Hi Javier,


 You're on the exact odd nature of crystals of macromolecules, i.e. the solvent content. Small molecule crystallographers have been FREEZING crystals in LiqN2 for data collection long before the method was introduced to macromolecular crystallography. This works perfectly well, since there is no disordered water in those crystals (at least in the ones I'm more familiar with, from my organic chemistry days) and there is no need for any cryoprotectant. In crystals  of macromolecules we want to prevent the solvent from freezing and form an ice lattice that will destroy our crystals, hence we use cryoprotectants which cause the ice to be vitirified (maybe, in any case not to crystallize). So we end up with a crystal of macromolecule with vitrified solvent. How we call this entity is one thing  and how we call the operation is another thing (some very creative suggestions have been made during the thread). So while vitrified crystal may well sound oxymoron linguistically, it may represent our true reality as protein crystallographers. And finally, I can't resist either: how about vitristal for what we get as the result of cryo-protection and freezing?

 Cheers,

          Boaz 








 

 

Boaz Shaanan, Ph.D.                                        


Dept. of Life Sciences                                      

Ben-Gurion University of the Negev                          

Beer-Sheva 84105                                            

Israel                                                      

                                                            

E-mail: [log in to unmask]

Phone: 972-8-647-2220  Skype: boaz.shaanan                  

Fax:   972-8-647-2992 or 972-8-646-1710    

 

 

                












From: CCP4 bulletin board [[log in to unmask]] on behalf of Javier Gonzalez [[log in to unmask]]

Sent: Friday, November 16, 2012 8:35 AM

To: [log in to unmask]

Subject: Re: [ccp4bb] vitrification vs freezing







Hi Sebastiano,



I think the term "vitrified crystal" could be understood as a very nice oxymoron (http://www.oxymoronlist.com/), but it is essentially self-contradictory
 and not technically correct. 



As Ethan said, "vitrify" means "turn into glass". Now, a glass state is a disordered solid state by definition, then it can't be a crystal. A vitrified crystal would be a crystal which has lost all three-dimensional ordering, pretty much like the material one
 gets when using the wrong "cryo-protectant".



What one usually does is to soak the crystal in a "cryo-protectant" and then flash-freeze the resulting material, hoping that the crystal structure will be preserved, while the rest remains disordered in a solid state (vitrified), so that it won't produce a
 diffraction pattern by itself, and will hold the crystal in a fixed position (very convenient for data collection).




Moreover, I would say that clarifying a material is vitrified when subjected to liquid N2 temperatures would be required only if you were working with some liquid solvent which might remain in the liquid phase at that temperature, instead of the usual solid
 disordered state, but this is never the case with protein crystals. 



So, I vote for "frozen crystal".-



Javier





PS: that comment by James Stroud "I forgot to mention that if any dictionary is an authority on the very cold, it would be the Penguin dictionary.", is hilarious, we need a "Like" button in the CCP4bb list!







--

Javier M. Gonzalez

Protein Crystallography Station

Bioscience Division

Los Alamos National Laboratory

TA-43, Building 1, Room 172-G

Mailstop M888

Phone: 
(505) 667-9376





On Thu, Nov 15, 2012 at 2:24 PM, Craig Bingman 
<[log in to unmask]> wrote:


 "cryopreserved"



It says that the crystals were transferred to cryogenic temperatures in an attempt to increase their lifetime in the beam, and avoids all of the other problems with all of the other language described.



I was really trying to stay out of this, because I understand what everyone means with all of their other word choices.






On Nov 15, 2012, at 2:07 PM, James Stroud wrote:



> Isn't "cryo-cooled" redundant?

>

> James

>

> On Nov 15, 2012, at 11:34 AM, Phil Jeffrey wrote:

>

>> Perhaps it's an artisan organic locavore fruit cake.

>>

>> Either way, your *crystal* is not vitrified.  The solvent in your crystal might be glassy but your protein better still hold crystalline order (cf. ice) or you've wasted your time.

>>

>> Ergo, "cryo-cooled" is the description to use.

>>

>> Phil Jeffrey

>> Princeton

>>

>> On 11/15/12 1:14 PM, Nukri Sanishvili wrote:

>>> s: An alternative way to avoid the argument and discussion all together

>>> is to use "cryo-cooled".

>>> Tim: You go to a restaurant, spend all that time and money and order a

>>> fruitcake?

>>> Cheers,

>>> N.

>>>