Instability and phase separation of a binary mixture: The role of short-range repulsion and core-size ratio

1992 ◽  
Vol 46 (2) ◽  
pp. 1014-1021 ◽  
Author(s):  
Shaw Kambayashi ◽  
Yasuaki Hiwatari
Keyword(s):  
Phase Separation ◽  
Binary Mixture ◽  
Short Range ◽  
Size Ratio ◽  
Core Size ◽  
Short Range Repulsion

TENSOR OPTIMIZED SHELL MODEL AND HYPERNUCLEI

2010 ◽  
Vol 19 (12) ◽  
pp. 2531-2537
Author(s):  
Hiroshi Toki ◽  
Teruaki Myo ◽  
Kiyomi Ikeda
Keyword(s):  
Nuclear Matter ◽  
Exchange Interaction ◽  
Shell Model ◽  
Short Range ◽  
Operator Method ◽  
Tensor Interaction ◽  
Pion Exchange ◽  
Correlation Operator ◽  
Short Range Repulsion

The pion plays an important role for the structure of nucleus and nuclear matter. We propose a new theoretical framework, named the tensor optimized shell model (TOSM) to calculate the tensor interaction together with the unitary correlation operator method (UCOM) for the short range repulsion. We are able to handle the pion exchange interaction directly in the proposed framework. We compare the calculated results for 4 He with the rigorous calculation to show the power of TOSM to treat the tensor interaction. We then discuss the important role of pion in hypernuclei due to excitation of Σ baryon from Λ state.

TENSOR OPTIMIZED SHELL MODEL AND THE ROLE OF PION IN FINITE NUCLEI

2009 ◽  
Vol 18 (10) ◽  
pp. 2040-2044
Author(s):  
HIROSHI TOKI ◽  
TAKAYUKI MYO ◽  
KIYOMI IKEDA
Keyword(s):  
Nuclear Matter ◽  
Exchange Interaction ◽  
Shell Model ◽  
Short Range ◽  
Operator Method ◽  
Tensor Interaction ◽  
Correlation Operator ◽  
Short Range Repulsion ◽  
Finite Nuclei

The pion plays an important role for the structure of nucleus and nuclear matter. We propose a new theoretical framework, named the tensor optimized shell model (TOSM) to calculate the tensor interaction together with the unitary correlation operator method (UCOM) for the short range repulsion. We are able to handle the pion exchange interaction directly in the proposed framework. We compare the calculated results for 4 He with the rigorous calculation to show the power of TOSM to treat the tensor interaction.

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

Polymers ◽  
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.

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

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.

scholarly journals Evolution of the hedgehog Gene Family

Genetics ◽  
1996 ◽  
Vol 142 (3) ◽  
pp. 965-972 ◽  
Author(s):  
Sudhir Kumar ◽  
Kristi A Balczarek ◽  
Zhi-Chun Lai
Keyword(s):  
Intercellular Communication ◽  
Short Range ◽  
Gene Duplications ◽  
Future Directions ◽  
Amino Terminal ◽  
Terminal Fragment ◽  
Carboxyl Terminal ◽  
Multicellular Organisms ◽  
Amino Terminal Fragment

Abstract Effective intercellular communication is an important feature in the development of multicellular organisms. Secreted hedgehog (hh) protein is essential for both long- and short-range cellular signaling required for body pattern formation in animals. In a molecular evolutionary study, we find that the vertebrate homologs of the Drosophila hh gene arose by two gene duplications: the first gave rise to Desert hh, whereas the second produced the Indian and Sonic hh genes. Both duplications occurred before the emergence of vertebrates and probably before the evolution of chordates. The amino-terminal fragment of the hh precursor, crucial in long- and short-range intercellular communication, evolves two to four times slower than the carboxyl-terminal fragment in both Drosophila hh and its vertebrate homologues, suggesting conservation of mechanism of hh action in animals. A majority of amino acid substitutions in the amino- and carboxyl-terminal fragments are conservative, but the carboxyl-terminal domain has undergone extensive insertion-deletion events while maintaining its autocleavage protease activity. Our results point to similarity of evolutionary constraints among sites of Drosophila and vertebrate hh homologs and suggest some future directions for understanding the role of hh genes in the evolution of developmental complexity in animals.

scholarly journals Adsorption in Mixtures with Competing Interactions

Molecules ◽  
2021 ◽  
Vol 26 (15) ◽  
pp. 4532
Author(s):  
Marek Litniewski ◽  
Alina Ciach
Keyword(s):  
Short Range ◽  
Selective Adsorption ◽  
Similar Amount ◽  
Particle Interactions ◽  
Near Surface ◽  
Gas Density ◽  
Short Range Repulsion ◽  
Adsorbed Layers ◽  
Dynamics Simulations ◽  
Oppositely Charged

A binary mixture of oppositely charged particles with additional short-range attraction between like particles and short-range repulsion between different ones in the neighborhood of a substrate preferentially adsorbing the first component is studied by molecular dynamics simulations. The studied thermodynamic states correspond to an approach to the gas–crystal coexistence. Dependence of the near-surface structure, adsorption and selective adsorption on the strength of the wall–particle interactions and the gas density is determined. We find that alternating layers or bilayers of particles of the two components are formed, but the number of the adsorbed layers, their orientation and the ordered patterns formed inside these layers could be quite different for different substrates and gas density. Different structures are associated with different numbers of adsorbed layers, and for strong attraction the thickness of the adsorbed film can be as large as seven particle diameters. In all cases, similar amount of particles of the two components is adsorbed, because of the long-range attraction between different particles.

scholarly journals Liquid–liquid phase separation in human health and diseases

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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