Showcasing research from Professor Herman Sintim’s laboratory, Department of Chemistry, Purdue University, West Lafayette, Indiana, USA. A STING-based fluorescent polarization assay for monitoring activities of cyclic dinucleotide metabolizing enzymes Cyclic dinucleotides are important second messengers in both prokaryotes and eukaryotes. Recently there have been efforts to identify small molecules that perturb cyclic dinucleotides in bacteria and immune cells. The Sintim group has developed a fluorescent polarization assay, which utilizes STING protein and fluorescein-labelled c-di-GMP, to detect all three cyclic dinucleotides (c-di-GMP, c-di-AMP and cGAMP). This assay could facilitate drug discovery efforts to identify small molecules that inhibit enzymes that synthesize or degrade cyclic dinucleotides or receptors that bind to these fascinating signalling molecules. As featured in: See Herman O. Sintim et al ., RSC Chem. Biol ., 2021, 2, 206. RSC Chemical Biology ISSN 2633-0679 rsc.li/rsc-chembio REVIEW ARTICLE Samya Banerjee and Peter J. Sadler Transfer hydrogenation catalysis in cells Volume 2 Number 1 February 2021 Pages 1–276 rsc.li/rsc-chembio Registered charity number: 207890