Protein crystals grown in Phosphate-Citrate buffer, pH 4.2 behave exactly the
way Richard described: they first turn blue then fade through yellow-brown.
Vaheh
-----Original Message-----
From: CCP4 bulletin board on behalf of Richard Gillilan
Sent: Mon 3/15/2010 2:23 PM
To: [email protected]
Subject: [ccp4bb] Fwd: [ccp4bb] Blue color upon X-ray exposure?
>
> I have personally noticed that the blue color only appears when the pH of the
> hyperquenched solution is higher than 7 or so. I assume this is because
> solvated electrons react with protons to form their conjugate base: the
> hydrogen atom. The latter species is highly reactive as well, but it is not
> colored.
...
We see a very strong dark blue in cryoSAXS experiments on lysozyme buffer at pH
4.5 (acetate) containing high glycerol content. We've also seen that color fade
to light yellow/brown over time while in the cryostream once irradiation has
stopped (I don't recall if that particular solution had protein or not). The
blue color appears long before the Henderson limit and does not seem to affect
the scattering profile.
I believe a similar effect is at work in bottle glass that has been exposed to
sunlight for a long time - color centers. Blue ice seen in the far north
however, appears to be purely a light-scattering phenomenon and not a result of
trapped electrons.
Richard Gillilan
MacCHESS
>
> -James Holton
> MAD Scientist
>
> Todd Geders wrote:
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