Adsorption of Proteins to Hydrophobic Sites on Mixed Self-Assembled Monolayers

Abstract

This paper describes a technique that uses mixed self-assembled monolayers of two alkanethiolates ( -S(CH2)11(OCH2CH2)6OR, R ) a hydrophobic group, and -S(CH2)11(OCH2CH2)nOH, n ) 3, 6, EGnOH), in combination with surface plasmon resonance spectroscopy, to study the influence of the size and shape of R, and its density at the surface, on the hydrophobic adsorption of proteins at solid-liquid interfaces. Detailed results were obtained for β-galactosidase, carbonic anhydrase, lysozyme, and RNase A using R ) C(C6H5)3, CH(C6H5)2, and CH2(C6H5). A hard-sphere model is used to rationalize the adsorption; this model, although very approximate, helps to interpret qualitative trends in the data. Using this model, the extent to which adsorbed proteins undergo conformational rearrangements appears to depend on the density of the hydrophobic groups at the surface and on the concentration of protein in solution. This paper describes the first step toward the development of a system that will allow the study of hydrophobic interactions of proteins with surfaces presenting organic groups of well-defined shape.

Interfacial assembly of proteins and peptides: recent examples studied by neutron reflection

“…(Su et al 2000) and PC-incorporated polymers . The amount of protein adsorption was found to be at the minimum over the range of intermediate surface hydrophobicity, consistent with the feature observed by other researchers (Chapman et al 2000Ostuni et al 2001Ostuni et al , 2003. On surfaces that were very hydrophilic (e.g.…”

Carbonic Anhydrase as a Model for Biophysical and Physical-Organic Studies of Proteins and Protein−Ligand Binding

“…489,491 SAMs presenting oligo(ethylene glycol) are particularly important in studies of protein-ligand interactions at surfaces, since they effectively resist the nonspecific adsorption of proteins and cells 481,[483][484][485] and provide an excellent baseline against which the specific binding of proteins to surface-bound ligands, [467][468][469]492 or the nonspecific binding of proteins to hydrophobic sites, can be measured. 493 8.5. Most Convenient Assays-As an aside, to researchers new to this area, our experience suggests that the most convenient assays for thermodynamic binding studies are the dansylamide displacement assay (section 8.…”

Suppression of Non-specific Adsorption Using Densified Tri(ethylene glycol) alkanethiols: Monolayer Characteristics Evaluated by Electrochemical Measurements

“…[5][6][7][8][9] The mechanism that prevents non-specific protein adsorption on PEG (OEG) layers has also been studied by using spectroscopic measurements (infrared spectroscopy, X-ray photoelectron spectroscopy) and other methods, including an electric charge technique and measurements of hydrophilicity, hydrophobicity and bulkiness of terminating groups. [10][11][12][13][14] The hydrophilicity and flexiblity of PEG (OEG) structures are largely responsible for its repellency. Although the larger OEG units are more effective in preventing non-specific adsorption (R-(CH2)11SH; R, ethylene glycol units), the di(ethylene glycol) unit is known to be the shortest unit capable of repelling protein adsorption.…”