Table 1.
Names of the ONs synthesised, their sequences, retention times on the ion-exchange columna, compositions, and isolated yields.
| sequence | retention time (min) | calculated MW | observed MWb | isolated yield (%) | |
| ON1 | 5'-CCCCTTTCTTTTTTc | 31.53 | 4121.7 | – | |
| 5ʼ-N+ON2 | 5'-CN+CCCTTTCTTTTTT | 27.76 | 4296.7958 | 4297.7588d | 9e |
| m-N+ON3 | 5'-CCCCTTTN+CTTTTTT | 27.43 | 4296.7958 | 4297.7455d | 11e |
| 3ʼ-N+ON4 | 5'-CCCCTTTCTTTTTN+T | 27.74 | 4296.7958 | 4297.7466d | 20f |
| 2N+ON5 | 5'-CN+CCCTTTCTTTTTN+T | 23.42 | 4473.9012 | 4473.8248d | 8e |
| 3N+ON6 | 5'-CN+CCCTTTN+CTTTTTN+T | 20.77 | 4649.0067 | 4650.1412d | 10e |
| 4N+ON7 | 5'-CN+CCCTN+TTCTN+TTTTN+T | 17.09 | 4826.0965 | 4826.0516d | 23f |
| 4N+{FAM} | 5'-CN+CCCTN+TTCTN+TTTTN+T{FAM} | –g | 5396.4012 | 5396.1460h | 20 |
| 5ʼ-Ts-ON8 | 5'-CTsCCCTTTCTTTTTT | 32.80 | 4272.7151 | 4274.6664d | 4e |
| m-Ts-ON9 | 5'-CCCCTTTTsCTTTTTT | 32.75 | 4272.7151 | 4273.4728d | 5e |
| 3ʼ-Ts-ON10 | 5'-CCCCTTTCTTTTTTsT | 32.81 | 4272.7151 | 4273.4694h | 8e |
| 2Ts-ON11 | 5'-CTsCCCTTTCTTTTTTsT | 35.67 | 4425.7398 | 4427.7401h | 6e |
| 3Ts-ON12 | 5'-CTsCCCTTTTsCTTTTTTsT | 36.76 | 4578.7646 | 4578.6076i | 30f |
| 4Ts-ON13 | 5'-CTsCCCTTsTTCTTsTTTTTsT | 40.07 | 4731.7893 | 4731.7620j | 39f |
| 4Ts-{FAM} | 5'-CTsCCCTTsTTCTTsTTTTTsT{FAM} | –g | 5301.2398 | 5302.8380h | 26 |
| m-N+ON14 | 5'-CCCCTTTCTTTN+TTT | 27.50 | 4296.7958 | 4296.7520d | 19f |
| m-N+ON15 | 5'-CCCCTTT CN+TTTTTT | 27.43 | 4296.7958 | 4296.7300d | 16f |
| m-N+ON16 | 5'-CCCCN+TTTCTTTTTT | 27.45 | 4296.7958 | 4296.7440d | 17f |
| m-N+ON17 | 5'-CCN+CCTTTCTTTTTT | 27.62 | 4296.7958 | 4296.7350d | 21f |
| 3N+ON18 | 5'-CN+CCCTTN+TCTTTTTN+T | 20.44 | 4649.0067 | 4649.937d | 17f |
aIE-HPLC was performed on an IE-column (TSKgel Super Q-5PW) using a gradient of NaCl concentration (0 → 0.5 M) in 20 mM Tris-HCl, 1 mM EDTA, pH 9.0 over 30 min; bbased on ESIMS in the negative mode; cobtained from Integrated DNA Technologies; dcalculated for [M − 6H]6−; esynthesised in a 1 µmol scale using a previously reported procedure with transferring the solid support from a column into a vial for reaction with sulfonyl azide for 30 min at room temperature. Afterwards, the solid support was transferred back to the column to continue DNA synthesis [39]. Some amount of the solid support was lost during the transfer and washing steps, especially for multiple modifications, which was the main reason for the low yields of these ONs. fsynthesised in a 1 µmol scale following a modified procedure using a microtube pump to deliver the sulfonyl azide solution onto the column with CPG-support at 37 °C [38]; gsynthesised in a 3–4 µmol scale, purified by 20% denaturing PAGE (7 M urea), followed by extraction from the gel and desalting. hfor [M − 7H]5−; ifor [M + K+ − 9H]8−; jfor [M − 4H]4−; the ESIMS spectra are provided in Supporting Information File 1.