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The complex coacervation of proteins with other macromolecules has applications in protein encapsulation and delivery and for determining the function of cellular coacervates. Theoretical or empirical predictions for protein coacervates would enable the design of these coacervates with tunable and predictable structure–function relationships; unfortunately, no such theories exist. To help establish predictive models, the impact of protein-specific parameters on complex coacervation were probed in this study. The complex coacervation of sequence-specific, polypeptide-tagged, GFP variants and a strong synthetic polyelectrolyte was used to evaluate the effects of protein charge patterning on phase behavior. Phase portraits for the protein coacervates demonstrated that charge patterning dictates the protein's binodal phase boundary. Protein concentrations over 100 mg mL −1 were achieved in the coacervate phase, with concentrations dependent on the tag polypeptide sequence covalently attached to the globular protein domain. In addition to shifting the binodal phase boundary, polypeptide charge patterning provided entropic advantages over isotropically patterned proteins. Together, these results show that modest changes of only a few amino acids in the tag polypeptide sequence alter the coacervation thermodynamics and can be used to tune the phase behavior of polypeptides or proteins of interest.
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Polyelectrolyte–Carbon Dot Complex Coacervation
This Letter presents complex coacervation between the biopolymer diethylaminoethyl dextran hydrochloride (DEAE-Dex) and carbon dots. The formation of these coacervates was dependent on both DEAE-Dex concentration and solution ionic strength. Fluorescence spectroscopy revealed that the blue fluorescence of the carbon dots was unaffected by coacervation. Additionally, microrheological studies were conducted to determine the viscosity of these coacervates. These complex coacervates, formed through the interaction of nanoparticles and polyelectrolytes, hold a promising role for future applications where the combination of optical properties from the carbon dots and encapsulation via coacervation can be leveraged.
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- Award ID(s):
- 1945521
- PAR ID:
- 10574728
- Editor(s):
- Stuart_Rowan
- Publisher / Repository:
- ACS Macro Letters
- Date Published:
- Journal Name:
- ACS Macro Letters
- Volume:
- 14
- Issue:
- 1
- ISSN:
- 2161-1653
- Page Range / eLocation ID:
- 43 to 50
- Subject(s) / Keyword(s):
- Complex coacervate carbon dot
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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Complex coacervation is a widely utilized technique for effecting phase separation, though predictive understanding of molecular-level details remains underdeveloped. Here, we couple coarse-grained Monte Carlo simulations with experimental efforts using a polypeptide-based model system to investigate how a comb-like architecture affects complex coacervation and coacervate stability. Specifically, the phase separation behavior of linear polycation-linear polyanion pairs was compared to that of comb polycation-linear polyanion and comb polycation-comb polyanion pairs. The comb architecture was found to mitigate cooperative interactions between oppositely charged polymers, as no discernible phase separation was observed for comb-comb pairs and complex coacervation of linear-linear pairs yielded stable coacervates at higher salt concentration than linear-comb pairs. This behavior was attributed to differences in counterion release by linear vs. comb polymers during polyeletrolyte complexation. Additionally, the comb polycation formed coacervates with both stereoregular poly( l -glutamate) and racemic poly( d , l -glutamate), whereas the linear polycation formed coacervates only with the racemic polyanion. In contrast, solid precipitates were obtained from mixtures of stereoregular poly( l -lysine) and poly( l -glutamate). Moreover, the formation of coacervates from cationic comb polymers incorporating up to ∼90% pendant zwitterionic groups demonstrated the potential for inclusion of comonomers to modulate the hydrophilicity and/or other properties of a coacervate-forming polymer. These results provide the first detailed investigation into the role of polymer architecture on complex coacervation using a chemically and architecturally well-defined model system, and highlight the need for additional research on this topic.more » « less
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Oppositely charged polymerized ionic liquids (PILs) were used to form complex coacervates in two different organic solvents, 2,2,2-trifluoroethanol (TFE) and hexafluoro-2-propanol (HFIP), and the corresponding phase diagrams were constructed using UV–vis, NMR, and turbidity experiments. While previous studies on complex coacervates have focused almost exclusively on aqueous environments, the use of PILs in the current work enabled studies in solvents with substantially lower dielectric constants (27.0 for TFE, 16.7 for HFIP). The critical salt concentration required to induce complete miscibility was roughly 2-fold larger in HFIP compared with TFE, and two different PIL complexes, solid-like precipitates and liquid-like coacervates, were found in both systems. This study provides insight into the effects of low-dielectric-constant solvents on complex coacervation, which has not been widely studied because of the limited solubility of conventional polyelectrolytes in these media.more » « less
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The phase behavior and chain conformational structure of biphasic polyzwitterion–polyelectrolyte coacervates in salted aqueous solution are investigated with a model weak cationic polyelectrolyte, poly(2-vinylpyridine) (P2VP), whose charge fraction can be effectively tuned by pH. It is observed that increasing the pH leads to the increase of the yielding volume fraction and the water content of dense coacervates formed between net neutral polybetaine and cationic P2VP in contrast to the decrease of critical salt concentration for the onset of coacervation, where the P2VP charge fraction is reduced correspondingly. Surprisingly, a single-molecule fluorescence spectroscopic study suggests that P2VP chains upon coacervation seem to adopt a swollen or an even more expanded conformational structure at higher pH. As the hydrophobicity of P2VP chains is accompanied by a reduced charge fraction by increasing the pH, a strong pH-dependent phase and conformational behaviors suggest the shift of entropic and enthalpic contribution to the underlying thermodynamic energy landscape and chain structural dynamics of polyelectrolyte coacervation involving weak polyelectrolytes in aqueous solution.more » « less
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- Free Publicly Accessible Full Text
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Accepted Manuscript
- Journal Article:
- https://doi.org/10.1021/acsmacrolett.4c00745
