Synthesis and relaxivities of oligonucleotides with TEMPO-labeled sugar moiety

5-Uridin derivative, UUT, having TEMPO radical at the 2'-position of sugar moiety, was prepared and characterized by X-ray crystallography. The single strands, ssUUT, incorporating UUT and the double strands, dsUUT, with complimentary strand were also obtained. Their EPR spectra and relaxivities (25 MHz and 0.59 T) in water were measured. The values of tau R obtained from the simulation of EPR spectra and the water-proton relaxivities, r1 and r2, increased in order of UUT, ssUUT, and dsUUT.