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: CCP4BB@JISCMAIL.AC.UK 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: To the extent this electronic communication or any of its attachments contain information that is not in the public domain, such information is considered by MedImmune to be confidential and proprietary. This communication is expected to be read and/or used only by the individual(s) for whom it is intended. If you have received this electronic communication in error, please reply to the sender advising of the error in transmission and delete the original message and any accompanying documents from your system immediately, without copying, reviewing or otherwise using them for any purpose. Thank you for your cooperation.