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This article is about a similar phenomenon, but not in GFPs. Nonetheless
it is so impressive you should have a look at it:
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Berglund, GL, Carlsson, GH, Smith, AT, Szoke, H, Henriksen, A, Hajdu, J,
The catalytic pathway of horseradish peroxidase at high resolution
NATURE 417 (6887): 463-468 MAY 23 2002
Abstract: A molecular description of oxygen and peroxide activation in
biological systems is difficult, because electrons liberated during
X-ray data collection reduce the active centres of redox enzymes
catalysing these reactions(1-5). Here we describe an effective strategy
to obtain crystal structures for high-valency redox intermediates and
present a three-dimensional movie of the X-ray-driven catalytic
reduction of a bound dioxygen species in horseradish peroxidase (HRP).
We also describe separate experiments in which high-resolution
structures could be obtained for all five oxidation states of HRP,
showing such structures with preserved redox states for the first time.
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On Mon, 2006-05-29 at 15:52 -0400, Artem Evdokimov wrote:
> ...I have noticed a peculiar phenomenon: during the very first X-ray
> exposure, the normally intensely greenish-yellow color of the crystals
> completely disappeared within the area that was hit by the beam. That
> was happening in real time, while the crystal was still frozen. There
> was no significant deterioration of diffraction quality, and the
> structures were successfully solved using these data. We noted no
> anomalies in the chromophore as such – it looks like a typical GFP
> heterocycle, although the resolution isn’t sufficient to refine w/o
> restraints and thus verify the exact bond types etc.
> Here’s the question – does anyone know of a published report of this
> phenomenon, as related to other GFPs, or other colored/fluorescent
> beta-barrel proteins? We couldn’t find any, but that doesn’t mean that
> there wasn’t a mention in one of the dozens of GFP structural papers.
--
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I think we're all bugs and mice, and are only different expressions
of an all-inclusive cheese. - Charles Fort
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David J. Schuller
modern man in a post-modern world
MacCHESS, Cornell University
[EMAIL PROTECTED]
