Protein crystals are so sensitive, that diffraction experiment conducted in room temperature could easily damage them. Therefore, an important preparation step for diffraction experiment is cooling protein crystals to around 100K. Water is significant part of protein crystals (even to 80%) and it’s a really love-hate relationship. On the one hand, high solvent content provides native environment for protein. Nevertheless, at the same time, during the cooling, water can cause crystals cracking (due to ice formation) or difficulties during diffraction data collection (because of visible ice rings on diffraction pattern). To avoid that, prior to the cooling, the crystals have to be treated using so-called cryo-protectants.Read More →