Selective modification of cytosines in oligodeoxyribonucleotides. |
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Authors: | P S Miller C D Cushman |
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Institution: | Department of Biochemistry, School of Hygiene and Public Health, Johns Hopkins University, Baltimore, Maryland 21205. |
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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. |
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