Conformation and Assembly of Polypeptide Scaffolds in Templating the Synthesis of Silica:  An Example of a Polylysine Macromolecular “Switch”

Abstract

Although the role of polycationic macromolecules in catalyzing the synthesis of silica structures is well established, detailed understanding of the mechanisms behind the production of silica structures of controlled morphologies remains unclear. In this study, we have used both poly-L-lysine (PLL) and/or poly-D-lysine (PDL) for silica synthesis to investigate mechanisms controlling inorganic morphologies. The formation of both spherical silica particles and hexagonal plates was observed. The formation of hexagonal plates was suggested, via circular dichroic spectroscopy (CD), to result from the assembly of helical polylysine molecules. We confirm that the formation of PLL helices is a prerequisite to the hexagonal silica synthesis. In addition, we present for the first time that the handedness of the helicity of the macromolecule does not affect the formation of hexagonal silica. We also show, by using two different silica precursors, that the precursor does not have a direct effect on the formation of hexagonal silica plates. Furthermore, when polylysine helices were converted to beta-sheet structure, only silica particles were obtained, thus suggesting that the adoption of a helical conformation by PLL is required for the formation of hexagonally organized silica. These results demonstrate that the change in polylysine conformation can act as a "switch" in silica structure formation and suggest the potential for controlling morphologies and structures of inorganic materials via control of the conformation of soft macromolecular templates.

Biogeochemical variability during the past 3.6 million years recorded by FTIR spectroscopy in the sediment record of Lake El'gygytgyn, Far East Russian Arctic

“…while the absorption band at around 800 cm −1 is caused by symmetric Si-O-Si stretching vibrations (Moenke, 1974b;Patwardhan et al, 2006). A FTIR spectrum of purified BSi from Lake El'gygytgyn sediment shows two additional absorption bands at around 471 and 945 cm −1 (Fig.…”

Poriferan Chitin as a Versatile Template for Extreme Biomimetics

“…In particular, the 2D and 3D nanostructural biocomposite-based scaffolds are crucial for a broad variety of advanced applications [147,148]. Biomimetic synthesis of materials is carried out with various biomolecules; especially enzymes [146], proteins [149,150] peptides [151,152] and polysaccharides [153][154][155][156][157]. These biomacromolecules play an important role in nucleation, thermodynamic and kinetic control of crystal growth, and also can be used as soft templates for inorganic structures [143].…”

“…These biomacromolecules play an important role in nucleation, thermodynamic and kinetic control of crystal growth, and also can be used as soft templates for inorganic structures [143]. However, traditionally, approaches related to the in vitro biomimetic mineralization of organic templates are carried out at temperatures between 20 and 37 °C and at near-neutral pH [149][150][151][152][153][154][155][156][157][158]. It is assumed that biological materials, especially protein-based ones, are not stable at temperatures higher than 40 °C.…”

Application of Fourier Transform Infrared Spectroscopy (FTIR) for assessing biogenic silica sample purity in geochemical analyses and palaeoenvironmental research

“…FTIR spectra of pure silica typically exhibits peaks in two distinct regions (Fidalgo and Ilharco, 2001;Patwardhan et al, 2006): peaks at > 2500 cm −1 and < 1300 cm −1 . The first region corresponds to hydroxyl (−OH) stretching from absorbed or molecular water, while the second region occurs due to several silica modes.…”

“…The FTIR method circumvents these issues as the spectra of a sample will be affected by all contaminants, regardless of whether they are inorganic or organic in origin, provided that suitable end-members are selected. This includes the presence of any organic matter and water content (for example see Patwardhan et al, 2006) with FTIR further able to differentiate between proteins, which typically mediate biogenic silica formation, and polysaccharides, which are predominantly found as a protective coating for diatoms.…”