Re: [ccp4bb] Color of heme containing Xtals

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CCP4bb <-- 2008 <-- March 2008 <-- 13 March 2008

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From: barry {- dot -} hardy {- at -} TELE2 {- dot -} CH barry {- dot -} hardy {- at -} TELE2 {- dot -} CH
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Subject: Re: Color of heme containing Xtals
From: Daniel Picot Daniel {- dot -} Picot {- at -} IBPC {- dot -} FR
Date: 2008-03-13

Subject: Re: Color of heme containing Xtals
From: Juan Sanchez Weatherby weatherby {- at -} EMBL {- dot -} FR
Date: 2008-03-13

Dear Jan,

I'll try to give you a few explanations that may not involve having
upset the hemes in your protein.

You say your crystals are not red but what about the solution? Could you
have salt or other protein crystals but your target protein be fine but
not crystallized. You can get some of the crystals and test them to see
if they are salts. Or run them on a native or SDS gel to see if they are
your protein.

The other thing is that they could only be colored in one direction.
Depending on the orientation off the hemes and the molecules in the
crystal they could not be showing their color. If the crystals are flat
plates or thin needles they could all be in an orientation that makes
them not show their color. If you try handling them or looking at them
from different sides they may be red. Finally I've sometimes had
problems with seeing the color of crystals because they are not very
strong and the background obscures them. Sometimes microscope lights are
very yellow and they also mask color. If you have a digital camera you
can tell it to compensate for this (automatic white background) or using
in photoshop (without tricking of course!). If the buffer is disturbing
the color you can try putting one or two crystals in mother liquor (from
the well) this way you'll have a clear background.

Finally, it could also happen that the plastic in the plate, as well as
your crystallization condition, could be affecting your protein. If you
are not sure try to do your sitting drops onto glass cover slips.

I hope this helps,

Juan

Jan Schoepe wrote:
> 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.*
> .

--
Juan Sanchez-WEATHERBY
Tel:33 (0) 47620 7266
Website: http://www.embl.fr

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CCP4bb <-- 2008 <-- March 2008 <-- 13 March 2008

Next message:
Subject: Re: Color of heme containing Xtals
From: Daniel Picot Daniel {- dot -} Picot {- at -} IBPC {- dot -} FR
Date: 2008-03-13