Tailored Synthetic Polyamines for Controlled Biomimetic Silica Formation

Abstract

Organic compounds isolated from diatoms contain long-chain polyamines with a propylamine backbone and variable methylation levels and chain lengths. These long-chain polyamines are thought to be one of the important classes of molecules that are responsible for the formation of the hierarchically structured silica-based cell walls of diatoms. Here we describe a synthetic route based on solid-phase peptide synthesis from which well-defined long-chain polyamines with different chain lengths, methylation patterns, and subunits can be obtained. Quantitative silica precipitation experiments together with structural information about the precipitated silica structures gained by scanning and transmission electron microscopy revealed a distinct dependence of the amount, size, and form of the silica precipitates on the molecular structure of the polyamine. Moreover, the influence of the phosphate concentration was elucidated, revealing the importance of divalent anions for the precipitation procedure. We were able to derive further insights into the precipitation properties of long-chain polyamines as functions of their hydrophobicity, protonation state, and phosphate concentration, which may pave the way for better control of the formation of nanostructured silica under ambient conditions.

Structural identification of long-chain polyamines associated with diatom biosilica in a Southern Ocean sediment core

“…This encapsulation would afford the LCPAs physical protection so long as the silica remains. In-vitro experiments have recently shown that natural and synthetic LCPAs (along with silaffins) induce silica precipi- tation when added to a metastable solution of monosilicic acid (Krö ger et al, 2000;Noll et al, 2002;Bernecker et al, 2010). The protonated amino groups of LCPAs may serve as binding sites for silicic acid (Coradin et al, 2002).…”

Graphene oxide single sheets as substrates for high resolution cryoTEM

“…[1][2][3][4][5][6] For the TEM analysis of specimens dispersed in liquids, samples are conventionally dried from suspension onto a 30-50 nm carbon or polymer covered metal grid. For organic materials, which are relatively transparent to the electron beam, drying is oen combined with negative staining to generate contrast.…”

Effect of pH and chitosan concentration on precipitation and morphology of hierarchical porous silica

“…Traditional syntheses of silica-based materials require elevated temperature, high pressure, strongly acidic or alkaline media, and a long time for the synthesis process [6]. By comparison, biologically controlled silica materials production not only occurs under benign conditions but also produces silica materials with hierarchically ordered pore structures ranging from the nanometer to micrometer domain [7,8]. Such materials can provide a high specific surface area and more interaction sites via nanopores, while the presence of additional macropores can enhance mass transport and easier accessibility to the active sites.…”