Molecular architecture of the hyphal wall of Achlya ambisexualis Raper. II. Ultrastructural analyses and a proposed model

1981 ◽  
Vol 27 (10) ◽  
pp. 1100-1105 ◽  
Author(s):  
Julia B. Reiskind ◽  
J. T. Mullins
Keyword(s):  
Molecular Model ◽  
Alkali Treatment ◽  
Molecular Architecture ◽  
Cellulose I ◽  
Cellulose Solvent ◽  
Surface Configuration ◽  
Proposed Model ◽  
Achlya Ambisexualis ◽  
Acid And Alkali Treatment ◽  
Hyphal Wall

The surface configuration of hyphal walls and various fractions of the wall were analyzed by electron microscopy using carbon–platinum replicas. Fractionation was carried out with both enzymes and chemical solvents. Laminarinase with or without protease and acid with alkali removed the acid- and alkali-soluble glucans revealing an underlying pattern of microfibrils. The combination of cellulase, laminarinase, and protease essentially dissolved the hyphae. The cellulose solvent cadoxen removed the microfibrillar pattern which was exposed following acid and alkali treatment. The acid-soluble fraction is amorphous, the alkali-soluble and the insoluble residuum is faintly microfibrillar, and the cellulose II preparation is strongly microfibrillar. Both the cellulose I and the chitinlike fractions are uniformly microfibrillar. Morphologically, the wall consists of an outer matrix of β-1,3- and β-1,6-glucans covering an inner cellulosic protein core. Both a diagrammatic and molecular model are proposed.

Molecular architecture of the hyphal wall of Achlya ambisexualis Raper. I. Chemical analyses

1981 ◽  
Vol 27 (10) ◽  
pp. 1092-1099 ◽  
Author(s):  
Julia B. Reiskind ◽  
J. T. Mullins
Keyword(s):  
Sugar Content ◽  
Periodate Oxidation ◽  
Gas Liquid Chromatography ◽  
Neutral Sugar ◽  
Molecular Architecture ◽  
Chemical Analyses ◽  
Full Spectrum ◽  
Linkage Pattern ◽  
Achlya Ambisexualis ◽  
Hyphal Wall

Chemical analyses of the hyphal wall of Achlya ambisexualis Raper were done in an attempt to provide a basis for understanding the molecular architecture of the wall. Walls were isolated, purified, and fractionated by differential solubility. The wall and its fractions were then hydrolyzed by acid or enzymes. The resulting hydrolysates were analyzed by paper and gas–liquid chromatography for their neutral sugar content and type of glycosidic linkages. The degree of branching was estimated by periodate oxidation. The only monosaccharide detected was glucose. Three disaccharides, laminaribiose gentiobiose, and cellobiose, were detected, thus indicating β-1,3, β-1,6, and β-1,4 linkages. Acid-soluble β-1,3-glucan with single β-1,6-linked residues represented 40% of the wall. Alkali-soluble glucan, a linear polymer of β-1,3 and β-1,4 linkage with occasional β-1,6 side chains, represented 7% of the wall. Cellulose, as determined by solubility and X-ray diffraction represented 21% of the wall. The insoluble residuum (6%) which remained after these solubilizations had a linkage pattern similar to the alkali-soluble fraction. An insoluble component consisting of glucosamine represented 3% of the wall. Protein comprised 10% of the wall and on hydrolysis gave the full spectrum of amino acids including hydroxyproline. Small amounts of phosphorus were detected.

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.

scholarly journals Addressing the Molecular Mechanism of Longitudinal Lamin Assembly Using Chimeric Fusions

Cells ◽  
2020 ◽  
Vol 9 (7) ◽  
pp. 1633 ◽  
Author(s):  
Giel Stalmans ◽  
Anastasia V. Lilina ◽  
Pieter-Jan Vermeire ◽  
Jan Fiala ◽  
Petr Novák ◽  
...  
Keyword(s):  
Cell Nucleus ◽  
Molecular Model ◽  
Coiled Coil ◽  
Cross Linking ◽  
Specific Interactions ◽  
Molecular Architecture ◽  
Filament Assembly ◽  
Assembly Mechanism ◽  
Recombinant Fragments ◽  
Chemical Cross Linking

The molecular architecture and assembly mechanism of intermediate filaments have been enigmatic for decades. Among those, lamin filaments are of particular interest due to their universal role in cell nucleus and numerous disease-related mutations. Filament assembly is driven by specific interactions of the elementary dimers, which consist of the central coiled-coil rod domain flanked by non-helical head and tail domains. We aimed to investigate the longitudinal ‘head-to-tail’ interaction of lamin dimers (the so-called ACN interaction), which is crucial for filament assembly. To this end, we prepared a series of recombinant fragments of human lamin A centred around the N- and C-termini of the rod. The fragments were stabilized by fusions to heterologous capping motifs which provide for a correct formation of parallel, in-register coiled-coil dimers. As a result, we established crystal structures of two N-terminal fragments one of which highlights the propensity of the coiled-coil to open up, and one C-terminal rod fragment. Additional studies highlighted the capacity of such N- and C-terminal fragments to form specific complexes in solution, which were further characterized using chemical cross-linking. These data yielded a molecular model of the ACN complex which features a 6.5 nm overlap of the rod ends.

Calculation of the effect of polymer additive in a converging flow

1987 ◽  
Vol 178 ◽  
pp. 423-440 ◽  
Author(s):  
G. Ryskin
Keyword(s):  
Stress Field ◽  
Channel Flow ◽  
Molecular Model ◽  
Two Dimensional ◽  
Polymer Additive ◽  
Polymer Molecules ◽  
Conical Channel ◽  
Proposed Model ◽  
Converging Flow ◽  
Good Agreement

The conical-channel flow of a dilute polymer solution is investigated theoretically. The stress field due to polymer additive is calculated using a new molecular model, based on the physical picture of the polymer molecules unravelling in strong flows and Batchelor's theory for the stress in a suspension of elongated particles. Good agreement is obtained with the experimental results of James & Saringer (1980). The absence of a significant polymer effect in a two-dimensional case (the wedge-channel flow), observed by the same authors (James & Saringer 1982a), is also explained. The fundamental differences between the proposed model and the elastic-dumbbell models are discussed.

scholarly journals Geometry induced sequence of nanoscale Frank–Kasper and quasicrystal mesophases in giant surfactants

2016 ◽  
Vol 113 (50) ◽  
pp. 14195-14200 ◽  
Author(s):  
Kan Yue ◽  
Mingjun Huang ◽  
Ryan L. Marson ◽  
Jinlin He ◽  
Jiahao Huang ◽  
...  
Keyword(s):  
Self Assembly ◽  
Brownian Dynamics ◽  
Molecular Model ◽  
Critical Role ◽  
Sphere Packing ◽  
Molecular Geometry ◽  
Soft Materials ◽  
Real Space ◽  
Molecular Architecture ◽  
Self Assembled

Frank–Kasper (F-K) and quasicrystal phases were originally identified in metal alloys and only sporadically reported in soft materials. These unconventional sphere-packing schemes open up possibilities to design materials with different properties. The challenge in soft materials is how to correlate complex phases built from spheres with the tunable parameters of chemical composition and molecular architecture. Here, we report a complete sequence of various highly ordered mesophases by the self-assembly of specifically designed and synthesized giant surfactants, which are conjugates of hydrophilic polyhedral oligomeric silsesquioxane cages tethered with hydrophobic polystyrene tails. We show that the occurrence of these mesophases results from nanophase separation between the heads and tails and thus is critically dependent on molecular geometry. Variations in molecular geometry achieved by changing the number of tails from one to four not only shift compositional phase boundaries but also stabilize F-K and quasicrystal phases in regions where simple phases of spheroidal micelles are typically observed. These complex self-assembled nanostructures have been identified by combining X-ray scattering techniques and real-space electron microscopy images. Brownian dynamics simulations based on a simplified molecular model confirm the architecture-induced sequence of phases. Our results demonstrate the critical role of molecular architecture in dictating the formation of supramolecular crystals with “soft” spheroidal motifs and provide guidelines to the design of unconventional self-assembled nanostructures.

scholarly journals Influence of Mercerization on Micro-structure and Properties of Kapok Blended Yarns with Different Blending Ratios

2011 ◽  
Vol 6 (3) ◽  
pp. 155892501100600 ◽  
Author(s):  
Jie Liu ◽  
Fumei Wang
Keyword(s):  
Alkali Treatment ◽  
Chemical Compositions ◽  
X Ray Diffraction ◽  
Cellulose I ◽  
Micro Structure ◽  
Obvious Effect ◽  
Kapok Fiber ◽  
X Ray ◽  
Before And After ◽  
Mercerization Treatment

To investigate the effect of mercerization on micro-structure and the properties of kapok/cotton blended yarns. FTIR spectra and x-ray diffraction (XRD) results, moisture regains and mechanical properties of blended yarns were compared before and after mercerization. The results show that mercerization treatment did not have an obvious effect on chemical compositions of cellulose, but did lead to decreasing on crystallinity of blended yarns, and transformed certain portion of cellulose I into cellulose II. When the NaOH concentration increased from 180g/L to 250 g/L, the strengths of blended yarns increased and elongations at breaking declined, and the extent of changes were lessened gradually with the increase of kapok fiber content, when the NaOH concentration further reached 280g/L, the strengths of blended yarns with high content of kapok fiber dropped dramatically, and elongations at breaking increased gradually, while hygroscopicities of blended yarns increased significantly. Different from cotton fiber, a more moderate alkali treatment condition should be chosen in mercerization process for kapok fiber.

PROSTAGLANDINS IN BRAIN AND THE RELEASE OF PROSTAGLANDIN-LIKE COMPOUNDS FROM THE CAT CEREBELLAR CORTEX

1965 ◽  
Vol 43 (3) ◽  
pp. 445-450 ◽  
Author(s):  
F. Coceani ◽  
L. S. Wolfe
Keyword(s):  
Brain Tissue ◽  
Alkali Treatment ◽  
Water Soluble ◽  
Rat Stomach ◽  
Tissue Extracts ◽  
Slow Type ◽  
Stomach Fundus ◽  
Acid And Alkali Treatment ◽  
Layer Chromatography ◽  
Isolated Rat

A water-soluble lipid material resistant to acid and alkali treatment was found in perfusates and extracts of brain tissue, which induced contraction of the 'slow type' on the isolated rat stomach fundus. The material isolated from brain tissue extracts behaved in solvent partition systems like the prostaglandin compounds and could be purified by silicic acid and thin-layer chromatography. The smooth-muscle-stimulating activity is likely due to the trihydroxyprostaglandin compounds.

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