phosphoramidite and 6-thioguanosine

Thionucleotides, especially 4-thiouridine and 6-thioguanosine, are photosensitive molecules that photocrosslink to both proteins and nucleic acids, and this feature is a major reason for their application in various investigations. To get insight into the thermodynamic and structural contributions of 6-thioguanosine to the properties of RNA duplexes a systematic study was performed. In a series of RNA duplexes, selected guanosine residues located in G-C base pairs, mismatches (G-G, G-U, and G-A), or 5' and 3'-dangling ends were replaced with 6-thioguanosine. Generally, the presence of 6-thioguanosine diminishes the thermodynamic stability of RNA duplexes. This effect depends on its position within duplexes and the sequence of adjacent base pairs. However, when placed at a dangling end a 6-thioguanosine residue actually exerts a weak stabilizing effect. Furthermore, the structural effect of 6-thioguanosine substitution appears to be minimal based on NMR and Circular Dichroism (CD) data.

Topics: Base Sequence; Circular Dichroism; Guanine Nucleotides; Guanosine; Magnetic Resonance Spectroscopy; Nucleic Acid Conformation; Organophosphorus Compounds; RNA; RNA, Double-Stranded; Thionucleosides

6-S-[2-[(2-ethylhexyl)oxycarbonyl]ethyl)}-3',5'-O-bis(tert-butyldimethylsilyl)-2'-deoxy-6-thiogua nosine (2) was synthesized in high yield from the corresponding 6-O-mesitylenesulfonyl derivative by the reaction with 2-ethylhexyl 3-mercapto-propionate. The phosphoramidite precursor derived from 2 was successfully applied to an automated DNA synthesizer to produce 2'-deoxy-6-thioguanosine containing ODN. The results showed that 2-ethylhexyl 3-mercaptopropionate is useful as an odor less reagent and also as an S-protecting group of 2'-deoxy-6-thioguanosine.

Topics: Chromatography, High Pressure Liquid; Deoxyguanosine; Guanosine; Molecular Structure; Odorants; Oligodeoxyribonucleotides; Organophosphorus Compounds; Thionucleosides

The preparation of N(2)-phenoxylacetyl-S(6)-(2,4-dinitrophenyl)-6-thioguanosine phosphoramidite and its subsequent incorporation into oligoribonucleotides is described. The identity of the oligonucleotides was confirmed by UV spectrophotometry and nucleoside composition analysis.

Topics: Dinitrobenzenes; Guanosine; Oligoribonucleotides; Organophosphorus Compounds; Spectrophotometry, Ultraviolet; Thionucleosides; Thionucleotides