Quinine may target the malaria purine nucleoside phosphorylase enzyme. ADK complements nucleoside diphosphate kinase deficiency. The purine nucleoside bases are notable polycyclic aromatic heterocycles. The guanine nucleoside is called guanosine. It is an ester of phosphoric acid with the nucleoside thymidine. It is an ester of phosphoric acid with the nucleoside uridine. Thymidine kinase is one of the many nucleoside kinases that are responsible for nucleoside phosphorylation. Aciclovir is a nucleoside analogue that mimics guanosine. It is an ester of phosphoric acid with the nucleoside guanosine. Brivudine is an analogue of the nucleoside thymidine. Nucleoside analogues can be used to treat viral infections. Nucleotides are molecules consisting of a nucleoside and a phosphate group. It is an ester of pyrophosphoric acid with the nucleoside guanosine. Chemically, it mimics the nucleoside adenosine. This can be achieved using nucleoside analogs such as EdU.