scholarly journals The relative contribution of calcium, zinc and oxidation-based cross-links to the stiffness of Arion subfuscus glue

2012 ◽  
Vol 216 (8) ◽  
pp. 1475-1483 ◽  
Author(s):  
M. Braun ◽  
M. Menges ◽  
F. Opoku ◽  
A. M. Smith
Keyword(s):  
Relative Contribution ◽  
Arion Subfuscus ◽  
Cross Links

scholarly journals Elasticity and energy dissipation in the double network hydrogel adhesive of the slug Arion subfuscus

2019 ◽  
Vol 374 (1784) ◽  
pp. 20190201 ◽  
Author(s):  
T.-M. Fung ◽  
C. Gallego Lazo ◽  
A. M. Smith
Keyword(s):  
Energy Dissipation ◽  
Time Course ◽  
Tensile Tests ◽  
Cyclic Stress ◽  
Mechanical Tests ◽  
Double Network ◽  
Ph Values ◽  
Arion Subfuscus ◽  
Synthetic Adhesives ◽  
Cross Links

The slug Arion subfuscus produces a mucus-based defensive secretion that is remarkably tough. This glue appears to be a double network hydrogel, gaining its toughness through the synergistic actions of two networks of polymers, a relatively stiff network and a relatively deformable network. The double network mechanism has great potential to guide the development of synthetic adhesives. Mechanical tests were performed to analyse key predictions of the mechanism. Stress relaxation tests and tensile tests support the presence of stable cross-links. Cyclic stress–strain tests demonstrate that the glue dissipates a great deal of energy through the failure of these cross-links as sacrificial bonds. Energy dissipation by failure of sacrificial bonds rather than viscous processes is supported by the minimal effect of the time course of the experiments on the measured properties. These sacrificial bonds appear able to reform within minutes after failure. Finally, the glue's stiffness decreases at pH values below 5.5, whereas magnesium and calcium rapidly dissociate from the glue at all pH values tested. Thus, these ions may not be the primary cross-linkers generating the glue's stiffness. This article is part of the theme issue ‘Transdisciplinary approaches to the study of adhesion and adhesives in biological systems’.

Study of eukaryotic flagellar components by cryo-electron microscopy

1986 ◽  
Vol 44 ◽  
pp. 98-101
Author(s):  
John M. Murray ◽  
Rob Ward
Keyword(s):  
Electron Microscopy ◽  
Primary Motion ◽  
Cryo Electron Microscopy ◽  
Cross Links ◽  
Cilia And Flagella

The eukaryotic flagellum is constructed from 11 parallel tubular elements arranged as 9 peripheral fibers (doublet microtubules) and 2 central fibers (singlet microtubules). The primary motion generating component has been found to be arranged as axially periodic “arms” bridging the adjacent doublets. The dynein, comprising the arms, has been isolated and characterized from several different cilia and flagella. Various radial and azimuthal cross-links stabilize the axially aligned microtubules, and probably play some role in controlling the form of the flagella beat cycle.

Electron microscopic study of the membrane glycoproteins in the rat kidney after cisplatin treatment

1989 ◽  
Vol 47 ◽  
pp. 912-913
Author(s):  
S.K. Aggarwal
Keyword(s):  
Alkaline Phosphatase ◽  
Rat Kidney ◽  
Light And Electron Microscopy ◽  
Kidney Tissue ◽  
Membrane Glycoproteins ◽  
Electron Microscopic ◽  
Before And After ◽  
Interstrand Cross Links ◽  
Cross Links

The proposed primary mechanism of action of the anticancer drug cisplatin (Cis-DDP) is through its interaction with DNA, mostly through DNA intrastrand cross-links or DNA interstrand cross-links. DNA repair mechanisms can circumvent this arrest thus permitting replication and transcription to proceed. Various membrane transport enzymes have also been demonstrated to be effected by cisplatin. Glycoprotein alkaline phosphatase was looked at in the proximal tubule cells before and after cisplatin both in vivo and in vitro for its inactivation or its removal from the membrane using light and electron microscopy.Outbred male Swiss Webster (Crl: (WI) BR) rats weighing 150-250g were given ip injections of cisplatin (7mg/kg). Animals were killed on day 3 and day 5. Thick slices (20-50.um) of kidney tissue from treated and untreated animals were fixed in 1% buffered glutaraldehyde and 1% formaldehyde (0.05 M cacodylate buffer, pH 7.3) for 30 min at 4°C. Alkaline phosphatase activity and carbohydrates were demonstrated according to methods described earlier.

Multidimensional Anxiety and Content-specificity Effects in Preferential Processing of Threat

2003 ◽  
Vol 8 (4) ◽  
pp. 252-265 ◽  
Author(s):  
Manuel G. Calvo ◽  
P. Avero ◽  
M. Dolores Castillo ◽  
Juan J. Miguel-Tobal
Keyword(s):  
Selective Attention ◽  
Cognitive Biases ◽  
Naming Task ◽  
Color Naming ◽  
Memory Bias ◽  
Ego Threat ◽  
Phobic Anxiety ◽  
Relative Contribution ◽  
Content Specificity ◽  
Specificity Effects

We examined the relative contribution of specific components of multidimensional anxiety to cognitive biases in the processing of threat-related information in three experiments. Attentional bias was assessed by the emotional Stroop word color-naming task, interpretative bias by an on-line inference processing task, and explicit memory bias by sensitivity (d') and response criterion (β) from word-recognition scores. Multiple regression analyses revealed, first, that phobic anxiety and evaluative anxiety predicted selective attention to physical- and ego-threat information, respectively; cognitive anxiety predicted selective attention to both types of threat. Second, phobic anxiety predicted inhibition of inferences related to physically threatening outcomes of ambiguous situations. And, third, evaluative anxiety predicted a response bias, rather than a genuine memory bias, in the reporting of presented and nonpresented ego-threat information. Other anxiety components, such as motor and physiological anxiety, or interpersonal and daily-routines anxiety made no specific contribution to any cognitive bias. Multidimensional anxiety measures are useful for detecting content-specificity effects in cognitive biases.

CROSS-LINKS IN POLYACETYLENE

1983 ◽  
Vol 44 (C3) ◽  
pp. C3-443-C3-446
Author(s):  
C. T. White ◽  
P. Brant ◽  
M. L. Elert
Keyword(s):  
Cross Links

Thoracic duct lymph. Relative contribution from splanchnic and muscle tissue

Diabetes ◽  
1993 ◽  
Vol 42 (5) ◽  
pp. 720-731 ◽  
Author(s):  
G. M. Steil ◽  
M. A. Meador ◽  
R. N. Bergman
Keyword(s):  
Muscle Tissue ◽  
Thoracic Duct ◽  
Thoracic Duct Lymph ◽  
Relative Contribution ◽  
Duct Lymph

Bacterial Peptidoglycan Stapling with Functionalized D-Amino Acids

2019 ◽  
Author(s):  
Sylvia L. Rivera ◽  
Akbar Espaillat ◽  
Arjun K. Aditham ◽  
Peyton Shieh ◽  
Chris Muriel-Mundo ◽  
...  
Keyword(s):  
Cell Wall ◽  
Clinical Success ◽  
Bacterial Species ◽  
Enzymatic Reaction ◽  
Amino Acid Derivative ◽  
Wall Structure ◽  
Live Bacteria ◽  
Cross Links ◽  
Osmotic Lysis ◽  
Bacterial Peptidoglycan

Transpeptidation reinforces the structure of cell wall peptidoglycan, an extracellular heteropolymer that protects bacteria from osmotic lysis. The clinical success of transpeptidase-inhibiting β-lactam antibiotics illustrates the essentiality of these cross-linkages for cell wall integrity, but the presence of multiple, seemingly redundant transpeptidases in many bacterial species makes it challenging to determine cross-link function precisely. Here we present a technique to covalently link peptide strands by chemical rather than enzymatic reaction. We employ bio-compatible click chemistry to induce triazole formation between azido- and alkynyl-D-alanine residues that are metabolically installed in the cell walls of Gram-positive and Gram-negative bacteria. Synthetic triazole cross-links can be visualized by substituting azido-D-alanine with azidocoumarin-D-alanine, an amino acid derivative that undergoes fluorescent enhancement upon reaction with terminal alkynes. Cell wall stapling protects the model bacterium Escherichia coli from β-lactam treatment. Chemical control of cell wall structure in live bacteria can provide functional insights that are orthogonal to those obtained by genetics.<br>

Bonded Force Constant Derivation of Lysine-Arginine Cross-linked Advanced Glycation End-Products

2018 ◽  
Author(s):  
Anthony Nash ◽  
Nora H de Leeuw ◽  
Helen L Birch
Keyword(s):  
Molecular Dynamics ◽  
Force Constant ◽  
Computational Study ◽  
Force Constants ◽  
Quantum Mechanical ◽  
Advanced Glycation ◽  
Partial Charges ◽  
Cross Links ◽  
Complete Set ◽  
Dynamics Simulations

<div> <div> <div> <p>The computational study of advanced glycation end-product cross- links remains largely unexplored given the limited availability of bonded force constants and equilibrium values for molecular dynamics force fields. In this article, we present the bonded force constants, atomic partial charges and equilibrium values of the arginine-lysine cross-links DOGDIC, GODIC and MODIC. The Hessian was derived from a series of <i>ab initio</i> quantum mechanical electronic structure calculations and from which a complete set of force constant and equilibrium values were generated using our publicly available software, ForceGen. Short <i>in vacuo</i> molecular dynamics simulations were performed to validate their implementation against quantum mechanical frequency calculations. </p> </div> </div> </div>

Infant-Directed Speech Effects in Adult Artificial Grammar Learning

2019 ◽  
Author(s):  
Krisztina Sára Lukics ◽  
Ágnes Lukács
Keyword(s):  
Language Acquisition ◽  
Natural Language ◽  
First Language ◽  
Higher Learning ◽  
Artificial Grammar ◽  
Combined Effect ◽  
First Language Acquisition ◽  
Relative Contribution ◽  
Grammar Learning ◽  
Learning Rates

First language acquisition is facilitated by several characteristics of infant-directed speech, but we know little about their relative contribution to learning different aspects of language. We investigated infant-directed speech effects on the acquisition of a linear artificial grammar in two experiments. We examined the effect of incremental presentation of strings (starting small) and prosody (comparing monotonous, arbitrary and phrase prosody). Presenting shorter strings before longer ones led to higher learning rates compared to random presentation. Prosody marking phrases had a similar effect, yet, prosody without marking syntactic units did not facilitate learning. These studies were the first to test the starting small effect with a linear artificial grammar, and also the first to investigate the combined effect of starting small and prosody. Our results suggest that starting small and prosody facilitate the extraction of regularities from artificial linguistic stimuli, indicating they may play an important role in natural language acquisition.

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