The adsorption of lysozymes: A model system

Abstract

Hen egg white lysozyme was adsorbed onto clean borosilicate glass and n‐pentyl silane‐treated glass surfaces. Both modified (reductively methylated) and native lysozyme were studied. Variable angle X‐ray photoelectron spectroscopy (VA‐XPS) suggested differences in the nature of the adsorbed layer depending on substrate properties, as well as on degree of methylation of the protein. Adsorbed film thickness (as measured in the dehydrated state by XPS) ranged from 14 Å on hydrophilic glass to 25 Å on the hydrophobic surface. Degree of surface coverage ranged from 45% on the hydrophobic to 69% on the hydrophilic surface. The results suggest that lysozyme unfolds to a greater extent and covers more surface on the hydrophilic glass, possibly due to strong electrostatic interactions at the pH 7.4 conditions used in the study. An analysis of the surface structure of native hen lysozyme by molecular graphics has also been performed, suggesting that adsorption on hydrophobic surfaces should occur via the hydrophobic patch opposite the enzyme active site cleft. A comparison with human lysozyme has also been made using total internal reflection fluorescence (TIRF) spectroscopy to measure protein adsorption on model surfaces. The two proteins have significantly different interfacial properties.

pH‐Induced Lignin Surface Modification to Reduce Nonspecific Cellulase Binding and Enhance Enzymatic Saccharification of Lignocelluloses

“…A negatively charged surface is less hydrophobic, which is not favorable for binding cellulase through hydrophobic interac- tions. [19][20][21] Similar results were observed for the other two lignin residues (data not shown). The slopes and intercepts obtained from linear regression of the zeta potential data with pH, Z = k pH + Z 0 , for the four hydrolysis lignin residues are listed in Table 4.…”

Lignosulfonate and elevated pH can enhance enzymatic saccharification of lignocelluloses

“…Increasing the hydrophobicity of a substrate results in enhanced adsorption of protein or cellulase [1,21]. This suggests that nonspecific binding (adsorption) of cellulase (made of protein) to lignin will be different for lignins of different hydrophobicities.…”

Biocoating of Implants with Mediator Molecules: Surface Enhancement of Metals by Treatment with Chromosulfuric Acid

“…The titanium powder, normal polished and special surfaceenhanced pure titanium and stainless steel plates were mod-ified by silanation with 3-aminopropyltriethoxysilane (APS) (in aqueous [11,12] or non-aqueous medium [13]) followed by activation by CDI as described for Silica gel [14]. For silanation in non-aqueous medium 1 g titanium powder prepared as described above was suspended in 45 ml dry toluol to which 5 ml APS was added.…”

“…We therefore defined that amount of immobilized protein as covalently linked which could not be removed by washing with NaOH/SDS and was in excess to the ªirreversiblyº adsorbed protein. The powder was either reacted with APS in aqueous medium (method 1) according to [11] or in non-aqueous medium (method 2, see Methods). Thus the covalent coupling of 125 I-ubiquitin to Ti-APS-CDI powder (method 1) followed by washing with NaOH/SDS solution led to a gross amount (non-covalent and covalent binding) of immobilized ubiquitin of 0.122 lg/cm 2 and a net amount of covalently coupled 125 I-ubiquitin of 0.015 lg/cm 2 .…”