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Published February 12, 1992 | public
Journal Article

Design of a nonnatural deoxyribonucleoside for recognition of GC base pairs by oligonucleotide-directed triple helix formation

Abstract

The deoxyribonucleoside 1-(2-deoxy-beta-D-ribofuranosyl)-3-methyl-5-amino-1H-pyrazolo4,3-d]py rimidin-7-one (P1) was designed such that two specific hydrogen bonds would form with guanine (G) of a Watson-Crick guanine-cytosine (GC) base pair in the major groove of double-helical DNA. One edge of the P1 heterocycle mimics N3-protonated cytosine, which would circumvent the pH dependence observed for the formation of triple helices containing C + GC base triplets. P1 was synthesized in five steps and incorporated by automated methods in pyrimidine oligodeoxyribonucleotides. From affinity cleaving analyses, the stabilities of base triplets decrease in the order P1.GC >> P1.CG >> P1.AT approximately P1.TA (pH 7.4, 35-degrees-C). P1 binds GC base pairs within a pyrimidinte triple-helix motif as selectively and strongly as C but over an extended pH range. Oligodeoxyribonucleotides containing P1 residues were shown to bind within plasmid DNA a single 15 base pair site containing five GC base pairs at pH 7.8 and a single 16 base pair site containing six contiguous GC base pairs at pH 7.4.

Additional Information

© 1992 American Chemical Society. Received August 8, 1991. We are grateful to the Office of Naval Research for support of this research. We thank Dr. David Horne for checking synthetic procedures, and careful reading of the manuscript.

Additional details

Created:
August 20, 2023
Modified:
October 18, 2023