Syn and anti nucleosides

From Proteopedia

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The objective of this article is to highlight aspects of the 3D structure of nucleosides, but there are links to more general descriptions of nucleosides and nucleotides available in the External Links section.

Contents 1 Purine Nucleosides 2 Pyrimidine Nucleosides 3 Examples of Nucleotides 4 Additional Resources 5 External Links

Purine Nucleosides

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Observe that the adenine ring of adenosine is nearly perpendicular to the furanose ring () and that a (colored green) connects adenine to ribofuranose. Groups on the ribofuranose, such as the on the 2' carbon, sterically hinder the rotation of the adenine about the glycosidic bond. This lack of ability to rotate results in two possible configurations. The anti configuration, which you have been viewing, but now in and the , , same view but in . With purines the anti configuration is favored, but the syn configuration can be formed and actually has a role in the formation of the Z-DNA, a conformation of DNA double helix.

Pyrimidine Nucleosides

of uridine in the anti conformation. of cytidine in the syn conformation. oxygen at the C-2 position of cytidine invading the space of both hydrogen at C-2' and the oxygen of the furanose ring. Since both pyrimidines found in DNA have an oxygen at the C-2 position, nucleosides and nucleotides of these pyrimidines only adopt the anti conformation and therefore can not be part of Z-DNA.

Examples of Nucleotides

AMP ;

UMP ;

cAMP ;

Additional Resources

For additional information, see: Nucleic Acids

External Links

• nucleosides
• nucleotides.