Dnucleotides

Dnucleotides are short oligomeric molecules consisting of two nucleotides linked by a phosphodiester bond. They are among the simplest units of nucleic acids and occur as transient intermediates during the synthesis and degradation of longer nucleic acid chains. A nucleotide comprises a sugar (deoxyribose in DNA or ribose in RNA), a phosphate group, and a nucleobase (adenine, thymine or uracil, cytosine, or guanine). In a dinucleotide, two such units are connected by a phosphodiester linkage formed between the 3' hydroxyl of the first sugar and the 5' phosphate of the second, resulting in a molecule with two nucleobases and a short backbone.

Dinucleotides arise mainly through the partial hydrolysis of longer nucleic acids or can be produced synthetically for study. They exist in both ribonucleotide and deoxynucleotide forms, reflecting the two types of nucleic acids. Numerous base combinations are possible, such as ApA or CpG, depending on which nucleobases occupy the two positions. In biology, dinucleotides are typically short-lived and are most commonly encountered as products of nucleic acid digestion rather than as functional signaling molecules.

In some contexts, related molecules called dinucleoside polyphosphates (for example diadenosine polyphosphates) play signaling roles in certain organisms, but these differ chemically from standard dinucleotides that contain a single phosphate linkage between two nucleotides. Analytical methods such as high-performance liquid chromatography and mass spectrometry are used to identify and quantify dinucleotides in biological samples. See also mononucleotides, oligonucleotides, and dinucleotide repeats.