Replacing H2O with D2O in cryo-EM reduces radiation damage in biological samples
Radiation damage limits the resolution achievable in electron microscopy of biological specimens. Hydrogen is the most abundant atom in these specimens, and its low mass maximizes the recoil energy it receives from incident electrons, making it the atom most readily lost under the beam. Substitution of hydrogen by deuterium halves this recoil energy and makes the bonds involved slightly harder to…
Radiation damage hampers the resolution in electron microscopy of biological samples. Hydrogen, being the most prevalent atom in such specimens, absorbs the maximum recoil energy from incoming electrons, which expedites its loss. Researchers have now discovered that replacing hydrogen with deuterium can mitigate this issue by halving the recoil energy, albeit with minimal impact on the protein structure.
In a study conducted using cryogenic electron diffraction at 200 kV, hen egg-white lysozyme crystals grown directly in deuterated water (D2O) were found to endure a radiation dose 1.7 times greater than those grown in regular water (H2O) before their Bragg intensity at 10^-7 [A] dropped to 1/e. This durability was observed in all D2O-grown crystals as opposed to H2O-grown crystals.
The protective effect was primarily due to the substitution of D2O in the solvent and the exchangeable hydrogens on the protein surface, which are crucial for forming hydrogen bonds that stabilize the crystal lattice.
Interestingly, the protein itself did not require deuteration through expression in deuterated media. The process of direct crystallization in D2O only necessitated a single substitution in the mother liquor, presenting an accessible strategy to enhance the usable dose in electron diffraction of protein crystals.
Written by urgent.news from bioRxiv's reporting — not their text. Machine-written — may contain errors; check the original before relying on it.
