Doxycycline hydrochloride is also commonly used in the TET-ON (rTTA dependent) and TET-OFF (TTA dependent) systems to regulate gene expression in both in vivo and in vitro cell cultures.It is a USP Grade reagent with a solubility of approximately 50 mg/mL in water and is heated moderately to promote complete dissolution.It is also reported to be soluble in DMSO (~1 mg/mL) and methanol, but insoluble in chloroform and ether.