High-throughput microscopy to determine morphology, microrheology, and phase boundaries applied to phase separating coacervates

Abstract

Evolution of composition, rheology, and morphology during phase separation in complex fluids is highly coupled to rheological and mass transport processes within the emerging phases, and understanding this coupling is...

Predicting Polyelectrolyte Coacervation from a Molecularly Informed Field-Theoretic Model

“…This reduces the excluded volume asymmetry between the two phases, and, as a result, the salt partitioning ratio increases from values less than 1 toward 1. Although experimental efforts have shown that the salt partitioning behavior is not universal and depends on other factors such as the chemistry of the PE and charge density, , our prediction of higher salt partitioning in the dilute phase is consistent with the experimental observations for the stoichiometric PAA/PAH mixture. , …”

“…The phase diagram from the Gaussian approximation for N = 150 at 1:1 stoichiometry is directly compared to experimental results of the similar system reported by Li et al and Luo et al at pH = 6.5 (Figure ). , While qualitatively capturing the screening effect of added salt, the phase diagram shown here (1) overestimates the critical salt concentration and (2) underestimates the PE compositions in the coacervate phase. Deficiency (1) is largely attributable to the Gaussian approximation which neglects higher-order fluctuations that become more important near the critical point (can be resolved by including fields other than the electrostatic potential).…”

“…Phase diagrams for stoichiometric mixtures at N = 150 from the Gaussian approximation (black line) and CG MD (circles) compared to those from the experimental data by Li et al (triangles) and Luo et al (squares). , MD simulations are conducted in the NPT ensemble at 298.15 K and P CG in a rectangular box of dimensions ∼11 × 11 × 80 nm 3 . Red circles reflect the PE and salt compositions in the coacervate, while black circles are the overall compositions.…”

“…Although experimental efforts have shown that the salt partitioning behavior is not universal and depends on other factors such as the chemistry of the PE and charge density, 77,78 our prediction of higher salt partitioning in the dilute phase is consistent with the experimental observations for the stoichiometric PAA/PAH mixture. 24,79 Using the same protocol, we construct phase diagrams for N = 150 under non-stoichiometric conditions. Although in general, the stoichiometry of the coacervate phase can be different from that of the initial mixtures and depends on the overall composition, we find that the coacervate maintains the overall stoichiometry, and this observation is mostly independent of the overall composition.…”

Competition between β-Sheet and Coacervate Domains Yields Diverse Morphologies in Mixtures of Oppositely Charged Homochiral Polypeptides

“…Low solution turbidity in this regime is consistent with the small fraction of droplets observed via optical microscopy. It is possible that differences in salt partitioning between polypeptide complexes and bulk solvent that is known to occur in coacervating systems − may result in phase instability under these conditions. It is important to note here that MD simulations were unable to delineate the nanostructure of the polypeptide complexes in region V due to the absence of force fields able to reproduce such high solubility of sodium chloride salt.…”