Influence of surface chemistry and protein concentration on the adsorption rate and S-layer crystal formation

Abstract

Bacterial crystalline surface layers (S-layers) are the outermost envelope of prokaryotic organisms representing the simplest biological membranes developed during evolution. In this context, the bacterial protein SbpA has already shown its intrinsic ability to reassemble on different substrates forming protein crystals of square lattice symmetry. In this work, we present the interaction between the bacterial protein SbpA and five self-assembled monolayers carrying methyl (CH(3)), hydroxyl (OH), carboxylic acid (COOH) and mannose (C(6)H(12)O(6)) as functional groups. Protein adsorption and S-layer formation have been characterized by atomic force microscopy (AFM) while protein adsorption kinetics, mass uptake and the protein layer viscoelastic properties were investigated with quartz crystal microbalance with dissipation monitoring (QCM-D). The results indicate that the protein adsorption rate and crystalline domain area depend on surface chemistry and protein concentration. Furthermore, electrostatic interactions tune different protein rate adsorption and S-layer recrystallization pathways. Electrostatic interactions induce faster adsorption rate than hydrophobic or hydrophilic interactions. Finally, the shear modulus and the viscosity of the recrystallized S-layer on CH(3)C(6)S, CH(3)C(11)S and COOHC(11)S substrates were calculated from QCM-D measurements. Protein-protein interactions seem to play a main role in the mechanical stability of the formed protein (crystal) bilayer.

Impact of surface wettability on S-layer recrystallization: a real-time characterization by QCM-D

“…However, because of the lack of resemblance to the natural case (in bacteria), these results were not considered for further comparison. However, similar results to those of the hydrophobic substrate in terms of frequency variation, as well as the presence of the structural transition peak in Δ D , have already been reported in previous studies as developed by our group for different types of hydrophobic alkylsilanes (octadecyltrichlorosilane) [17] and alkylthiols (dodecanethiol and hexanethiol) [18] on silica and gold, respectively. In those cases the real-time analysis differed significantly from the one carried out here.…”

“…In this regard, the quartz crystal microbalance with dissipation monitoring (QCM-D) has proven to be a powerful technique to follow in situ the binding of S-layers on different supports [17–18]. The QCM-D responses, i.e., the resonance frequency f and the energy dissipation D of the shear oscillatory motion of a piezoelectric quartz crystal sensor, change upon adsorption or desorption of material on the surface of that sensor.…”

S-Layer Protein Self-Assembly

“…In another set of experiments [69] the reassembly of the S-layer protein SbpA, again using AFM and QCM-D, was studied on different self-assembled monolayers carrying methyl (CH 3 ), hydroxyl (OH), carboxylic acid (COOH), and mannose (C 6 H 12 O 6 ) as terminating functional groups. It was found that the protein adsorption rate and the size of the crystalline domains were influenced by the introduced surface chemistry and protein concentration.…”

Making novel bio-interfaces through bacterial protein recrystallization on biocompatible polylactide derivative films

“…[32][33][34][35] Differential scanning calorimetry (DSC) was carried out to determine the glass transition, crystallization and melting temperatures of the polymers. Finally Tensile tests were performed to evaluate the Young's modulus (E), stress and strain at yield (σ y , ε y ), and stress and strain at break (σ b , ε b ) of the polymers.…”