Kinetics of liquid–liquid phase separation in protein solutions exhibiting LCST phase behavior studied by time-resolved USAXS and VSANS

Vela, Stefano Da; Braun, Michal K.; Dörr, Andreas; Greco, Alessandro; Möller, Johannes; Fu, Zhendong; Zhang, Fajun; Schreiber, Frank

doi:10.1039/c6sm01837h

Cited by 59 publications

(91 citation statements)

References 60 publications

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“…The growth law associated with the assembly process might also be instructive to distinguish between PPPS and LLPS. For LLPS, the size of the body increases over time with a power of one-third if growth is mainly driven by diffusion (79). In contrast, PPPS-driven formation occurs via clusters organized in a beads-ona-string-like manner with a different time dependence (52,80).…”

Section: Regulation Of Chromatin Body Formation By Active Processesmentioning

confidence: 99%

Formation of Chromatin Subcompartments by Phase Separation

Erdel

Rippe

2018

Biophysical Journal

319

340

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Chromatin is partitioned on multiple length scales into subcompartments that differ from each other with respect to their molecular composition and biological function. It is a key question how these compartments can form even though diffusion constantly mixes the nuclear interior and rapidly balances concentration gradients of soluble nuclear components. Different biophysical concepts are currently used to explain the formation of "chromatin bodies" in a self-organizing manner and without consuming energy. They rationalize how soluble protein factors that are dissolved in the liquid nuclear phase, the nucleoplasm, bind and organize transcriptionally active or silenced chromatin domains. In addition to cooperative binding of proteins to a preformed chromatin structure, two different mechanisms for the formation of phase-separated chromatin subcompartments have been proposed. One is based on bridging proteins that cross-link polymer segments with particular properties. Bridging can induce a collapse of the nucleosome chain and associated factors into an ordered globular phase. The other mechanism is based on multivalent interactions among soluble molecules that bind to chromatin. These interactions can induce liquid-liquid phase separation, which drives the assembly of liquid-like nuclear bodies around the respective binding sites on chromatin. Both phase separation mechanisms can explain that chromatin bodies are dynamic spherical structures, which can coalesce and are in constant and rapid exchange with the surrounding nucleoplasm. However, they make distinct predictions about how the size, density, and stability of chromatin bodies depends on the concentration and interaction behavior of the molecules involved. Here, we compare the different biophysical mechanisms for the assembly of chromatin bodies and discuss experimental strategies to distinguish them from each other. Furthermore, we outline the implications for the establishment and memory of functional chromatin state patterns.

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Section: Regulation Of Chromatin Body Formation By Active Processesmentioning

confidence: 99%

Formation of Chromatin Subcompartments by Phase Separation

Erdel

Rippe

2018

Biophysical Journal

319

340

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“…It has been found that Y 3+ cations introduce a short-range attraction between the protein molecules by forming cation bridges between negatively charged residues of protein molecules, 5 leading to a variety of phenomena including crystallisation, 5,38,39 cluster formation, 39 reentrant condensation, 38,40,41 and metastable LLPS 39 with a lower critical solution temperature (LCST-LLPS). [42][43][44] A representative salt-protein concentration (c s -c p ) phase diagram of a negatively charged globular protein in the presence of a trivalent salt describing our experimental systems is shown in Fig. 1.…”

Section: Introductionmentioning

confidence: 99%

Tuning phase transitions of aqueous protein solutions by multivalent cations

Matsarskaia

Roosen-Runge

Lötze

et al. 2018

Phys. Chem. Chem. Phys.

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In the presence of trivalent cations, negatively charged globular proteins show a rich phase behaviour including reentrant condensation, crystallisation, clustering and lower critical solution temperature metastable liquid-liquid phase separation (LCST-LLPS). Here, we present a systematic study on how different multivalent cations can be employed to tune the interactions and the associated phase behaviour of proteins. We focus our investigations on the protein bovine serum albumin (BSA) in the presence of HoCl 3 , LaCl 3 and YCl 3 . Using UV-Vis spectroscopy and small-angle X-ray scattering (SAXS), we find that the interprotein attraction induced by Ho 3+ is very strong, while the one induced by La 3+ is comparatively weak when comparing the data to BSA-Y 3+ systems based on our previous work. Using zeta potential and isothermal titration calorimetry (ITC) measurements, we establish different binding affinities of cations to BSA with Ho 3+ having the highest one. We propose that a combination of different cation features such as radius, polarisability and in particular hydration effects determine the proteinprotein interaction induced by these cations. Our findings imply that subtle differences in cation properties can be a sensitive tool to fine-tune protein-protein interactions and phase behaviour in solution.

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“…The LCST-LLPS of BSA-YCl 3 systems has been shown to occur via spinodal decomposition and the kinetics of the latter have been studied using ultra small-angle scattering. [340] It was found that the characteristic length ξ of the respective systems grows as a function of time t as x � t 1=3 for T < 45°C. For T < 45°C and at t > 30 s, the growth of ξ slows down.…”

Section: 3)mentioning

confidence: 99%

Multivalent ions and biomolecules: Attempting a comprehensive perspective

2020

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Ions are ubiquitous in nature. They play a key role for many biological processes on the molecular scale, from molecular interactions, to mechanical properties, to folding, to self‐organisation and assembly, to reaction equilibria, to signalling, to energy and material transport, to recognition etc. Going beyond monovalent ions to multivalent ions, the effects of the ions are frequently not only stronger (due to the obviously higher charge), but qualitatively different. A typical example is the process of binding of multivalent ions, such as Ca2+, to a macromolecule and the consequences of this ion binding such as compaction, collapse, potential charge inversion and precipitation of the macromolecule. Here we review these effects and phenomena induced by multivalent ions for biological (macro)molecules, from the “atomistic/molecular” local picture of (potentially specific) interactions to the more global picture of phase behaviour including, e. g., crystallisation, phase separation, oligomerisation etc. Rather than attempting an encyclopedic list of systems, we rather aim for an embracing discussion using typical case studies. We try to cover predominantly three main classes: proteins, nucleic acids, and amphiphilic molecules including interface effects. We do not cover in detail, but make some comparisons to, ion channels, colloidal systems, and synthetic polymers. While there are obvious differences in the behaviour of, and the relevance of multivalent ions for, the three main classes of systems, we also point out analogies. Our attempt of a comprehensive discussion is guided by the idea that there are not only important differences and specific phenomena with regard to the effects of multivalent ions on the main systems, but also important similarities. We hope to bridge physico‐chemical mechanisms, concepts of soft matter, and biological observations and connect the different communities further.

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Kinetics of liquid–liquid phase separation in protein solutions exhibiting LCST phase behavior studied by time-resolved USAXS and VSANS

Cited by 59 publications

References 60 publications

Formation of Chromatin Subcompartments by Phase Separation

Formation of Chromatin Subcompartments by Phase Separation

Tuning phase transitions of aqueous protein solutions by multivalent cations

Multivalent ions and biomolecules: Attempting a comprehensive perspective

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