Enolase Adsorption onto Hydrophobic and Hydrophilic Solid Substrates

Abstract

The understanding of the adsorption process of biomolecules is very important for biological and engineering applications. Enolase is an enzyme of glycolytic pathway that catalyses a reversible conversion of 2-phosphoglycerate to phosphoenolpyruvate. In this work the adsorption behavior of enolase (2-phospho-D-glycerayte hydrolyase) onto hydrophilic silicon wafers and amino-terminated surfaces (APS) and onto hydrophobic polymer polystyrene (PS) was studied by means of null-ellipsometry. The adsorption kinetics of enolase onto these substrates presented three distinct regions: (i) a diffusion-controlled one; (ii) an adsorption plateau; (iii) continuous, irreversible, and asymptotic increase of the adsorbed amount with time. Atomic force microscopy (AFM) showed that well-packed entities formed an enolase biofilm, which might correspond to the monolayer formation. With increase of the adsorption time, aggregates appeared on the surface, suggesting multilayer formation. The early stages might be predicted by the random sequential adsorption model (RSA), while the cooperative sequential adsorption (CSA) model seems to describe regions ii and iii. No significant influence of ionic strength was observed on the adsorption behavior of enolase onto the present substrates. The adsorption isotherms show that enolase has no preferential adhesion onto hydrophilic or hydrophobic substrates. Contact angle measurements showed that PS surfaces became hydrophilic and silicon surfaces turned hydrophobic after the formation of the enolase biofilm. The study of the influence of pH on the enolase adsorption on silicon and APS surfaces showed that the higher adsorbed amount occurs when pH is close to enolase pI. Far from pI the enzyme solubility decreases and some repulsive forces come out, leading to a decrease in the adsorbed amount.

Characterization of Ultrathin Films of Cellulose Esters

“…This finding indicates that the adsorbed BSA molecules expose their hydrophilic residues to the substrates, while the hydrophobic residues are oriented to the air. Such molecular orientation driven by the substrate wettability has been already observed for enolase, an enzyme of the glycolytic pathway, on Si wafers and on hydrophobic polystyrene films (Almeida et al 2002). Regardless the type of cellulose ester film, the variation in h A values measured after the adsorption of lipase lies in the standard deviation.…”

Assembly of Graphene Oxide–Enzyme Conjugates through Hydrophobic Interaction

“…In addition, the higher the enzyme loading, the thicker is the CRGO and the lower the immobilized enzyme activity (Figure S4). This result also suggests that more than one layer of enzymes is possibly loaded on the highly reduced CRGO 17. Nevertheless, the results further convinced us that hydrophobic interaction between CRGO and the enzyme is the driving force for enzyme immobilization.…”

Conditioning materials with biomacromolecules: Composition of the adlayer and influence on cleanability

“…This is in relation with the measurement of the contact angle in advancing conditions, and the fact that BSA was not present on the surface to be wetted. The influence of protein adsorption and subsequent drying on the water contact angle was reported for several systems: non-annealed and annealed films of cellulose derivatives conditioned with BSA (Kosaka et al, 2005); silicon wafer, silanized silicon wafer and polystyrene conditioned with enolase (Almeida et al, 2002); set of materials with water contact angle ranging from 11 to 100° fouled with β-lactoglobulin and rinsed (Yang et al, 1991). In these works, protein conditioning of hydrophilic substrates led to an increase of the water contact angle while conditioning of hydrophobic substrates led to a decrease of the contact angle.…”