Guanidine thiocyanate (also known as guanidine isothiocyanate or GITC) is a potent protein denaturant widely utilized to deactivate endogenous RNases during RNA isolation from diverse tissues and bacteria. When combined with acid-balanced phenol or phenol:chloroform, solutions containing guanidine thiocyanate and beta-mercaptoethanol effectively disrupt cytoplasmic and nuclear membranes while preserving RNA integrity. Additionally, it functions as a storage buffer for blood samples.