Table 2. Examples of Discrete Amino Acid Modifications and Impact on EPSA and Permeability.

| ID | EPSA | RRCK Papp (10–6 cm/s) | AA1 | AA2 | AA3 | AA4 | AA5 | AA6 |
|---|---|---|---|---|---|---|---|---|
| 11 | 75 | 8.9 | Leu | N-Me-d-Leu | N-Me-Ile | Leu | d-Pro | N-Me-Tyr |
| 12 | 76 | 5.5 | Leu | N-Me-d-Leu | N-Me-Ala | Leu | d-Pro | N-Me-Tyr |
| 5 | 78 | 13.0 | Leu | N-Me-d-Leu | N-Me-Leu | Leu | d-Pro | N-Me-Tyr |
| 13 | 83 | 1.6 | Leu | N-Me-d-Leu | N-Me-Ser | Leu | d-Pro | N-Me-Tyr |
| 14 | 83 | 4.7 | Leu | N-Me-d-Leu | N-Me-Thr | Leu | d-Pro | N-Me-Tyr |
| 15 | 100 | 1.3 | Leu | N-Me-d-Leu | N-Me-Tyr | Leu | d-Pro | N-Me-Tyr |
| 16 | 103 | 0.3 | Leu | N-Me-d-Leu | N-Me-Lys | Leu | d-Pro | N-Me-Tyr |
| 17 | 125 | 0.6 | Leu | N-Me-d-Leu | N-Me-Asp | Leu | d-Pro | N-Me-Tyr |
| 6 | 84 | 0.5 | d-Leu | Leu | Leu | Leu | d-Pro | Tyr |
| 7 | 76 | 4.1 | N-Me-d-Leu | N-Me-Leu | Leu | N-Me-Leu | d-Pro | N-Me-Tyr |
| 8 | 79 | 6.1 | N-Me-d-Leu | N-Me-Leu | N-Me-Leu | N-Me-Leu | d-Pro | N-Me-Tyr |
| 6 | 84 | 0.5 | d-Leu | Leu | Leu | Leu | d-Pro | Tyr |
| 9 | 85 | 1.8 | Leu | d-Leu | Leu | Leu | d-Pro | Tyr |
| 16 | 103 | 0.3 | Leu | N-Me-d-Leu | N-Me-Lys | Leu | d-Pro | N-Me-Tyr |
| 18 | 98 | 0.2 | Leu | N-Me-d-Leu | N-Me-Lys(N-Me) | Leu | d-Pro | N-Me-Tyr |