Guanidine thiocyanate is a chaotropic and firmly denaturing agent.

It is used for COVID-19 research, virus inactivation, protein denaturation, RNase inactivation, and to isolate RNA (as well as DNA and proteins in some cases). Except as a strong protein denaturing effect, extreme concentrations of chaotropic agents are involved in cell lysis. 

Guanidine thiocyanate is commonly used in combination with phenol-chloroform for RNA extraction and isolation. It is used by kit manufacturers, in molecular biology laboratories and in the medical and biopharmaceutical industry.