scholarly journals Lamina and Heterochromatin Direct Chromosome Organisation in Senescence and Progeria

2018 ◽  
Author(s):  
Michael Chiang ◽  
Davide Michieletto ◽  
Chris A. Brackley ◽  
Nattaphong Rattanavirotkul ◽  
Hisham Mohammed ◽  
...  
Keyword(s):  
Phase Transitions ◽  
Human Genome ◽  
Physical Mechanism ◽  
Polymer Physics ◽  
Senescent Phenotype ◽  
Wide Range ◽  
Nuclear Organisation ◽  
Chromosome Organisation

Lamina-associated domains (LADs) cover a large part of the human genome and are thought to play a major role in shaping the nuclear architectural landscape. Here, we use simulations based on concepts from polymer physics to dissect the roles played by heterochromatin- and lamina-mediated interactions in nuclear organisation. Our model explains the conventional organisation of heterochromatin and euchromatin in growing cells, as well as the pathological organisation found in oncogene-induced senescence and progeria. We show that the experimentally observed changes in the locality of contacts in senescent and progeroid cells can be explained naturally as arising due to phase transitions in the system. Our model predicts that LADs are highly stochastic, and that, once established, the senescent phenotype should be metastable even if lamina-mediated interactions were reinstated. Overall, our simulations uncover a universal physical mechanism that can regulate heterochromatin segregation and LAD formation in a wide range of mammalian nuclei.

Graft copolymers that exhibit temperature-induced phase transitions over a wide range of pH

Nature ◽  
1995 ◽  
Vol 373 (6509) ◽  
pp. 49-52 ◽  
Author(s):  
Guohua Chen ◽  
Allan S. Hoffman
Keyword(s):  
Phase Transitions ◽  
Graft Copolymers ◽  
Wide Range

scholarly journals Supramolecular Fuzziness of Intracellular Liquid Droplets: Liquid–Liquid Phase Transitions, Membrane-Less Organelles, and Intrinsic Disorder

Molecules ◽  
2019 ◽  
Vol 24 (18) ◽  
pp. 3265 ◽  
Author(s):  
Vladimir N. Uversky
Keyword(s):  
Phase Transitions ◽  
Liquid Phase ◽  
Intrinsically Disordered Proteins ◽  
Intrinsically Disordered Protein ◽  
Disordered Proteins ◽  
Bacterial Cells ◽  
Liquid Droplets ◽  
Intrinsically Disordered ◽  
Wide Range ◽  
Characteristic Features

Cells are inhomogeneously crowded, possessing a wide range of intracellular liquid droplets abundantly present in the cytoplasm of eukaryotic and bacterial cells, in the mitochondrial matrix and nucleoplasm of eukaryotes, and in the chloroplast’s stroma of plant cells. These proteinaceous membrane-less organelles (PMLOs) not only represent a natural method of intracellular compartmentalization, which is crucial for successful execution of various biological functions, but also serve as important means for the processing of local information and rapid response to the fluctuations in environmental conditions. Since PMLOs, being complex macromolecular assemblages, possess many characteristic features of liquids, they represent highly dynamic (or fuzzy) protein–protein and/or protein–nucleic acid complexes. The biogenesis of PMLOs is controlled by specific intrinsically disordered proteins (IDPs) and hybrid proteins with ordered domains and intrinsically disordered protein regions (IDPRs), which, due to their highly dynamic structures and ability to facilitate multivalent interactions, serve as indispensable drivers of the biological liquid–liquid phase transitions (LLPTs) giving rise to PMLOs. In this article, the importance of the disorder-based supramolecular fuzziness for LLPTs and PMLO biogenesis is discussed.

scholarly journals Aspiration-assisted bioprinting for precise positioning of biologics

2020 ◽  
Vol 6 (10) ◽  
pp. eaaw5111 ◽  
Author(s):  
Bugra Ayan ◽  
Dong Nyoung Heo ◽  
Zhifeng Zhang ◽  
Madhuri Dey ◽  
Adomas Povilianskas ◽  
...  
Keyword(s):  
Self Assembly ◽  
Physical Mechanism ◽  
Single Cells ◽  
Three Dimensional ◽  
3D Bioprinting ◽  
Precise Control ◽  
3D Space ◽  
Magnitude Range ◽  
Wide Range ◽  
Order Of Magnitude

Three-dimensional (3D) bioprinting is an appealing approach for building tissues; however, bioprinting of mini-tissue blocks (i.e., spheroids) with precise control on their positioning in 3D space has been a major obstacle. Here, we unveil “aspiration-assisted bioprinting (AAB),” which enables picking and bioprinting biologics in 3D through harnessing the power of aspiration forces, and when coupled with microvalve bioprinting, it facilitated different biofabrication schemes including scaffold-based or scaffold-free bioprinting at an unprecedented placement precision, ~11% with respect to the spheroid size. We studied the underlying physical mechanism of AAB to understand interactions between aspirated viscoelastic spheroids and physical governing forces during aspiration and bioprinting. We bioprinted a wide range of biologics with dimensions in an order-of-magnitude range including tissue spheroids (80 to 600 μm), tissue strands (~800 μm), or single cells (electrocytes, ~400 μm), and as applications, we illustrated the patterning of angiogenic sprouting spheroids and self-assembly of osteogenic spheroids.

Understanding Biological Structures Through Exploring the Mechanical Response of Cell-Like Systems

2008 ◽  
Author(s):  
Ying Zhang ◽  
Philip R. LeDuc
Keyword(s):  
Actin Cytoskeleton ◽  
Actin Filaments ◽  
Living Cell ◽  
Cellular Response ◽  
Cancer Metastasis ◽  
Cell Structure ◽  
Polymer Physics ◽  
Wide Range

The actin cytoskeleton provides mechanical support for the cell and influences activities such as cancer metastasis and chemotaxis. While their mechanical responses have been studied in vivo and in vitro, understanding the link between these two forms remains challenging. To explore this gap and further understand cell structure, we reconstructed the cell cytoskeleton in a membrane-like spherical liposome to mimic the cellular environment; this enables an artificial “cell like” system. Through this approach, we are pursuing a path to compare in vitro mechanics from a polymer physics perspective of individual actin filaments with the in vivo mechanics of a living cell [1]. A living cell contains many organelles, which are in a highly packed environment and require significant organization to function. The actin cytoskeleton provides both structural and organizational regulation that is essential for cellular response. Here, we first encapsulated G-actin into giant unilamellar vesicles through an electroformation technique and then polymerized them into actin filaments (F-actin) within individual vesicles. To probe their conformation, we visualized these vesicles with fluorescence and laser scanning confocal microscopy. We then used a tapping mode atomic force microscopy to determine the mechanical properties of these cell-like systems. These results provide insight into a wide range of fields and studies including polymer physics, cell biology, and biotechnology.

scholarly journals Wide range optical and electrical contrast modulation by laser-induced phase transitions in GeTe thin films

2020 ◽  
Vol 19 ◽  
pp. 103466
Author(s):  
N.N. Eliseev ◽  
A.V. Kiselev ◽  
V.V. Ionin ◽  
V.A. Mikhalevsky ◽  
A.A. Burtsev ◽  
...  
Keyword(s):  
Thin Films ◽  
Phase Transitions ◽  
Wide Range

Phase Transitions of Pea Starch over a Wide Range of Water Content

2012 ◽  
Vol 60 (25) ◽  
pp. 6439-6446 ◽  
Author(s):  
Shujun Wang ◽  
Les Copeland
Keyword(s):  
Phase Transitions ◽  
Water Content ◽  
Wide Range ◽  
Pea Starch

TOWARDS A MOLECULAR THEORY FOR THE VAN DER WAALS–MAXWELL DESCRIPTION OF FLUID PHASE TRANSITIONS

2002 ◽  
Vol 01 (02) ◽  
pp. 381-406 ◽  
Author(s):  
ANDRIY KOVALENKO ◽  
FUMIO HIRATA
Keyword(s):  
Hydrogen Bonding ◽  
Phase Transitions ◽  
Phase Diagrams ◽  
Equations Of State ◽  
Van Der Waals ◽  
Fluid Phase ◽  
Carbon Aerogel ◽  
Molecular Fluids ◽  
Wide Range ◽  
Realistic Interaction

We briefly review developments of theories for phase transitions of molecular fluids and mixtures, from semi-phenomenological approaches providing equations of state with adjustable parameters to first-principles microscopic methods qualitatively correct for a variety of molecular models with realistic interaction potentials. We further present the generalization of the van der Waals–Maxwell description of fluid phase diagrams to account for chemical specificities of polar molecular fluids, such as hydrogen bonding. Our theory uses the reference interaction site model (RISM) integral equation approach complemented with the new closure we have proposed (KH approximation), successful over a wide range of density from gas to liquid. The RISM/KH theory is applied to the known three-site models of water, methanol, and hydrogen fluoride. It qualitatively reproduces their vapor-liquid phase diagrams and the structure in the gas as well as liquid phases, including hydrogen bonding. Furthermore, phase transitions of water and methanol sorbed in nanoporous carbon aerogel are described by means of the replica generalization of the RISM approach we have developed. The changes as compared to the bulk fluids are in agreement with simulations and experiment. The RISM/KH theory is promising for description of phase transitions in various associating fluids, in particular, electrolyte as well as non-electrolyte solutions and ionic liquids.

Phase transitions of pea starch over a wide range of water content

CFW Plexus ◽  
2012 ◽  
Author(s):  
Les Copeland ◽  
Shujun Wang
Keyword(s):  
Phase Transitions ◽  
Water Content ◽  
Wide Range ◽  
Pea Starch

Mathematical Modeling of Solid-State Diffusion during Mechanical Alloying

2006 ◽  
Vol 249 ◽  
pp. 105-110 ◽  
Author(s):  
Boris B. Khina ◽  
Boleslaw Formanek
Keyword(s):  
Plastic Deformation ◽  
Solid State ◽  
Mechanical Alloying ◽  
Solid Solutions ◽  
Point Defects ◽  
Physical Mechanism ◽  
Solid State Diffusion ◽  
State Diffusion ◽  
Wide Range ◽  
Supersaturated Solid Solutions

It is known experimentally that solid-state interdiffusion is substantially enhanced during plastic deformation. This is especially noticeable in Mechanical Alloying (MA) which is used for producing a wide range of metastable materials (supersaturated solid solutions, amorphous phases, nanostructures) with unique properties. However, a physical mechanism of enhanced diffusion during MA is not clearly understood yet, and a comprehensive model of this complex phenomenon has not been developed so far. Moreover, the role of the diffusion process in MA is hotly debated in literature. In this work a new, self-consistent mathematical model of solid-state interdiffusion in a binary substitutional system A-B during periodic plastic deformation is developed. The model includes basic physical factors that affect diffusion, such as generation of non-equilibrium point defects by gliding screw dislocations during deformation and their relaxation in periods between impacts. The cross-link terms are considered, and interaction of point defects with edge dislocations and incoherent phase boundary A/B is taken into account. Computer simulation is performed using realistic data (e.g., quasi-equilibrium self-diffusion coefficients known in literature) and the process parameters typical of MA in a vibratory mill. A repeated “deformation-rest” cycle is considered. The results of modeling reveal the physical mechanism of the enhancement of solid-state diffusion by periodic plastic deformation during MA and demonstrate that within the frame of this approach supersaturated solid solutions can form within a reasonably short processing time.

scholarly journals High-Resolution Thermal Imaging and Analysis of TIG Weld Pool Phase Transitions

Sensors ◽  
2020 ◽  
Vol 20 (23) ◽  
pp. 6952
Author(s):  
Nicholas Boone ◽  
Matthew Davies ◽  
Jon Raffe Willmott ◽  
Hector Marin-Reyes ◽  
Richard French
Keyword(s):  
Phase Transitions ◽  
High Resolution ◽  
Weld Pool ◽  
Thermal Imaging ◽  
Near Infrared ◽  
Imaging System ◽  
Travel Speed ◽  
Tig Welding ◽  
Infrared Radiance ◽  
Wide Range

Tungsten inert gas (TIG) welding is a well-established joining process and offers the user flexibility to weld a large range of materials. Ultra-thin turbine tipping is an important application for TIG welding that is exceptionally challenging due to the wide range of variables needed to accurately control the process: slope times, arc control, travel speed, etc. We offer new insight into weld pool characteristics, utilizing both on- and off-line measurements of weld tracks. High-resolution thermal imaging yields spatially and temporally resolved weld pool phase transitions coupled with post-weld photographs, which gives a novel perspective into the thermal history of a weld. Our imaging system is filtered to measure a 10 nm window at 950 nm and comprises a commercial Sigma lens to produce a near-infrared (NIR) camera. The measured near-infrared radiance is calibrated for temperature over the range of from 800 to 1350 °C.

Sign in / Sign up

Export Citation Format

Share Document