Cell and protein contractions with cooling for tetragonal thermolysin. Crystal parameters were measured for four RT conditions and ∼20 LT conditions. Cell-volume contractions were then calculated according to Δcell = (VLTcell − 〈VRTcell〉)/〈VRTcell〉, with the average taken over the four RT samples measured. An analogous calculation was performed for protein volume contractions, with protein volumes determined for two RT conditions and seven LT conditions. Dashed lines are fits of Δcell = νprotΔprot + (1 − νprot)Δchan, with Δchan given by (2). The horizontal axis plots the fractional change in specific volume of solvent with cooling: ΔTsol ≡ (ν77 K − ν294 K)/ν294 K = 〈β〉ΔT, where ν77 K and ν294 K are specific volumes based on density measurements in bulk (Alcorn & Juers, 2010), 〈β〉 represents the average thermal expansivity of the solution and ΔT = −217 K.