On the Complexation of Proteins and Polyelectrolytes

Silva, Fernando Luís Barroso da; Lund, Mikael; Jönsson, Bo; Åkesson, Torbjörn

doi:10.1021/jp054880l

Cited by 98 publications

(130 citation statements)

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“…Recent theories have focused on more detailed treatment of electrostatics, including the effects of ion size and charge connectivity on the polyion [23,24], ion-pair formation and solute-solvent interactions [25], and charge regulation [26][27][28]. Moreover, the possibility of microstructure formation has also been explored [29].…”

Section: Introductionmentioning

confidence: 99%

pH and Salt Effects on the Associative Phase Separation of Oppositely Charged Polyelectrolytes

et al. 2014

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Abstract:The classical Voorn-Overbeek thermodynamic theory of complexation and phase separation of oppositely charged polyelectrolytes is generalized to account for the charge accessibility and hydrophobicity of polyions, size of salt ions, and pH variations. Theoretical predictions of the effects of pH and salt concentration are compared with published experimental data and experiments we performed, on systems containing poly(acrylic acid) (PAA) as the polyacid and poly(N,N-dimethylaminoethyl methacrylate) (PDMAEMA) or poly(diallyldimethyl ammonium chloride) (PDADMAC) as the polybase. In general, the critical salt concentration below which the mixture phase separates, increases with degree of ionization and with the hydrophobicity of polyelectrolytes. We find experimentally that as the pH is decreased below 7, and PAA monomers are neutralized, the critical salt concentration increases, while the reverse occurs when pH is raised above 7. We predict this asymmetry theoretically by introducing a large positive Flory parameter (= 0.75) for the interaction of neutral PAA monomers with water. This large positive Flory parameter is supported by molecular dynamics simulations, which show much weaker hydrogen bonding between neutral PAA and water than between charged PAA and water, while neutral and charged PDMAEMA show similar numbers of hydrogen bonds. This increased hydrophobicity of neutral PAA at reduced pH increases the tendency towards phase separation despite the reduction in charge interactions between the polyelectrolytes. Water content and volume of coacervate are found to be a strong function of the pH and salt concentration.

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Section: Introductionmentioning

confidence: 99%

pH and Salt Effects on the Associative Phase Separation of Oppositely Charged Polyelectrolytes

et al. 2014

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“…Other electrostatic properties of the protein, however, may be more important and Kirkwood and Shumaker [20] demonstrated theoretically already in 1952 that fluctuations of residue charges in two proteins can result in an attractive force. Recently, we have taken up this idea and used MC simulations and a charge regulation theory in order to explain protein-protein and protein-polyelectrolyte association in a purely electrostatic model [21,41]. A charge regulation mechanism has also been suggested by Biesheuvel and Cohen-Stuart [42].…”

Section: Protein Polyelectrolyte Complexationmentioning

confidence: 99%

Chapter 9. Electrostatics in Macromolecular Solutions

Jönsson¹,

Lund²,

Silva³

Food Colloids

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An overview of the interaction between charged macromolecules in aqueous solution is presented. The starting point is the dielectric continuum model and the Debye-Hückel equation. The usefulness of the simple theory is emphasized in particular for biological macromolecules, whose net charge or surface charge density often is low. With more highly charged macromolecules or aggregates it may be necessary to go beyond the simple Debye-Hückel theory and invoke the non-linear Poisson-Boltzmann equation or even to approach an exact solution using Monte Carlo simulations or similar techniques. The latter approach becomes indispensable when studying systems with divalent or multivalent (counter)-ions. The long range character of the electrostatic interactions means that charged systems of varying geometry -spheres, planes, cylinders... -often have many properties in common. Another consequence is that the detailed charge distribution on a macromolecule is less important. Many biological macromolecules contain titratable groups, which means that the net charge will vary as a consequence of solution conditions. This gives an extra attractive contribution to the interaction between two macromolecules, which might be particularly important close to their respective isoelectric points. The treatment of flexible polyelectrolytes/polyampholytes requires some extra efforts in order to handle the increasingly complex geometry. A theoretical consequence is that the number of parameters -chain length, charge density, polydispersity etc -prohibits the presentation of a simple unified picture. An additional experimental, and theoretical, difficulty in this context is the slow approach towards equilibrium, in particular with high molecular weight polymers. A few generic situations where polyelectrolytes can act both as stabilizers and coagulants can, however, be demonstrated using simulation techniques.

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“…There are many examples for using this procedure to deliver bioactive molecules, and different materials have been employed for such as purpose. Chitosan with ␤-lactoglobulin (Chen & Subirade 2005), chitosan and gelatin (Shu & Zhu 2002), gelatin and carrageenan (Jonganurakkun et al 2006), pectin and chitosan (Chang & Lin 2000), ␤ lactoglobulin and gum arabic (Schmitt et al 1999), gelatin and gum arabic (Bungenberg de Jong & Kruyt 1924;de Kruif et al 2004), and protein-polyelectrolyte (Da Silva et al 2006) are among the complexes which have been studied.…”

Section: Coacervationmentioning

confidence: 99%