Cells step back in time

Models based on the crystal structure of interleukin-1 vary significantly. D eP ri st o/ El se vi er UK) warns that, for any given structure in the Protein Data Bank (PDB), there will be many other overlooked structures that are equally consistent with the data. Crystallized proteins retain the ability to move around, thus making interpretations of diffraction data an imprecise process. Crystallographers fit their data to models that pass quality controls, but they usually report only one such model. The Cambridge group generated alternate models that fit the data for several proteins. “We found a reasonable number of structures that are surprisingly different in their finer details,” says