Monday, May 9, 2011

Double Stranded Oligo

Since 1984, Bio-Synthesis, the first company to provide commercial custom oligonucleotide synthesis services, has remained a major force in advancing biotechnology research both as leading supplier and developer of new technologies for oligo synthesis. Combining unique know-how, constantly evolving technology and wide experience in oligo manufacturing and services, BSI expanded its oligo synthesis from custom DNA, RNA, Constrained Nucleotide BNA (bridged nucleic acid) synthesis with SPEED and QUALITY.

Oligonucleotide Synthesis

Oligonucleotide synthesis is the non-biological, chemical synthesis of defined short sequences of nucleic acids. It is extremely useful in laboratory procedures covering a wide range of molecular biology applications. Automated synthesizers allow the synthesis of oligonucleotides up to 160 to 200 bases. Typically, synthesized oligonucleotides are single-stranded DNA molecules around 15-20 bases in length.

Synthesis Substrates

Oligonucleotides are chemically synthesized using phosphoramidites. A phosphoramidite is a normal nucleotide with protection groups added to its reactive amine, hydroxyl and phosphate groups. These protection groups prevent unwanted side reactions and force the formation of the desired product during synthesis. The 5' hydroxyl group is protected by DMT (dimethoxytrityl), the phosphate group by a diisopropylamino (iPr2N) group and a 2-cyanoethyl (OCH2CH2CN) group. The bases also have protecting groups on the exocyclic amine group (benzoyl or isobutyryl).

Sequential Synthesis

Whereas enzymes synthesize DNA in a 5' to 3' direction, chemical DNA synthesis is done backwards in a 3' to 5' reaction. Based on the desired nucleotide sequence of the product, the phosphoramidites for the bases A, C, G, and T are added sequentially to react with the growing chain in a repeating cycle until the sequence is complete. In each cycle, the product's 5' phosphate is deprotected and a new base is added for extension.

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