Single 6-formylcytidine was introduced into a oligonucleotide duplex (23 me
rs) as a substitute for thymidine in the Myb binding sequence of 3'-TTGAC-5
'. The modified duplex showed Tm of 67 degrees C, which was six degrees low
er than the Tm of the native duplex. Binding affinity of the 23-mers to the
Myb protein was estimated by electrophoretic mobility shift assays, and th
e binding was almost completely abolished.