35phosphodiester

35phosphodiester is not a standard term in biochemistry or molecular biology. If encountered, it is likely a misnomer or shorthand for concepts related to phosphodiester linkages that connect nucleotides in nucleic acids, most commonly the 3',5'-phosphodiester bond that forms the backbone of DNA and RNA.

A phosphodiester bond is a covalent linkage where a phosphate group bridges the 3' carbon of one sugar to the 5' carbon of the next sugar in a polynucleotide chain. In natural nucleic acids, the backbone is composed of repeating 3'-5' phosphodiester linkages, producing directionality from the 5' end to the 3' end. These bonds are negatively charged due to the phosphate groups and are hydrolytically cleaved by nucleases and phosphodiesterases.

In some contexts, unusual 2'-5' phosphodiester bonds can occur transiently, for example in certain RNA processing or secondary structures, though these are noncanonical compared to the standard 3'-5' linkage.

Variants and related concepts include phosphorothioate (thio-phosphodiester) linkages, in which a non-bridging oxygen is replaced by sulfur. Phosphorothioates are used to increase nuclease resistance in antisense and siRNA therapeutics. Other modifications may alter stability, charge, or binding properties of the nucleic acid backbone.

If the term was intended to refer to a specific molecule, radiolabel, or modification (for example a labeled or altered phosphodiester in an experimental context), additional context would be needed to identify it precisely.