Couldn't they simply be too thin?  After all, unit cell dimensions are
routinely about 0.01um, so if these needles are only fraction of a
micron thick, there is simply not enough material for diffraction.

Nice looking but non-diffracting protein crystals are too disordered
(i.e. while packing is present, there is no long-range spatial
correlation among individual unit cells).

On Mon, 2010-04-19 at 11:35 +0800, tat cheung cheng wrote:
> Thank you. Forget to mention, no diffraction observed no matter with
> or without cyro cooling. 
> 
> 
> 
> ______________________________________________________________________
> 寄件人﹕ "[log in to unmask]" <[log in to unmask]>
> 收件人﹕ [log in to unmask]
> 傳送日期﹕ 2010/4/19 (一) 11:29:38 AM
> 主題： RE: [ccp4bb] Re： [ccp4bb] Mysterious Crystals?
> 
> Hello Tc,
> 
>  
> 
> It isn’t that unusual to get protein crystals that don’t diffract.
> This happens probably 50% of the time.  One can try dehydration of the
> crystals, crystal annealing and additive screens to see if any of
> these things will give you some diffraction.  In addition, you didn’t
> mention whether you froze these crystals- one should also try putting
> a crystal in the beam without cryo-cooling, as cryo-cooling can often
> be detrimental to diffraction.
> 
>  
> 
> Cheers, tom
> 
>  
> 
>                                    
> ______________________________________________________________________
> From:CCP4 bulletin board [mailto:[log in to unmask]] On Behalf Of
> tat cheung cheng
> Sent: Monday, 19 April 2010 1:26 PM
> To: [log in to unmask]
> Subject: [ccp4bb] Re： [ccp4bb] Mysterious Crystals?
> 
> 
>  
> 
> Yes, I have just done that. They are protein. But if they are protein,
> why no diffraction? That's intriguing.
> 
> 
>  
> 
>                                    
> ______________________________________________________________________
> 寄件人﹕ Jürgen Bosch <[log in to unmask]>
> 收件人﹕[log in to unmask]
> 傳送日期﹕ 2010/4/19 (一) 10:57:40 AM
> 主題： Re: [ccp4bb] Mysterious Crystals?
> 
> Fish and wash some crystals then run them on a SDS-gel, then you will
> know for sure if it's protein or not.
> 
>  
> 
> 
> J僡gen
> 
> On Apr 18, 2010, at 10:46 PM, tat cheung cheng wrote:
> 
> 
> 
> 
> Hi all, 
> 
> I have got some crystals, the purified protein was in Tris buffer with
> 300mM NaCl for crystallization. they grew in light weight PEG, PEG400
> or monomethyl ethyl PEG500, they were needle shaped, could be long
> (~0.2mm) but very thin all the time and sometimes grew into sea-urchin
> like needle cluster.
> What interesting is, when i gridded crystallization conditions against
> pH or PEG amount, the crystals sizes and shapes varied, and the
> crystals were fragile so i believed they were protein crystals in
> nature. But upon X-ray diffraction, they gave no reflection at all,
> not even a faint spot. 
> I wonder, beside silly mistakes like misalignment of the crystal to
> the beam, not enough exposure time, what could be the reason for this
> mysterious crystals? Are they protein or PEG or what?
> Thanks very much.
> 
> Tc
> 
> 
> 
> 
> 
> 
>  
> 
> -
> 
> 
> J僡gen 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/
> 
> 
>  
> 
> 
> 
>  
> 
> 
> 
>  


-- 
Edwin Pozharski, PhD, Assistant Professor
University of Maryland, Baltimore
----------------------------------------------
When the Way is forgotten duty and justice appear;
Then knowledge and wisdom are born along with hypocrisy.
When harmonious relationships dissolve then respect and devotion arise;
When a nation falls to chaos then loyalty and patriotism are born.
------------------------------   / Lao Tse /