Poster presented at the Cambridge Chemistry of Nucleic Acids and Biology conference, 2011.
As with cholesterol modifications, tocopherol has been shown to have potential use in the delivery of oligonucleotides into cells. Vitamins such as tocopherol are not produced by the target cells, but are used by the latter and therefore vitamins are recognised. They are thought to be internalised by cells only after interaction with a binding protein and therefore have the potential for specific targeting of a cell type.
The hydrophobic nature of tocopherol has also been utilised as a means of improving the purification of ribozymes. As an extension to previous work, therefore, we have investigated the use of tocopherol CEP and octyltocopherol CEP as a means of allowing an initial purification of thiol-modified oligos with a view to improving the efficiency of a second ion-exchange purification. Thiol-modified oligonucleotides are often used as a means of incorporating labels such as dyes by reaction with maleimides or acetamides. There is often a need to carry out multiple purifications in order to ensure the purity of the thiol-modified oligonucleotide prior to conjugation and a simple, efficient method of removing DMT-containing N-1 failures would be advantageous.
Our aims were three-fold, to show: (1) tocopherol is sufficiently hydrophobic that a tocopherol-modified oligo will be retained on a TOPS-DNA cartridge; (2) purification by TOPS-DNA cartridge of tocopherol-S-S-oligonucleotides result in a purer thiol-modified oligo than a standard TOPS-DNA purification of a DMT-S-S-oligo; and (3) there is no adverse effect on the functional use of the thiolmodified oligo by using tocopherol to enhance purification.