Fig. 7: Molecular dynamics simulations of the mechanism of Phov-ACP self-assembly.

a Monomer peptide from the C-terminal domain of Phov (Asp-195 to Phe-220). b Snapshots showing the binding of calcium and phosphate ions (ACP) to peptide subsegments. Pristine single β-sheets (six peptide monomers) were prebuilt and simulated in TIP3P water at pH 7.4. c Root mean square deviation (RMSD) plot for the conformational stability of β-sheets until 100 ns. d Intermolecular and intramolecular hydrogen bond (H-bond) numbers in β-sheets (t = 100 ns). e Molecular dynamics simulation trajectories of six Phov peptide monomers at times t = 0, 10, and 100 ns. The intermolecular H-bonds (red dotted lines) in the hydrophobic region contribute to the stable β-sheet configuration. f Coulomb energy (E_coul) of Ca²⁺-peptides, HPO₄^2--peptides, and Ca²⁺-HPO₄^2-. g Radius of gyration (Rg) versus time plot during the 100 ns simulation for pristine β-sheets. Rg analysis showed that the β-sheets became more compact when ACP bound to the negative hydrophilic domain. h Snapshots showing two individual β-sheets loaded with ACP self-assembled into a cross-β-sheet structure. i Variations in the centroid distance of two individual β-sheets. j Van der Waal’s energy (E_vdw) is favourable for the binding of two individual β-sheets. k Snapshot view of the binding sites between two individual β-sheets. An intermolecular association between Phe and Trp could be observed. l Scheme of the Phov-ACP structure with a cross-β-sheet conformation. Hydrophilic acidic side chains from Phov stabilize ACP droplets (yellow globules) and protrude into the solution. The hydrophobic domain facilitates the formation of hydrophobic interfaces (purple arrow), which are shielded from the solvent. m Cryo-TEM image showing the amyloid-like nanofibrous assembly of Phov-ACP at 24 h (high-magnification image of Fig. 5b). The red dashed circles indicate the electron-dense ACP nanoparticulates. The purple arrows indicate the hydrophobic gaps. Scale bar: 50 nm.