[ccp4bb] radiation damage question

[Patrick Loll]

Hi all,

I had an interesting experience, and wonder if others have seen  
similar things.


I was collecting data from a crystal that contains an iodinated  
macromolecule. After 2 days on a copper rotating anode, with the  
crystal at 100 K, we experienced a detector problem, so I put the  
crystal back into the dewar; it was diffracting nicely when I took it  
off. For various reasons, I didn't get back to this crystal until  
about 3 weeks later. When I put it back on the goniostat, the mother  
liquor was milky white in appearance. There were no ice rings, but  
alas the crystal only gave a few anemic spots around the beamstop.  
Annealing didn't help, and I noticed that when I blocked the cold  
stream, the milky white appearance didn't go away when the sample  
thawed. I finally took the crystal off and looked at it under a  
microscope, at which point I discovered that the milky white  
appearance was due to the presence of bubbles in the mother liquor.


I seem to recall some talks on radiation damage in which people  
mention the evolution of a gas (H2?).


So: Does this seem like a radiation damage phenomenon?  And have  
others seen this kind of delay in the manifestation of damage during  
storage at liquid N2 temperatures?


Thanks,

Pat

 
---

Patrick J. Loll, Ph. D. (215) 762-7706
Professor   FAX: 
(215) 762-4452
Department of Biochemistry  Molecular Biology
Director, Biochemistry Graduate Program
Drexel University College of Medicine
Room 10-102 New College Building
245 N. 15th St., Mailstop 497
Philadelphia, PA  19102-1192  USA

[EMAIL PROTECTED]

Re: [ccp4bb] radiation damage question

[Philippe DUMAS]

Yes indeed ! H2 is one product of H2O radiolysis by recombination of two H
radicals.
Whether or not the cleavage of iodine (quite efficient under X-rays) is a
factor increasing H2 production, I don't know.

Philippe Dumas
IBMC-CNRS, UPR9002
15, rue Rene Descartes 67084 Strasbourg cedex
tel: +33 (0)3 88 41 70 02
[EMAIL PROTECTED]


  -Message d'origine-
  De : CCP4 bulletin board [mailto:[EMAIL PROTECTED] la part de
Patrick Loll
  Envoye : Monday, March 03, 2008 6:00 PM
  A : CCP4BB@JISCMAIL.AC.UK
  Objet : [ccp4bb] radiation damage question


  Hi all,


  I had an interesting experience, and wonder if others have seen similar
things.


  I was collecting data from a crystal that contains an iodinated
macromolecule. After 2 days on a copper rotating anode, with the crystal at
100 K, we experienced a detector problem, so I put the crystal back into the
dewar; it was diffracting nicely when I took it off. For various reasons, I
didn't get back to this crystal until about 3 weeks later. When I put it
back on the goniostat, the mother liquor was milky white in appearance.
There were no ice rings, but alas the crystal only gave a few anemic spots
around the beamstop. Annealing didn't help, and I noticed that when I
blocked the cold stream, the milky white appearance didn't go away when the
sample thawed. I finally took the crystal off and looked at it under a
microscope, at which point I discovered that the milky white appearance was
due to the presence of bubbles in the mother liquor.


  I seem to recall some talks on radiation damage in which people mention
the evolution of a gas (H2?).


  So: Does this seem like a radiation damage phenomenon? And have others
seen this kind of delay in the manifestation of damage during storage at
liquid N2 temperatures?


  Thanks,


  Pat


  --
-

  Patrick J. Loll, Ph. D. (215) 762-7706

  Professor FAX: (215) 762-4452

  Department of Biochemistry  Molecular Biology

  Director, Biochemistry Graduate Program

  Drexel University College of Medicine

  Room 10-102 New College Building

  245 N. 15th St., Mailstop 497

  Philadelphia, PA 19102-1192 USA




  [EMAIL PROTECTED]