Print

Print


Hi -

My two cents:

First, you say:

I assume the bigger crystal might have lot of solvent which prevent for high resolution. If it is true what could be the best way to dehydrate crystal without affecting crystal quality?

I think this assumption is confusing. If the crystals were grown in the same drop/condition, they have identical percentage solvent content. Thus, you do not want to look at dehydration, the 'percentage solvent content' is fine. What you want to look at is the mechanics of vitrification. Big crystals, are simply hard to freeze: because of their volume they cannot be vitrified as rapidly and uniformly as smaller crystals. I will not be surprised if there are papers that quantify that, but what I am saying here is only from experience and adding a 'logical' explanation to that experience. 

Thus, I would simply stay with the smaller crystals (I have a feeling that you 'small' crystals are 'big' for many other people) and be happy they diffract to 2.5 A (is that SR or RA?)

A.


On Apr 15, 2010, at 3:16, syed ibrahim wrote:


Dear Jurgen and Ho Leung

To add few more point regarding my question:

1. Crystal was first  frozen in LN2 and then transfered to cryo stream (in presence of LN2 in vial)
2. Anealing did not help (both short time and long time) -  perhaps the crystal dies.
3.  Spots are clear to available resolution (is:  6-7A). In the high resolution region there is no spot but looks like smear in the whole area.
4. The crystal was approximately 1.0mm length and 0.4mm dia. I mounted on 0.5mm loop. So the liquid around the crystal was very less. I deliberately avoided more solvent in the loop to help diffraction.

Thanks

Syed



--- On Thu, 4/15/10, Jürgen Bosch <[log in to unmask]> wrote:

From: Jürgen Bosch <[log in to unmask]>
Subject: Re: [ccp4bb] Cryo Vs crystal size
To: [log in to unmask]
Date: Thursday, April 15, 2010, 3:46 AM

There are a couple of additional factors not taken into account here.

1. LN2 versus frozen in strem or propane etc
2. did you try to flash anneal the larger crystal
3. smeary diffraction from the big crystal or not ?
4. how much residual solvent was around your crystal when freezing ?

In general smaller crystals are anyhow better in my hands.

Jürgen

On Apr 14, 2010, at 5:36 PM, syed ibrahim wrote:

Hi All

I had two crystals grown in same well, one is small and other is 10 times bigger. I treated both crystal in same cryo and same time. The smaller one diffracted to 2.5A and the bigger one to 6-7A. I was expecting the bigger one to diffract high resolution.

I assume the bigger crystal might have lot of solvent which prevent for high resolution. If it is true what could be the best way to dehydrate crystal without affecting crystal quality?

Thank you

Syed

PS: Taken care of less solvent to be present in the loop




-
Jürgen Bosch
Johns Hopkins Bloomberg School of Public Health
Department of Biochemistry & Molecular Biology
Johns Hopkins Malaria Research Institute
615 North Wolfe Street, W8708
Baltimore, MD 21205
Phone: +1-410-614-4742
Lab:      +1-410-614-4894
Fax:      +1-410-955-3655
http://web.mac.com/bosch_lab/



P please don't print this e-mail unless you really need to
Anastassis (Tassos) Perrakis, Principal Investigator / Staff Member
Department of Biochemistry (B8)
Netherlands Cancer Institute, 
Dept. B8, 1066 CX Amsterdam, The Netherlands
Tel: +31 20 512 1951 Fax: +31 20 512 1954 Mobile / SMS: +31 6 28 597791