In this task, you are given a sentence. You are expected to recognize the name of any form of chemical substances. Although there might be several correct answers, you need to write one of them.

[EX Q]: Binding and GTPgammaS autoradiographic analysis of preproorphanin precursor peptide products at the ORL1 and opioid receptors.
[EX A]: GTPgammaS

[EX Q]: Adhesion of osteoblasts to a vertically aligned TiO2 nanotube surface.
[EX A]: TiO2

[EX Q]: Mifepristone alters expression of endometrial steroid receptors and their cofactors in new users of medroxyprogesterone acetate.
[EX A]:
steroid