scholarly journals Pectin methylesterase selectively softens the onion epidermal wall yet reduces acid-induced creep

2019 ◽  
Author(s):  
Xuan Wang ◽  
Liza Wilson ◽  
Daniel J. Cosgrove
Keyword(s):  
Cell Walls ◽  
Tensile Force ◽  
Pectin Methylesterase ◽  
Tensile Tests ◽  
Indentation Modulus ◽  
Force Extension ◽  
Biological Responses ◽  
Physical Consequences ◽  
Living Tissues ◽  
Pectin Gels

AbstractDe-esterification of homogalacturonan (HG) is thought to stiffen pectin gels and primary cell walls by increasing calcium crosslinking between HG chains. Contrary to this idea, recent studies found that HG de-esterification correlated with reduced stiffness of living tissues, measured by surface indentation. The physical basis of such apparent wall softening is unclear, but possibly involves complex biological responses to HG modification. To assess the direct physical consequences of HG de-esterification on wall mechanics without such complications, we treated isolated onion (Allium cepa) epidermal walls with pectin methylesterase (PME) and assessed wall biomechanics with indentation and tensile tests. In nanoindentation assays, PME action softened the wall (reduced the indentation modulus). In tensile force/extension assays, PME increased plasticity, but not elasticity. These softening effects are attributed, at least in part, to increased electrostatic repulsion and swelling of the wall after PME treatment. Despite softening and swelling upon HG de-esterification, PME treatment alone failed to induce cell wall creep. Instead, acid-induced creep, mediated by endogenous α expansin, was reduced. We conclude that HG de-esterification physically softens the onion wall, yet reduces expansin-mediated wall extensibility.HighlightAfter enzymatic de-esterification without added calcium, the onion epidermal wall swells and becomes softer, as assessed by nanoindentation and tensile plasticity tests, yet exhibits reduced expansin-mediated creep.

scholarly journals Pectin methylesterase selectively softens the onion epidermal wall yet reduces acid-induced creep

2020 ◽  
Vol 71 (9) ◽  
pp. 2629-2640 ◽  
Author(s):  
Xuan Wang ◽  
Liza Wilson ◽  
Daniel J Cosgrove
Keyword(s):  
Cell Walls ◽  
Tensile Force ◽  
Pectin Methylesterase ◽  
Tensile Tests ◽  
Indentation Modulus ◽  
Force Extension ◽  
Biological Responses ◽  
Physical Consequences ◽  
Living Tissues ◽  
Pectin Gels

Abstract De-esterification of homogalacturonan (HG) is thought to stiffen pectin gels and primary cell walls by increasing calcium cross-linking between HG chains. Contrary to this idea, recent studies found that HG de-esterification correlated with reduced stiffness of living tissues, measured by surface indentation. The physical basis of such apparent wall softening is unclear, but possibly involves complex biological responses to HG modification. To assess the direct physical consequences of HG de-esterification on wall mechanics without such complications, we treated isolated onion (Allium cepa) epidermal walls with pectin methylesterase (PME) and assessed wall biomechanics with indentation and tensile tests. In nanoindentation assays, PME action softened the wall (reduced the indentation modulus). In tensile force/extension assays, PME increased plasticity, but not elasticity. These softening effects are attributed, at least in part, to increased electrostatic repulsion and swelling of the wall after PME treatment. Despite softening and swelling upon HG de-esterification, PME treatment alone failed to induce cell wall creep. Instead, acid-induced creep, mediated by endogenous α-expansin, was reduced. We conclude that HG de-esterification physically softens the onion wall, yet reduces expansin-mediated wall extensibility.

scholarly journals Chemical and physical interactions of regenerated cellulose yarns and isocyanate-based matrix systems

2021 ◽  
Vol 11 (1) ◽  
Author(s):  
Bernhard Ungerer ◽  
Ulrich Müller ◽  
Antje Potthast ◽  
Enrique Herrero Acero ◽  
Stefan Veigel
Keyword(s):  
Mechanical Performance ◽  
Tensile Force ◽  
Tensile Modulus ◽  
Tensile Tests ◽  
Size Exclusion ◽  
Regenerated Cellulose ◽  
Hydrolytic Cleavage ◽  
Yarn Twist ◽  
Exclusion Chromatography ◽  
Physical And Chemical

AbstractIn the development of structural composites based on regenerated cellulose filaments, the physical and chemical interactions at the fibre-matrix interphase need to be fully understood. In the present study, continuous yarns and filaments of viscose (rayon) were treated with either polymeric diphenylmethane diisocyanate (pMDI) or a pMDI-based hardener for polyurethane resins. The effect of isocyanate treatment on mechanical yarn properties was evaluated in tensile tests. A significant decrease in tensile modulus, tensile force and elongation at break was found for treated samples. As revealed by size exclusion chromatography, isocyanate treatment resulted in a significantly reduced molecular weight of cellulose, presumably owing to hydrolytic cleavage caused by hydrochloric acid occurring as an impurity in pMDI. Yarn twist, fibre moisture content and, most significantly, the chemical composition of the isocyanate matrix were identified as critical process parameters strongly affecting the extent of reduction in mechanical performance. To cope with the problem of degradative reactions an additional step using calcium carbonate to trap hydrogen ions is proposed.

Systematic Experimental Investigation of Dielectric Electroactive Polymers Using a Custom-Built Uniaxial Tensile Test Rig

2015 ◽  
Author(s):  
Micah Hodgins ◽  
Alexander York ◽  
Stefan Seelecke
Keyword(s):  
Pure Shear ◽  
Tensile Force ◽  
Tensile Tests ◽  
Uniaxial Tensile ◽  
Uniaxial Tensile Test ◽  
Specimen Preparation ◽  
Testing Device ◽  
Test Results ◽  
Test Rig ◽  
Geometry Test

This work presents the design, fabrication and testing of a comprehensive DEAP test station. The tester is designed to perform tensile tests of planar DEAPs while measuring quantities such as tensile force, stretch, film thickness and voltage/current. The work details the specimen preparation and how the specimen is placed in the clamps. While the assembly process is performed by hand features were built-in to the design of the specimen frame and clamps to enable reliable placement and specimen geometry. Test results of the pure-shear specimen demonstrated good performance of the testing device. Although the electrode surface was rough the thickness stretch was evident during the stretching/actuation of the DEAP actuator.

Effect of polymer-coated silica particles in a Portland cement matrix via in-situ infrared spectroscopy

2020 ◽  
pp. 002199832095215
Author(s):  
Tahereh Mohammadi Hafshejani ◽  
Chao Feng ◽  
Jonas Wohlgemuth ◽  
Felix Krause ◽  
Andreas Bogner ◽  
...  
Keyword(s):  
Molecular Weight ◽  
Infrared Spectroscopy ◽  
Energy Dissipation ◽  
Tensile Force ◽  
Testing Machine ◽  
Length Change ◽  
Cement Matrix ◽  
Force Extension ◽  
Bending Vibrations ◽  
Tensile Testing Machine

It is often of great importance in engineering to know precisely the properties of a material used with regard to its strength, its plasticity or its brittleness, its elasticity, and some other properties. For this purpose, material samples are tested in a tensile test by clamping the sample with a known starting cross-section in a tensile testing machine and loading it with a tensile force F. The force is then graphically displayed over the length change ΔL caused. This curve is called the force-extension diagram. In this study, a new measurement method enables for the first time, depending on the applied uniaxial stress, an insight at the atomic level into various energy dissipation processes at cement-based materials with the help of infrared spectroscopy. The samples are modified by adding SiO2 particles, which are coated by a polymer (PEG-MDI-DMPA) of different PEG molecular weights. Results show that elongating and breakage of [Formula: see text] and [Formula: see text] bonds play an essential role in the strain energy dissipation. Compared to the pure cement, the modified samples are affected more by elongating and breakage of [Formula: see text] as the admixture can effectively reduce the energy barrier of the hydrolytic reaction. The incorporating of particles into the cement matrix induces new mechanisms for energy dissipation by stretching of [Formula: see text] bending vibrations. Stretching vibration of the [Formula: see text] group indicates that part of the energy is dissipated by breakage of hydrogen bonding between the carboxyl group and PEG chains. Besides, a higher value of the ultimate fracture force following an increase in the molecular weight of PEG shows stronger bonding between particles and the cement matrix. As the chain-length of PEG is increased, less energy is absorbed through the other processes (especially at a higher level of strain). Thus, there is a balance between the whole deformation (toughness) and the strength of samples with the increase of the PEG molecular weight.

scholarly journals The structure of rice weevil pectin methylesterase

2014 ◽  
Vol 70 (11) ◽  
pp. 1480-1484 ◽  
Author(s):  
David C. Teller ◽  
Craig A. Behnke ◽  
Kirk Pappan ◽  
Zicheng Shen ◽  
John C. Reese ◽  
...  
Keyword(s):  
Reaction Mechanisms ◽  
Cell Walls ◽  
Sitophilus Oryzae ◽  
Pectin Methylesterase ◽  
Crystal Form ◽  
Erwinia Chrysanthemi ◽  
Rice Weevil ◽  
Molecular Replacement ◽  
Structural Comparison ◽  
Structure Solution

Rice weevils (Sitophilus oryzae) use a pectin methylesterase (EC 3.1.1.11), along with other enzymes, to digest cell walls in cereal grains. The enzyme is a right-handed β-helix protein, but is circularly permuted relative to plant and bacterial pectin methylesterases, as shown by the crystal structure determination reported here. This is the first structure of an animal pectin methylesterase. Diffraction data were collected to 1.8 Å resolution some time ago for this crystal form, but structure solution required the use of molecular-replacement techniques that have been developed and similar structures that have been deposited in the last 15 years. Comparison of the structure of the rice weevil pectin methylesterase with that fromDickeya dandantii(formerlyErwinia chrysanthemi) indicates that the reaction mechanisms are the same for the insect, plant and bacterial pectin methylesterases. The similarity of the structure of the rice weevil enzyme to theEscherichia colilipoprotein YbhC suggests that the evolutionary origin of the rice weevil enzyme was a bacterial lipoprotein, the gene for which was transferred to a primitive ancestor of modern weevils and other Curculionidae. Structural comparison of the rice weevil pectin methylesterase with plant and bacterial enzymes demonstrates that the rice weevil protein is circularly permuted relative to the plant and bacterial molecules.

Structure and properties of pectin gels in plant cell walls

1984 ◽  
Vol 7 (3) ◽  
pp. 153-164 ◽  
Author(s):  
MICHAEL C. JARVIS
Keyword(s):  
Plant Cell ◽  
Cell Walls ◽  
Plant Cell Walls ◽  
Structure And Properties ◽  
Pectin Gels

scholarly journals Alterations in the mechanical, chemical and biocompatibility properties of low-cost polyethylene and polyester meshes after steam sterilization

Hernia ◽  
2020 ◽  
Vol 24 (6) ◽  
pp. 1345-1359 ◽  
Author(s):  
Reiko Wiessner ◽  
R. Lorenz ◽  
A. Gehring ◽  
T. Kleber ◽  
C. Benz ◽  
...  
Keyword(s):  
Melting Point ◽  
Low Cost ◽  
Tensile Force ◽  
Human Fibroblasts ◽  
Chemical Properties ◽  
Tensile Tests ◽  
Steam Sterilization ◽  
Tensile Forces ◽  
Mechanical Tensile ◽  
And Chemical Properties

Abstract Introduction In Africa and other Low Resource Settings (LRS), the guideline-based and thus in most cases mesh-based treatment of inguinal hernias is only feasible to a very limited extent. This has led to an increased use of low cost meshes (LCMs, mostly mosquito meshes) for patients in LRS. Most of the LCMs used are made of polyethylene or polyester, which must be sterilized before use. The aim of our investigations was to determine changes in the biocompatibility of fibroblasts as well as mechanical and chemical properties of LCMs after steam sterilization. Material and methods Two large-pored LCMs made of polyester and polyethylene in a size of 11 x 6 cm were cut and steam sterilized at 100, 121 and 134 °C. These probes and non-sterile meshes were then subjected to mechanical tensile tests in vertical and horizontal tension, chemical analyses and biocompatibility tests with human fibroblasts. All meshes were examined by stereomicroscopy, scanning electron microscopy (SEM), LDH (cytotoxicity) measurement, viability testing, pH, lactate and glycolysis determination. Results Even macroscopically, polyethylene LCMs showed massive shrinkage after steam sterilization, especially at 121 and 134 °C. While polyester meshes showed no significant changes after sterilization with regard to deformation and damage as well as tensile force and stiffness, only the unsterile polyethylene mesh and the mesh sterilized at 100 °C could be tested mechanically due to the shrinkage of the other specimen. For these meshes the tensile forces were about four times higher than for polyester LCMs. Chemical analysis showed that the typical melting point of polyester LCMs was between 254 and 269 °C. Contrary to the specifications, the polyethylene LCM did not consist of low-density polyethylene, but rather high-density polyethylene and therefore had a melting point of 137 °C, so that the marked shrinkage described above occurred. Stereomicroscopy confirmed the shrinkage of polyethylene LCMs already after sterilization at 100 °C in contrast to polyester LCMs. Surprisingly, cytotoxicity (LDH measurement) was lowest for both non-sterile LCMs, while polyethylene LCMs sterilized at 100 and 121 °C in particular showed a significant increase in cytotoxicity 48 hours after incubation with fibroblasts. Glucose metabolism showed no significant changes between sterile and non-sterile polyethylene and polyester LCMs. Conclusion The process of steam sterilization significantly alters mechanical and structural properties of synthetic hernia mesh implants. Our findings do not support a use of low-cost meshes because of their unpredictable properties after steam sterilization.

Force extension analysis of Avena coleoptile cell walls

Planta ◽  
1965 ◽  
Vol 66 (2) ◽  
pp. 126-134 ◽  
Author(s):  
Alfred C. Olson ◽  
James Bonner ◽  
D. James Morr�
Keyword(s):  
Cell Walls ◽  
Force Extension ◽  
Avena Coleoptile ◽  
Extension Analysis

scholarly journals Experimental Analysis of Self Piercing Riveted Joint

2019 ◽  
pp. 303-310
Author(s):  
R. T. Kolhe ◽  
V. L. Kadlag
Keyword(s):  
Finite Element ◽  
Solid State ◽  
Adhesive Bonding ◽  
Oil And Gas ◽  
Tensile Force ◽  
Statistical Design ◽  
Element Model ◽  
Tensile Tests ◽  
State Process

Joining is an important process in a number of industries, such as aerospace, automotive, oil, and gas. Many products cannot be fabricated as a single piece, so components are fabricated first and assembled later. Joining technology can be classified as a liquid-solid-state process and mechanical means. Liquid-solid-state joining includes welding, brazing, soldering, and adhesive bonding. Mechanical joining includes fasteners, bolts, nuts, and rivets. Metal joining is a process that uses heat to melt or heat metal just below the melting temperature. The main principle is a shear condition of material. In case of shear test of conventional riveting joints, their strength is determined by the mechanical properties of the fastener material is high. Hence, it is expedient to have more insight on the fracture mechanism of various joints during tensile tests. This paper discusses the strength of self piercing rivets of sheet materials that is aluminum alloy, and their arrangements. This thesis presents a study of the effect of controllable self piercing rivet parameters, mainly tensile force, rivet length, rivet diameter tolerance, hole countersunk depth and hole diameter tolerance, on the quality of formed rivet. The quality of a formed rivet is determined by the geometry of its head formation and the extent to which the hole is filled. The study determines. The study is performed using finite element simulation of the riveting process. Theoretical relations between tensile force and formed rivet geometry derived in this study is used to validate the finite element model. Statistical design of experiment is employed to analyze the simulation data of riveting and determine the effect of individual factors, their interactions and relationship with the quality of formed self piercing rivet. The results demonstrate that the correct formation of rivet head geometry depends upon all the factors studied.

scholarly journals Ductility and Seismic Suitability of Locally Sourced High Yield Rebars in Benin City

2020 ◽  
Vol 4 (2) ◽  
pp. 458-462
Author(s):  
E. Nwankwo ◽  
E. Attama
Keyword(s):  
Plastic Deformation ◽  
Strain Hardening ◽  
Tensile Force ◽  
Tensile Tests ◽  
High Yield ◽  
Damping Capacity ◽  
Eurocode 8 ◽  
Deformation Capacity ◽  
Benin City ◽  
Energy Absorbing

Ductility is the ability of a system to sustain large deformations beyond its yield point without breaking or failing. Eurocode 8 makes allowance for receipt of seismic forces using the damping capacity of ductile members. This allows for the absorption of energy and helps increase the amount of energy absorbed by ductile structures before failure. This paper investigates the maximum ductility locally sourced steel rebars in Benin City structure can sustain without damage by establishing parameters that influence ductility. Tensile tests were conducted for rebar sizes of 10 mm, 12 mm, and 16 mm diameters, which were sourced from three different vendors within Benin City, Nigeria. The strain-hardening ratio Stu/Sty, i.e. the ratio of tensile strength Stu to yield strength Sty, and the elongation at maximum tensile force Agt were investigated in order to determine plastic deformation capacity and the degree of ductility of these rebars. A numerical model – the modified Ramberg- Osgood and Rasmussen equations – was modified in order to predict the experimentally obtained ductility parameters of these locally sourced rebars. The model collaborates well with experiments and could be used to establish ductility parameters of local rebars. Also, ductility test results showed that strain hardening ratios and elongation were relatively low (Recommended strain hardening ratio of rebar for seismic design is 1.15) and this could result in reinforced concrete structures made with these rebar exhibiting moderate ductility, i.e. a moderate plastic deformation capacity which might not have sufficient energy absorbing capacity in events of large earthquakes.

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