Figure 3.
Change in properties of crambin crystals as a function of temperature (K). In a and b, the equations for the lines above and below 180 K (y = mx + b) are indicated. Similar slopes (m) are found whether the break point is taken at 160 K. (a) Average B (Debye-Waller factor) in Å2 for all atoms, for protein and for water vs. temperature. Note the negative slope for water. B factors for water greater than 30 Å2 were judged unreliable and excluded. Refinement with prolsq (30) is designated by filled diamonds, by filled circles, or by filled triangles. The same data refined with shelxl (32) is shown with open diamonds, open circles, or with open triangles. (b) Average B factor in Å2 (Debye-Waller factor) for multisubstate (discretely disordered) side-chain atoms, for one-substate atoms in the protein, and for crystalline hexagonal ice water alone (41) vs. temperature. The equation of each line above and below 180 K is given, except for water alone, where the equation is only above 180 K. Note that, below 180 K, the negative slope for multisubstate atoms (m = −0.01) is close to that for the water in a (m = −0.03). Symbols are defined as in Fig. 3a above. Note that the slope for water above 180 K (m = 0.025) is the same as that for the one-substate protein atoms in b (m = 0.025). (c) Rg (Å) for the protein vs. temperature from 100 K to 293 K. The Rg is calculated with x-plor (33).