: [ccp4bb] Color of heme containing Xtals |
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CCP4bb navigationCCP4bb <-- 2008 <-- March 2008 <-- 12 March 2008Subject: Re: Color of heme containing Xtals From: R Michael Garavito garavito {- at -} MSU {- dot -} EDU Date: 2008-03-12 Are you saying that the protein you are starting with is not colored (heme is gone or damaged) or that the native protein is only weakly colored (low extinction coefficient at the Soret wavelength)? The former is more disturbing than the latter. For some heme proteins, like peroxidases, you can bleach the heme. DTT and some sulfide containing compound can do this quite easily and I have watched in horror as my brown crystals turned clear (and lost diffraction). If the heme ligand is a histidine, you might knock out a non-covalently bound heme during purification on a Ni-/Co-chelation column. However, the heme is usually tightly bound in most, but not all, heme proteins under non-denaturing conditions. If the problem is the latter, cyanide, carbon monoxide, and other heme ligands can shift the Soret band to a different lambda and, occasionally, enhance the extinction coefficient. Normally, crystallizing heme proteins is not a problem with respect to the heme behavior if the heme is in its resting ferric state. Just avoid detrimental heme ligands and possible reductants (unless you want the ferrous state) and oxidants. But to answer your question better, more information is needed. Cheers, Michael ***************************************** R. Michael Garavito, Ph.D. Professor of Biochemistry Michigan State University East Lansing, MI 48824-1319 517-355-9724 (Office) 517-353-9334 (Fax) garavito@msu.edu ***************************************** > Hello everybody, > > I wonder if anybody has experience with heme (or to be more precise: heme b) containing proteins which Xtals do not look red under the microscope. How might the technique for crystallization (e.g. sitting drop, hanging drop) influence the intensity of the color? Many thanks! > > Jan > > > --------------------------------- > Lesen Sie Ihre E-Mails jetzt einfach von unterwegs.. CCP4bb navigationCCP4bb <-- 2008 <-- March 2008 <-- 12 March 2008 |
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