| RESEARCH |
An example is work being carried out by chemistry professor Willi Bannwarth's group at the University of Freiburg, in Germany. At the Bordeaux meeting, he described the use of a solid-phase extraction technique that employs fluorous reversed-phase silica gel as the sorbent for the purification of synthetic DNA fragments. The technique uses a column packed with silica bound to a fluorocarbon phase, for example, silicaOSi(CH3)2(CH2)2C8F17. When a solution of perfluoro-tagged and nontagged compounds is added to the column, the fluorous molecules selectively adsorb on the fluorous silica gel. The gel is first washed with a fluorophobic solvent to remove the nontagged organic compounds. After cleavage of the fluorous tags, the desired compound is obtained and the tags remain on the column. Bannwarth noted that perfluoro-tagged compounds are highly hydrophobic compared with those carrying linear alkyl chains. "In the aqueous phase, interactions between perfluoro tags on water-soluble biomolecules like DNA and RNA can become very intense. We have used these interactions to immobilize DNA fragments noncovalently on fluorous silica gel as a basis to develop a simple purification system for synthetic oligonucleotides." In a recent paper, Bannwarth and coworker Christian Beller used this approach to separate a perfluoro-tagged 30-nucleotide sequence from shorter and longer nontagged DNA sequences (Helv. Chim. Acta 2005, 88, 171). They found that the interaction between the perfluoro-tagged oligonucleotide and the fluorous silica gel was so intense that all the other sequences could be removed by a neutral aqueous-phase washing step. "We are currently extending the approach to the immobilization of RNA and proteins and applications in molecular biology," Bannwarth said. |
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