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DNA_XTAL

In response to a question on bboard... Nessie asked how 		       
DNA could possibly crystallize, wouldn't the kinetics be 
awful? 									       
       									       
My first thought was to point out
that people have been
crystallizing proteins for a long
time, that's been one of the main
methods to determine their
structure: x-ray diffraction             C.P. Snow shows people
requires crystallization first.          doing it in his novel 
                                         _The Search_ which    
                                         takes place pre-world 
                                         war II.               
                                                               
Sure getting crystals of such
things is a bitch (the guys at
Stanford's CMR doing this who
would be pleased to get a
cubic millimeter of solid
Urea, I'm sure).  But you
don't need very much just to
do crystallography.

Ah, but she probably knew all this. 					       
The point probably was that given 
the structure of DNA -- a hugely 
long, floppy protein chain -- how is 
it possible to get a crystal of 
it at *any* size? 			

I thought of two possibilities: 
				

(1) Maybe each DNA                (2) Maybe they work with
molecule xtalizes with            short pieces of DNA     
itself first, forming a           chain at a time, really 
predictable shape that            crystallyzing only a    
then links with other             small sub-set of a DNA  
molecules.                        at any given time.      
                        

I thought this seemed a
little too weird to be
right. 
       

                                   I looked at a few   
                                   papers, and got the 
                                   impression that the 
                                   latter was correct.    
						       	  
							  
But from a talk at AACG			           The "web" of information 
West, I gather that my				   represented by 
first thought was				   technical literature is 
correct.  The DNA				   very poor in some 
molecules form a kind of			   respects: in particular 
colloidal suspension				   it's difficult to follow 
that crystallyzes with a			   the chain back to 
layer of water between				   basic explanatory 
the DNA molecules.				   material. 
                                                           



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