2 research outputs found
Diatom Mimics: Directing the Formation of Biosilica Nanoparticles by Controlled Folding of Lysine-Leucine Peptides
Silaffins, long chain polyamines,
and other biomolecules found
in diatoms are involved in the assembly of a large number of silica
nanostructures under mild, ambient conditions. Nanofabrication researchers
have sought to mimic the diatom’s biosilica production capabilities
by engineering proteins to resemble aspects of naturally occurring
biomolecules. Such mimics can produce monodisperse biosilica nanospheres,
but in vitro production of the variety of intricate biosilica nanostructures
that compose the diatom frustule is not yet possible. In this study
we demonstrate how LK peptides, composed solely of lysine (K) and
leucine (L) amino acids arranged with varying hydrophobic periodicities,
initiate the formation of different biosilica nanostructures in vitro.
When L and K residues are arranged with a periodicity of 3.5 the α-helical
form of the LK peptide produces monodisperse biosilica nanospheres.
However, when the LK periodicity is changed to 3.0, corresponding
to a 3<sub>10</sub> helix, the morphology of the nanoparticles changes
to elongated rod-like structures. β-strand LK peptides with
a periodicity of 2.0 induce wire-like silica morphologies. This study
illustrates how the morphology of biosilica can be changed simply
by varying the periodicity of polar and nonpolar amino acids
Calcium-Induced Molecular Rearrangement of Peptide Folds Enables Biomineralization of Vaterite Calcium Carbonate
Proteins
can control mineralization of CaCO<sub>3</sub> by selectively
triggering the growth of calcite, aragonite or vaterite phases. The
templating of CaCO<sub>3</sub> by proteins must occur predominantly
at the protein/CaCO<sub>3</sub> interface, yet molecular-level insights
into the interface during active mineralization have been lacking.
Here, we investigate the role of peptide folding and structural flexibility
on the mineralization of CaCO<sub>3</sub>. We study two amphiphilic
peptides based on glutamic acid and leucine with β-sheet and
α-helical structures. Though both sequences lead to vaterite
structures, the β-sheets yield free-standing vaterite nanosheet
with superior stability and purity. Surface-spectroscopy and molecular
dynamics simulations reveal that reciprocal structuring of calcium
ions and peptides lead to the effective synthesis of vaterite by mimicry
of the (001) crystal plane