deoxyribose

D-Deoxyribose
IUPAC name	2-Deoxy-D-ribose
Other names	2-Deoxy-D-erythro-pentose Thyminose
Identifiers
CAS number	533-67-5 Y
PubChem	5460005
EC-number	208-573-0
SMILES	O=CC[C@H](O)[C@H](O)CO
InChI	1/C5H10O4/c6-2-1-4(8)5(9)3-7/h2,4-5,7-9H,1,3H2/t4-,5+/m0/s1
InChI key	ASJSAQIRZKANQN-CRCLSJGQBK
ChemSpider ID	4573703
Properties[1]
Molecular formula	C5H10O4
Molar mass	134.13 g/mol
Appearance	White solid
Melting point	91 °C, 364 K, 196 °F
Solubility in water	Very soluble
Y (what is this?)  (verify) Except where noted otherwise, data are given for materials in their standard state (at 25 °C, 100 kPa)
Infobox references

Deoxyribose, more precisely 2-deoxyribose, is an organic compound with formula C₅H₁₀O₄; specifically, a monosaccharide with linear form H-(C=O)-(CH₂)-(CHOH)₄-H, which has a vertical chain and all the hydroxyl groups on the right 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 stereoisomers: 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.^[2]

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)₄-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).

Chemical equilibrium of deoxyribose in solution.

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-stranedd 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.

See also

• Arabinose
• Lyxose
• Ribose
• Ribulose
• Xylose
• Xylulose

References

1. ^ The Merck Index: An Encyclopedia of Chemicals, Drugs, and Biologicals (11th ed.), Merck, 1989, ISBN 091191028X , 2890.
2. ^ 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.