Figure 1. Required thickness of protein (C₃₀H₅₀N₉O₁₀ S and density of 1.35 gcm²)²² in water to induce a phase change of more than 0.01 radians greater than the surrounding water.

For photon energy of 500 eV, the required thickness is 100 times less than for 10 keV, allowing 100 times greater sensitivity to fine features. The k_α line position for a selection of biologically relevant elements is also included (arrows). Figure prepared using data from²²,³¹.