Table 2.
Properties of peptides used in parameter optimization: Ala5 and Ac-(AAQAA)3-NH2. J-couplings calculated with “DFT2” set of Karplus parameters20 and chemical shifts with SPARTA+61 at 300 K. Statistical errors from a block error analysis92 are given in brackets.
| Peptide | Property | ff99SB | ff99SB* | C22/CMAP | C36 |
|---|---|---|---|---|---|
| Ala5 | |||||
| % α+ | 15.7 (1.2) | 22.5 (2.2) | 41.5 (3.2) | 13.1 (1.3) | |
| % β | 37.8 (1.4) | 34.5 (1.3) | 25.3 (2.2) | 30.8 (1.3) | |
| % ppII | 42.3 (1.9) | 39.8 (1.6) | 26.2 (1.8) | 51.9 (1.1) | |
| % α-helix | 0.0 (0.2) | 0.6 (0.3) | 3.7 (2.1) | 0.1 (0.1) | |
| χ2(J) | 1.7 | 1.7 | 2.0 | 1.2 | |
| Ac-(AAQAA)3-NH2 | |||||
|
| |||||
| % α+ | 26.9 (1.2) | 48.5 (1.3) | 98.7 (0.4) | 44.0 (1.8) | |
| % β | 32.4 (0.8) | 22.7 (0.7) | 0.46 (0.2) | 19.1 (0.6) | |
| % ppII | 31.8 (0.9) | 21.8 (0.6) | 0.41 (0.2) | 29.5 (1.2) | |
| % α-helix | 1.8 (0.3) | 14.2 (2.1) | 95.3 (0.1) | 21.0 (1.7) | |
| χ2(δC′) | 0.5 | 0.06 | 2.6 | 0.04 | |