Signal turn-on probe for nucleic acid detection based on (19)F nuclear magnetic resonance.

To image gene expression in vivo, we designed and synthesized a novel signal turn-on probe for (19)F nuclear magnetic resonance (MR) imaging based on paramagnetic relaxation enhancement. The stem-loop structured oligodeoxyribonucleotide (ODN) having a molecular beacon sequence for point mutated K-ras mRNA was doubly labeled with bis(trifluoromethyl)benzene moiety and Gd-1,4,7,10-tetraazacyclododecane-1,4,7,10-tetraacetic acid chelate moiety at the each termini of the ODN probe, respectively. We found that the (19)F MR signal of the bis(trifluoromethyl)benzene moiety tethered at the 5' termini of the probe turned on by the addition of complementary ODN. The probe has the potential to image gene expressions in vivo.