Electrohydrodynamic Properties of Succinoglycan as Probed by Fluorescence Correlation Spectroscopy, Potentiometric Titration and Capillary Electrophoresis

Abstract

The electrostatic, hydrodynamic and conformational properties of aqueous solutions of succinoglycan have been analyzed by fluorescence correlation spectroscopy (FCS), proton titration, and capillary electrophoresis (CE) over a large range of pH values and electrolyte (NaCl) concentrations. Using the theoretical formalism developed previously for the electrokinetic properties of soft, permeable particles, a quantitative analysis for the electrohydrodynamics of succinoglycan is performed by taking into account, in a self-consistent manner, the measured values of the diffusion coefficients, electric charge densities, and electrophoretic mobilities. For that purpose, two limiting conformations for the polysaccharide in solution are tested, i.e. succinoglycan behaves as (i) a spherical, random coil polymer or (ii) a rodlike particle with charged lateral chains. The results show that satisfactory modeling of the titration data for ionic strengths larger than 50 mM can be accomplished using both geometries over the entire range of pH values. Electrophoretic mobilities measured for sufficiently large pH values (pH > 5-6) are in line with predictions based on either model. The best manner to discriminate between these two conceptual models is briefly discussed. For low pH values (pH < 5), both models indicate aggregation, resulting in an increase of the hydrodynamic permeability and a decrease of the diffusion coefficient.

On electrophoresis of a pH‐regulated nanogel with ion partitioning effects

“…Figure A shows that the present numerical solutions are in very good agreement with the experimental results of Duval et al. .…”

“…(A) Comparison of our computed electrophoretic mobility for ε r = 1 with the experimental results of Duval et al. as a function of salt NaCl concentration, radius of the PE a = 10.8 nm, pH = 10.3, p K A = 4.58, p K B = 8.6, N A = 213 mM, N B = 26 mM, ℓ = 0.635 nm, and E 0 = 10 4 V/m. Variation of mobility with C KCl for (B) N A = N B = 100 mM and (C) N A = N B = 900 mM for different ε r ( = 0.5, 0.75, 1) and different pH ( = 3, 5, 8, 10) when p K A = 2.5, p K B = 9.5, and β = 2.…”

Impact of the virulence-associated MAb3/1 epitope on the physicochemical surface properties of Legionella pneumophila sg1: An issue to explain infection potential?

“…(1)-(7) disregard (i) polarization of electric double layer by the applied field and (ii) the possible heterogeneity in soft material density distribution within the permeable part of the bacteria, heterogeneity occasioned by possible swelling of the soft bacterial component under low ionic-strength conditions. As extensively demonstrated in previous work [33,36,37], phenomena (i) and (ii) effectively lead to reduced mobility (in magnitude) as compared to those obtained from Eqs. (1)- (7).…”

“…In case of bacteria, the soft component is identified as the cell wall and/or possible surface structures like lipopolysaccharides, fimbriae or pili that may extend in aqueous media from few nms up to tenths of microns from the anchoring membrane [34]. The very presence of such components that are permeable to electroosmotic flow while bacteria migrate under action of applied field (electrophoresis), leads to electrokinetic response that substantially differs from that expected on the basis of formalisms valid for conventional hard impermeable particles [34][35][36]. This response is further reflecting the electrostatic and permeability features of the bacteria, both being intrinsically related to the nature, chemical composition and compactness of the soft bacterial component.…”

Nanofibrils and other colloidal biopolymers binding trace elements in coastal seawater: Significance for variations in element size distributions

“…Comparable diffusion coefficients have also been determined on isolated succinoglycan, a polysaccharide produced by bacteria (Duval et al 2006). These types of gelforming plankton exudates represent a major component of the colloidal organic matter in the ocean (Aluwihare et al 1997), and have previously been shown to occur in large amounts in the surface water of the Gullmarsfjord, where they are important for the scavenging of organic carbon through their formation of TEP (Waite et al 2005).…”