Directed Motion of Proteins along Tethered Polyelectrolytes

Abstract

We present the first time-resolved investigation of motions of proteins in densely grafted layers of spherical polyelectrolyte brushes. Using small-angle x-ray scattering combined with rapid stopped-flow mixing, we followed the uptake of bovine serum albumin by poly(acrylic acid) layer with high spatial and temporal resolution. We find that the total amount of adsorbed protein scales with time as t 1=4 . This subdiffusive behavior is explained on the basis of directed motion of the protein along the polyelectrolyte chains. DOI: 10.1103/PhysRevLett.100.158301 PACS numbers: 82.35.Rs, 87.15.Vv The adsorption and immobilization of proteins from aqueous solutions onto solid surfaces is among the most important problems in biochemical research. Many biotechnological processes require immobilization of enzymes with full retention of their biological activity [1][2][3][4]. Reversible adsorption of proteins onto charged surfaces is involved in protein purification by ion exchange chromatography [5] and in many natural processes such as cell adhesion [3]. On the other hand, unspecific adsorption of proteins must be suppressed in many practical applications in order to prevent biofouling [6]. Very often, charged and uncharged polymers attached to surfaces are used to tune the interaction with proteins. Tethered chains of poly(ethylene oxide) are now widely used to prevent protein adsorption [7] while polyelectrolyte multilayers [8,9] or dense layers of polyelectrolytes [9][10][11] are utilized to immobilize proteins on surfaces.Despite numerous studies, little is known about the kinetics of protein adsorption and the self-organization of biomolecules with tethered polymer chains on a molecular level. Evidently, the kinetics of protein adsorption plays a major role in these processes [4,5,8,10 -13] and it is necessary to determine the position of the protein molecules on a molecular scale as a function of time. In this letter, we demonstrate for the first time that protein adsorption can be monitored directly with high temporal and spatial resolution on surface-modified colloidal spheres. We present the first study of the motion of a protein in a layer of tethered polyelectrolyte chains of a spherical polyelectrolyte brush [14] using time-resolved small-angle x-ray scattering (TR-SAXS) [15].Figure 1 schematically displays a colloidal particle composed of poly(styrene) spheres with chemically grafted chains of poly(acrylic acid). The grafting of the polyelectrolyte chains is dense, with the average distance of the chains on the surface much smaller than their contour length L c resulting in a spherical polyelectrolyte brush (SPB) [14]. The radius R of the cores of the SPB is 46 nm ( R 4%) and the thickness of the shell L is 58 nm ( L 25%). Here we study the spontaneous adsorption of bovine serum albumin (BSA). Despite the fact that both the SPB as well as the protein carry an overall negative charge, proteins can spontaneously adsorb onto these SPBs [12] at low ionic strength without inducing denaturation. Moreover, the...

Supramolecular Structures Generated by Spherical Polyelectrolyte Brushes and their Application in Catalysis

“…Thus the motion into the layer is slowed down by the electrostatic repulsion among the like-charged protein molecules and the SPB. The overall amount of adsorbed BSA scales with time as t This could be explained by a simple model: [66] The protein undergoes a directed motion within the brush layer which leads to a subdiffusive behavior.…”

“…(6) The kinetics of the adsorption of enzymes onto the SPB can be monitored by time-resolved SAXS. [66] The uptake of proteins into the brush layer can be followed by high temporal and spatial resolution. Hence, one can localize the proteins within the brush at each stage of adsorption.…”

Distribution of counterions and interaction between two similarly charged dielectric slabs: Roles of charge discreteness and dielectric inhomogeneity

“…Therefore, our study of the interaction between two flat dielectric slabs could be useful in enlightening the phenomenon of interaction between biological charged macromolecules in the presence of multivalent counterions. As examples, like-charge attraction between actin filaments [25], the interaction between DNA and charged proteins [2] and a system of proteins confined in a polyelectrolyte brush [26] can be considered. In most of computer simulation studies of such systems dielectric inhomogeneity and real charge distribution on the surface of the macromolecules have not been taken into account.…”

Two‐Dimensional Oligo(phenylene‐ethynylene‐butadiynylene)s: All‐Covalent Nanoscale Spoked Wheels

“…[11b, 16,47,49] Small-angle neutron scattering was performed on several samples of 1 in CDCl 3 and in a contrast series of THF/ [D 8 ]THF mixtures. As a result of the limited solubility of 1, the investigations were restricted to low concentrations.…”