title: Selective modification of cytosines in oligodeoxyribonucleotides.
abstract: A single deoxycytidine residing in an oligodeoxyribonucleotide which also contains 5-methyldeoxycytidines can be selectively derivatized with various alkylamines by sodium bisulfite-catalyzed transamination. Selective transamination results because 5-methylcytosine, unlike cytosine, does not form a bisulfite adduct. When the reaction is carried out at pH 7.1, transamination in the oligomer appears to occur to greater than 95% with little or no deamination. This procedure has been used to introduce aminoalkyl or carboxyalkyl side chains at the N4-position of a deoxycytidine in oligonucleotides. These side chains contain potentially reactive amine or carboxy groups which could serve as a sites for further conjugation of the oligomer with a variety functional groups. Oligonucleotides which carry these side chain form duplexes and triplexes with appropriate complementary single-stranded or double-stranded oligodeoxyribonucleotide target molecules. The stabilities of the duplexes are similar to those formed by unmodified oligomers, whereas the stability of the triplexes is approximately 18 degrees C lower than that formed by unmodified oligomers.
authors.affiliation: Department of Biochemistry, School of Hygiene and Public Health, Johns Hopkins University, Baltimore, Maryland 21205.
authors.forename: P S
authors.initials: PS
authors.lastname: Miller
authors.forename: C D
authors.initials: CD
authors.lastname: Cushman
mesh_terms: D001483:Base Sequence; D004247:DNA / Q000378:metabolism; D003841:Deoxycytidine / Q000031:analogs & derivatives* / Q000737:chemistry* / Q000378:metabolism; D009682:Magnetic Resonance Spectroscopy; D008969:Molecular Sequence Data; D009838:Oligodeoxyribonucleotides / Q000737:chemistry* / Q000378:metabolism
chemical_list: D009838:Oligodeoxyribonucleotides; D003841:Deoxycytidine; D004247:DNA; C016569:5-methyldeoxycytidine