More than eight years ago, we introduced an oligo affinity support (OAS)1 which allowed normal oligonucleotide synthesis but on treatment with ammonium hydroxide, the fully-deprotected oligonucleotide remained attached to the support. After annealing the complementary strand to the support-bound oligonucleotide, an affinity support for the purification of DNA binding proteins was generated.2,3 Unfortunately, the process used to make the support proved to be hazardous and we had to discontinue the product.
In the meantime, highly effective affinity supports could still be prepared by a two-step process in which the oligonucleotide is amino-modified and reacted with a suitable activated support.4,5 However, we have remained intrigued by the elegance of direct production of the support and we continued evaluating potential supports. The criteria for a successful affinity support are simple:
We are now happy to offer two oligo affinity supports: polystyrene/polyethyleneglycol copolymer (PS), designed primarily for affinity purification of biomolecules; and controlled pore glass (CPG), which is less suitable for purification of proteins but ideal for chromatographic applications.
While these supports may find immediate use in the preparation of affinity matrices, we also envisage other potential applications, including enzymatic reactions with ligase and kinase. Also, synthesis in the 5' to 3' sense with 5'-phosphoramidites would yield a supported oligonucleotide with the 3'-terminus available for extension with polymerases.
Synthesize the oligonucleotide using standard cycles. (The 3'-base should be entered into the synthesizer as A but it is non-coding. The real 3'-terminal nucleoside is the first monomer added.)
Treat OAS PS with ammonium hydroxide or other deprotecting solutions as normal. OAS CPG can be deprotected with ammonium hydroxide at elevated temperatures but stronger bases may damage the silica structure of the support. In either case, decant or pipet the liquid from the support and wash the support with water until neutral pH is achieved. DO NOT DISCARD THE SUPPORT. The support can be air-dried for storage but it should not be lyophilized.
After synthesis, oligonucleotides are not cleaved from the support by basic media. However, occasionally it may be necessary to cleave the oligonucleotide from the support for anaytical purposes. The attachment to the support is through the N6 position of Adenosine and the oligonucleotide can be cleaved specifically from the support by periodate oxidation followed by ß-elimination yielding the 3'-phosphate.
Oligo-Affinity Support CPG (20-4001) has been discontinued.