An Orthogonal Dynamic Covalent Polymer Network with Distinctive Topology Transformations for Shape‐ and Molecular Architecture Reconfiguration

2022 ◽  
Author(s):  
Wusha Miao ◽  
Bo Yang ◽  
Binjie Jin ◽  
Chujun Ni ◽  
Haijun Feng ◽  
...  
Keyword(s):  
Polymer Network ◽  
Molecular Architecture

Study of the Molecular Architecture of Keratin Filaments by Electron Microscopy

1982 ◽  
Vol 40 ◽  
pp. 118-119
Author(s):  
U. Aebi ◽  
P. Rew ◽  
T.-T. Sun
Keyword(s):  
Electron Microscopy ◽  
Structural Organization ◽  
Cell Types ◽  
Structural Features ◽  
Molecular Architecture ◽  
The Past ◽  
Keratin Filaments ◽  
Different Types ◽  
10 Nm Filaments ◽  
Different Cell Types

Various types of intermediate-sized (10-nm) filaments have been found and described in many different cell types during the past few years. Despite the differences in the chemical composition among the different types of filaments, they all yield common structural features: they are usually up to several microns long and have a diameter of 7 to 10 nm; there is evidence that they are made of several 2 to 3.5 nm wide protofilaments which are helically wound around each other; the secondary structure of the polypeptides constituting the filaments is rich in ∞-helix. However a detailed description of their structural organization is lacking to date.

Freeze-etch TEM of aqueous polymer gel network morphology

1986 ◽  
Vol 44 ◽  
pp. 796-797
Author(s):  
J. A. N. Zasadzinski ◽  
R. K. Prud'homme
Keyword(s):  
Metal Ion ◽  
Polymer Network ◽  
Polymer Gels ◽  
Polymer Gel ◽  
Deformation History ◽  
Crosslinked Polymer ◽  
Aqueous Polymer ◽  
History Of ◽  
Gel Network ◽  
Network Morphology

The rheological and mechanical properties of crosslinked polymer gels arise from the structure of the gel network. In turn, the structure of the gel network results from: thermodynamically determined interactions between the polymer chain segments, the interactions of the crosslinking metal ion with the polymer, and the deformation history of the network. Interpretations of mechanical and rheological measurements on polymer gels invariably begin with a conceptual model of,the microstructure of the gel network derived from polymer kinetic theory. In the present work, we use freeze-etch replication TEM to image the polymer network morphology of titanium crosslinked hydroxypropyl guars in an attempt to directly relate macroscopic phenomena with network structure.

Exploration of cell wall architecture with the rapid-freeze deep-etch technique

1993 ◽  
Vol 51 ◽  
pp. 128-129
Author(s):  
Béatrice Satiat-Jeunemaitre ◽  
Chris Hawes
Keyword(s):  
Plant Cell ◽  
Cell Walls ◽  
Cell Biology ◽  
Molecular Model ◽  
Three Dimensional ◽  
Secretory Activity ◽  
Wall Structure ◽  
Specimen Preparation ◽  
Molecular Architecture ◽  
Plant Cell Walls

The comprehension of the molecular architecture of plant cell walls is one of the best examples in cell biology which illustrates how developments in microscopy have extended the frontiers of a topic. Indeed from the first electron microscope observation of cell walls it has become apparent that our understanding of wall structure has advanced hand in hand with improvements in the technology of specimen preparation for electron microscopy. Cell walls are sub-cellular compartments outside the peripheral plasma membrane, the construction of which depends on a complex cellular biosynthetic and secretory activity (1). They are composed of interwoven polymers, synthesised independently, which together perform a number of varied functions. Biochemical studies have provided us with much data on the varied molecular composition of plant cell walls. However, the detailed intermolecular relationships and the three dimensional arrangement of the polymers in situ remains a mystery. The difficulty in establishing a general molecular model for plant cell walls is also complicated by the vast diversity in wall composition among plant species.

Molecular architecture and functions of the neuronal cytoskeleton

1990 ◽  
Vol 48 (3) ◽  
pp. 2-3
Author(s):  
Nobutaka Hirokawa
Keyword(s):  
Major Elements ◽  
Molecular Structures ◽  
Organelle Transport ◽  
Molecular Architecture ◽  
Neuronal Morphogenesis ◽  
Microtubule Associated Proteins ◽  
Associated Proteins ◽  
And Function ◽  
Small Clusters

In this symposium I will present our studies about the molecular architecture and function of the cytomatrix of the nerve cells. The nerve cell is a highly polarized cell composed of highly branched dendrites, cell body, and a single long axon along the direction of the impulse propagation. Each part of the neuron takes characteristic shapes for which the cytoskeleton provides the framework. The neuronal cytoskeletons play important roles on neuronal morphogenesis, organelle transport and the synaptic transmission. In the axon neurofilaments (NF) form dense arrays, while microtubules (MT) are arranged as small clusters among the NFs. On the other hand, MTs are distributed uniformly, whereas NFs tend to run solitarily or form small fascicles in the dendrites Quick freeze deep etch electron microscopy revealed various kinds of strands among MTs, NFs and membranous organelles (MO). These structures form major elements of the cytomatrix in the neuron. To investigate molecular nature and function of these filaments first we studied molecular structures of microtubule associated proteins (MAP1A, MAP1B, MAP2, MAP2C and tau), and microtubules reconstituted from MAPs and tubulin in vitro. These MAPs were all fibrous molecules with different length and formed arm like projections from the microtubule surface.

Projected Structure of the Surface Protein of Sulfolobus Spec. B12 Determined to a Resolution of 1.0 NM by Cryo-Electronmicroscopy

1990 ◽  
Vol 48 (1) ◽  
pp. 102-103
Author(s):  
G. Lembcke ◽  
F. Zemlin
Keyword(s):  
Low Dose ◽  
Maximum Dose ◽  
Three Dimensional ◽  
Surface Protein ◽  
Protein S ◽  
Radiation Sensitivity ◽  
Specimen Preparation ◽  
Molecular Architecture ◽  
High Radiation ◽  
Fritz Haber

The thermoacidophilic archaebacterium Sulfolobus spec. B12 , which is closely related to Sulfolobus solfataricus , possesses a regularly arrayed surface protein (S-layer), which is linked to the plasma membrane via spacer elements spanning a distinct interspace of approximately 18 nm. The S-layer has p3-Symmetry and a lattice constant of 21 nm; three-dimensional reconstructions of negatively stained fragments yield a layer thickness of approximately 6-7 nm.For analysing the molecular architecture of Sulfolobus surface protein in greater detail we use aurothioglucose(ATG)-embedding for specimen preparation. Like glucose, ATG, is supposed to mimic the effect of water, but has the advantage of being less volatile. ATG has advantages over glucose when working with specimens composed exclusively of protein because of its higher density of 2.92 g cm-3. Because of its high radiation sensitivity electromicrographs has to be recorded under strict low-dose conditions. We have recorded electromicrographs with a liquid helium-cooled superconducting electron microscope (the socalled SULEIKA at the Fritz-Haber-lnstitut) with a specimen temperature of 4.5 K and with a maximum dose of 2000 e nm-2 avoiding any pre-irradiation of the specimen.

Investigation of the Microscopic Viscoelastic Property for Cross-linked Polymer Network by Molecular Dynamics Simulation

2011 ◽  
Vol 39 (1) ◽  
pp. 44-58 ◽  
Author(s):  
Y. Masumoto ◽  
Y. Iida
Keyword(s):  
Molecular Dynamics ◽  
Molecular Dynamics Simulation ◽  
Analytical Method ◽  
Viscoelastic Properties ◽  
Polymer Network ◽  
Dynamics Simulation ◽  
Coarse Grained ◽  
The Cross ◽  
Microscopic Dynamic ◽  
Coarse Grained Molecular Dynamics

Abstract The purpose of this work is to develop a new analytical method for simulating the microscopic mechanical property of the cross-linked polymer system using the coarse-grained molecular dynamics simulation. This new analytical method will be utilized for the molecular designing of the tire rubber compound to improve the tire performances such as rolling resistance and wet traction. First, we evaluate the microscopic dynamic viscoelastic properties of the cross-linked polymer using coarse-grained molecular dynamics simulation. This simulation has been conducted by the coarse-grained molecular dynamics program in the OCTA) (http://octa.jp/). To simplify the problem, we employ the bead-spring model, in which a sequence of beads connected by springs denotes a polymer chain. The linear polymer chains that are cross-linked by the cross-linking agents express the three-dimensional cross-linked polymer network. In order to obtain the microscopic dynamic viscoelastic properties, oscillatory deformation is applied to the simulation cell. By applying the time-temperature reduction law to this simulation result, we can evaluate the dynamic viscoelastic properties in the wide deformational frequency range including the rubbery state. Then, the stress is separated into the nonbonding stress and the bonding stress. We confirm that the contribution of the nonbonding stress is larger at lower temperatures. On the other hand, the contribution of the bonding stress is larger at higher temperatures. Finally, analyzing a change of microscopic structure in dynamic oscillatory deformation, we determine that the temperature/frequency dependence of bond stress response to a dynamic oscillatory deformation depends on the temperature dependence of the average bond length in the equilibrium structure and the temperature/frequency dependence of bond orientation. We show that our simulation is a useful tool for studying the microscopic properties of a cross-linked polymer.

Multi-Stimuli-Responsive Mesoporous Membranes and Effect of Molecular Architecture on Thermo- and pH-Responsive Behavior of the grafted Block Copolymer brushes

2019 ◽  
Author(s):  
Yanchun Tang ◽  
Kohzo Ito ◽  
Hideaki Yokoyama
Keyword(s):  
Polymer Brushes ◽  
Diblock Copolymers ◽  
Neutron Reflectivity ◽  
Molecular Architecture ◽  
Stimuli Responsive ◽  
Responsive Polymer ◽  
The Matrix ◽  
Stable Part ◽  
Copolymer Brushes ◽  
Mesoporous Membranes

In this study, we prepared ultrafiltration membranes with a decoupled responses of filtration property to temperature and pH. The membrane preparation method was developed based on our previous work. We utilized methanol-supercritical carbon dioxide (methanol-scCO<sub>2</sub>) selective swelling method to introduce nanopores to block copolymers containing poly(diethylene glycol) methyl ether methacrylate (PMEO<sub>2</sub>MA), poly(N,N-dimethylaminoethyl methacrylate) (PDMAEMA) and polystyrene (PS) blocks. Formation of the mesoporous barrier layer with PS being the mechanically stable part of the matrix was driven by selective swelling of the PMEO<sub>2</sub>MA-b-PDMAEMA domains. Due to the selective swelling of PMEO<sub>2</sub>MA or PDMAEMA domains to introduce pores, the interior of the pores are covered with PMEO<sub>2</sub>MA or PDMAEMA blocks after pore formation. The PMEO<sub>2</sub>MA-b-PDMAEMA polymer brushes are naturally attached on the pore walls and worked as functional gates. PMEO<sub>2</sub>MA is a non-toxic, neutral thermo-responsive polymer with LCST at 26 ᴼC. PDMAEMA is a typical weak polyelectrolyte with pK<sub>a</sub> value at 7.0-7.5 and also a thermo-responsive polymer revealed a LCST of 20-80 °C in aqueous solution. Therefore, these membranes were expected to have multi dimensions as function of the combination of temperature and pH. Moreover, to understand the detail of the temperature and pH depended conformation transitions of PMEO<sub>2</sub>MA-b-PDMAEMA brushes, those diblock copolymers were end-tethered on flat substrates and analyzed via neutron reflectivity (NR).

Sign in / Sign up

Export Citation Format

Share Document