What they found
RADA16-I nanofiber scaffold sonicated into 20–100 nm fragments reassembles to original length (hundreds of nm to few microns) within 2 hours; this cycles reproducibly. Key geometry data from AFM: nanofiber height 1.3–1.5 nm (single peptide thickness); individual peptide monomer ~5 nm long × 1.3 nm wide × 0.8 nm thick. Assembled fibers reach 615 ± 104 nm mean length. Hydrogel forms at 0.6–3 mM (1–5 mg/ml), >99.5% water. Storage modulus G′ ~50 Pa at full reassembly. pH 7.5, 20 mM Tris.
How this applies to h09
AFM length distribution directly supports the model’s fibril_length_nm = 1000 — fibers reach several hundred nm to low microns, so 1 μm is a plausible upper-range estimate. The 1.3–1.5 nm AFM height matches a single-peptide-layer tape, consistent with the bilayer (double-sheet) model that underlies the 4.35 peptides/nm packing estimate. No direct statement of peptides/nm, but the monomer dimensions are consistent with H-bond spacing ~0.47 nm.
Key numbers — CRITICAL GEOMETRY
- Peptide monomer: 5 nm long × 1.3 nm wide × 0.8 nm thick
- Nanofiber AFM height: 1.3–1.5 nm (single peptide layer)
- Nanofiber length (intact): several hundred nm to few μm; mean ~615 ± 104 nm
- Post-sonication fragments: 20–100 nm
- Reassembly complete: ~2 hours
- Hydrogel concentration: 0.6–3 mM (1–5 mg/ml)
- G′ (storage modulus): ~50 Pa at full reassembly (1 Hz, 25°C)
- Assembly conditions: 20 mM Tris pH 7.5, >99.5% water
Links
- PubMed: https://pubmed.ncbi.nlm.nih.gov/15939888/
- PMC: https://pmc.ncbi.nlm.nih.gov/articles/PMC1150805/
- DOI: https://doi.org/10.1073/pnas.0407843102
Connections
- STRC Phase 4d F-actin Bundling Model — fibril_length_nm = 1000 justified; peptide monomer dims
- STRC Horizontal Top Connector Hydrogel Hypothesis — AFM geometry, reassembly kinetics
[see-also]1993-zhang-eak16-rada16-spontaneous-assembly — original discovery[see-also]Paravastu 2014 RADA16 Molecular Structure — atomic model of packing