Evidence that solution and crystal structures are similar

Positions of these molecules are indicated by red crosses. Assignment of water molecules to these isolated areas of electron density improves the overall accuracy of the model, and for reasons I will discuss in Chapter 7, improvements in accuracy in one area of the model gives accompanying improvements in other regions. 

Evidence that solution and crystal structures are similar 

Knowing that crystallographers study proteins in the crystalline state, you may be wondering if these molecules are altered when they crystallize, and whether the structure revealed by X rays is pertinent to the molecule s action in solution. Crystallographers worry about this problem also, and with a few proteins, it has been found that crystal structures are in conflict with chemical or spectroscopic evidence about the protein in solution. These cases are rare, however, and the large majority of crystal structures appear to be identical to the solution structure. Because of the slight possibility that crystallization will alter molecular structure, an essential part of any structure determination project is an effort to show that the crystallized protein is not significantly altered. 

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II. Evidence that solution and crystal structures are similar... 

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