Phase Transitions in Chemically Fueled, Multiphase Complex Coacervate Droplets

Abstract

Membraneless organelles are droplets in the cytosol that are regulated by chemical reactions. Increasing studies suggest that they are internally organized. However, how these subcompartments are regulated remains elusive. Herein, we describe a complex coacervate‐based model composed of two polyanions and a short peptide. With a chemical reaction cycle, we control the affinity of the peptide for the polyelectrolytes leading to distinct regimes inside the phase diagram. We study the transitions from one regime to another and identify new transitions that can only occur under kinetic control. Finally, we show that the chemical reaction cycle controls the liquidity of the droplets offering insights into how active processes inside cells play an important role in tuning the liquid state of membraneless organelles. Our work demonstrates that not only thermodynamic properties but also kinetics should be considered in the organization of multiple phases in droplets.

Multiphase Coacervation of Polyelectrolytes Driven by Asymmetry of Charged Sequence

“…The above calculation for our system indicates the large asymmetry of charge patterns of polyions may generate different attractions to oppositely charged polymers (accordingly producing effective repulsion between same charged polyions), which gives the similar mechanism as Boeynaems et al’s work. On the other hand, the prediction on our previous article about the multiphase coacervation driven by asymmetry of linear charge density is in accord with experiments. , Specifically, a recent work by Donau et al shows a mixture of two miscible polyanions in water will form multiphase droplets with adding positively charged peptide, in which the asymmetry of linear charge density should play an important role, demonstrating the robustness of our calculation. Therefore, we believe the charge patterns is important in regulating multiphase coacervation and hope our theoretical predictions can receive further direct evidence from experiments or simulations.…”

Visualizing formation and dynamics of a three-dimensional sponge-like network of a coacervate in real time

“…47 Inspired by these biological events, a few synthetic multiphase LLPS materials have been developed by careful combination of different coacervates with distinct physicochemical properties (e.g., interfacial tension). 34,42,[48][49][50] However, transient multiphase coacervation is carried out in a different manner, i.e., the in situ generation of distinct coacervate phases consisting of a single dipeptide derivative by integration of its thermally induced response and the photothermal effect of AuNPs. Such stimulus-triggered control of the sponge-like network in terms of mesh size and dynamics could provide a new way of manipulating the liquidlike properties of synthetic and biological LLPS materials.…”

“…After further incubation, the membranes suddenly burst producing numerous spherical coacervates. It was not possible to stain the interiors of the budded thin-layer membranes and inner-separated regions with BODIPY-FF-OtBu, suggesting that their interiors were filled with water/buffer (thus, the inner darker regions can be ascribed to vacuoles 16,33,[42][43][44] ). Temperature-dependent phase transition was also confirmed in the bulk state (Supplementary Fig.…”

Non-enzymatic oligonucleotide ligation in coacervate protocells sustains compartment-content coupling

“…Membrane-free droplets produced by complex coacervation between oppositely charged polyions have recently received increasing attention as viable alternative protocells 5 – 7 and surrogates of intracellular biomolecular condensates 8 . Coacervates assemble from a diversity of species, including prebiotically plausible molecules 6 , 9 , guide the interfacial assembly of lipid membranes 10 , 11 , can organize into multiple sub-compartments 12 – 14 and be formed and dissolved in response to physical and chemical stimuli 15 – 21 . Owing to their lack of a membrane, liquid-like nature, low internal polarity, and high local charge density 8 , coacervate microdroplets also spontaneously uptake and accumulate various guest solutes by partitioning 22 , 23 , including nucleotides, RNA, and divalent ions 24 .…”