Favourable influence of hydrophobic surfaces on protein structure in porous organically-modified silica glasses

Abstract

Organically-modified siloxanes were used as host materials to examine the influence of surface chemistry on protein conformation in a crowded environment. The sol-gel materials were prepared from tetramethoxysilane and a series of monosubstituted alkoxysilanes, RSi(OR′) 3 , featuring alkyl groups of increasing chain length in the R-position. Using circular dichroism spectroscopy in the far-UV region, apomyoglobin was found to transit from an unfolded state to a native-like helical state as the content of the hydrophobic precursor increased from 0-15%. At a fixed molar content of 5% RSi(OR') 3 , the helical structure of apomyoglobin increased with the chain length of the R-group, i.e. methyl < ethyl < n-propyl < n-butyl < n-hexyl. This trend also was observed for the tertiary structure of ribonuclease A, suggesting that protein folding and biological activity are sensitive to the hydrophilic/hydrophobic balance of neighboring surfaces. The observed changes in protein structure did not correlate with total surface area or the average pore size of the modified glasses, but scanning electron microscopy images revealed an interesting relationship between surface morphology and alkyl chain length. The unexpected benefit of incorporating a low content of hydrophobic groups into a hydrophilic surface may lead to materials with improved biocompatibility for use in biosensors and implanted devices.

Development of effective nanobiocatalytic systems through the immobilization of hydrolases on functionalized carbon-based nanomaterials

“…In this case, the CalA exhibited increased esterification activity compared to the free enzyme (Table 4), which indicates a correlation between the increase in a-helix content and the enhanced catalytic activity. A similar correlation between a-helix content and activity was also observed for CalB when covalently immobilized on both nanomaterials, which is in agreement with recently reports on enzymes immobilized on various hydrophobic organically modified silica glasses (Menaa et al, 2008).…”

Chemistry in nanochannel confinement

“…Similar effects were observed by Menaa et al [59]. However, these authors used modified siloxanes as host materials, and the modification was performed using monosubstituted alkoxysilanes with alkyl groups of increasing chain length.…”

Overview of the main methods used to combine proteins with nanosystems: absorption, bioconjugation, and encapsulation

“…Furthermore, functional activity of proteins entrapped into the sol-gel matrix needs to be accurately analyzed case-by-case using several techniques such as CD spectropolarimetry. 144,145 The drug release and the capability of the carrier to be metabolized can be important factors to be considered when chronic or repeated treatments are necessary. The disadvantage associated with inorganic and synthetic carriers are the poor or slow biodegradability and possible inflammatory responses.…”