STRC h26 Phase 1d AF3 Final 2026-04-27
The last missing Phase 1d AlphaFold Server result, engineered_homodimer_A1078C, was retrieved from AFS fold 27162e77fc95333e and downloaded to models/fold_engineered_homodimer_A1078C_afs.zip.
Result
Gate G1 requires ipTM >= 0.50 and pTM >= 0.60. A1078C fails decisively across all five AF3 models.
| Model | ranking_score | ipTM | pTM | G1 |
|---|---|---|---|---|
| 0 | 0.34 | 0.25 | 0.39 | FAIL |
| 1 | 0.32 | 0.24 | 0.37 | FAIL |
| 2 | 0.31 | 0.24 | 0.40 | FAIL |
| 3 | 0.31 | 0.23 | 0.39 | FAIL |
| 4 | 0.30 | 0.23 | 0.39 | FAIL |
Phase 1d final set:
| Mutant | ipTM | pTM | G1 | AFS fold |
|---|---|---|---|---|
| A1078C | 0.25 | 0.39 | FAIL | /fold/27162e77fc95333e |
| S1080C | 0.33 | 0.41 | FAIL | /fold/73b2ae8798b7a3fe |
| S1579C | 0.23 | 0.39 | FAIL | /fold/69aa00e31b6c2c6f |
| A1078W negative control | 0.23 | 0.37 | FAIL | /fold/5403b988473e6dca |
Interpretation
The disulfide-engineering rescue path is closed. Phase 1 already falsified the ARM aromatic/arginine-repulsion idea. Phase 1c found plausible cysteine geometry, but Phase 1d shows that the best remaining cysteine candidates do not produce an AF3-supported homodimer complex.
No G2 contact parser, G4 energy job, G5 MD, or G9 h03 drop-in test is justified because no candidate clears the upstream AF3 confidence gate.
Ranking delta - 2026-04-27
h26 before: tier=B, mech=2, deliv=5, misha_fit=4, next=Retrieve/finish Phase 1d A1078C AF3; if FAIL, demote h26 to C; if PASS, parse contacts then score G4/G5 as h03 drop-in candidate.
h26 after: tier=C, mech=2, deliv=5, misha_fit=4, next=Paused: Phase 1d A1078C/S1080C/S1579C/A1078W all fail AF3 G1; no further compute unless a new scaffold/interface appears.
Evidence: A1078C final AF3 best model is ipTM 0.25 / pTM 0.39 against a 0.50 / 0.60 G1 gate; all four Phase 1d candidates fail. The only fast B-to-S route for h26 is gone, so h26 leaves B-tier.
Connections
[part-of]h26 hub[see-also]h26 log[see-also]STRC B-Tier Promotion Triage 2026-04-27[see-also]STRC Hypothesis Ranking