Protein Adsorption onto Organically Modified Silica Glass Leads to a Different Structure than Sol-Gel Encapsulation

Abstract

The secondary structures of two proteins were examined by circular dichroism spectroscopy after adsorption onto a series of organically modified silica glasses. The glasses were prepared by the sol-gel technique and were varied in hydrophobicity by incorporation of 5% methyl, propyl, trifluoropropyl, or n-hexyl silane. Both cytochrome c and apomyoglobin were found to lose secondary structure after adsorption onto the modified glasses. In the case of apomyoglobin, the alpha-helical content of the adsorbed protein ranged from 21% to 28%, well below the 62% helix found in solution. In contrast, these same glasses led to a striking increase in apomyoglobin structure when the protein was encapsulated within the pores during sol-gel processing: the helical content of apomyoglobin increased with increasing hydrophobicity from 18% in an unmodified glass to 67% in a 5% hexyl-modified glass. We propose that proteins preferentially adsorb onto unmodified regions of the silica surface, whereas encapsulated proteins are more susceptible to changes in surface hydration due to the proximity of the alkyl chain groups.

Characteristics, Chemical Modification Processes as well as the Application of Silica and its Modified Forms

“…Differences in gained volume of aerogels influenced their thickness. Aerogels obtained using TMS and MTMS were characterized by lower thickness, around 0.1 g/cm 3 and higher porosity, around 95%; however, aerogels prepared with the use of TMBS contained a thickness of 0.23 g/cm 3 and porosity of about 88%. It was also determined that silica aerogels prepared with use of organosiles containing metalohalogenic were turbid (clearness < 8%), and aerogels prepared with alkylalcoxysilanes were clear (80%).…”

“…For many years, a search for new methods of chemical surface modifications has been conducted for different forms of silica (2)(3)(4)(5). The presence of hydroxyl on the surface of silica materials greatly facilitates their modification, which allows for their wide application in analytical chemistry.…”

Review Article: Immobilized Molecules Using Biomaterials and Nanobiotechnology

“…The first industrially used immobilized enzyme was prepared by adsorption of amino acid acylase on DEAE-cellulose [16]. Menaa et al (2008a) [17] reported the role of hydrophobic surfaces of nanoporous silica glasses on protein folding enhancement.…”

Surface Coating Rescues Proteins from Magnetite Nanoparticle Induced Damage

“…Instead, the formation of FeN Mod , which occurs at a higher protein to NP ratio, is responsible for the loss of helical content. It can also be argued that the formation of FeN Mod at high NP concentration is the result of less number of Cytc bound per NP molecule as discussed previously . Alternatively, at low NP concentration, the number of protein molecules adsorbed on the NP surface would increase.…”