What GFP did you use, your pH is 4.6 or something around there according to your picture. If the pH is true GFP will be colorless. You certainly have some more GFP lying around (without your protein fused to it), just titrate it and see what pH dependency you have.

Jürgen

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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/

On Sep 29, 2010, at 4:41 AM, Tri Ngo wrote:

Dear CCP4 community,

I wonder if anybody has experience about the color of GFP crystals. Is there any chance that the GFP crystal will become colorless? We are working on one membrane protein fused with GFP. Since we got some crystals which didn't show any color (Condition 01), I am not sure if I should go for optimization.

Please check the link below for the image details: http://www.docstoc.com/docs/55950590/GFP-crystals

Because of the limited amount of sample, we used Topaz system (screening chip) to do the screening and there is no way to confirm these crystals are actually protein crystals. I noticed that the crystals are bigger day by day. Is it a good sign to confirm the protein crystals? 

Thank you very much for your helpful information!

Best wishes,

TriNgo

Structural Biology Lab
School of Medicine - Sungkyunkwan University
Phone: 031-299-6150