dThd

dThd is the abbreviation for deoxythymidine, a deoxyribonucleoside composed of the pyrimidine base thymine attached to a 2′-deoxyribose sugar. The glycosidic bond links the N1 position of thymine to the C1′ atom of the deoxyribose, placing it among the four canonical deoxyribonucleosides that constitute DNA. The absence of a 2′-hydroxyl group on the sugar distinguishes deoxyribonucleosides from ribonucleosides.

In biological systems, dThd serves as a building block for DNA. It is not used in RNA. dThd participates in nucleotide metabolism through phosphorylation: thymidine kinase converts dThd to deoxythymidine monophosphate (dTMP), which can be further phosphorylated to dTDP and then to dTTP. The pool of dTTP is used by DNA polymerases during replication and repair. dThd can arise from DNA turnover and can be salvaged from extracellular nucleosides and recycled within cells.

In laboratory settings, dThd is used as a standard substrate in studies of nucleotide metabolism, enzyme assays, and DNA synthesis experiments. It is also contrasted with its phosphorylated derivatives, dTMP and dTTP, which participate directly in polymerase reactions.

See also: thymidine, dTMP, dTTP, thymidine kinase. Synonyms include deoxythymidine and thymidine (nucleoside) in certain contexts. It should be distinguished from thymine (the base) and from the ribonucleoside counterpart, uridine.