Proteins solution versus crystal structures

Because nearly all currently used methods for secondary structural analysis by CD use crystal structure data, two concerns need to be addressed. Are protein structures the same in solution as they are in the crystal In a few specific cases, significant differences have been proposed on the basis of CD or VCD. The most definitive comparisons of solution versus crystal structure are provided by multidimensional NMR studies, which can yield solution structures for small proteins (< 20 kDa), comparable in accuracy to those from X-ray diffraction. One review concludes that, in most cases, the solution and crystal structures are very similar, allowing for some differences in the local conformation and dynamics of surface residues. In a few cases, distinct differences have been demon-... 

Figure 1.11. Correlation between average charge state of protein ions generated by ESI under near-native conditions (10 mM ammonium acetate, pH adjusted to 7) and their surface areas in solution whose calculation was based on their crystal structures. The data are plotted in In (natural logarithmic) versus In scale (a graph using linear scales is shown in the inset). A gray-shaded dot represents a data point for pepsin, and the open circle underneath represents the maximum charge expected for pepsin if the extent of multiple charging was limited by the number of basic residues within the pepsin molecule. (Figure and text reprinted from Kaltashov and Mohimen," with permission from the American Chemical Society.)...

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