Electrostatic Effect of Functional Surfaces on the Activity of Adsorbed Enzymes: Simulations and Experiments

Abstract

The efficient immobilization of haloalkane dehalogenase (DhaA) on carriers with retaining of its catalytic activity is essential for its application in environmental remediation. In this work, adsorption orientation and conformation of DhaA on different functional surfaces were investigated by computer simulations; meanwhile, the mechanism of varying the catalytic activity was also probed. The corresponding experiments were then carried out to verify the simulation results. (The simulations of DhaA on SAMs provided parallel insights into DhaA adsorption in carriers. Then, the theory-guided experiments were carried out to screen the best surface functional groups for DhaA immobilization.) The electrostatic interaction was considered as the main impact factor for the regulation of enzyme orientation, conformation, and enzyme bioactivity during DhaA adsorption. The synergy of overall conformation, enzyme substrate tunnel structural parameters, and distance between catalytic active sites and surfaces codetermined the catalytic activity of DhaA. Specifically, it was found that the positively charged surface with suitable surface charge density was helpful for the adsorption of DhaA and retaining its conformation and catalytic activity and was favorable for higher enzymatic catalysis efficiency in haloalkane decomposition and environmental remediation. The neutral, negatively charged surfaces and positively charged surfaces with high surface charge density always caused relatively larger DhaA conformation change and decreased catalytic activity. This study develops a strategy using a combination of simulation and experiment, which can be essential for guiding the rational design of the functionalization of carriers for enzyme adsorption, and provides a practical tool to rationally screen functional groups for the optimization of adsorbed enzyme functions on carriers. More importantly, the strategy is general and can be applied to control behaviors of different enzymes on functional carrier materials.

Between two walls: Modeling the adsorption behavior of β-glucosidase A on bare and SAM-functionalised gold surfaces

“…This observation can be related to the interaction energies between the enzyme and the two solid surfaces which are shown on Figure SI-3. The energy values, which are agreement with those obtained in earlier simulation studies on proteins adsorbed on SAMs 43, 49, 58 or bare-gold surfaces, 48, 59-60 are significantly more favorable for the protein-bare gold interaction (down to −400 kcal.mol -1 ) as compared to the protein-SAM-OH interaction (down to −150 kcal.mol -1 ), thus accounting for the increased stability of βGA adsorbed on gold. These results also concur with earlier experimental work showing the preferential adsorption of proteins on apolar (here the bare gold) substrates compared to polar (SAM-OH covered gold) substrates.…”

“…We will use the term rigidity profile to describe the ordered set of force constants for all the residues of the protein. simulation studies on proteins adsorbed on SAMs 43,49,58 or bare-gold surfaces, 48,[59][60] are significantly more favorable for the protein-bare gold interaction (down to -400 kcal.mol -1 ) as compared to the protein-SAM-OH interaction (down to -150 kcal.mol -1 ), thus accounting for the increased stability of βGA adsorbed on gold. These results also surface, seem to converge toward the same area of the graph (highlighted by a black circle in Figure 3).…”

“…Altogether, the molecular mechanisms taking place upon enzyme immobilization are not well understood. While most experiments on immobilized proteins, either via a covalent [28][29] or non-covalent [30][31][32] strategy, report a decrease in their catalytic activity, sometimes enzyme immobilization can also result in an important increase of the catalytic performance. 33 Numerous enzyme immobilization strategies have been developed, that involve simple adsorption via electrostatic or van der Waals interactions, the use of porous materials, crosslinking, or multipoint-covalent attachment, [33][34][35] and many experimental approaches are now available to investigate protein immobilization on solid surfaces, including atomic force microscopy, mass spectrometry and spectroscopic methods.…”

First-Principles Simulation of Dielectric Function in Biomolecules

“…In addition to the dielectric spectra, the partial charge (PC) distribution is also crucial for determining and elucidating the electrostatic Coulomb interactions that play a major role in catalysis [ 71 ], drug engineering [ 72 ], etc. For different models studied here, the PC values are calculated based on the reliable orthogonalized linear combination of atomic orbitals (OLCAO) methodology [ 35 ] to understand the electrostatic effects but also the impact due to aqueous environments.…”

Ab Initio Electronic Dielectric “Constant” of Proteins: A Baseline for Electrostatic Interaction in Biomolecular Systems

“…In addition to the static electronic dielectric constant, the partial charge (PC) distribution is also crucial for determining and elucidating the electrostatic effects that play major role in catalysis [62], drug engineering [63] etc. For different models studied here, the PC values are calculated based on the reliable orthogonalized linear combination of atomic orbitals (OLCAO) methodology [27] to understand the electrostatic effects but also the impact due to aqueous environments.…”