Nucleotidenucleotide

Nucleotidenucleotide, commonly referred to as a dinucleotide, is a molecule consisting of two nucleotides linked by a phosphodiester bond. Nucleotides themselves are the basic units of nucleic acids, formed from a sugar, a nucleobase, and one or more phosphate groups; a dinucleotide is the simplest linked pair of these units and can be viewed as a building block of DNA and RNA.

In a typical linear dinucleotide, the two nucleotides are joined by a single phosphodiester linkage between the 3' carbon of one sugar and the 5' phosphate of the adjacent sugar. The molecule therefore has a 5'-phosphate at one end and a 3'-hydroxyl at the other. While the backbone of longer nucleic acids is composed of many such linkages, a dinucleotide represents just two units in a short segment.

Dinucleotides occur transiently during nucleic acid metabolism, including synthesis and repair, where they can arise as intermediates. They also include a distinct class of signaling molecules known as cyclic dinucleotides, such as cyclic di-GMP, cyclic di-AMP, and cyclic GMP-AMP, which function as second messengers in bacteria and eukaryotes, helping regulate immune responses and other cellular processes.

Chemically and enzymatically, dinucleotides can be synthesized or hydrolyzed in laboratory and cellular contexts. They are studied through methods such as chromatography and mass spectrometry, and they serve as useful references for understanding the chemistry and biology of nucleic acids.