ESI-MS/MS spectra were obtained on a Micromass Q-TOF Micro mass spectrometer (Micromass (Waters), Wythenshaw, UK). The TNT-PNA oligonucleotides were denatured from the Dynabeads into 50:50 Methanol:Water with 1% formic acid. Mass spectra were externally calibrated using the manufacturer's standards and calibration protocols.