1,6-Hexanediol, commonly used to dissolve liquid-liquid phase separated condensates, directly impairs kinase and phosphatase activities.

The concept of liquid-liquid phase separation (LLPS) has emerged as an intriguing mechanism for the organization of membraneless compartments in cells. The alcohol 1,6-hexanediol is widely used as a control to dissolve LLPS assemblies in phase separation studies in diverse fields. However, little is known about potential side effects of 1,6-hexanediol, which could compromise data interpretation and mislead the scientific debate. To examine this issue, we analyzed the effect of 1,6-hexanediol on the activities of various enzymes in vitro. Already at 1% volume concentration, 1,6-hexanediol strongly impaired kinases and phosphatases and partly blocked DNA polymerases, while it had no effect on DNase activity. At concentrations that are usually used to dissolve LLPS droplets (5-10%), both kinases and phosphatases were virtually inactive. Given the widespread function of protein phosphorylation in cells, our data argue for a careful review of 1,6-hexanediol in phase separation studies.