TABLE 5.
Proton Affinity (top) and Gas-Phase Basicity (bottom) values for DNA and RNA bases. The uncertainty of the experimental values is ~ 2.0 kcal/mol78. All quantities are in kcal/mol.
| Basea | CBS | G3B3 | G3MP2 | PBE0 | B1B95 | B3LYP | QCRNA | Expt |
|---|---|---|---|---|---|---|---|---|
| Proton Affinity | ||||||||
| A:N1(+) | 223.6 | 224.9 | 224.7 | 227.1 | 227.1 | 226.7 | 226.8 | 225.3 |
| C:N3(+) | 226.9 | 227.6 | 227.4 | 229.5 | 229.3 | 228.9 | 228.8 | 227.0 |
| G:N7(+) | 227.6 | 228.2 | 227.9 | 231.0 | 230.8 | 230.5 | 230.5 | 229.3 |
| G:N1(−) | 337.7 | 338.2 | 338.0 | 340.9 | 341.0 | 339.9 | 339.9 | - |
| T:O4(+) | 206.1 | 207.1 | 207.3 | 209.2 | 209.3 | 208.1 | 208.2 | 210.5 |
| T:N3(−) | 346.3 | 347.0 | 346.9 | 348.2 | 348.1 | 347.1 | 346.9 | - |
| U:O4(+) | 204.4 | 205.4 | 205.5 | 207.3 | 207.4 | 206.4 | 206.4 | 208.6 |
| U:N3(−) | 346.3 | 347.0 | 346.9 | 348.2 | 348.1 | 347.1 | 346.9 | - |
| Gas Phase Basicity | ||||||||
| A:N1(+) | 216.3 | 217.1 | 217.0 | 218.3 | 218.4 | 218.2 | 218.3 | 218.1 |
| C:N3(+) | 218.9 | 219.8 | 219.7 | 220.9 | 220.2 | 220.4 | 219.9 | 219.0 |
| G:N7(+) | 220.2 | 220.9 | 220.6 | 223.6 | 223.3 | 223.0 | 223.0 | 221.7 |
| G:N1(−) | 330.2 | 330.6 | 330.4 | 333.3 | 333.5 | 332.4 | 332.3 | - |
| T:O4(+) | 198.4 | 199.3 | 199.5 | 201.4 | 201.5 | 200.4 | 200.5 | 203.2 |
| T:N3(−) | 338.5 | 339.1 | 339.1 | 340.4 | 340.4 | 339.3 | 339.0 | - |
| U:O4(+) | 196.7 | 197.6 | 197.8 | 199.6 | 199.6 | 198.6 | 198.7 | 201.2 |
| U:N3(−) | 338.1 | 338.6 | 338.5 | 339.9 | 340.0 | 338.7 | 338.4 | - |
a
Base identifies the nucleic acid base (A, C, G, T, or U) and the position the proton is being removed (−) or added (+).