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Christine D. Keating - One of the best experts on this subject based on the ideXlab platform.
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Impact of wet-dry cycling on the phase behavior and compartmentalization properties of complex Coacervates.
Nature communications, 2020Co-Authors: Hadi M. Fares, Matthew Tirrell, Alexander E. Marras, Jeffrey M. Ting, Christine D. KeatingAbstract:Wet-dry cycling on the early Earth is thought to have facilitated production of molecular building blocks of life, but its impact on self-assembly and compartmentalization remains largely unexplored. Here, we investigate dehydration/rehydration of complex Coacervates, which are membraneless compartments formed by phase separation of polyelectrolyte solutions. Solution compositions are identified for which tenfold water loss results in maintenance, disappearance, or appearance of Coacervate droplets. Systems maintaining Coacervates throughout the dehydration process are further evaluated to understand how their compartmentalization properties change with drying. Although added total RNA concentrations increase tenfold, RNA concentration within Coacervates remains steady. Exterior RNA concentrations rise, and exchange rates for encapsulated versus free RNAs increase with dehydration. We explain these results in light of the phase diagram, with dehydration-driven ionic strength increase being particularly important in determining Coacervate properties. This work shows that wet-dry cycling can alter the phase behavior and protocell-relevant functions of complex Coacervates. Wet-dry cycling is thought to have enabled the production of molecular building blocks of life. Here, the authors investigate the impact of dehydration/rehydration on RNA-containing complex Coacervates, which are membraneless compartments formed by phase separation of polyelectrolyte solutions.
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lipid vesicle coated complex Coacervates
Langmuir, 2019Co-Authors: Fatma Pir Cakmak, Alex T. Grigas, Christine D. KeatingAbstract:Compartmentalization by complex coacervation is important across a range of different fields including subcellular and prebiotic organization, biomedicine, food science, and personal care products. Often, lipid self-assemblies such as vesicles are also present intracellularly or in commercial formulations. A systematic understanding of how phospholipid vesicles interact with different complex Coacervates could provide insight and improve control over these systems. In this manuscript, anionic phospholipid vesicles were added to a series of different complex Coacervate samples in which Coacervates were formed by mixing one of five polycations with one of three (poly)anions that varied in chemical structure and length. Vesicles were found to assemble at the Coacervate/continuous phase interface and/or form aggregates. We report how factors such as the charge density of polyelectrolytes and the charge ratio of cationic-to-anionic moieties impact the vesicle distribution in Coacervate samples. Our findings em...
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lipid vesicle coated complex Coacervates
Langmuir, 2019Co-Authors: Fatma Pir Cakmak, Alex T. Grigas, Christine D. KeatingAbstract:Compartmentalization by complex coacervation is important across a range of different fields including subcellular and prebiotic organization, biomedicine, food science, and personal care products. Often, lipid self-assemblies such as vesicles are also present intracellularly or in commercial formulations. A systematic understanding of how phospholipid vesicles interact with different complex Coacervates could provide insight and improve control over these systems. In this manuscript, anionic phospholipid vesicles were added to a series of different complex Coacervate samples in which Coacervates were formed by mixing one of five polycations with one of three (poly)anions that varied in chemical structure and length. Vesicles were found to assemble at the Coacervate/continuous phase interface and/or form aggregates. We report how factors such as the charge density of polyelectrolytes and the charge ratio of cationic to anionic moieties impacts vesicle distribution in Coacervate samples. Our findings empha...
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template directed rna polymerization and enhanced ribozyme catalysis inside membraneless compartments formed by Coacervates
Nature Communications, 2019Co-Authors: Raghav R Poudyal, Christine D. Keating, Rebecca M Guthmetzler, Andrew Veenis, Erica A Frankel, Philip C BevilacquaAbstract:Membraneless compartments, such as complex Coacervates, have been hypothesized as plausible prebiotic micro-compartments due to their ability to sequester RNA; however, their compatibility with essential RNA World chemistries is unclear. We show that such compartments can enhance key prebiotically-relevant RNA chemistries. We demonstrate that template-directed RNA polymerization is sensitive to polycation identity, with polydiallyldimethylammonium chloride (PDAC) outperforming poly(allylamine), poly(lysine), and poly(arginine) in polycation/RNA Coacervates. Differences in RNA diffusion rates between PDAC/RNA and oligoarginine/RNA Coacervates imply distinct biophysical environments. Template-directed RNA polymerization is relatively insensitive to Mg2+ concentration when performed in PDAC/RNA Coacervates as compared to buffer, even enabling partial rescue of the reaction in the absence of magnesium. Finally, we show enhanced activities of multiple nucleic acid enzymes including two ribozymes and a deoxyribozyme, underscoring the generality of this approach, in which functional nucleic acids like aptamers and ribozymes, and in some cases key cosolutes localize within the Coacervate microenvironments.
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template directed rna polymerization and enhanced ribozyme catalysis inside membraneless compartments formed by Coacervates
Nature Communications, 2019Co-Authors: Raghav R Poudyal, Christine D. Keating, Rebecca M Guthmetzler, Andrew Veenis, Erica A Frankel, Philip C BevilacquaAbstract:Membraneless compartments, such as complex Coacervates, have been hypothesized as plausible prebiotic micro-compartments due to their ability to sequester RNA; however, their compatibility with essential RNA World chemistries is unclear. We show that such compartments can enhance key prebiotically-relevant RNA chemistries. We demonstrate that template-directed RNA polymerization is sensitive to polycation identity, with polydiallyldimethylammonium chloride (PDAC) outperforming poly(allylamine), poly(lysine), and poly(arginine) in polycation/RNA Coacervates. Differences in RNA diffusion rates between PDAC/RNA and oligoarginine/RNA Coacervates imply distinct biophysical environments. Template-directed RNA polymerization is relatively insensitive to Mg2+ concentration when performed in PDAC/RNA Coacervates as compared to buffer, even enabling partial rescue of the reaction in the absence of magnesium. Finally, we show enhanced activities of multiple nucleic acid enzymes including two ribozymes and a deoxyribozyme, underscoring the generality of this approach, in which functional nucleic acids like aptamers and ribozymes, and in some cases key cosolutes localize within the Coacervate microenvironments. Membraneless compartments have been theorized to be prebiotic micro-compartments as they spontaneously encapsulate RNA and proteins. Here, the authors report membraneless compartments can enhance RNA chemistries, affecting template directed RNA polymerization and stimulating nucleic acid enzymes.
Benu Adhikari - One of the best experts on this subject based on the ideXlab platform.
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microencapsulation of chia seed oil using chia seed protein isolate chia seed gum complex Coacervates
International Journal of Biological Macromolecules, 2016Co-Authors: Yakindra Prasad Timilsena, Raju Adhikari, Colin J. Barrow, Benu AdhikariAbstract:Chia seed oil (CSO) microcapsules were produced by using chia seed protein isolate (CPI)-chia seed gum (CSG) complex Coacervates aiming to enhance the oxidative stability of CSO. The effect of wall material composition, core-to-wall ratio and method of drying on the microencapsulation efficiency (MEE) and oxidative stability (OS) was studied The microcapsules produced using CPI-CSG complex Coacervates as wall material had higher MEE at equivalent payload, lower surface oil and higher OS compared to the microcapsules produced by using CSG and CPI individually. CSO microcapsules produced by using CSG as wall material had lowest MEE (67.3%) and oxidative stability index (OSI=6.6h), whereas CPI-CSG complex Coacervate microcapsules had the highest MEE (93.9%) and OSI (12.3h). The MEE and OSI of microcapsules produced by using CPI as wall materials were in between those produced by using CSG and CPI-CSG complex Coacervates as wall materials. The CSO microcapsules produced by using CPI-CSG complex Coacervate as shell matrix at core-to-wall ratio of 1:2 had 6 times longer storage life compared to that of unencapsulated CSO. The peroxide value of CSO microcapsule produced using CPI-CSG complex Coacervate as wall material was <10meq O2/kg oil during 30 days of storage.
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preparation and characterization of chia seed protein isolate chia seed gum complex Coacervates
Food Hydrocolloids, 2016Co-Authors: Yakindra Prasad Timilsena, Raju Adhikari, Bo Wang, Benu AdhikariAbstract:Chia seed protein isolate (CPI) and chia seed gum (CSG) were extracted and complex coacervation between these two was studied. The pH and the CPI-to-CSG ratio were optimized to obtain the highest yield of complex Coacervates underpinned by zeta potential and turbidity values. CPI-CSG complex Coacervates were found to form primarily due to electrostatic interaction and remained stable within a pH range of 2.1-2.9 at ambient temperature. The optimum pH and CPI-to-CSG ratio for complex coacervation was found to be 2.7 and 6:1, respectively. Spray dried complex Coacervate particles possessed smoother surface morphology compared to the freeze dried ones. CPI-CSG complex Coacervates demonstrated better thermal stability as compared to that of individual CPI and CSG. The crosslinking of these complex Coacervates by transglutaminase further improved their thermal stability. Therefore, the crosslinked CPI-CSG complex Coacervates will be able to better protect the oxygen and heat sensitive food and pharmaceutical ingredients.
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Optimisation of the complex coacervation between canola protein isolate and chitosan
Journal of Food Engineering, 2016Co-Authors: Peg Gee Chang, Yakindra Prasad Timilsena, Rahul K. Gupta, Benu AdhikariAbstract:Abstract The complex coacervation phenomenon between canola protein isolate (CPI) and chitosan (CS) was studied. CPI was extracted in the laboratory from canola meal and used in this study. The factors affecting the yield of CPI-chitosan complex Coacervates such as CPI-to-chitosan ratio, pH and strength of the electrostatic interaction (SEI) were investigated. The thermal characteristics of the un-cross-linked and transglutaminase cross-linked complex Coacervates were also determined. The optimum complex coacervation between CPI and CS occurred at the CPI-to-chitosan mass ratio of 16 and the pH range of 5.8–6.2. The peak denaturation temperature and the denaturation enthalpy of CPI in CPI-chitosan complex were higher than those of the uncompleted or free CPI indicating that the complexation made the CPI more thermally stable. The thermal stability of the Coacervates was further enhanced when cross-linked with transglutaminase. The increased thermal stability of CPI in CPI-chitosan Coacervate indicated that CPI-chitosan Coacervates would be suitable for encapsulation of thermally sensitive food and pharmaceutical ingredients.
Yakindra Prasad Timilsena - One of the best experts on this subject based on the ideXlab platform.
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microencapsulation of chia seed oil using chia seed protein isolate chia seed gum complex Coacervates
International Journal of Biological Macromolecules, 2016Co-Authors: Yakindra Prasad Timilsena, Raju Adhikari, Colin J. Barrow, Benu AdhikariAbstract:Chia seed oil (CSO) microcapsules were produced by using chia seed protein isolate (CPI)-chia seed gum (CSG) complex Coacervates aiming to enhance the oxidative stability of CSO. The effect of wall material composition, core-to-wall ratio and method of drying on the microencapsulation efficiency (MEE) and oxidative stability (OS) was studied The microcapsules produced using CPI-CSG complex Coacervates as wall material had higher MEE at equivalent payload, lower surface oil and higher OS compared to the microcapsules produced by using CSG and CPI individually. CSO microcapsules produced by using CSG as wall material had lowest MEE (67.3%) and oxidative stability index (OSI=6.6h), whereas CPI-CSG complex Coacervate microcapsules had the highest MEE (93.9%) and OSI (12.3h). The MEE and OSI of microcapsules produced by using CPI as wall materials were in between those produced by using CSG and CPI-CSG complex Coacervates as wall materials. The CSO microcapsules produced by using CPI-CSG complex Coacervate as shell matrix at core-to-wall ratio of 1:2 had 6 times longer storage life compared to that of unencapsulated CSO. The peroxide value of CSO microcapsule produced using CPI-CSG complex Coacervate as wall material was <10meq O2/kg oil during 30 days of storage.
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preparation and characterization of chia seed protein isolate chia seed gum complex Coacervates
Food Hydrocolloids, 2016Co-Authors: Yakindra Prasad Timilsena, Raju Adhikari, Bo Wang, Benu AdhikariAbstract:Chia seed protein isolate (CPI) and chia seed gum (CSG) were extracted and complex coacervation between these two was studied. The pH and the CPI-to-CSG ratio were optimized to obtain the highest yield of complex Coacervates underpinned by zeta potential and turbidity values. CPI-CSG complex Coacervates were found to form primarily due to electrostatic interaction and remained stable within a pH range of 2.1-2.9 at ambient temperature. The optimum pH and CPI-to-CSG ratio for complex coacervation was found to be 2.7 and 6:1, respectively. Spray dried complex Coacervate particles possessed smoother surface morphology compared to the freeze dried ones. CPI-CSG complex Coacervates demonstrated better thermal stability as compared to that of individual CPI and CSG. The crosslinking of these complex Coacervates by transglutaminase further improved their thermal stability. Therefore, the crosslinked CPI-CSG complex Coacervates will be able to better protect the oxygen and heat sensitive food and pharmaceutical ingredients.
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Optimisation of the complex coacervation between canola protein isolate and chitosan
Journal of Food Engineering, 2016Co-Authors: Peg Gee Chang, Yakindra Prasad Timilsena, Rahul K. Gupta, Benu AdhikariAbstract:Abstract The complex coacervation phenomenon between canola protein isolate (CPI) and chitosan (CS) was studied. CPI was extracted in the laboratory from canola meal and used in this study. The factors affecting the yield of CPI-chitosan complex Coacervates such as CPI-to-chitosan ratio, pH and strength of the electrostatic interaction (SEI) were investigated. The thermal characteristics of the un-cross-linked and transglutaminase cross-linked complex Coacervates were also determined. The optimum complex coacervation between CPI and CS occurred at the CPI-to-chitosan mass ratio of 16 and the pH range of 5.8–6.2. The peak denaturation temperature and the denaturation enthalpy of CPI in CPI-chitosan complex were higher than those of the uncompleted or free CPI indicating that the complexation made the CPI more thermally stable. The thermal stability of the Coacervates was further enhanced when cross-linked with transglutaminase. The increased thermal stability of CPI in CPI-chitosan Coacervate indicated that CPI-chitosan Coacervates would be suitable for encapsulation of thermally sensitive food and pharmaceutical ingredients.
Dong Soo Hwang - One of the best experts on this subject based on the ideXlab platform.
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bicontinuous fluid structure with low cohesive energy molecular basis for exceptionally low interfacial tension of complex Coacervate fluids
ACS Nano, 2016Co-Authors: Kuoying Huang, Dong Soo HwangAbstract:An exceptionally low interfacial tension of a dense fluid of concentrated polyelectrolyte complexes, phase-separated from a biphasic fluid known as complex Coacervates, represents a unique and highly sought-after materials property that inspires novel applications from superior coating to wet adhesion. Despite extensive studies and broad interest, the molecular and structural bases for the unique properties of complex Coacervates are unclear. Here, a microphase-separated complex Coacervate fluid generated by mixing a recombinant mussel foot protein-1 (mfp-1) as the polycation and hyaluronic acid (HA) as the polyanion at stoichiometric ratios was macroscopically phase-separated into a dense complex Coacervate and a dilute supernatant phase to enable separate characterization of the two fluid phases. Surprisingly, despite up to 4 orders of magnitude differing density of the polyelectrolytes, the diffusivity of water in these two phases was found to be indistinguishable. The presence of unbound, bulk-like, w...
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bicontinuous fluid structure with low cohesive energy molecular basis for exceptionally low interfacial tension of complex Coacervate fluids
ACS Nano, 2016Co-Authors: Kuoying Huang, Hee Young Yoo, Yongseok Jho, Songi Han, Dong Soo HwangAbstract:An exceptionally low interfacial tension of a dense fluid of concentrated polyelectrolyte complexes, phase-separated from a biphasic fluid known as complex Coacervates, represents a unique and highly sought-after materials property that inspires novel applications from superior coating to wet adhesion. Despite extensive studies and broad interest, the molecular and structural bases for the unique properties of complex Coacervates are unclear. Here, a microphase-separated complex Coacervate fluid generated by mixing a recombinant mussel foot protein-1 (mfp-1) as the polycation and hyaluronic acid (HA) as the polyanion at stoichiometric ratios was macroscopically phase-separated into a dense complex Coacervate and a dilute supernatant phase to enable separate characterization of the two fluid phases. Surprisingly, despite up to 4 orders of magnitude differing density of the polyelectrolytes, the diffusivity of water in these two phases was found to be indistinguishable. The presence of unbound, bulk-like, water in the dense fluid can be reconciled with a water population that is only weakly perturbed by the polyelectrolyte interface and network. This hypothesis was experimentally validated by cryo-TEM of the macroscopically phase-separated dense complex Coacervate phase that was found to be a bicontinuous and biphasic nanostructured network, in which one of the phases was confirmed by staining techniques to be water and the other polyelectrolyte complexes. We conclude that a weak cohesive energy between water-water and water-polyelectrolytes manifests itself in a bicontinuous network, and is responsible for the exceptionally low interfacial energy of this complex fluid phase with respect to virtually any surface within an aqueous medium.
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complexation and coacervation of like charged polyelectrolytes inspired by mussels
Proceedings of the National Academy of Sciences of the United States of America, 2016Co-Authors: Jun Huang, Sandipan Dutta, Young Mee Jung, Hongbo Zeng, Dong Soo HwangAbstract:It is well known that polyelectrolyte complexes and Coacervates can form on mixing oppositely charged polyelectrolytes in aqueous solutions, due to mainly electrostatic attraction between the oppositely charged polymers. Here, we report the first (to the best of our knowledge) complexation and coacervation of two positively charged polyelectrolytes, which provides a new paradigm for engineering strong, self-healing interactions between polyelectrolytes underwater and a new marine mussel-inspired underwater adhesion mechanism. Unlike the conventional complex Coacervate, the like-charged Coacervate is aggregated by strong short-range cation–π interactions by overcoming repulsive electrostatic interactions. The resultant phase of the like-charged Coacervate comprises a thin and fragile polyelectrolyte framework and round and regular pores, implying a strong electrostatic correlation among the polyelectrolyte frameworks. The like-charged Coacervate possesses a very low interfacial tension, which enables this highly positively charged Coacervate to be applied to capture, carry, or encapsulate anionic biomolecules and particles with a broad range of applications.
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viscosity and interfacial properties in a mussel inspired adhesive Coacervate
Soft Matter, 2010Co-Authors: Dong Soo Hwang, Matthew Tirrell, Hongbo Zeng, Jacob N Israelachvili, Aasheesh Srivastava, Daniel V Krogstad, Herbert J WaiteAbstract:The chemistry of mussel adhesion has commanded the focus of much recent research activity on wet adhesion. By comparison, the equally critical adhesive processing by marine organisms has been little examined. Using a mussel-inspired Coacervate formed by mixing a recombinant mussel adhesive protein (fp-151-RGD) with hyaluronic acid (HA), we have examined the nanostructure, viscosity, friction, and interfacial energy of fluid-fluid phase-separated Coacervates using the surface forces apparatus and microscopic techniques. At mixing ratios of fp-151-RGD:HA resulting in marginal coacervation, the Coacervates showed shear-thickening viscosity and no structure by cryo-transmission electron microscopy (cryo-TEM). However, at the mixing ratio producing maximum coacervation, the Coacervate showed shear-thinning viscosity and a transition to a bicontinuous phase by cryo-TEM. The shear-thinning viscosity, high friction coefficient (>1.2), and low interfacial energy (<1 mJ m−2) observed at the optimal mixing ratio for coacervation are promising delivery, spreading and adhesion properties for future wet adhesive and coating technologies.
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promotion of osteoblast proliferation on complex coacervation based hyaluronic acid recombinant mussel adhesive protein coatings on titanium
Biomaterials, 2010Co-Authors: Dong Soo Hwang, Herbert J Waite, Matthew TirrellAbstract:Many biological polyelectrolytes are capable of undergoing a fluid–fluid phase separation known as complex coacervation. Coacervates were prepared using hyaluronic acid (HA) and a recombinant fusion protein consisting of mussel adhesive motifs and the RGD peptide (fp-151-RGD). The low interfacial energy of the Coacervate was exploited to coat titanium (Ti), a metal widely used in implant materials. The Coacervate effectively distributed both HA and fp-151-RGD over the Ti surfaces and enhanced osteoblast proliferation. Approximately half of total fp-151-RGD and HA in the solution transferred to the titanium surface within 2 h. Titanium coated with Coacervates having high residual negative surface charge showed the highest cell proliferation of preosteoblast cells (MC-3T3) compared to the treatments tested. Indeed, MC-3T3 cells on complex Coacervate coated titanium foils exhibited over 5 times greater cell proliferation than bare, HA coated or fp-151-RGD coated titanium.
Philip C Bevilacqua - One of the best experts on this subject based on the ideXlab platform.
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template directed rna polymerization and enhanced ribozyme catalysis inside membraneless compartments formed by Coacervates
Nature Communications, 2019Co-Authors: Raghav R Poudyal, Christine D. Keating, Rebecca M Guthmetzler, Andrew Veenis, Erica A Frankel, Philip C BevilacquaAbstract:Membraneless compartments, such as complex Coacervates, have been hypothesized as plausible prebiotic micro-compartments due to their ability to sequester RNA; however, their compatibility with essential RNA World chemistries is unclear. We show that such compartments can enhance key prebiotically-relevant RNA chemistries. We demonstrate that template-directed RNA polymerization is sensitive to polycation identity, with polydiallyldimethylammonium chloride (PDAC) outperforming poly(allylamine), poly(lysine), and poly(arginine) in polycation/RNA Coacervates. Differences in RNA diffusion rates between PDAC/RNA and oligoarginine/RNA Coacervates imply distinct biophysical environments. Template-directed RNA polymerization is relatively insensitive to Mg2+ concentration when performed in PDAC/RNA Coacervates as compared to buffer, even enabling partial rescue of the reaction in the absence of magnesium. Finally, we show enhanced activities of multiple nucleic acid enzymes including two ribozymes and a deoxyribozyme, underscoring the generality of this approach, in which functional nucleic acids like aptamers and ribozymes, and in some cases key cosolutes localize within the Coacervate microenvironments.
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template directed rna polymerization and enhanced ribozyme catalysis inside membraneless compartments formed by Coacervates
Nature Communications, 2019Co-Authors: Raghav R Poudyal, Christine D. Keating, Rebecca M Guthmetzler, Andrew Veenis, Erica A Frankel, Philip C BevilacquaAbstract:Membraneless compartments, such as complex Coacervates, have been hypothesized as plausible prebiotic micro-compartments due to their ability to sequester RNA; however, their compatibility with essential RNA World chemistries is unclear. We show that such compartments can enhance key prebiotically-relevant RNA chemistries. We demonstrate that template-directed RNA polymerization is sensitive to polycation identity, with polydiallyldimethylammonium chloride (PDAC) outperforming poly(allylamine), poly(lysine), and poly(arginine) in polycation/RNA Coacervates. Differences in RNA diffusion rates between PDAC/RNA and oligoarginine/RNA Coacervates imply distinct biophysical environments. Template-directed RNA polymerization is relatively insensitive to Mg2+ concentration when performed in PDAC/RNA Coacervates as compared to buffer, even enabling partial rescue of the reaction in the absence of magnesium. Finally, we show enhanced activities of multiple nucleic acid enzymes including two ribozymes and a deoxyribozyme, underscoring the generality of this approach, in which functional nucleic acids like aptamers and ribozymes, and in some cases key cosolutes localize within the Coacervate microenvironments. Membraneless compartments have been theorized to be prebiotic micro-compartments as they spontaneously encapsulate RNA and proteins. Here, the authors report membraneless compartments can enhance RNA chemistries, affecting template directed RNA polymerization and stimulating nucleic acid enzymes.