instruction:
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.
question:
The structures of thymidine kinase from herpes simplex virus type 1 in complex with substrates and a substrate analogue.
answer:
thymidine

question:
Reinforcement enhancing effects of nicotine via smoking.
answer:
nicotine

question:
Investigation of astatine(III) hydrolyzed species: experiments and relativistic calculations.
answer:
astatine(III)