Monomeric Amelogenin’s C-Terminus Modulates Biomineralization Dynamics of Calcium Phosphate

Abstract

The organic matrix in forming enamel consists largely of the self-assembled nanospheres of amelogenin monomers that play a critical role in controlling crystal growth of the highly organized apatites. However, little is known about the mechanisms of the monomeric form of the C-terminal tail of the molecule in regulating biomineralization dynamics. We investigated brushite-amelogenin's C-terminus interactions by in situ atomic force microscopy (AFM). At very low concentrations (1-10 nM) within a monomeric form of amelogenin, we directly observe a strong interaction of monomeric amelogenin's C-terminus binding to the brushite (010) face, which modulates the critical length and terrace width of moving steps through modification of the brushite-water interfacial energies. This in turn inhibits crystallization by delaying the formation of active steps on the growing crystal face. These findings provide the underlying thermodynamics for understanding

Mechanisms of Modulation of Calcium Phosphate Pathological Mineralization by Mobile and Immobile Small-Molecule Inhibitors

“…The present study of two structural analogues reveals the mechanism that is different from step density determined crystallization rates 29,50 and kink blocking. 26,27 Commonly, inhibitors adsorb to step edges or terraces ahead of migrating steps and impede the addition of solute molecules.…”

“…The measured surface free energy determines the strength of substrate interaction with liquid and is supposed to manifest in the extent of the hydrophilicity of the substrates. , The difference of γ S–air , a proxy for γ SL at the solid (S)–liquid (L) interface, showed that HCA, at concentrations greater than 8.5 μM, dramatically increased DCPD–liquid interfacial energy compared to CA (Figure C). Because of γ SL correlating with the mean value of all crystal-plane-step energies, , a higher γ SL is associated with higher step edge free energy (γ step ) that will delay the formation of critical 1D steps . Consequently, the high affinity of HCA bound to DCPD displays stronger potency in decreasing step density than that of CA (Figure C,D).…”

Controlling Enamel Remineralization by Amyloid‐Like Amelogenin Mimics

“…Once secreted into the extracellular space, amelogenin undergoes a series of proteolytic cleavages starting at the C‐Ame and assemble into nanospheres with a diameter of ≈10–20 nm, which are believed to play a key role in the mineralization and structural organization of enamel. [ 7–9 ] The N‐Ame is crucial for amelogenin self‐assembly into amyloid‐like aggregation through β‐sheet stacking to template the growth of HAp crystals, [ 10,11 ] and the C‐Ame mediate parallel alignment of these crystals [ 12–14 ] ( Scheme ). Hierarchically organized HAp nanorods are further formed in nature involving an aggregation of amorphous calcium phosphate (ACP) nanospheres and a transformation of ACP to HAp crystals (Figure S1, Supporting Information).…”

A Parametric Rosetta Energy Function Analysis with LK Peptides on SAM Surfaces

“…For example, solid-state nuclear magnetic resonance (ssNMR), which accurately determines distances between specific atoms, is costly and difficult to perform on substrates lacking phosphorus or carbon. Single-molecule force spectroscopy (SMFS) techniques, such as atomic force microscopy ,− (AFM), can determine the energy (Δ G ) of protein adsorption, yielding thermodynamic information about protein–surface binding, but they do not provide sufficient imaging resolution to determine biomolecular structures …”