posted on 2023-05-18, 21:13authored byGomathi Mahadevan, Rajeev Kungur Brahma, R. Manjunatha Kini, Suresh Valiyaveettil
Living organisms develop functional hard structures such
as teeth,
bones, and shells from calcium salts through mineralization for managing
vital functions to sustain life. However, the exact mechanism or role
of biomolecules such as proteins and peptides in the biomineralization
process to form defect-free hierarchical structures in nature is poorly
understood. In this study, we have extracted, purified, and characterized
five major peptides (CBP1–CBP5) from the soluble organic materials
(SOMs) of cuttlefish bone (CB) and used for the in vitro mineralization
of calcium carbonate crystals. The SOMs induced nucleation of the
calcite phase at low concentrations and the vaterite phase at high
concentrations. The purified peptides nucleated calcite crystals and
enhanced aggregation under laboratory conditions. Among five peptides,
only CBP2 and CBP3 showed concentration-dependent nucleation, aggregation,
and morphological changes of the calcite crystals within 12 h. Circular
dichroism studies showed that the peptides CBP2 and CBP3 are in alpha
helix and β-sheet conformation, respectively, in solution. CBP1
and CBP4 and CBP5 are in random coil and β-sheet conformation,
respectively. In addition, the peptides showed different sizes in
solution in the absence (∼27 nm, low aggregation) and presence
(∼118 nm, high aggregation) of calcium ions. Aragonite crystals
with needle-type morphologies were nucleated in the presence of Mg2+ ions in solution. Overall, exploring the activities of such
intramineral peptides from CB help to unravel the mechanism of calcium
salt deposition in nature.