Figure 8: Permeability of the protein structure at room temperature. Fluorescence quenching experiments on psychrophilic (circles, blue) mesophilic (triangles, black), and thermophilic (squares, red) proteins. The steep slope recorded for the psychrophilic protein indicates that its structure is easily penetrated by a small quencher molecule (acrylamide), resulting in a larger attenuation of the intrinsic fluorescence , whereas the thermophilic protein is more rigid and displays fewer internal motions. Adapted from [160].