2 research outputs found
Comparative Study of Secondary Structure and Interactions of the R5 Peptide in Silicon Oxide and Titanium Oxide Coprecipitates Using Solid-State NMR Spectroscopy
A biomimetic,
peptide-mediated approach to inorganic nanostructure
formation is of great interest as an alternative to industrial production
methods. To investigate the role of peptide structure on silica (SiO<sub>2</sub>) and titania (TiO<sub>2</sub>) morphologies, we use the R5
peptide domain derived from the silaffin protein to produce uniform
SiO<sub>2</sub> and TiO<sub>2</sub> nanostructures from the precursor
silicic acid and titanium bisÂ(amÂmonium lacÂtato)ÂdiÂhydroxide,
respectively. The resulting biosilica and biotitania nanostructures
are characterized using scanning electron microscopy. To investigate
the process of R5-mediated SiO<sub>2</sub> and TiO<sub>2</sub> formation,
we carry out 1D and 2D solid-state NMR (ssNMR) studies on R5 samples
with uniformly <sup>13</sup>C- and <sup>15</sup>N-labeled residues
to determine the backbone and side-chain chemical shifts. <sup>13</sup>C chemical shift data are in turn used to determine peptide backbone
torsion angles and secondary structure for the R5 peptide neat, in
silica, and in titania. We are thus able to assess the impact of the
different mineral environments on peptide structure, and we can further
elucidate from <sup>13</sup>C chemical shifts change the degree to
which various side chains are in close proximity to the mineral phases.
These comparisons add to the understanding of the role of R5 and its
structure in both SiO<sub>2</sub> and TiO<sub>2</sub> formation
Serine–Lysine Peptides as Mediators for the Production of Titanium Dioxide: Investigating the Effects of Primary and Secondary Structures Using Solid-State NMR Spectroscopy and DFT Calculations
A biomimetic
approach to the formation of titania (TiO<sub>2</sub>) nanostructures
is desirable because of the mild conditions required
in this form of production. We have identified a series of serine–lysine
peptides as candidates for the biomimetic production of TiO<sub>2</sub> nanostructures. We have assayed these peptides for TiO<sub>2</sub>-precipitating activity upon exposure to titanium bisÂ(ammonium lactato)Âdihydroxide
and have characterized the resulting coprecipitates using scanning
electron microscopy. A subset of these assayed peptides efficiently
facilitates the production of TiO<sub>2</sub> nanospheres. Here, we
investigate the process of TiO<sub>2</sub> nanosphere formation mediated
by the S–K peptides KSSKK- and SKSK<sub>3</sub>SKS using one-dimensional
and two-dimensional solid-state NMR (ssNMR) on peptide samples with
uniformly <sup>13</sup>C-enriched residues. ssNMR is used to assign <sup>13</sup>C chemical shifts (CSs) site-specifically in each free peptide
and TiO<sub>2</sub>-embedded peptide, which are used to derive secondary
structures in the neat and TiO<sub>2</sub> coprecipitated states.
The backbone <sup>13</sup>C CSs are used to assess secondary structural
changes undergone during the coprecipitation process. Side-chain <sup>13</sup>C CS changes are analyzed with density functional theory
calculations and used to determine side-chain conformational changes
that occur upon coprecipitation with TiO<sub>2</sub> and to determine
surface orientation of lysine side chains in TiO<sub>2</sub>–peptide
composites