Faculty Opinions recommendation of Charge-driven condensation of RNA and proteins suggests broad role of phase separation in cytoplasmic environments.

Phase separation processes are increasingly being recognized as important organizing mechanisms of biological macromolecules in cellular environments. Well-established drivers of phase separation are multi-valency and intrinsic disorder. Here, we show that globular macromolecules may condense simply based on electrostatic complementarity. More specifically, phase separation of mixtures between RNA and positively charged proteins is described from a combination of multiscale computer simulations with microscopy and spectroscopy experiments. Phase diagrams were mapped out as a function of molecular concentrations in experiment and as a function of molecular size and temperature via simulations. The resulting condensates were found to retain at least some degree of internal dynamics varying as a function of the molecular composition. The results suggest a more general principle for phase separation that is based primarily on electrostatic complementarity without invoking polymer properties as in most previous studies. Simulation results furthermore suggest that such phase separation may occur widely in heterogenous cellular environment between nucleic acid and protein components.

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Role of Liat1 phase separation in ribosome biogenesis

10.26226/morressier.5ebd45acffea6f735881b19b ◽

2020 ◽

Author(s):

Akshaya Arva

Keyword(s):

Phase Separation ◽

Ribosome Biogenesis

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Deciphering the Role of π-Interactions in Polyelectrolyte Complexes Using Rationally Designed Peptides

Polymers ◽

10.3390/polym13132074 ◽

2021 ◽

Vol 13 (13) ◽

pp. 2074

Author(s):

Sara Tabandeh ◽

Cristina Elisabeth Lemus ◽

Lorraine Leon

Keyword(s):

Hydrogen Bonding ◽

Phase Separation ◽

Liquid Phase ◽

Charge Density ◽

Secondary Structures ◽

Liquid Phase Separation ◽

Polyelectrolyte Complexes ◽

Π Interactions ◽

Liquid Liquid Phase Separation

Electrostatic interactions, and specifically π-interactions play a significant role in the liquid-liquid phase separation of proteins and formation of membraneless organelles/or biological condensates. Sequence patterning of peptides allows creating protein-like structures and controlling the chemistry and interactions of the mimetic molecules. A library of oppositely charged polypeptides was designed and synthesized to investigate the role of π-interactions on phase separation and secondary structures of polyelectrolyte complexes. Phenylalanine was chosen as the π-containing residue and was used together with lysine or glutamic acid in the design of positively or negatively charged sequences. The effect of charge density and also the substitution of fluorine on the phenylalanine ring, known to disrupt π-interactions, were investigated. Characterization analysis using MALDI-TOF mass spectroscopy, H NMR, and circular dichroism (CD) confirmed the molecular structure and chiral pattern of peptide sequences. Despite an alternating sequence of chirality previously shown to promote liquid-liquid phase separation, complexes appeared as solid precipitates, suggesting strong interactions between the sequence pairs. The secondary structures of sequence pairs showed the formation of hydrogen-bonded structures with a β-sheet signal in FTIR spectroscopy. The presence of fluorine decreased hydrogen bonding due to its inhibitory effect on π-interactions. π-interactions resulted in enhanced stability of complexes against salt, and higher critical salt concentrations for complexes with more π-containing amino acids. Furthermore, UV-vis spectroscopy showed that sequences containing π-interactions and increased charge density encapsulated a small charged molecule with π-bonds with high efficiency. These findings highlight the interplay between ionic, hydrophobic, hydrogen bonding, and π-interactions in polyelectrolyte complex formation and enhance our understanding of phase separation phenomena in protein-like structures.

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Membrane-associated phase separation: organization and function emerge from a two-dimensional milieu

Journal of Molecular Cell Biology ◽

10.1093/jmcb/mjab010 ◽

2021 ◽

Author(s):

Jonathon A Ditlev

Keyword(s):

Phase Separation ◽

Cell Biology ◽

Cellular Environment ◽

Condensate Formation ◽

Associated Proteins ◽

Available Technology ◽

And Function ◽

Surrounding Membrane

Abstract Liquid‒liquid phase separation (LLPS) of biomolecules has emerged as an important mechanism that contributes to cellular organization. Phase separated biomolecular condensates, or membrane-less organelles, are compartments composed of specific biomolecules without a surrounding membrane in the nucleus and cytoplasm. LLPS also occurs at membranes, where both lipids and membrane-associated proteins can de-mix to form phase separated compartments. Investigation of these membrane-associated condensates using in vitro biochemical reconstitution and cell biology has provided key insights into the role of phase separation in membrane domain formation and function. However, these studies have generally been limited by available technology to study LLPS on model membranes and the complex cellular environment that regulates condensate formation, composition, and function. Here, I briefly review our current understanding of membrane-associated condensates, establish why LLPS can be advantageous for certain membrane-associated condensates, and offer a perspective for how these condensates may be studied in the future.

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Liquid–liquid phase separation in human health and diseases

Signal Transduction and Targeted Therapy ◽

10.1038/s41392-021-00678-1 ◽

2021 ◽

Vol 6 (1) ◽

Author(s):

Bin Wang ◽

Lei Zhang ◽

Tong Dai ◽

Ziran Qin ◽

Huasong Lu ◽

...

Keyword(s):

Phase Separation ◽

Liquid Phase ◽

Human Health ◽

Essential Role ◽

Current Knowledge ◽

Vital Role ◽

Liquid Phase Separation ◽

Eukaryotic Cells ◽

Liquid Liquid Phase Separation

AbstractEmerging evidence suggests that liquid–liquid phase separation (LLPS) represents a vital and ubiquitous phenomenon underlying the formation of membraneless organelles in eukaryotic cells (also known as biomolecular condensates or droplets). Recent studies have revealed evidences that indicate that LLPS plays a vital role in human health and diseases. In this review, we describe our current understanding of LLPS and summarize its physiological functions. We further describe the role of LLPS in the development of human diseases. Additionally, we review the recently developed methods for studying LLPS. Although LLPS research is in its infancy—but is fast-growing—it is clear that LLPS plays an essential role in the development of pathophysiological conditions. This highlights the need for an overview of the recent advances in the field to translate our current knowledge regarding LLPS into therapeutic discoveries.

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Emerging Silk Material Trends: Repurposing, Phase Separation and Solution-Based Designs

Materials ◽

10.3390/ma14051160 ◽

2021 ◽

Vol 14 (5) ◽

pp. 1160

Author(s):

F. Philipp Seib

Keyword(s):

Phase Separation ◽

Recent Progress ◽

Fiber Formation ◽

Live Cells ◽

Specific Reference ◽

New Developments ◽

Silk Fabrics ◽

Induced Crystallization ◽

Liquid Liquid Phase Separation

Silk continues to amaze. This review unravels the most recent progress in silk science, spanning from fundamental insights to medical silks. Key advances in silk flow are examined, with specific reference to the role of metal ions in switching silk from a storage to a spinning state. Orthogonal thermoplastic silk molding is described, as is the transfer of silk flow principles for the triggering of flow-induced crystallization in other non-silk polymers. Other exciting new developments include silk-inspired liquid–liquid phase separation for non-canonical fiber formation and the creation of “silk organelles” in live cells. This review closes by examining the role of silk fabrics in fashioning facemasks in response to the SARS-CoV-2 pandemic.

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