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Deoxyribose

Deoxyribose, more precisely 2-deoxyribose, is an organic compound with formula C₅H₁₀O₄; specifically, a monosaccharide with linear form H-(C=O)-(CH₂)-(CHOH)₃-H, which has all the hydroxyl groups on the same side in the Fischer projection. It is also a deoxy sugar, that can be seen as derived from the sugar ribose by loss of an oxygen atom; hence its name.

The term "2-deoxyribose" may refer to any of two enantiomers: the biologically important D-2-deoxyribose, covered here, and (rarely) to its synthetic mirror image L-2-deoxyribose.

D-2-Deoxyribose is an important part of the nucleic acid DNA. It was discovered in 1929 by Phoebus Levene.

The term "deoxyribose" may also refer to the structural isomer 3-deoxyribose H-(C=O)-(CHOH)-(CH₂)-(CHOH)₃-H, which occurs rarely in nature, e.g. in damaged DNA.C Bernelot-Moens and B Demple (1989), ''Multiple DNA repair activities for 3'-deoxyribose fragments in Escherichia coli.''. Nucleic Acids Research, Volume 17, issue 2, pp. 587–600.

Structure

2-Deoxyribose is an aldopentose, that is, a monosaccharide with five carbon atoms and having an aldehyde functional group. It can be seen as derived from the sugar ribose through replacement of the hydroxyl group OH nearest to the aldehyde end by a hydrogen atom, leading to the net loss of an oxygen atom. In the conventional numbering of carbons, that is the C2' ("C-2 prime") carbon.

Deoxyribose occurs in water as the linear form H-(C=O)-(CH₂)-(CHOH)₃-H and any of two ring forms: deoxyribofuranose ("C3'-endo"), with a five-membered ring, and deoxyribopyranose ("C2'-endo"), with a six-membered ring. The latter form is predominant (whereas the C3'-endo form is favored for ribose).

Since the pentose sugar arabinose differs from ribose only by the placement of the hydroxyl at position C2', D-2-deoxyribose is the same substance as D-2-deoxyarabinose.

Biological importance

2-Deoxyribose derivatives have an important role in biology. The DNA (deoxyribonucleic acid) molecule, which is the main repository of genetic information in bacteria and higher organisms, is a double helix, each of whose strands is a long chain of deoxyribose-containing units called nucleosides, alternating with phosphate groups. In the standard nucleic acid nomenclature], a DNA nucleoside consists of a deoxyribose molecule with an organic base (usually adenine, thymine, guanine or cytosine) attached to the 1' ribose carbon. The 5' hydroxyl of each deoxyribose unit is replaced by a phosphate (forming a nucleotide) that is attached to the 3' carbon of the deoxyribose in the preceding unit. Therefore the last unit has a phosphate bound only to a 5' carbon, and first unit has a free OH group bound to the 3' carbon. The two strands of DNA have oppositely oriented backbones, and are held together by hydrogen bonds between complementary bases. The genetic information carried by the DNA is encoded in the sequence of bases along the chain.

The other important genetic storage molecule, RNA, has a chemical structure similar to a single strand of DNA, but with ribose instead of deoxyribose, and uracil substituted for thymine. The lack of the 2' hydroxyl group in deoxyribose is apparently responsible for the increased flexibility of DNA compared to RNA, which allows it to assume the double-helix conformation, and also (in the eukaryotes) to be compactly coiled inside the small cell nucleus. The double-stranded DNA molecules are also typically much longer than RNA molecules, and allow various DNA repair mechanisms.

Other biologically important derivatives of deoxyribose include mono-, di-, and triphosphates, as well as 3'-5' cyclic monophosphates.

deoxyribose
Source: Wikipedia