Research highlights.

This article focuses on research highlights of chemical biology. First article focuses onlight-switchable activity. An enzyme has been given light-switchable activity by having one of its key amino acids replaced with a 'photocaged' version. The tRNA molecule carries the amino acid to the cell's protein-synthesizing machinery, the ribosome, where it is stitched into the growing protein chain. Another article focuses on structural biology. Although X-ray crystallography has been used to elucidate the molecular mechanisms of many biological processes, it rarely reveals the exact position of important hydrogen atoms. Low-temperature neutron structures of other proteins have been solved.