Insight into the Supramolecular Architecture of Intact Diatom Biosilica from DNP‐Supported Solid‐State NMR Spectroscopy

Abstract

Diatom biosilica is an inorganic/organic hybrid with interesting properties. The molecular architecture of the organic material at the atomic and nanometer scale has so far remained unknown, in particular for intact biosilica. A DNP-supported ssNMR approach assisted by microscopy, MS, and MD simulations was applied to study the structural organization of intact biosilica. For the first time, the secondary structure elements of tightly biosilica-associated native proteins in diatom biosilica were characterized in situ. Our data suggest that these proteins are rich in a limited set of amino acids and adopt a mixture of random-coil and β-strand conformations. Furthermore, biosilica-associated long-chain polyamines and carbohydrates were characterized, thereby leading to a model for the supramolecular organization of intact biosilica.

1H-detected solid-state NMR of proteins entrapped in bioinspired silica: a new tool for biomaterials characterization

“…Of note, in a recent paper, DNP was used to detect the signals from the biosilica-forming peptide PL12, also detecting correlation of silica with lysine sidechains21. Another recent paper used DNP to study the proteic component of the biosilica of intact diatoms22.…”

Biosilica and bioinspired silica studied by solid-state NMR

“…By investigating the spin-diffusion properties of the composite, an estimate of the arrangement of different biomolecules inside the siliceous cell wall was performed. [161] It is however of remarkable importance to note that for different silica precipitating peptides, different secondary structures were found. This implies that the local secondary structure of individual peptides is not the main factor for enabling silica polymerization.…”

Structural Insights into Peptides Bound to the Surface of Silica Nanopores

“…To answer these questions, more sophisticated solid‐state NMR experiments, such as two‐dimensional correlation techniques employing homonuclear proton frequency switched Lee–Goldburg (FSLG) decoupling ( 1 H FSLG and 1 H– 29 Si CP MAS FSLG HETCOR) as well as DNP‐enhanced ( 15 N CP MAS, 1 H– 15 N and 1 H– 13 C CP MAS FSLG HETCOR) are necessary. Employing these solid‐state NMR techniques, for example, detailed information on the linkage of amino acids and peptides to the surface as well as on their orientation have been obtained. DNP‐enhanced solid‐state NMR experiments of non‐isotope‐labeled amino acids or peptides grafted on silica surfaces, or on MOFs have been able to confirm the binding and interaction between the peptide or amino acid and the carrier material.…”