Noncovalent spin-labeling of RNA: the aptamer approachElectronic supplementary information (ESI) available. See DOI: 10.1039/c8cc05597a

In the first example of site-directed spin-labeling of unmodified RNA, a pyrrolidine-nitroxide derivative of tetramethylrosamine (TMR) was shown to bind with high affinity to the malachite green (MG) aptamer, as determined by continuous-wave (CW) electron paramagnetic resonance (EPR), pulsed electron-electron double resonance (PELDOR) and fluorescence spectroscopies. In the first example of noncovalent spin-labeling of unmodified RNA, the MG aptamer was used to capture a tetramethylrosamine-based nitroxide spin label with high affinity.