Superhelices with tunable twisting power directed from supramolecular pairing of focal asymmetry in achiral dendron-jacketed block copolymers

2020 ◽  
Vol 8 (6) ◽  
pp. 1923-1932 ◽  
Author(s):  
I-Ming Lin ◽  
Che-Min Chou ◽  
Ming-Chia Li ◽  
Rong-Hao Guo ◽  
Cheng-Kuang Lee ◽  
...  
Keyword(s):  
Block Copolymers ◽  
Quaternary Structure ◽  
Molecular Level ◽  
Helical Structures

Focal asymmetry was introduced into achiral dendron-jacketed block copolymers for the formation of hierarchical helical structures via transfer of helical twisting from a primary molecular level to a quaternary structure.

Tunable helical structures formed by ABC triblock copolymers under cylindrical confinement

2019 ◽  
Vol 21 (48) ◽  
pp. 26333-26341
Author(s):  
Meijiao Liu ◽  
Ka Chen ◽  
Weihua Li ◽  
Xinping Wang
Keyword(s):  
Block Copolymers ◽  
Triblock Copolymers ◽  
Helical Structures ◽  
Abc Triblock Copolymers

Block copolymers confined in nanopores provide unique achiral systems for the formation of helical structures.

scholarly journals Phase manipulation of topologically engineered AB-type multi-block copolymers

RSC Advances ◽  
2019 ◽  
Vol 9 (72) ◽  
pp. 42029-42042
Author(s):  
Sai Li ◽  
Wei Tao ◽  
Ke Gao ◽  
Naveed Athir ◽  
Fanzhu Li ◽  
...  
Keyword(s):  
Block Copolymers ◽  
Molecular Level ◽  
Scientific Interest ◽  
Recent Advances ◽  
Ordered Phases ◽  
Fundamental Understanding ◽  
Phase Manipulation

Recent advances in the fundamental understanding of the ordered phases of multi-block copolymers (MBCPs) at the molecular level have attracted considerable scientific interest in recent years.

A simulation study of controlling chirality and number of strands for helices self-assembled from achiral block copolymers under confinement of a nanopore

Soft Matter ◽  
2021 ◽  
Author(s):  
Xiejun Hu ◽  
Zheng Wang ◽  
Yuhua Yin ◽  
Run Jiang ◽  
Baohui Li
Keyword(s):  
Block Copolymers ◽  
Simulation Study ◽  
Helical Structures ◽  
Self Assembled

Achiral block copolymers can self-assemble into helical structures when confined within a cylindrical nanopore. Controlling the chirality and number of strands of helices, however, is challenging. We present our simulation...

scholarly journals Divergent CPEB prion-like domains reveal different assembly mechanisms for a generic amyloid-like fold

BMC Biology ◽  
2021 ◽  
Vol 19 (1) ◽  
Author(s):  
Rubén Hervás ◽  
María del Carmen Fernández-Ramírez ◽  
Albert Galera-Prat ◽  
Mari Suzuki ◽  
Yoshitaka Nagai ◽  
...  
Keyword(s):  
Single Molecule ◽  
Quaternary Structure ◽  
Coiled Coil ◽  
Random Coil ◽  
Helical Structures ◽  
Filament Axis ◽  
Assembly Pathway ◽  
Functional Amyloids ◽  
Amyloid Assembly

Abstract Background Amyloids are ordered, insoluble protein aggregates, characterized by a cross-β sheet quaternary structure in which molecules in a β-strand conformation are stacked along the filament axis via intermolecular interactions. While amyloids are typically associated with pathological conditions, functional amyloids have also been identified and are present in a wide variety of organisms ranging from bacteria to humans. The cytoplasmic polyadenylation element-binding (CPEB) prion-like protein is an mRNA-binding translation regulator, whose neuronal isoforms undergo activity-dependent aggregation, a process that has emerged as a plausible biochemical substrate for memory maintenance. CPEB aggregation is driven by prion-like domains (PLD) that are divergent in sequence across species, and it remains unknown whether such divergent PLDs follow a similar aggregating assembly pathway. Here, we describe the amyloid-like features of the neuronal Aplysia CPEB (ApCPEB) PLD and compare them to those of the Drosophila ortholog, Orb2 PLD. Results Using in vitro single-molecule and bulk biophysical methods, we find transient oligomers and mature amyloid-like filaments that suggest similarities in the late stages of the assembly pathway for both ApCPEB and Orb2 PLDs. However, while prior to aggregation the Orb2 PLD monomer remains mainly as a random coil in solution, ApCPEB PLD adopts a diversity of conformations comprising α-helical structures that evolve to coiled-coil species, indicating structural differences at the beginning of their amyloid assembly pathways. Conclusion Our results indicate that divergent PLDs of CPEB proteins from different species retain the ability to form a generic amyloid-like fold through different assembly mechanisms.

Quaternary structure of Limulus polyphemus hemocyanin

1978 ◽  
Vol 36 (2) ◽  
pp. 176-177
Author(s):  
T. Wichertjes ◽  
E.J. Kwak ◽  
E.F.J. Van Bruggen
Keyword(s):  
Electron Microscopy ◽  
Functional Properties ◽  
Horseshoe Crab ◽  
Temperature Jump ◽  
Quaternary Structure ◽  
Crystallographic Analysis ◽  
Limulus Polyphemus ◽  
Oxygen Binding ◽  
X Ray ◽  
Intact Molecule

Hemocyanin of the horseshoe crab (Limulus polyphemus) has been studied in nany ways. Recently the structure, dissociation and reassembly was studied using electron microscopy of negatively stained specimens as the method of investigation. Crystallization of the protein proved to be possible and X-ray crystallographic analysis was started. Also fluorescence properties of the hemocyanin after dialysis against Tris-glycine buffer + 0.01 M EDTA pH 8.9 (so called “stripped” hemocyanin) and its fractions II and V were studied, as well as functional properties of the fractions by NMR. Finally the temperature-jump method was used for assaying the oxygen binding of the dissociating molecule and of preparations of isolated subunits. Nevertheless very little is known about the structure of the intact molecule. Schutter et al. suggested that the molecule possibly consists of two halves, combined in a staggered way, the halves themselves consisting of four subunits arranged in a square.

Preparatory Procedures for Electron Microscopic Analysis at the Molecular Level of Resolution

1978 ◽  
Vol 36 (3) ◽  
pp. 516-520
Author(s):  
F.J. Sjostrand
Keyword(s):  
Electron Microscope ◽  
Molecular Level ◽  
Microscopic Analysis ◽  
Resolving Power ◽  
Cellular Structures ◽  
Electron Microscopic ◽  
Systematic Analysis ◽  
Technical Developments ◽  
Thin Sectioning ◽  
Obvious Reason

In the 1940's and 1950's electron microscopy conferences were attended with everybody interested in learning about the latest technical developments for one very obvious reason. There was the electron microscope with its outstanding performance but nobody could make very much use of it because we were lacking proper techniques to prepare biological specimens. The development of the thin sectioning technique with its perfectioning in 1952 changed the situation and systematic analysis of the structure of cells could now be pursued. Since then electron microscopists have in general become satisfied with the level of resolution at which cellular structures can be analyzed when applying this technique. There has been little interest in trying to push the limit of resolution closer to that determined by the resolving power of the electron microscope.

Characterization of Tamm-Horsfall Urinary Glycoprotein

1973 ◽  
Vol 31 ◽  
pp. 420-421
Author(s):  
John P. Robinson ◽  
J. David Puett
Keyword(s):  
Electron Microscopy ◽  
Circular Dichroism ◽  
Secondary Structure ◽  
Quaternary Structure ◽  
Normal Adult ◽  
Morphological Properties ◽  
Adult Males ◽  
Circular Dichroïsm ◽  
Urinary Glycoprotein

Much work has been reported on the chemical, physical and morphological properties of urinary Tamm-Horsfall glycoprotein (THG). Although it was once reported that cystic fibrotic (CF) individuals had a defective THG, more recent data indicate that THG and CF-THG are similar if not identical.No studies on the conformational aspects have been reported on this glycoprotein using circular dichroism (CD). We examined the secondary structure of THG and derivatives under various conditions and have correlated these results with quaternary structure using electron microscopy.THG was prepared from normal adult males and CF-THG from a 16-year old CF female by the method of Tamm and Horsfall. CF female by the method of Tamm and Horsfall.

RNA polymerase: Preparation and structural analysis of helical polymers

1984 ◽  
Vol 42 ◽  
pp. 152-153
Author(s):  
E. Loren Buhle ◽  
Pamela Rew ◽  
Ueli Aebi
Keyword(s):  
Structural Analysis ◽  
Rna Polymerase ◽  
Molecular Level ◽  
X Ray Diffraction ◽  
Helical Polymers ◽  
X Ray ◽  
E Coli ◽  
The Past ◽  
Ordered Arrays ◽  
Low Ionic Strength

While DNA-dependent RNA polymerase represents one of the key enzymes involved in transcription and ultimately in gene expression in procaryotic and eucaryotic cells, little progress has been made towards elucidation of its 3-D structure at the molecular level over the past few years. This is mainly because to date no 3-D crystals suitable for X-ray diffraction analysis have been obtained with this rather large (MW ~500 kd) multi-subunit (α2ββ'ζ). As an alternative, we have been trying to form ordered arrays of RNA polymerase from E. coli suitable for structural analysis in the electron microscope combined with image processing. Here we report about helical polymers induced from holoenzyme (α2ββ'ζ) at low ionic strength with 5-7 mM MnCl2 (see Fig. 1a). The presence of the ζ-subunit (MW 86 kd) is required to form these polymers, since the core enzyme (α2ββ') does fail to assemble into such structures under these conditions.

The Current Situation in Chemical Stabilization of Biological Materials

1972 ◽  
Vol 30 ◽  
pp. 132-133
Author(s):  
John H. Luft
Keyword(s):  
Electron Microscopy ◽  
Electron Microscope ◽  
Osmium Tetroxide ◽  
Molecular Level ◽  
Cross Linking ◽  
Chemical Stabilization ◽  
Specimen Preparation ◽  
Sufficient Condition ◽  
Radio Telescopes

With information processing devices such as radio telescopes, microscopes or hi-fi systems, the quality of the output often is limited by distortion or noise introduced at the input stage of the device. This analogy can be extended usefully to specimen preparation for the electron microscope; fixation, which initiates the processing sequence, is the single most important step and, unfortunately, is the least well understood. Although there is an abundance of fixation mixtures recommended in the light microscopy literature, osmium tetroxide and glutaraldehyde are favored for electron microscopy. These fixatives react vigorously with proteins at the molecular level. There is clear evidence for the cross-linking of proteins both by osmium tetroxide and glutaraldehyde and cross-linking may be a necessary if not sufficient condition to define fixatives as a class.

Studies of a Defective Measles Virus

1968 ◽  
Vol 26 ◽  
pp. 208-209
Author(s):  
R. M. McCombs ◽  
M. Benyesh-Melnick ◽  
J. P. Brunschwig
Keyword(s):  
Inclusion Bodies ◽  
Measles Virus ◽  
Giant Cells ◽  
Helical Structures ◽  
Thin Sections ◽  
Virus Particles ◽  
Extracellular Virus ◽  
Culture Cells ◽  
Infected Cells ◽  
Eosinophilic Inclusions

Measles virus is an agent that is capable of replicating in a number of different culture cells and generally causes the formation of multinucleated giant cells. As a result of infection, virus is released from the cells into the culture fluids and reinfection can be initiated by this cell-free virus. The extracellular virus has been examined by negative staining with phosphotungstic acid and has been shown to be a rather pleomorphic particle with a diameter of about 140 mμ. However, no such virus particles have been detected in thin sections of the infected cells. Rather, the only virus-induced structures present in the giant cells are eosinophilic inclusions (intracytoplasmic or intranuclear). These inclusion bodies have been shown to contain helical structures, resembling the nucleocapsid observed in negatively stained preparations.

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