To confirm that the TNT-PNA oligonucleotide conjugates cleave as they are expected to (see expected fragment structures and mass-to-charge ratios in Figure 2 ), the TNT-PNA oligonucleotides were analysed by ESI-MS/MS on a micromass quadrupole-time-of-flight (Q-TOF) mass spectrometer. The complete TNT-PNA probe molecules were initially ionized with the cone voltage (an accelerating voltage in the ESI source that can be varied on the micromass instrument to control the levels of collision induced dissociation) set to minimize fragmentation of the whole TNT-PNA probe conjugate ions. The whole molecular ions were selected using the first quadrupole of the instrument and were then subjected to collision induced dissociation at different collision energies. Fragmentation of the complete TNT-PNA conjugate ions was carried out as it allows both the cleavage of the TNT parent tag from the PNA and the cleavage of the tag fragment from the parent tag to be seen simultaneously in the TOF analyser of the Q-TOF instrument thus demonstrating both cleavage processes and their relative efficiencies. Typical results are shown in Figure 4 , in which it can be seen that, as the collision energy is increased, the whole TNT-PNA probe ion fragments to release the parent tag ion as the predominant fragmentation product. As the fragmentation energy is increased further, the parent tag ion undergoes subsequent consecutive fragmentation to give the desired daughter fragment ion. As the collision energy increases further, the intensity of the parent tag ion increases. Similarly, the ratio of the daughter ion to parent ion increases more. These results show that the TNT-PNA probe molecules fragment as anticipated with the aspartic acid/proline linkage cleaving more easily than the piperazine linkage. The higher collision energy spectra are quite noisy as these also contain other products from the fragmentation of the TNT-PNA probe molecule, which would not normally be present when the TNT parent tag ions are analysed by themselves.