scholarly journals Identifying the origin of local flexibility in a carbohydrate polymer

2021 ◽  
Vol 118 (23) ◽  
pp. e2102168118
Author(s):  
Kelvin Anggara ◽  
Yuntao Zhu ◽  
Giulio Fittolani ◽  
Yang Yu ◽  
Theodore Tyrikos-Ergas ◽  
...  
Keyword(s):  
Secondary Structure ◽  
Primary Structure ◽  
Material Properties ◽  
Single Linkage ◽  
Chain Flexibility ◽  
Carbohydrate Polymers ◽  
Monomer Sequence ◽  
Structures And Properties ◽  
Local Flexibility ◽  
Carbohydrate Polymer

Correlating the structures and properties of a polymer to its monomer sequence is key to understanding how its higher hierarchy structures are formed and how its macroscopic material properties emerge. Carbohydrate polymers, such as cellulose and chitin, are the most abundant materials found in nature whose structures and properties have been characterized only at the submicrometer level. Here, by imaging single-cellulose chains at the nanoscale, we determine the structure and local flexibility of cellulose as a function of its sequence (primary structure) and conformation (secondary structure). Changing the primary structure by chemical substitutions and geometrical variations in the secondary structure allow the chain flexibility to be engineered at the single-linkage level. Tuning local flexibility opens opportunities for the bottom-up design of carbohydrate materials.

The Third Dimension of Carbon Black Structure

1976 ◽  
Vol 49 (4) ◽  
pp. 1068-1075 ◽  
Author(s):  
H. N. Mercer ◽  
A. H. Boyer ◽  
P. L. Bhusky ◽  
M. L. Deviney
Keyword(s):  
Secondary Structure ◽  
Carbon Black ◽  
Primary Structure ◽  
Structure Characterization ◽  
Automated Image Analysis ◽  
Initial Report ◽  
Direct Measurements ◽  
Realistic View ◽  
Third Dimension ◽  
The Individual

Abstract Structure is probably the most difficult characteristic of carbon black to define. Electron microscopy has shown that the individual particles of a black are fused together into a variety of shapes, collectively defined as the structure. Here, particle is used to refer to that entity which is somewhat spherical in shape and is the smallest “building block” of structure. These particles have also been called “domains” of rotational graphitic layers and “nodules”. The larger unit resulting from the fusion of these particles forms an “aggregate” or a “primary structure” unit. A collection of aggregates, held together by some other force (e.g , van der Waals force), is called an “agglomerate” or “secondary structure”. With dry black, it is difficult to completely eliminate all secondry structure. However, main emphasis in this study was on primary structure, because it has the greater influence on rubber properties and because secondary structure is greatly reduced in good rubber mixing. Many recent characterization studies have been concerned with making direct measurements on primary structure units (aggregates) by automated image analysis techniques, a pencil following device, and a comparative chart method. In the work described here, a different approach has been taken to viewing carbon black primary structure units, an approach using the scanning electron microscope combined with stereoscopic methods. This initial report will be mainly concerned with a description of the techniques and results on several individual primary structure units. It is suggested that the efforts described here provide a realistic view of carbon black primary structure and that a third dimension term is essential for primary structure characterization.

scholarly journals Wirtszellreaktivierung chemisch induzierter Letalschäden im DNS-haltigen Serratia-Phagen Kappa

1965 ◽  
Vol 20 (9) ◽  
pp. 864-867 ◽  
Author(s):  
Ulrich Winkler
Keyword(s):  
Secondary Structure ◽  
Host Cell ◽  
Primary Structure ◽  
Nitrous Acid ◽  
Cell Reactivation ◽  
Lethal Damage ◽  
Phage Dna ◽  
Free Phage ◽  
Host Cell Reactivation

After treating free phage Kappa with nitrous acid, triethylenemelamine, ethylmethanesulfonate, or hydroxylamin and using these phages for infecting Serratia HY wildtype cells, at least 20% of the lethal damage in the phage-DNA can be reactivated by the host (= host cell reactivation). It is known that all lethal agents tested so far attack the primary structure of the DNA in different ways. Therefore, we assume that the target for the host cell reactivation consists of some damage in the secondary structure of the DNA, because there is probably some coincidence in the action of all agents. The hypothesis that in the DNA changes of thymine are a prerequisite for host cell reactivation has been disproved by the experiments with nitrous acid and ethylmethanesulfonate because both substances do not act on thymine.

scholarly journals Cellulose-starch Hybrid Films Plasticized by Aqueous ZnCl2 Solution

2019 ◽  
Vol 20 (3) ◽  
pp. 474 ◽  
Author(s):  
Xiaoqin Shang ◽  
Huihua Jiang ◽  
Qingling Wang ◽  
Peng Liu ◽  
Fengwei Xie
Keyword(s):  
Mechanical Properties ◽  
Material Properties ◽  
Cellulose Content ◽  
Natural Polymers ◽  
Hybrid Films ◽  
Materials Development ◽  
Chemical Structures ◽  
Structural Conformation ◽  
Similar Chemical ◽  
Structures And Properties

Starch and cellulose are two typical natural polymers from plants that have similar chemical structures. The blending of these two biopolymers for materials development is an interesting topic, although how their molecular interactions could influence the conformation and properties of the resultant materials has not been studied extensively. Herein, the rheological properties of cellulose/starch/ZnCl2 solutions were studied, and the structures and properties of cellulose-starch hybrid films were characterized. The rheological study shows that compared with starch (containing mostly amylose), cellulose contributed more to the solution’s viscosity and has a stronger shear-thinning behavior. A comparison between the experimental and calculated zero-shear-rate viscosities indicates that compact complexes (interfacial interactions) formed between cellulose and starch with ≤50 wt % cellulose content, whereas a loose structure (phase separation) existed with ≥70 wt % cellulose content. For starch-rich hybrid films prepared by compression molding, less than 7 wt % of cellulose was found to improve the mechanical properties despite the reduced crystallinity of the starch; for cellulose-rich hybrid films, a higher content of starch reduced the material properties, although the chemical interactions were not apparently influenced. It is concluded that the mechanical properties of biopolymer films were mainly affected by the structural conformation, as indicated by the rheological results.

scholarly journals Evidence on the conformation of HeLa-cell 5.8S ribosomal ribonucleic acid from the reaction of specific cytidine residues with sodium bisulphite

1978 ◽  
Vol 173 (2) ◽  
pp. 521-532 ◽  
Author(s):  
J M Kelly ◽  
J P Goddard ◽  
B E H Maden
Keyword(s):  
Secondary Structure ◽  
Nucleotide Sequence ◽  
Hela Cell ◽  
Primary Structure ◽  
The Other ◽  
Structure Model ◽  
Secondary Structure Model ◽  
Sodium Bisulphite ◽  
5.8S Rrna ◽  
Ribosomal Ribonucleic Acid

The reaction of HeLa-cell 5.8S rRNA with NaHSO3 under conditions in which exposed cytidine residues are deaminated to uridine was studied. It was possible to estimate the reactivities of most of the 46 cytidine residues in the nucleotide sequence by comparing ‘fingerprints’ of the bisulphite-treated RNA with those of untreated RNA. The findings were consistent with the main features of the secondary-structure model for mammalian 5.85S rRNA proposed by Nazar, Sitz, & Busch [J. Biol. Chem (1975) 250, 8591–8597]. Five out of six regions that are depicted in the model as single-stranded loops contain cytidine residues that are reactive towards bisulphite at 25 degrees C (the other loop contains no cytidine). The cytidine residue nearest to the 3′-terminus is also reactive. Several cytidines residues that are internally located within proposed double-helical regions show little or no reactivity towards bisulphite, but the cytidine residues of several C.G pairs at the ends of helical regions show some reactivity, and one of the proposed loops appears to contain six nucleotides, rather than the minimum of four suggested by the primary structure. Two cytidine residues that are thought to be ‘looped out’ by small helix imperfections also show some reactivity.

EFFECTS OF FOUNDATION STIFFNESS ON VIBRATION BEHAVIOR OF SECONDARY STRUCTURES DUE TO EXTERNAL AND INTERNAL EXCITATIONS

2001 ◽  
Vol 01 (02) ◽  
pp. 247-261
Author(s):  
GUANMO XIE ◽  
TAKEO TANIGUCHI
Keyword(s):  
Secondary Structure ◽  
Dynamic Behavior ◽  
Seismic Design ◽  
Primary Structure ◽  
Secondary Structures ◽  
Relative Displacement ◽  
Frame Structure ◽  
Rayleigh Damping ◽  
Vibration Behavior ◽  
Internal Production

In this paper, the vibration behavior of a secondary structure in a frame structure under combined excitations of external earthquake and internal production machinery is investigated. The effects of stiffness of the foundation springs of the primary structure on dynamic behavior of the secondary structure are evaluated. The primary structure is modeled by FEM in which consistent mass and Rayleigh damping matrices are adopted. The secondary structure consists of one mass connected to a beam mounted on a member of the primary structure. Numerical results show that the foundation stiffness has considerable influences on relative displacement response of the secondary structure and provide guidelines for the seismic design of factory buildings with production machinery.

Effects of Processing Variables on the Mechanical Properties of Carbon Black Filled Rubber

1978 ◽  
Vol 51 (5) ◽  
pp. 1006-1022 ◽  
Author(s):  
B. Wijayarathna ◽  
W. V. Chang ◽  
R. Salovey
Keyword(s):  
Mechanical Properties ◽  
Particle Size ◽  
Secondary Structure ◽  
Carbon Black ◽  
Term Structure ◽  
Primary Structure ◽  
Filler Particle ◽  
Structural Heterogeneity ◽  
Mixing Process ◽  
High Structure

Abstract Vulcanizate properties such as tensile strength, abrasion resistance, and tear resistance, are often enhanced by the introduction of structural heterogeneity. This is usually achieved by incorporating fillers into the polymer matrix. In addition to the type of filler and polymer used, mechanical properties depend on factors such as filler particle size, distribution, filler-polymer interaction, and network homogeneity. These factors are largely governed by the conditions of the mixing. The most widely used filler in rubber is carbon black. Carbon black, produced by the pyrolysis of hydrocarbons, is in the form of fused primary aggregates which flocculate to form large secondary aggregates held together by van der Waal forces. The term structure, as applied to carbon black, commonly refers to both primary and secondary aggregates and is designated as primary or secondary structure. The reinforcement of rubber by carbon black depends considerably on the particle size and structure of the black used. Voet and associates have shown evidence that the primary structure is not broken down by shearing action during mixing. However, Heckman and Medalia and Gessler claim that fracture of the primary structure could result from severe mechanical shear. The general consensus is that breakdown of the primary structure of carbon black is not extensive in the usual mixing process. Boonstra and Medalia, among others, reported that large agglomerates remaining after insufficient mixing have a deleterious effect on the rupture properties of vulcanizates. Hence, an optimal mixing process does not destroy secondary aggregates. The secondary structure plays an important role in the dispersion of carbon black during mixing as rubber is squeezed into both primary and secondary aggregates. Low structure blacks pack much more tightly than high structure ones and are more difficult to disperse.

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