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.

scholarly journals Fractionation of Regenerated Silk Fibroin and Characterization of the Fractions

Molecules ◽  
2021 ◽  
Vol 26 (20) ◽  
pp. 6317
Author(s):  
Masaaki Aoki ◽  
Yu Masuda ◽  
Kota Ishikawa ◽  
Yasushi Tamada
Keyword(s):  
Mechanical Properties ◽  
Secondary Structure ◽  
Silk Fibroin ◽  
Gel Permeation Chromatography ◽  
Precipitation Process ◽  
Regenerated Silk Fibroin ◽  
Sds Page ◽  
Fractionation Method ◽  
Nonwoven Mats

The molecular weight (MW) of regenerated silk fibroin (RSF) decreases during degumming and dissolving processes. Although MW and the MW distribution generally affect polymer material processability and properties, few reports have described studies examining the influences of MW and the distribution on silk fibroin (SF) material. To prepare different MW SF fractions, the appropriate conditions for fractionation of RSF by ammonium sulfate (AS) precipitation process were investigated. The MW and the distribution of each fraction were found using gel permeation chromatography (GPC) and SDS-polyacrylamide electrophoresis (SDS-PAGE). After films of the fractionated SFs formed, the secondary structure, surface properties, and cell proliferation of films were evaluated. Nanofiber nonwoven mats and 3D porous sponges were fabricated using the fractionated SF aqueous solution. Then, their structures and mechanical properties were analyzed. The results showed AS precipitation using a dialysis membrane at low temperature to be a suitable fractionation method for RSF. Moreover, MW affects the nanofiber and sponge morphology and mechanical properties, although no influence of MW was observed on the secondary structure or crystallinity of the fabricated materials.

Nanofibrous Membrane of Silk Fibroin/Cellulose Acetate Blend for Heavy Metal Ion Adsorption

2010 ◽  
Vol 148-149 ◽  
pp. 1431-1435 ◽  
Author(s):  
Wei Tao Zhou ◽  
Jian Xin He ◽  
Shi Zhong Cui ◽  
Wei Dong Gao
Keyword(s):  
Heavy Metal ◽  
Metal Ions ◽  
Cellulose Acetate ◽  
Silk Fibroin ◽  
Metal Ion ◽  
Nanofibrous Membrane ◽  
Heavy Metal Ion ◽  
Ion Adsorption ◽  
Metal Ion Adsorption ◽  
Nanofibrous Membranes

Silk fibroin/cellulose acetate blend Nanofibrous membranes were prepared by electro- spinning and their performances were evaluated as a heavy metal ion adsorbent. The electrospun nanofibrous membranes were comprised of randomly oriented ultra-fine fibers of 100-600nm diameters. As a result of field emission electron microscope (FEEM), compared with pure nanofibrous membranes, the anti-felting shrinkage of SF/CA blend nanofibrous membranes with 20% CA content was markedly improved after treatment with 100% ethanol. Metal ion adsorption test was performed with Cu2+ as a model heavy metal ion in a stock solution. The pure SF nanofibrous membranes exhibited high metal ion capacities compared with that pure CA nanofibrous membrane. Especially, the SF/CA blend nanofibrous membranes had an exceptional performance for the adsorption of metal ions, and the maximum milligrams per gram of metal ions adsorbed reached 22.8mg/g for Cu2+. This indicated that SF and CA had synergetic effect.

scholarly journals Effect of pH on the Conformational Transition of Silk Fibroin in Aqueous Solution Monitored by Thioflavin-T Fluorescence

2021 ◽  
Author(s):  
Ben Jia ◽  
Lan Jia ◽  
Jingxin Zhu
Keyword(s):  
Aqueous Solution ◽  
Secondary Structure ◽  
Silk Fibroin ◽  
Conformational Transition ◽  
Thioflavin T ◽  
Random Coil ◽  
Fluorescence Dye ◽  
Assembly Behavior ◽  
Β Sheet

Abstract In this work, the potential application of the fluorescence dye Thioflavin-T (ThT), which can specifically bind to amyloid, as a powerful tool for monitoring secondary structure transitions of silk fibroin (SF) induced by pH was examined. Results showed that ThT emission intensities substantially increased when pH decreased from 6.8 to 4.8. This increase may be due to conformational transitions from random coil to β-sheet. The morphology and secondary structure of SF were also investigated via TEM, AFM and circular dichroism spectroscopy. The information obtained herein can be utilized not only for the development of convenient and efficient noninvasive method for monitoring the assembly behavior of SF in aqueous solution but also for in vitro fluorescence imaging.

Silk fabric protection obtained via chemical conjugation of transglutaminase and silk fibroin reinforcement

2019 ◽  
Vol 89 (21-22) ◽  
pp. 4581-4594 ◽  
Author(s):  
Suhua Zhao ◽  
Hongliang Pan ◽  
Yali Liu ◽  
Yirong Zeng ◽  
Hongling Liu ◽  
...  
Keyword(s):  
Mechanical Properties ◽  
Secondary Structure ◽  
Silk Fibroin ◽  
Self Assembly ◽  
Sodium Caseinate ◽  
Solution Concentration ◽  
Breaking Stress ◽  
Silk Fabric ◽  
Chemical Conjugation ◽  
Washing Durability

Historic silk fabric is an important part of Chinese precious cultural heritage and its protection has always been a major challenge. This paper proposes a bio-safety method by the chemical conjugation of transglutaminase (TGase or TG) and sodium caseinate (SC), which produced a macromolecular polymer between protein molecules and enhanced silk fabrics. The changes of the mechanical properties of the reinforced silk fabric after washing by 10 cycles were not obvious, indicating good washing durability. After TGase and SC reinforcement, the silk fibroin (SF) solution was sprayed on the surface of silk fabric to improve the mechanical properties, where the secondary structure were formed by the self-assembly of SF to improve the mechanical properties. Therefore, the breaking stress attained the maximum value when the SF solution concentration was 1.0%. Meanwhile, the breaking stress increased by about 20.89% compared with untreated silk fabric. When the artificially alkali aged silk fabric is reinforced, the breaking stress and strain of the reinforced sample increased by 37.77% relative to the alkali aged fabric. The surface morphology and secondary structure transformation of the samples were also analyzed by scanning electron microscopy and Fourier transform infrared spectroscopy, respectively. The results indicated that a significant SF layer was introduced on the surface of the silk fabric and the β-sheet structure increased due to the synergetic role of the macromolecular polymer and SF. Moreover, it is concluded that an increase in temperature and humidity will result in a decrease in the preservation index, which caused the degradation of silk fabric and proved that the preservation time of the reinforced silk fabric in the same environment was longer than that of the unreinforced sample. The biological enzyme chemical conjugation with silk fabric and physical combination of the pure SF solution is expected to be applied to the protection and enhancement of silk cultural relics.

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.

A pseudo threefold helical structure found in silk Langmuir-Blodgett films by electron diffraction

1993 ◽  
Vol 51 ◽  
pp. 1216-1217
Author(s):  
Weiping Zhang ◽  
Samual P. Gido ◽  
Wayne S. Muller ◽  
Stephen A. Fossey ◽  
David L. Kaplan
Keyword(s):  
Protein Structure ◽  
Silk Fibroin ◽  
High Performance ◽  
Helical Structure ◽  
Silk Gland ◽  
Fiber Spinning ◽  
Silk Fiber ◽  
Helical Chain ◽  
Langmuir Blodgett ◽  
Β Sheet

The high performance tensile properties of silkworm (Bombyx mori) silk fiber has resulted in a long standing interest in the semicrystalline morphology of this material. The properties of silk fiber depend not only on the chemical composition (primary protein structure) but also on the fiber spinning conditions present in the silk gland which induce the formation of a (β-sheet based crystalline morphology (secondary protein structure). Knowledge of the silk structure is essential for understanding how the natural spinning processes results in such excellent material properties, but surprisingly few experimental results are available concerning the detailed structures of silk proteins. Two β-sheet based silk fibroin crystalline structures (e.g. silk I and silk II) have been studied by many authors, but the silk I structure remains largely uncharacterized. Here we report results from thin silk films prepared by the Langmuir-Blodgett (LB) technique which display a new silk fibroin structure with a threefold helical chain conformation.

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 The nature of the slow metal ion-dependent conformational transition in bovine prothrombin

1979 ◽  
Vol 183 (3) ◽  
pp. 513-517 ◽  
Author(s):  
H C Marsh ◽  
M E Scott ◽  
R G Hiskey ◽  
K A Koehler
Keyword(s):  
Fluorescence Quenching ◽  
Metal Ions ◽  
Kinetic Parameters ◽  
Equilibrium Constant ◽  
Rate Constants ◽  
Metal Ion ◽  
Conformational Transition ◽  
The Other ◽  
Proline Residue ◽  
Structural Isomerization

Kinetic parameters characterizing the slow structural isomerization observed via metal ion-dependent intrinsic fluorescence quenching of bovine prothrombin Fragment 1 have been determined. From forward and reverse rate constants, an equilibrium constant of approx. 0.25 is calculated. This result is consistent with the hypothesis that there exists, in the absence of metal ions, an equilibrium between two forms of bovine Fragment 1, one of which can interact rapidly with Ca2+ and subsequently with phospholipid. The other form of Fragment 1 cannot interact with Ca2+ in a manner that yields a phospholipid-binding form of the protein. Interconversion of these two forms of Fragment 1 occurs and may involve the isomerization of a proline residue.

scholarly journals Tunable Structures and Properties of Electrospun Regenerated Silk Fibroin Mats Annealed in Water Vapor at Different Times and Temperatures

2014 ◽  
Vol 2014 ◽  
pp. 1-7 ◽  
Author(s):  
Xiangyu Huang ◽  
Suna Fan ◽  
Alhadi Ibrahim Mohammed Altayp ◽  
Yaopeng Zhang ◽  
Huili Shao ◽  
...  
Keyword(s):  
Mechanical Properties ◽  
Water Vapor ◽  
Silk Fibroin ◽  
Conformational Transition ◽  
Breaking Strength ◽  
Electrospinning Technique ◽  
Structures And Properties ◽  
Regenerated Silk Fibroin ◽  
Vapor Annealing ◽  
Breaking Energy

Regenerated silk fibroin (SF) mats were fabricated using electrospinning technique, followed by mild water vapor annealing to effectively tune the structures and improve the mechanical properties of the mats at different annealing times and temperatures. The breaking strength and the breaking energy of the mats treated with water vapor at 65°C for 12 h reached 6.0 MPa and 171.7 J/kg, respectively. The conformational transition of the SF mats was significantly influenced by the treating temperature, while the influence of time was comparatively limited. The influence is consistent with the time-temperature equivalent principle and would be helpful for the preparation of water-vapor-annealed silk-based biomaterials for various applications.

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