Phosphodiester

Phosphodiester is a term that can refer to a diester of phosphoric acid with two alcohol groups, or more specifically to the phosphodiester linkage that connects nucleotides in nucleic acids. In DNA and RNA, the backbone consists of alternating sugar and phosphate groups connected by phosphodiester bonds. Each bond forms between the 3' hydroxyl of one sugar and the 5' phosphate of the next, yielding a repeating sugar–phosphate backbone with directed 5'→3' polarity. At physiological pH, the phosphate typically carries negative charges, contributing to solubility and structure.

In chemistry, a phosphodiester describes the diester formed when phosphoric acid is esterified with two alcohols. The biological relevance lies in the phosphodiester bonds that join nucleotide units in nucleic acids. These bonds are formed by condensation reactions catalyzed by polymerase enzymes during replication and transcription and are cleaved by nucleases during DNA and RNA processing or degradation.

Phosphodiester linkages also occur in phospholipids, where a phosphate group forms phosphodiester bonds with glycerol and a polar head group. This arrangement helps create the amphipathic properties of membranes, with the phosphate-containing head groups oriented toward the aqueous environment.

Overall, phosphodiesters are essential chemical motifs that confer structural integrity to genetic material and contribute to membrane architecture. Their selective hydrolysis and resilience under different conditions underpin many cellular processes and biotechnological applications.