scholarly journals Structure Water-Solubility Relationship in α-Helix-Rich Films Cast from Aqueous and 1,1,1,3,3,3-Hexafluoro-2-Propanol Solutions of S. c. ricini Silk Fibroin

Molecules ◽  
2019 ◽  
Vol 24 (21) ◽  
pp. 3945
Author(s):  
Moseti ◽  
Yoshioka ◽  
Kameda ◽  
Nakazawa
Keyword(s):  
Silk Fibroin ◽  
Water Solubility ◽  
Silk Gland ◽  
Post Treatment ◽  
Water Soluble ◽  
Cast Film ◽  
Silk Glands ◽  
Α Helix ◽  
Β Sheet ◽  
Structure Water

Silk fibroin (SF) produced by the domesticated wild silkworm, Samia cynthia ricini (S. c. ricini) is attracting increasing interest owing to its unique mechanical properties, biocompatibility, and abundance in nature. However, its utilization is limited, largely due to lack of appropriate processing strategies. Various strategies have been assessed to regenerate cocoon SF, as well as the use of aqueous liquid fibroin (LFaq) prepared by dissolution of silk dope obtained from the silk glands of mature silkworm larvae in water. However, films cast from these fibroin solutions in water or organic solvents are often water-soluble and require post-treatment to render them water-stable. Here, we present a strategy for fabrication of water-stable films from S. c. ricini silk gland fibroin (SGF) without post-treatment. Aqueous ethanol induced gelation of fibroin in the posterior silk glands (PSG), enabling its separation from the rest of the silk gland. When dissolved in 1,1,1,3,3,3-hexafluoro-2-propanol (HFIP), the SGF-gel gave a solution from which a transparent, flexible, and water-insoluble film (SGFHFIP) was cast. Detailed structural characterization of the SGFHFIP as-cast film was carried out and compared to a conventional, water-soluble film cast from LFaq. FTIR and 13C solid-state NMR analyses revealed both cast films to be α-helix-rich. However, gelation of SGF induced by the 40%-EtOH-treatment resulted in an imperfect β-sheet structure. As a result, the SGF-gel was soluble in HFIP, but some β-sheet structural memory remains, and the SGFHFIP as-cast film obtained has some β-sheet content which renders it water-resistant. These results reveal a structure water-solubility relationship in S. c. ricini SF films that may offer useful insights towards tunable fabrication of novel biomaterials. A plausible model of the mechanism that leads to the difference in water resistance of the two kinds of α-helix-rich films is proposed.

scholarly journals Effects of Chemical Post-treatments on Structural and Physicochemical Properties of Silk Fibroin Films Obtained From Silk Fibrous Waste

2020 ◽  
Vol 8 ◽  
Author(s):  
Melissa Puerta ◽  
Maria S. Peresin ◽  
Adriana Restrepo-Osorio
Keyword(s):  
Thermal Stability ◽  
Silk Fibroin ◽  
Water Solubility ◽  
Aqueous Media ◽  
Post Treatment ◽  
Water Soluble ◽  
Added Value ◽  
Degree Of Crystallinity ◽  
Crystalline Structures ◽  
Amorphous Structures

Silk fibroin (SF) is a protein polymer claimed to have outstanding potential for medical applications. However, because of the manufacturing process, materials from regenerated SF exhibit a higher percentage of amorphous structures. The amorphous structures cause the material to be water soluble and can significantly limit its applications in wet biological environments. In order to increase the amount of crystalline structures and decrease the water solubility of SF materials, post-treatment with alcohols is usually employed. SF can be obtained from silk fibrous wastes (SFW), usually discarded in silk textile processes. This represents an opportunity to produce materials with high added value from low-cost natural sources. In this study, SF was obtained from SFW, and films were made thereof followed by a post-treatment by immersion or in a saturated atmosphere of methanol (MeOH) or ethanol (EtOH), using different exposure times. The resulting films were analyzed according to crystallinity, the percentage of crystalline and amorphous structures, and thermal stability. Also, water absorption and weight loss in aqueous media were determined. The results showed a significant increase in crystalline structures in all treated samples, varying according to the type and time of exposure to post-treatment conducted. The highest increase was shown in the case of the post-treatment by immersion in MeOH for 1 h, with a 23% increase over the untreated sample. This increase in crystallinity was reflected in an increase in the degradation temperature and a degradation rate of 5.3% on day 7. The possibility of tuning the degree of crystallinity, as well as thermal stability and aqueous integrity of thin films of SFW, can be applied to adjust these materials to the requirements of specific biomedical applications.

scholarly journals Structural and characterization studies of insoluble thai bombyx mori silk fibroin films

2019 ◽  
Vol 15 (1) ◽  
pp. 18-22 ◽  
Author(s):  
Noor Izyan Syazana Mohd Yusoff ◽  
Mat Uzir Wahit ◽  
Juhana Jaafar ◽  
Tuck-Whye Wong
Keyword(s):  
Bombyx Mori ◽  
Silk Fibroin ◽  
Protein Structures ◽  
Xrd Analysis ◽  
Post Treatment ◽  
Water Soluble ◽  
Stable Form ◽  
Structural Protein ◽  
Water Saturated ◽  
Β Sheet

Bombyx Mori fiber consists of two major proteins which are fibroin and sericin. The silk fibroin (SF) is the core structural protein of silk fiber. SF protein structures comprise of primary and secondary structures; where the primary structure contains series of amino acid and secondary structure with Silk I refers to the water-soluble and Silk II, high β sheet extent which is insoluble. This study was conducted to compare the structural and characterization of insoluble Thai Bombyx Mori SF with different types of post-treatement.  Thai silk cocoons, which were degummed and dissolved in 9.3 M LiBr solution at 60 °C. The obtained SF solutions were dialyzed and purified. SF films were prepared by solution casting and immersing in methanol and ethanol, followed by water annealing in water saturated  vacuum. Post-treatment was purposely done to regenerate and induce of the β sheet structure to enhance the insolubilities and the stabilities properties of the SF films. The SF films structural conformation, characterization and thermal stability were characterized. Attenuated total reflectance-Fourier transformed infrared spectroscopy (ATR-FTIR) showed that SF films were presented in a more stable form after ethanol post treatment, which also supporting by X-ray diffraction (XRD) analysis which indicated the tendency to higher structural organization.  Thermal analysis resutls showed that SF was thermally stable and improved after post treatment.  The contact angle of post treated SF increased the hydrophobicity of the  films. The  thai SF films could be the promising candidate for applications in tissue regeneration, optical devices, and flexible electronic displays with the possibility  to control the SF structure and properties.

EDC-Crosslinked Electrospun Silk-Fibroin Fiber Mats

2011 ◽  
Vol 175-176 ◽  
pp. 170-175 ◽  
Author(s):  
Rong Liu ◽  
Feng Zhang ◽  
Bao Qi Zuo ◽  
Huan Xiang Zhang
Keyword(s):  
Silk Fibroin ◽  
Rupture Strength ◽  
Mechanical Test ◽  
Crosslinking Agent ◽  
Water Soluble ◽  
Random Coil ◽  
Crosslinking Reaction ◽  
Elongation Ratio ◽  
Silk Fibroin Fiber ◽  
Α Helix

Electrospun Silk-Fibroin (SF) mats were fabricated by electrospinning with regenerated Bombyx mori silk-fibroin/formic acid solutions. After spinning, the water soluble and mechanical properties of pure fibroin nanofibers were poor. So electrospun SF mats were crosslinked with N-(3-dimethylaminopropyl)-N′-ethylcarbodiimide hydrochloride (EDC), a low cell cytotoxicity crosslinking agent, and N-hydroxysuccinimide (NHS), which can increase the reaction rate. The scanning electron microscope images indicated that the diameter of fibers increased with crosslinking reaction. When EDC/NHS reached to 7.5wt.%, the diameter of fibers achieved the maximum. The mechanical test showed that tensile strength enhanced after crosslinking with EDC/ NHS. While EDC/NHS reached to 7.5wt %, the rupture strength reached to (38.31±5.30) Mpa, and the breaking elongation ratio reached to (182.00±31.27) %. FTIR results showed the the proportion of β-sheet increased while random coil and α-helix decreased after treatment.

Raman Spectroscopic Investigation of the Denaturation Process of Silk Fibroin

1989 ◽  
Vol 43 (7) ◽  
pp. 1269-1272 ◽  
Author(s):  
Siding Zheng ◽  
Guanxian Li ◽  
Wenhuo Yao ◽  
Tongyin Yu
Keyword(s):  
Raman Spectroscopy ◽  
Silk Fibroin ◽  
Conformational Transition ◽  
Transition Process ◽  
Random Coil ◽  
Helical Conformation ◽  
Extension Rate ◽  
Α Helix ◽  
Β Sheet ◽  
Denaturation Process

The mechanical denaturation process of silk fibroin is examined by Raman spectroscopy. The fresh silk fibroins from the middle gland of mature silkworms are drawn to various ratios on a tensile tester ( R = ldrawn/ linitial, where l is length) and their conformations are measured with Raman spectroscopy. Undrawn silk fibroin is mainly in the random coil structure with some α-helical conformation, the characteristic bands appearing at 1252 and 1660 (random coil) and at 942, 1106, and 1270 cm−1 (α-helix). When the samples are drawn up to R = 4 at an extension rate of 500 mm/min, two peaks at 1233 cm−1 (the amide III band) and 1085 cm−1 appear; it is shown that the β-sheet conformation is then formed. With an increase in drawing ratios, the intensities of these β-sheet bands increase and those of the random coil and α-helical bands decrease gradually. These changes indicate that, under the action of stress, the conformation of fibroin is altered from random coil and α-helix to β-sheet structures. This result is quite similar to the results achieved by the spinning of the silkworm. The effect of the water content in liquid silk on this conformational transition process is revealed and discussed.

Enhanced mechanical performance of biocompatible silk fibroin films through mesoscopic construction of hierarchical structures

2020 ◽  
pp. 004051752097562
Author(s):  
Yifan Zhang ◽  
Ronghui Wu ◽  
Aniruddha Patil ◽  
Liyun Ma ◽  
Rui Yu ◽  
...  
Keyword(s):  
Silk Fibroin ◽  
Mechanical Performance ◽  
Hierarchical Structures ◽  
Rheological Measurement ◽  
Mesoscopic Structure ◽  
Flexible Protein ◽  
Α Helix ◽  
Β Sheet ◽  
Structure Properties

Silk fibroin (SF) material receives a great deal of attention in the biomedical field for its extensive mechanical performance and applications due to its singular structure/properties and applications, especially hierarchical structure. Here, we blended polyethylene glycol (PEG) into SF solutions that reconstruct the hierarchical micro structure of SF. The effect of PEG on the SF gelation process was in situ observed through rheological measurement and optical density changes. The structural change of SF/PEG blended films with different concentrations and their effects on the mechanical performance were investigated. The results indicated that with increasing PEG content, the β-sheet content of the films increased with the α-helix declining, which enables a composite film with a fracture strain exceeding 300%, Young's modulus exceeding 200 MPa and a fracture strength exceeding 20 MPa. The culture of MC-3T3 proves that the film is beneficial for cell proliferation and adhesion. By constructing the mesoscopic structure of SF, the plasticized silk materials provide great options for biodegradable and flexible protein-based materials.

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.

Alpha and beta conformations of water soluble sequential iso polypeptides

1988 ◽  
Vol 53 (11) ◽  
pp. 2825-2832 ◽  
Author(s):  
Bernard Barbier ◽  
Margarita Perello ◽  
André Brack
Keyword(s):  
Circular Dichroism ◽  
Water Soluble ◽  
Helical Conformation ◽  
Molecular Weights ◽  
Helix Formation ◽  
Α Helix ◽  
Circular Dichroïsm ◽  
Β Sheet ◽  
Protected Peptides

Alternating poly(Leu-Lys) and its isopolypeptide poly(Leu-Lys-Lys-Leu) were synthesized via polycondensation of p-nitrophenyl esters of the corresponding protected peptides. Addition of one equivalent of 1-hydroxybenzotriazole and varying amounts of a tertiary base allowed to control the molecular weights of the samples. The conformation of the water soluble polypeptides was investigated by circular dichroism. Poly(Leu-Lys) adopts a β-sheet conformation in the presence of salt while poly(Leu-Lys-Lys-Leu) adopts an α-helical conformation. For polypeptides based on a 1 : 1 composition of hydrophobic (A) and hydrophilic (B) residues, the shortest repeat for the formation of a β-sheet is -AB- whereas -AABB- represents the shortest repeat for an α-helix formation.

Effect of Concentration on Structure and Properties of Concentrated Regenerated Silk Fibroin Solution

2011 ◽  
Vol 311-313 ◽  
pp. 1653-1656 ◽  
Author(s):  
Fang Xie ◽  
Hao Liang
Keyword(s):  
Silk Fibroin ◽  
Conformational Transition ◽  
Random Coil ◽  
Scanning Calorimetry ◽  
Regenerated Silk Fibroin ◽  
Lower Temperature ◽  
Α Helix ◽  
Β Sheet ◽  
Dsc Curves ◽  
Fibroin Solution

The thermal properties and rheological behavior of concentrated regenerated silk fibroin aqueous solution from 15% to 37% was investigated by differential scanning calorimetry (DSC) and rheometer. Also the conformation of solutions was characterized by Raman spectra. It was discovered that the major endothermic peak in the DSC curves shifted toward the lower temperature region with increasing the concentration. This behavior suggests increasing the concentration can accelerate conformational transition of silk fibroin from random coil and α-helix to β-sheet structure. In addition, it was found that the viscosity of solution increased with increasing concentration in favor of spinning.

Preparation of Water-Insoluble Antheraea Pernyi Silk Fibroin Films

2012 ◽  
Vol 569 ◽  
pp. 311-315 ◽  
Author(s):  
Shen Zhou Lu ◽  
Li Mao ◽  
Yu Liu ◽  
Shan Sun ◽  
Gui Jun Li
Keyword(s):  
Silk Fibroin ◽  
Diffraction Method ◽  
Random Coil ◽  
X Ray Diffraction ◽  
Antheraea Pernyi ◽  
Blend Film ◽  
Blend Films ◽  
Thiocyanate Solution ◽  
Α Helix ◽  
Β Sheet

Antheraea pernyi silk fibroin (ASF) solution was prepared by dissolving Antheraea pernyi silk fiber in lithium thiocyanate solution. The ASF/glycol blend films were prepared by casting aqueous solution of ASF mixed with glycol. The structure of blend film was investigated by the X-ray diffraction method and infrared spectroscopy. The result showed that the structure of regenerated ASF film was α-helix and random coil conformation. After mixing with glycol, it resulted in significant increase in β-sheet structure with the improvement of water resistance of the films. This effect was strongly dependent on glycol content in the blend film. When the glycol content was more than 45 wt%, the structure of ASF changed to β-sheet and the film became water-insoluble. The breaking strength and elongation of ASF/glycol blend film were 30 Mpa and 50 %, respectively. In summary, the ASF/glycol blend film provided a great potential as a biological material.

Effect of Different Post-Treatment on the Morphology, Structure and Property of Electrospun SF Nanofiber Mats

2012 ◽  
Vol 557-559 ◽  
pp. 607-610
Author(s):  
Tao Liu ◽  
Feng Zhang ◽  
Bao Qi Zuo
Keyword(s):  
Water Resistance ◽  
Post Treatment ◽  
Treatment System ◽  
Random Coil ◽  
Structure And Property ◽  
Before And After ◽  
Α Helix ◽  
Nanofiber Mats ◽  
Β Sheet ◽  
Conformation Transition

In this paper, we employed Methanol, 75% Ethanol, 100%Ethanol, and Isopropanol to treat electrospun SF nanofiber mats, and studied the morphology, structure and property of SF nanofiber before and after treatment by means of SEM, and FTIR. While the as-spun SF nanofiber mats consisted of α-helix and random coil, post-treatment of the SF nanofiber resulted in significant increase in β-sheet component and improvement of water resistance of the SF nanofiber mats. This effect was not obvious affected when different post-treatment system was used, but methanol and 75% was more effective in inducing conformation transition from α-helix and random coil to β-sheet.

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