scholarly journals Effect of histone H4 tail on nucleosome stability and internucleosomal interactions

2021 ◽  
Vol 11 (1) ◽  
Author(s):  
Tommy Stormberg ◽  
Sridhar Vemulapalli ◽  
Shaun Filliaux ◽  
Yuri L. Lyubchenko
Keyword(s):  
Chromatin Structure ◽  
Histone H4 ◽  
Nucleosome Assembly ◽  
Dna Templates ◽  
Histone Tails ◽  
Force Microscopy ◽  
Atomic Force ◽  
Dna Unwrapping ◽  
Nucleosome Stability

AbstractChromatin structure is dictated by nucleosome assembly and internucleosomal interactions. The tight wrapping of nucleosomes inhibits gene expression, but modifications to histone tails modulate chromatin structure, allowing for proper genetic function. The histone H4 tail is thought to play a large role in regulating chromatin structure. Here we investigated the structure of nucleosomes assembled with a tail-truncated H4 histone using Atomic Force Microscopy. We assembled tail-truncated H4 nucleosomes on DNA templates allowing for the assembly of mononucleosomes or dinucleosomes. Mononucleosomes assembled on nonspecific DNA led to decreased DNA wrapping efficiency. This effect is less pronounced for nucleosomes assembled on positioning motifs. Dinucleosome studies resulted in the discovery of two effects- truncation of the H4 tail does not diminish the preferential positioning observed in full-length nucleosomes, and internucleosomal interaction eliminates the DNA unwrapping effect. These findings provide insight on the role of histone H4 in chromatin structure and stability.

The role of cross-linking in the scratch resistance of organic coatings: An investigation using Atomic Force Microscopy

Wear ◽  
2019 ◽  
Vol 418-419 ◽  
pp. 151-159 ◽  
Author(s):  
Juan F. Gonzalez-Martinez ◽  
Erum Kakar ◽  
Stefan Erkselius ◽  
Nicola Rehnberg ◽  
Javier Sotres
Keyword(s):  
Atomic Force Microscopy ◽  
Scratch Resistance ◽  
Organic Coatings ◽  
Cross Linking ◽  
Force Microscopy ◽  
Atomic Force

scholarly journals Morphometric characterization of fibrinogen's αC regions and their role in fibrin self-assembly and molecular organization

Nanoscale ◽  
2017 ◽  
Vol 9 (36) ◽  
pp. 13707-13716 ◽  
Author(s):  
Anna D. Protopopova ◽  
Rustem I. Litvinov ◽  
Dennis K. Galanakis ◽  
Chandrasekaran Nagaswami ◽  
Nikolay A. Barinov ◽  
...  
Keyword(s):  
Atomic Force Microscopy ◽  
Self Assembly ◽  
Molecular Organization ◽  
Microscopy Imaging ◽  
Force Microscopy ◽  
Atomic Force ◽  
Atomic Force Microscopy Imaging ◽  
Morphometric Characterization

High-resolution atomic force microscopy imaging reveals the role of fibrinogen αC regions in the early stages of fibrin self-assembly.

scholarly journals Nanostructural and mechanical changes in the sclera following proteoglycan depletion

2018 ◽  
Vol 2 (2) ◽  
pp. 14-17
Author(s):  
Zhuola Zhuola ◽  
Steve Barrett ◽  
Yalda Ashraf Kharaz ◽  
Riaz Akhtar
Keyword(s):  
Mechanical Properties ◽  
Collagen Fibril ◽  
Enzymatic Degradation ◽  
Ocular Tissues ◽  
Force Microscopy ◽  
Nanomechanical Properties ◽  
Atomic Force ◽  
Fibril Morphology

The mechanical properties of ocular tissues, such as the sclera, have a major impact on healthy eye function, and are governed by the properties and composition of the microstructural components. For example, biomechanical degradation associated with myopia occurs alongside a reduction of proteoglycans (PGs). In this study, the role of PG degradation in the nanomechanical properties of the porcine sclera is explored. In-vitro enzymatic degradation of PGs was conducted with α-amylase and chondroitinase ABC enzymes. Collagen fibril morphology and nanomechanical stiffness were measured with atomic force microscopy (AFM). The elastic modulus of the tissue was reduced in all enzyme-treated samples relative to controls. In addition, collagen fibril organization was disrupted by PG depletion. Our data demonstrate that PGs play an important role in determining not only the mechanical properties at these length scales, but also collagen fibril arrangement.

A haploid affair: core histone transitions during spermatogenesis

2003 ◽  
Vol 81 (3) ◽  
pp. 131-140 ◽  
Author(s):  
John D Lewis ◽  
D Wade Abbott ◽  
Juan Ausió
Keyword(s):  
Histone Modifications ◽  
Chromatin Structure ◽  
Critical Role ◽  
Diploid Cell ◽  
Histone Variants ◽  
Histone H4 ◽  
Dna Compaction ◽  
Dynamic Composition ◽  
Shed Light

The process of meiosis reduces a diploid cell to four haploid gametes and is accompanied by extensive recombination. Thus, the dynamics of chromatin during meiosis are significantly different than in mitotic cells. As spermatogenesis progresses, there is a widespread reorganization of the haploid genome followed by extensive DNA compaction. It has become increasingly clear that the dynamic composition of chromatin plays a critical role in the activities of enzymes and processes that act upon it. Therefore, an analysis of the role of histone variants and modifications in these processes may shed light upon the mechanisms involved and the control of chromatin structure in general. Histone variants such as histone H3.3, H2AX, and macroH2A appear to play key roles in the various stages of spermiogenesis, in addition to the specifically modulated acetylation of histone H4 (acH4), ubiquitination of histones H2A and H2B (uH2A, uH2B), and phosphorylation of histone H3 (H3p). This review will examine recent discoveries concerning the role of histone modifications and variants during meiosis and spermatogenesis.Key words: histone variants, histone modifications, chromatin structure, meiosis.

Self-affine Fracture Surface Parameters and Their Relationship with Microstructure in a Cast Aluminum Alloy

2002 ◽  
Vol 17 (6) ◽  
pp. 1276-1282 ◽  
Author(s):  
M. Hinojosa ◽  
J. Aldaco
Keyword(s):  
Aluminum Alloy ◽  
Fracture Surface ◽  
The Self ◽  
Cast Aluminum Alloy ◽  
Cast Aluminum ◽  
Force Microscopy ◽  
Fracture Surfaces ◽  
Atomic Force ◽  
Roughness Exponent

The possible role of microstructural features in determining the self-affinity of the fracture surface of a cast aluminum alloy is explored in this work. Fracture surfaces generated both in tension and impact tests were topometrically analyzed by atomic force microscopy, scanning electron microscopy, and stylus profilometry. The roughness exponent exhibited the “universal” value ζ ≈ 0.78, and the correlation length ζ was of the order of the grain size. The brittle intermetallic compounds known to be important in crack initiation did not show any correlation with the self-affine parameters of the resulting fracture surfaces in this particular case.

scholarly journals Nanomechanical properties of enucleated cells: contribution of the nucleus to the passive cell mechanics

2020 ◽  
Vol 18 (1) ◽  
Author(s):  
Yuri M. Efremov ◽  
Svetlana L. Kotova ◽  
Anastasia A. Akovantseva ◽  
Peter S. Timashev
Keyword(s):  
Mechanical Properties ◽  
Cell Mechanics ◽  
Normal Cells ◽  
Force Microscopy ◽  
Nanomechanical Properties ◽  
Atomic Force ◽  
Fibrosarcoma Cells ◽  
Actomyosin Cytoskeleton ◽  
Small Deformations

Abstract Background The nucleus, besides its functions in the gene maintenance and regulation, plays a significant role in the cell mechanosensitivity and mechanotransduction. It is the largest cellular organelle that is often considered as the stiffest cell part as well. Interestingly, the previous studies have revealed that the nucleus might be dispensable for some of the cell properties, like polarization and 1D and 2D migration. Here, we studied how the nanomechanical properties of cells, as measured using nanomechanical mapping by atomic force microscopy (AFM), were affected by the removal of the nucleus. Methods The mass enucleation procedure was employed to obtain cytoplasts (enucleated cells) and nucleoplasts (nuclei surrounded by plasma membrane) of two cell lines, REF52 fibroblasts and HT1080 fibrosarcoma cells. High-resolution viscoelastic mapping by AFM was performed to compare the mechanical properties of normal cells, cytoplasts, and nucleoplast. The absence or presence of the nucleus was confirmed with fluorescence microscopy, and the actin cytoskeleton structure was assessed with confocal microscopy. Results Surprisingly, we did not find the softening of cytoplasts relative to normal cells, and even some degree of stiffening was discovered. Nucleoplasts, as well as the nuclei isolated from cells using a detergent, were substantially softer than both the cytoplasts and normal cells. Conclusions The cell can maintain its mechanical properties without the nucleus. Together, the obtained data indicate the dominating role of the actomyosin cytoskeleton over the nucleus in the cell mechanics at small deformations inflicted by AFM.

scholarly journals All chemical YBa2Cu3O7 superconducting multilayers: Critical role of CeO2 cap layer flatness

2009 ◽  
Vol 24 (4) ◽  
pp. 1446-1455 ◽  
Author(s):  
M. Coll ◽  
J. Gàzquez ◽  
R. Huhne ◽  
B. Holzapfel ◽  
Y. Morilla ◽  
...  
Keyword(s):  
Critical Role ◽  
High Energy ◽  
Buffer Layers ◽  
Solution Deposition ◽  
Ybco Films ◽  
Force Microscopy ◽  
Atomic Force ◽  
Current Densities ◽  
Atomically Flat

New advances toward microstructural improvement of epitaxial CeO2 films grown by chemical solution deposition and their use as buffer layers for YBa2Cu3O7 (YBCO) films are presented. We demonstrate that the degree of epitaxy and the fraction of (001) atomically flat surface area are controlled by the incorporation of tetravalent (Zr4+) or trivalent (Gd3+) cations into the ceria lattice. The degree of epitaxy has been investigated by means of Rutherford backscattering spectroscopy-channeling and reflection high-energy electron diffraction, and a new methodology is also presented to quantify the fraction of (001) atomically flat area from atomic force microscopy images. Results are further correlated with the superconducting properties, microstructure, and texture of YBCO films grown by the trifluoroacetate route. A comparison with pulsed laser deposition and YBCO films grown on the same ceria layers is also presented. This growth procedure has allowed us to obtain all chemical multilayer films with controlled microstructure and critical current densities above 4 MA cm−2 at 77 K.

Sign in / Sign up

Export Citation Format

Share Document