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]: Expression and 1,4-dihydropyridine-binding properties of brain L-type calcium channel isoforms.
[EX A]: calcium

[EX Q]: Distinct role of PYK2 in mediating thromboxane generation downstream of both G12/13 and integrin αiibβ in platelets.
[EX A]: thromboxane

[EX Q]: Diels-Alder mediated controlled release from a poly(ethylene glycol) based hydrogel.
[EX A]:
poly(ethylene glycol)