Mechanical Properties of Biopolymer Chains

AbstractMolecular simulations that predict the molecular mechanical response of alpha-helical biopolymers with a reinforcing intra-molecular hydrogen bonding network, viz,, a ‘spring-like’ behavior, are presented in this study. Mechanical properties of extended biopolymer strands based on naturally occurring amino acids, namely poly(L-A1a) and for comparison poly(LGlu), versus synthetic PPTA containing an amide bond, are compared to those assuming alpha-helical structures. Thus, the pivotal role of such motifs in biological systems utilizing superior compressive mechanical properties can be inferred.

Download Full-text

Computational and Experimental Study of Phenolic Resins: Thermal–Mechanical Properties and the Role of Hydrogen Bonding

Macromolecules ◽

10.1021/acs.macromol.5b01183 ◽

2015 ◽

Vol 48 (20) ◽

pp. 7670-7680 ◽

Cited By ~ 23

Author(s):

Joshua D. Monk ◽

Eric W. Bucholz ◽

Tane Boghozian ◽

Shantanu Deshpande ◽

Jay Schieber ◽

...

Keyword(s):

Mechanical Properties ◽

Experimental Study ◽

Hydrogen Bonding ◽

Phenolic Resins ◽

Thermal Mechanical Properties

Download Full-text

The role of hydrogen bonding in tuning CEST contrast efficiency: A comparative study of intra and inter molecular hydrogen bonding

New Journal of Chemistry ◽

10.1039/d1nj04637c ◽

2022 ◽

Author(s):

Shalini Pandey ◽

Subhayan Chakraborty ◽

Rimilmandrita Ghosh ◽

Divya Radhakrishnan ◽

Saravanan Peruncheralathan ◽

...

Keyword(s):

Hydrogen Bonding ◽

Comparative Study ◽

Contrast Agents ◽

Diagnostic Tool ◽

Molecular Hydrogen

The effectiveness of MRI as a diagnostic tool have increased tremendously after the discovery of contrast agents (CA). Most of the clinically approved CAs at present are relaxation based and...

Download Full-text

Mutational analysis and an alternatively spliced product of B7 defines its CD28/CTLA4-binding site on immunoglobulin C-like domain.

Journal of Experimental Medicine ◽

10.1084/jem.181.4.1345 ◽

1995 ◽

Vol 181 (4) ◽

pp. 1345-1355 ◽

Cited By ~ 37

Author(s):

Y Guo ◽

Y Wu ◽

M Zhao ◽

X P Kong ◽

Y Liu

Keyword(s):

Amino Acids ◽

T Cell ◽

Binding Site ◽

Mutational Analysis ◽

Critical Role ◽

Surface Receptors ◽

Naturally Occurring ◽

Alternatively Spliced ◽

Single Binding Site

Costimulatory molecules B7 and B7-2 interact with T cell surface receptors CD28/CTLA4 and deliver a costimulatory signal essential for T cell growth. However, the structure basis of this interaction is not known. B7 and B7-2 are members of immunoglobulin (Ig) superfamily and their extracellular portion consists of an IgV- and IgC-like domain. Here we report that a naturally occurring, alternatively spliced form of B7 reveals that exon 3-encoded IgC domain is essential for CD28/CTLA4 binding. Mutational analysis of B7 demonstrates a critical role of several amino acids around loops between strands B and C and D and E, for binding CTLA4/CD28. These amino acids are clustered to form a single binding site centered at 201Y. A comparison of the effects of mutations on the binding of CD28 and CTLA4 reveals that CD28 and CTLA4 binds to the same site on B7. These results have important implications on the role of CTLA4 and CD28 in T cell costimulation. The structure of the CD28/CTLA4-binding site also provides valuable information for immune intervention targeted at the B7/B7-2-CD28/CTLA4 interactions.

Download Full-text

A Study on the Structure of Novel Polyurethanes Derived from γ-Valerolactone-Based Diol Precursors

Advanced Materials Research ◽

10.4028/www.scientific.net/amr.789.274 ◽

2013 ◽

Vol 789 ◽

pp. 274-278 ◽

Cited By ~ 4

Author(s):

Mochamad Chalid ◽

Hans J. Heeres ◽

Antonius A. Broekhuis

Keyword(s):

Mechanical Properties ◽

Hydrogen Bonding ◽

Molecular Hydrogen ◽

Hexamethylene Diisocyanate ◽

Thermal And Mechanical Properties ◽

H Nmr ◽

Molecular Behavior ◽

Wave Numbers ◽

C Nmr ◽

Hydrogen Bonded

As versatile biomass-based diol precursors, N,N'-1,2-ethanediylbis-(4-hydroxy-pentanamide) (1) and 4-hydroxy-N-(2-hydroxyethyl)-pentanamide (2) are potential monomers to synthesize novel polyurethanes through adding di-isocyanates. This study reported the structural analysis and molecular behavior of polyurethanes obtained from polymerization of the diol precursors with aliphatic and aromatic di-isocyanates (hexamethylene diisocyanate, HDI (3), and phenyl-diisocyanate, PDI (4)) in (N,N-dimethylacetamide (DMA) solvents with triethylamine (TEA) catalysts.1H-NMR,13C-NMR and Elemental Analysis confirmed structure of the polyurethanes built from both diols and di-isocyanates and FTIR indicated interaction among polyurethane molecules showed at lower wave numbers such as 2855-2976 cm-1for hydrogen-bonded NH groups and 1621-1643 cm-1for hydrogen-bonded C=O groups. Furthermore a study on influence of the inter-and intra-molecular hydrogen bonding on the thermal and mechanical properties of the polyurethanes would be an interesting investigation for the next study.

Download Full-text

Competition for S-containing amino acids between rhizosphere microorganisms and plant roots: the role of cysteine in plant S acquisition

Biology and Fertility of Soils ◽

10.1007/s00374-021-01572-2 ◽

2021 ◽

Author(s):

Qingxu Ma ◽

Paul W. Hill ◽

David R. Chadwick ◽

Lianghuan Wu ◽

Davey L. Jones

Keyword(s):

Amino Acids ◽

Oilseed Rape ◽

Soil Microorganisms ◽

Inorganic N ◽

Rhizosphere Microorganisms ◽

Naturally Occurring ◽

S Deficiency ◽

S Uptake ◽

Elemental Uptake

AbstractPlant S deficiency is common, but the role of S-containing amino acids such as cysteine in plant S uptake is unknown. We applied 14C-, 35S-, 13C-, and 15N-labelled cysteine to wheat and oilseed rape rhizospheres and traced the plants’ elemental uptake. Both plants absorbed 0.37–0.81% of intact cysteine after 6 h with no further increase after 24 h. They absorbed 1.6–11.5% 35S and 12.3–7.6% 15N from cysteine after 24 h and utilised SO42− as their main S source (75.5–86.4%). Added and naturally occurring cysteine-S contributed 5.6 and 1.1% of total S uptake by wheat and oilseed rape, respectively. Cysteine and inorganic S derived from cysteine contributed 24.5 and 13.6% of uptake for wheat and oilseed rape, respectively, after 24 h. Oilseed rape absorbed ~10-fold more S from cysteine and SO42− than did wheat. The highest absorption of free cysteine should be in the organic-rich soil patches. Soil microorganisms rapidly decomposed cysteine (t1/2 = 1.37 h), and roots absorbed mineralised inorganic N and S. After 15 min, 11.7–14.3% of the 35S-cysteine was retained in the microbial biomass, while 30.2–36.7% of the SO42− was released, suggesting that rapid microbial S immobilisation occurs after cysteine addition. Plants acquire N and S from cysteine via unidirectional soil-to-root nutrient flow, and cysteine is an important S source for plants.

Download Full-text

Diamond Indenter Shaping Using Focused Ion Beam

Microscopy and Microanalysis ◽

10.1017/s1431927600021723 ◽

1998 ◽

Vol 4 (S2) ◽

pp. 320-321

Author(s):

J.R. Phillips ◽

K.F. Jarausch ◽

T.J. Stark ◽

J.E. Houston ◽

D.P. Griffis ◽

...

Keyword(s):

Mechanical Properties ◽

Focused Ion Beam ◽

Mechanical Response ◽

Ion Beam ◽

Nanometer Scale ◽

Naturally Occurring ◽

Diamond Indenter ◽

Properties Of Materials ◽

Indenter Geometry

Nanoindentation is becoming an increasingly important tool for the characterization of the mechanical properties of materials on the nanometer scale. The mechanical response of a material is measured by recording the force acting between an indenter and the material while displacing the indenter into the material. The shape of the recorded load displacement curves is not only dependent on the mechanical properties of the material, but also strongly dependent on indenter geometry. To minimize difficulties in the extraction of quantitative material mechanical property information from the force curve, indenter geometry must be controlled and characterized on the same scale as the indentation, i.e. on the nanometer scale. Diamond, the hardest naturally occurring material, is an obvious choice as the indenter material. Conventional lapping techniques4 do not provide sufficient control to produce indenter geometries of the shapes and to the precision required for optimal nanoindentation measurements.

Download Full-text

Oxidative Damage in Aliphatic Amino Acids and Di- and Tripeptides by the Environmental Free Radical Oxidant NO3•: The Role of the Amide Bond Revealed by Kinetic and Computational Studies

The Journal of Organic Chemistry ◽

10.1021/acs.joc.8b03224 ◽

2019 ◽

Vol 84 (6) ◽

pp. 3405-3418 ◽

Cited By ~ 2

Author(s):

Joses G. Nathanael ◽

Uta Wille

Keyword(s):

Amino Acids ◽

Free Radical ◽

Oxidative Damage ◽

Amide Bond ◽

Computational Studies

Download Full-text

Antiwear Chemistry in Presence of ZDDP

World Tribology Congress III, Volume 1 ◽

10.1115/wtc2005-63960 ◽

2005 ◽

Cited By ~ 1

Author(s):

J. M. Martin ◽

C. Minfray

Keyword(s):

Mechanical Properties ◽

Abrasive Wear ◽

Metal Surfaces ◽

Mechanical Response ◽

Adhesive Wear ◽

Physical And Mechanical Properties ◽

Hard Metal ◽

Antiwear Additives ◽

Sulphur Species

Antiwear chemistry is related to the role of tribochemical reactions in controlling abrasive wear, adhesive wear as well as physical and mechanical properties of tribofilms. In the case of additives in boundary lubrication, three different chemical reactions have been found to be directly connected to mechanical response. First one is the digestion of hard metal oxides in the glassy tribofilm formed from the antiwear additives, thus combating with abrasive wear. Second reaction is the reaction of sulphur species with nascent metal surfaces, reducing adhesive wear between antagonist metal surfaces. The third reaction is an equilibrium one in the stressed tribofilm, leading to a change of mechanical properties of the tribofilm and explaining its smart behavior.

Download Full-text

The Role of Synergies of MWCNTs and Carbon Black in the Enhancement of the Electrical and Mechanical Response of Modified Epoxy Resins

Applied Sciences ◽

10.3390/app9183757 ◽

2019 ◽

Vol 9 (18) ◽

pp. 3757 ◽

Cited By ~ 3

Author(s):

Georgios Foteinidis ◽

Kyriaki Tsirka ◽

Lazaros Tzounis ◽

Dimitrios Baltzis ◽

Alkiviadis S. Paipetis

Keyword(s):

Mechanical Properties ◽

Fracture Toughness ◽

Carbon Black ◽

Mechanical Response ◽

Fracture Mechanisms ◽

Factors Affecting ◽

Pull Out ◽

Carbon Nano Tubes ◽

Crack Pinning

Nano-reinforced composites are widely studied by the scientific community. The main factors affecting the final nanocomposite performance are the filler type and content, as well as the duration of the dispersion. In this work, we report the effects of Multi-Walled Carbon Nano Tubes (MWCNTs) and milled Carbon Black (CB) dispersion in epoxy resin on the electrical and mechanical properties of the resulting composites. Impedance Spectroscopy (IS) was utilized to assess the dielectric properties of the specimens. The mechanical properties were evaluated by fracture toughness tests, while Scanning Electron Microscopy (SEM) was performed to study the influence of the reinforcement on the failure mechanisms acting on the fracture surfaces of the specimens. IS results for epoxy/CNT systems revealed the creation of a 3D conductive network for concentrations above 0.3 wt. %, while CB did not result in the formation of such a network for filler contents up to 2 wt. %. However, the synergistic effect of CNTs/CB was successfully manifested by both the optimal electrical properties and the 81% enhanced fracture toughness in comparison to the neat resin. Fractography confirmed the aforementioned results and revealed the fracture mechanisms of all systems, such as crack pinning and deflection, and particle pull-out phenomena.

Download Full-text