scholarly journals Connecting caddisworm silk structure and mechanical properties: combined infrared spectroscopy and mechanical analysis

Open Biology ◽  
2016 ◽  
Vol 6 (6) ◽  
pp. 160067 ◽  
Author(s):  
Nicholas N. Ashton ◽  
Huaizhong Pan ◽  
Russell J. Stewart
Keyword(s):  
Mechanical Properties ◽  
Metal Ions ◽  
Metal Ion ◽  
Large Strain ◽  
Fibre Strength ◽  
Silk Fibre ◽  
Initial Stiffness ◽  
Stress Plateau ◽  
Transition Dipole ◽  
Initial Strength

The underwater silk of an aquatic casemaking caddisfly larvae ( Hesperophylax occidentalis) is viscoelastic, and displays distinct yield behaviour, large strain cycle hysteresis and near complete recovery of its initial strength and stiffness when unloaded. Yield followed by a stress plateau has been attributed to sequential rupture of serial Ca 2+ -cross-linked phosphoserine (pS) β-domains. Spontaneous recovery has been attributed to refolding of the Ca 2+ /pS domains powered by an elastic network. In this study, native Ca 2+ ions were exchanged with other metal ions, followed by combined mechanical and FTIR analysis to probe the contribution of pS/metal ion complexes to silk mechanical properties. After exchange of Ca 2+ with Na + , the fibres are soft elastomers and the infrared spectra are consistent with C v3 symmetry of the – groups. Multivalent metal ions decreased the – symmetry and the symmetric stretching modes ( v s ) split in a manner characteristic of ordered phosphate compounds, such as phosphate minerals and lamellar bilayers of phosphatidic acid lipids. Integrated intensities of the v s bands, indicative of the metal ion's effect on transition dipole moment of the P–O bonds, and thereby the strength of the phosphate metal complex, increased in the order: Na + < Mg 2+ < Sr 2+ < Ba 2+ < Ca 2+ < Eu 3+ < La 3+ < Zn 2+ < Fe 2+ . With a subset of the metal ion series, the initial stiffness and yield stress of metal ion-exchanged fibres increased in the same order: establishing the link between phosphate transition dipole moments and silk fibre strength.

scholarly journals Amino acid-based amphiphilic hydrogels: metal ion induced tuning of mechanical and thermal stability

RSC Advances ◽  
2017 ◽  
Vol 7 (24) ◽  
pp. 14461-14465 ◽  
Author(s):  
Shibaji Basak ◽  
Ishwar Singh ◽  
Arindam Banerjee ◽  
Heinz-Bernhard Kraatz
Keyword(s):  
Mechanical Properties ◽  
Thermal Stability ◽  
Amino Acid ◽  
Metal Ions ◽  
Phosphate Buffer ◽  
Metal Ion ◽  
Phosphate Buffer Solution ◽  
Buffer Solution

A phenylalanine based gelator was found to form a hydrogel in phosphate buffer solution. Its mechanical properties are influenced by a range of metal ions.

scholarly journals A Short Review on the N,N-Dimethylacrylamide-Based Hydrogels

Gels ◽  
2021 ◽  
Vol 7 (4) ◽  
pp. 234
Author(s):  
Ayatzhan Akhmetzhan ◽  
Nurbala Myrzakhmetova ◽  
Nurgul Amangeldi ◽  
Zhanar Kuanyshova ◽  
Nazgul Akimbayeva ◽  
...  
Keyword(s):  
Mechanical Properties ◽  
Heavy Metal ◽  
Metal Ions ◽  
Metal Ion ◽  
Heavy Metal Ions ◽  
Large Scale ◽  
Short Review ◽  
Self Healing ◽  
Practical Applications ◽  
Metal Ion Removal

Scientists have been encouraged to find different methods for removing harmful heavy metal ions and dyes from bodies of water. The adsorption technique offers promising outcomes for heavy metal ion removal and is simple to run on a large scale, making it appropriate for practical applications. Many adsorbent hydrogels have been developed and reported, comprising N,N-dimethylacrylamide (DMAA)-based hydrogels, which have attracted a lot of interest due to their reusability, simplicity of synthesis, and processing. DMAA hydrogels are also a suitable choice for self-healing materials and materials with good mechanical properties. This review work discusses the recent studies of DMAA-based hydrogels such as hydrogels for dye removal and the removal of hazardous heavy metal ions from water. Furthermore, there are also references about their conduct for self-healing materials and for enhancing mechanical properties.

scholarly journals Application of Hydrophobic Alkylimidazoles in the Separation of Non-Ferrous Metal Ions across Plasticised Membranes—A Review

Membranes ◽  
2020 ◽  
Vol 10 (11) ◽  
pp. 331 ◽  
Author(s):  
Malgorzata Ulewicz ◽  
Elzbieta Radzyminska-Lenarcik
Keyword(s):  
Mechanical Properties ◽  
Metal Ions ◽  
Metal Ion ◽  
Chemical Resistance ◽  
Ferrous Metal ◽  
Morphological Structure ◽  
Imidazole Ring ◽  
Review Of The Literature ◽  
Separation Of Metal Ions ◽  
The Stability

Currently, a lot of attention is paid to polymer inclusion membranes (PIMs). Their particular advantages include effective support fixation, easy preparation, versatility, stability, good mechanical properties and good chemical resistance. The paper presents a review of the literature related to the applications of polymer inclusion membranes containing alkylimidazole derivatives as carriers in the processes of transporting ions of heavy and toxic metals, such as Zn(II), Cu(II), Cd(II), Co(II), Ni(II), and Mn(II). It has been proven that alkylimidazoles exhibit varying complex-forming properties towards metal ions, and that their properties (hydrophobic and alkaline) can be modified easily by changing the size of the alkyl group and its position in the imidazole ring, which allows obtaining efficiently working metal ion carriers. The stability of an imidazole derivative-metal ion complex determines the speed and selectivity of the process of transporting metal ions across polymer inclusion membranes. Also, the morphological structure of polymer inclusion membranes impacts the efficiency of the process involving the release and separation of metal ions.

scholarly journals Disruption of the Metal Ion Environment by EDTA for Silk Formation Affects the Mechanical Properties of Silkworm Silk

2019 ◽  
Vol 20 (12) ◽  
pp. 3026 ◽  
Author(s):  
Qingsong Liu ◽  
Xin Wang ◽  
Xiaoyin Tan ◽  
Xiaoqian Xie ◽  
Haonan Dong ◽  
...  
Keyword(s):  
Mechanical Properties ◽  
Secondary Structure ◽  
Metal Ions ◽  
Silk Fibroin ◽  
Metal Ion ◽  
Conformational Transition ◽  
Direct Injection ◽  
Silk Gland ◽  
Silk Fiber ◽  
Edta Treatment

Silk fiber has become a research focus because of its comprehensive mechanical properties. Metal ions can influence the conformational transition of silk fibroin. Current research is mainly focused on the role of a single ion, rather than the whole metal ion environment. Here, we report the effects of the overall metal ion environment on the secondary structure and mechanical properties of silk fibers after direct injection and feeding of silkworms with EDTA. The metal composition of the hemolymph, silk gland, and silk fiber changed significantly post EDTA treatment. Synchrotron FTIR analysis indicated that the secondary structure of silk fiber after EDTA treatment changed dramatically; particularly, the β-sheets decreased and the β-turns increased. Post EDTA treatment, the silk fiber had significantly decreased strength, Young’s modulus, and toughness as compared with the control groups, while the strain exhibited no obvious change. These changes can be attributed to the change in the metal ion environment in the silk fibroin and sericin in the silk gland. Our investigation provides a new theoretical basis for the natural silk spinning process, and our findings could help develop a method to modify the mechanical properties of silk fiber using metal ions.

Molecularly Imprinted Ionomers

2002 ◽  
Vol 723 ◽  
Author(s):  
George M. Murray ◽  
Glen E. Southard
Keyword(s):  
Mechanical Properties ◽  
Ion Exchange ◽  
Metal Ions ◽  
Binding Site ◽  
Molecular Imprinting ◽  
Metal Ion ◽  
Ion Exchange Resins ◽  
Molecularly Imprinted ◽  
Ionic Groups ◽  
Exchange Resins

AbstractIonomers have been defined as copolymers that have a certain proportion of ionic groups. The ionic groups have a significant effect on the mechanical properties of the copolymers. This is generally due to aggregation of ions in a low dielectric medium. The primary result is to restrict chain motion and raise the glass transition temperature. These attributes have relevance to molecular imprinting, since restricted chain motion should help preserve the integrity of the binding site. The connection between ionomers and molecular imprinting has come from the production of metal ion imprinted resins. Metal ions are used in the production of molecularly imprinted polymer ion exchange resins and ionically permeable membranes. The polymers have applications as separations media, sequestering media and as ion selective sensors. Metal ions are also being used to form imprinted polymers based on metal mediated imprint binding. We have prepared ion exchange resins, selectively permeable polymer membranes, ion selective electrodes and ion selective optical sensors using a modified version of the molecular imprinting technique. The modification is a reduction in the amount of covalent crosslinking used to form the polymers. This reduction may be justified by the presence of residual metal ion crosslinking in the immediate region of the imprinted binding site. The effects of metal ions on the thermal and mechanical properties of the polymers, as well their impact on binding selectivity are critical variables.

Use of agro-waste (Musa paradisiaca peels) as a sustainable biosorbent for toxic metal ions removal from contaminated water

2019 ◽  
Author(s):  
Chem Int
Keyword(s):  
Heavy Metal ◽  
Metal Ions ◽  
Contact Time ◽  
Metal Ion ◽  
Equilibrium Concentration ◽  
Ion Concentration ◽  
Contaminated Water ◽  
Musa Paradisiaca ◽  
Percentage Removal ◽  
Adsorbent Dose

A study of removal of heavy metal ions from heavy metal contaminated water using agro-waste was carried out with Musa paradisiaca peels as test adsorbent. The study was carried by adding known quantities of lead (II) ions and cadmium (II) ions each and respectively into specific volume of water and adding specific dose of the test adsorbent into the heavy metal ion solution, and the mixture was agitated for a specific period of time and then the concentration of the metal ion remaining in the solution was determined with Perkin Elmer Atomic absorption spectrophotometer model 2380. The effect of contact time, initial adsorbate concentration, adsorbent dose, pH and temperature were considered. From the effect of contact time results equilibrium concentration was established at 60minutes. The percentage removal of these metal ions studied, were all above 90%. Adsorption and percentage removal of Pb2+ and Cd2+ from their aqueous solutions were affected by change in initial metal ion concentration, adsorbent dose pH and temperature. Adsorption isotherm studies confirmed the adsorption of the metal ions on the test adsorbent with good mathematical fits into Langmuir and Freundlich adsorption isotherms. Regression correlation (R2) values of the isotherm plots are all positive (&gt;0.9), which suggests too, that the adsorption fitted into the isotherms considered.

Cellulose Nanofibrils-based Hydrogels for Biomedical Applications: Progresses and Challenges

2020 ◽  
Vol 27 (28) ◽  
pp. 4622-4646 ◽  
Author(s):  
Huayu Liu ◽  
Kun Liu ◽  
Xiao Han ◽  
Hongxiang Xie ◽  
Chuanling Si ◽  
...  
Keyword(s):  
Mechanical Properties ◽  
Metal Ion ◽  
Biomedical Applications ◽  
Biomedical Application ◽  
Cellulose Nanofibrils ◽  
Wound Dressings ◽  
Preparation Methods ◽  
Tissue Scaffold ◽  
Surface Areas ◽  
Mechanical Methods

Background: Cellulose Nanofibrils (CNFs) are natural nanomaterials with nanometer dimensions. Compared with ordinary cellulose, CNFs own good mechanical properties, large specific surface areas, high Young's modulus, strong hydrophilicity and other distinguishing characteristics, which make them widely used in many fields. This review aims to introduce the preparation of CNFs-based hydrogels and their recent biomedical application advances. Methods: By searching the recent literatures, we have summarized the preparation methods of CNFs, including mechanical methods and chemical mechanical methods, and also introduced the fabrication methods of CNFs-based hydrogels, including CNFs cross-linked with metal ion and with polymers. In addition, we have summarized the biomedical applications of CNFs-based hydrogels, including scaffold materials and wound dressings. Results: CNFs-based hydrogels are new types of materials that are non-toxic and display a certain mechanical strength. In the tissue scaffold application, they can provide a micro-environment for the damaged tissue to repair and regenerate it. In wound dressing applications, it can fit the wound surface and protect the wound from the external environment, thereby effectively promoting the healing of skin tissue. Conclusion: By summarizing the preparation and application of CNFs-based hydrogels, we have analyzed and forecasted their development trends. At present, the research of CNFs-based hydrogels is still in the laboratory stage. It needs further exploration to be applied in practice. The development of medical hydrogels with high mechanical properties and biocompatibility still poses significant challenges.

The Binding and Viscometric Studies of Ni+2, Co+2 and Mn+2 Ions with Protein by Spectrometric and pH Metric Techniques

2019 ◽  
Vol 9 (2) ◽  
pp. 151-162
Author(s):  
Shveta Acharya ◽  
Arun Kumar Sharma
Keyword(s):  
Metal Ions ◽  
Metal Ion ◽  
Protein Molecule ◽  
Vital Role ◽  
Sufficient Evidence ◽  
Structural Requirement ◽  
Nickel Ions ◽  
Cobalt Ions ◽  
Lower Temperature ◽  
Specific Oxidation

Background: The metal ions play a vital role in a large number of widely differing biological processes. Some of these processes are quite specific in their metal ion requirements. In that only certain metal ions, in specific oxidation states, can full fill the necessary catalytic or structural requirement, while other processes are much less specific. Objective: In this paper we report the binding of Mn (II), Ni (II) and Co (II) with albumin are reported employing spectrophotometric and pH metric method. In order to distinguish between ionic and colloidal linking, the binding of metal by using pH metric and viscometric methods and the result are discussed in terms of electrovalent and coordinate bonding. Methods: The binding of Ni+2, Co+2 and Mn+2 ions have been studied with egg protein at different pH values and temperatures by the spectrometric technique. Results: The binding data were found to be pH and temperature dependent. The intrinsic association constants (k) and the number of binding sites (n) were calculated from Scatchard plots and found to be at the maximum at lower pH and at lower temperatures. Therefore, a lower temperature and lower pH offered more sites in the protein molecule for interaction with these metal ions. Statistical effects seem to be more significant at lower Ni+2, Co+2 and Mn+2 ions concentrations, while at higher concentrations electrostatic effects and heterogeneity of sites are more significant. Conclusion: The pH metric as well as viscometric data provided sufficient evidence about the linking of cobalt, nickel and manganese ions with the nitrogen groups of albumin. From the nature and height of curves in the three cases it may be concluded that nickel ions bound strongly while the cobalt ions bound weakly.

Efficient Preconcentration of Cu2+, Zn2+ and Fe3+ with an Agarose-Schiff Base Sorbent

2007 ◽  
Vol 72 (7) ◽  
pp. 908-916 ◽  
Author(s):  
Payman Hashemi ◽  
Hatam Hassanvand ◽  
Hossain Naeimi
Keyword(s):  
Schiff Base ◽  
Metal Ions ◽  
Metal Ion ◽  
Good Accuracy ◽  
Kinetic Studies ◽  
Sample Volume ◽  
Effects Of Ph ◽  
Glass Column ◽  
High Concentrations ◽  
Ph Range

Sorption and preconcentration of Cu2+, Zn2+ and Fe3+ on a salen-type Schiff base, 2,2'- [ethane-1,2-diylbis(nitrilomethylidyne)]bis(2-methylphenol), chemically immobilized on a highly crosslinked agarose support, were studied. Kinetic studies showed higher sorption rates of Cu2+ and Fe3+ in comparison with Zn2+. Half-times (t1/2) of 31, 106 and 58 s were obtained for sorption of Cu2+, Zn2+ and Fe3+ by the sorbent, respectively. Effects of pH, eluent concentration and volume, ionic strength, buffer concentration, sample volume and interferences on the recovery of the metal ions were investigated. A 5-ml portion of 0.4 M HCl solution was sufficient for quantitative elution of the metal ions from 0.5 ml of the sorbent packed in a 6.5 mm i.d. glass column. Quantitative recoveries were obtained in a pH range 5.5-6.5 for all the analytes. The volumes to be concentrated exceeding 500 ml, ionic strengths as high as 0.5 mol l-1, and acetate buffer concentrations up to 0.3 mol l-1 for Zn2+ and 0.4 mol l-1 for Cu2+ and Fe3+ did not have any significant effect on the recoveries. The system tolerated relatively high concentrations of diverse ions. Preconcentration factors up to 100 and detection limits of 0.31, 0.16 and 1.73 μg l-1 were obtained for Cu2+, Zn2+ and Fe3+, respectively, for their determination by a flame AAS instrument. The method was successfully applied to the metal ion determinations in several river water samples with good accuracy.

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