Molecular weight of silk fibroin

Hyde, A. J.; Wippler, C.

doi:10.1002/pol.1962.1205816667

Cited by 20 publications

(11 citation statements)

References 10 publications

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“…The relatively high chain length of the phase III fragments that have now been isolated (about 230 residues), considered with the fact that this phase represents only about nine amino acid residues/100 residues in fibroin, suggests that if the fibroin molecule is a unique entity it contains more than 2000 residues and thus must have a molecular weight in excess of 170 000. Recent evidence accords with the view that the molecular weight of fibroin is very high; ultracentrifuge studies by Prati, Moruzzi & Centola (1958), with a solution of fibroin in aqueous lithium bromide, afforded a value 270000, and light-scattering experiments gave values around 300000 (Hyde & Wippler, 1962). Moreover the end-group estimations quoted in Table 2 of this paper imply a mean chain weight of about 120000 (taking 78 as the mean residue weight); consequently, if a four-chain molecule with terminal alanine, aspartic acid, glycine and serine residues is postulated, a molecular weight of at least 400000 must be envisaged for fibroin.…”

Section: Discussionsupporting

confidence: 67%

Fractionation of the fibroin of Bombyx mori with alkali

Shaw¹

1964

Biochemical Journal

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not at present much information concerning the effect of limited attack by alkali upon fibroin, or indeed upon proteins in general, and it seemed worthwhile to investigate the situation more fully. MATERIALS AND METHODS Bombyx mori silk fibroin. Japanese B. mori silk was purchased from H. T. Gaddum and Co. Ltd., Manchester, and was degummed as described by Drucker, Hainsworth & Smith (1953). Solutions were prepared by dissolving the fibroin in aq. 60% (w/v) LiSCN (1 g. in 5 ml.), diluting with water to 50 ml. and dialysing the solution in Visking II in. cellophan dialysis tubing against a stream of water until free from SCNions. Chemicals. 6,9-Diamino-2-ethoxyacridine lactate was a commercial sample purporting to be of not less than 97 % purity, purchased from the Aldrich Chemical Co. Inc., Milwaukee 10, Wis., U.S.A. I-Fluoro-2,4-dinitrobenzene was also a commercial preparation, obtained from L. Light and Co. Ltd., Colnbrook, Bucks. Other chemicals were of analytical reagent grade. Alkali-treatment. Solutions of fibroin containing about 2 % (w/v) of protein were diluted with N-NaOH and with water so that they were 1 % in protein and 0-1 N in NaOH. The pH of such solutions was found to be 12-8. In most of the experiments described in this paper the solutions were kept at 30 in a refrigerator, and were then brought to pH 6-2 by the addition of N-phosphoric acid. Such a preparation resulting from an alkali-treatment lasting 48 hr. is subsequently referred to as a solution of A-fibroin (Gk. Au'etv, to loose). Similar experiments were performed in which the solution at pH 12-8 was maintained at 250. Solutions at pH 110, 11-5, 12-0 and 12-5 were also prepared from 2 % solutions of fibroin in water by the addition of equal volumes of an appropriate sodium borate buffer, 0-2M in Na+ ions: the pH values were finally adjusted by the addition of a few drops of N-NaOH or m-boric acid. The solution at pH 13-0 was obtained by the cautious addition of N-NaOH to the standard pH 12-8 solution described above.

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Section: Discussionsupporting

confidence: 67%

Fractionation of the fibroin of Bombyx mori with alkali

Shaw¹

1964

Biochemical Journal

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“…The plot was fitted by a polynomial to obtain the intercept at zero angle and the slope at zero angle as well. In this study, the fit was of the fifth order, as there was highly pronounced curvature on Debye's plot, which is assigned to find the presence of aggregates [37][38][39]. This curvature was presented independently of the fitting model used (comparison presented on Berry's model, which is suitable for large molecules, too).…”

Section: Chromatographic Resultsmentioning

confidence: 99%

Size exclusion chromatography for analyses of fibroin in silk: optimization of sampling and separation conditions

et al. 2013

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A direct goal of this paper was to improve the methods of sample preparation and separation for analyses of fibroin polypeptide with the use of size exclusion chromatography (SEC). The motivation for the study arises from our interest in natural polymers included in historic textile and paper artifacts, and is a logical response to the urgent need for developing rationale-based methods for materials conservation. The first step is to develop a reliable analytical tool which would give insight into fibroin structure and its changes caused by both natural and artificial ageing. To investigate the influence of preparation conditions, two sets of artificially aged samples were prepared (with and without NaCl in sample solution) and measured by the means of SEC with multi angle laser light scattering detector. It was shown that dialysis of fibroin dissolved in LiBr solution allows removal of the salt which destroys stacks chromatographic columns and prevents reproducible analyses. Salt rich (NaCl) water solutions of fibroin improved the quality of chromatograms. Abbreviations A 2 Second virial coefficient in Rayleigh equation c Concentration of a solution, mg/ml k Wavelength of incidental beam (in vacuum), nm M w Weight average molar mass, derived from Rayleigh equation, g/mol n 0 Refractive index of a solvent N A Avogadro constant dn/dc Refractive index increment P(h) Form factor in Rayleigh equation R(h) Excess Rayleigh ratio, the difference between Rayleigh ratio for a solution and a pure solvent g Branching ratio R 2 lin Mean square radius of linear sample R 2 br

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“…2% (wt/v) was prepared for the thin-fi lm deposition in accordance with the published procedure. [ 21 ] Cocoons of Bombyx mori were boiled for 20 min in an aqueous solution of 0.5% Na 2 CO 3 , and then rinsed with deionized water to extract the glue-like sericin proteins. The leftover silk fi broin was dissolved in 85% phosphoric acid at 60 ° C for 1 h, yielding a 50% (wt/v) solution.…”

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Flexible Organic Thin‐Film Transistors with Silk Fibroin as the Gate Dielectric

2011

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Organic thin-fi lm transistors (OTFTs) are promising components for fl exible and portable electronics, such as e-paper, [1][2][3] radio-frequency identifi cation (RFID) tags, [ 4,5 ] and biosensors. [ 6,7 ] OTFTs usually exhibit very low switching speed and are diffi cult to use instead of inorganic thin-fi lm transistors (TFTs), although they possess the merits of fl exibility and low cost. Several challenges for OTFTs of large area are high fi eld-effect mobility ( μ FE ), low operating voltage, and solution processing. The μ FE value and operating voltage of pentacene OTFTs strongly depend on the gate dielectric material. [8][9][10] Pentacene is usually deposited on various organic and inorganic dielectrics, such as poly(methyl methacrylate) (PMMA), poly(vinyl pyrrolidone) (PVP), SiO 2 , and AlN, using the bottom gate OTFT confi guration. [11][12][13] The reported μ FE values are in the range of 0.5-4 cm 2 V − 1 s − 1 and the operating voltages vary from -5 to -40 V. The low μ FE values are mainly limited by the quality of pentacene and the interface scattering in OTFTs. Many attempts have been made to improve the μ FE value by modifying the surface of the gate dielectric. The maximum μ FE value has been improved to ca. 6 cm 2 V − 1 s − 1 . [ 14 ] In 2004, Hosono's group reported a μ FE value larger than 10 cm 2 V − 1 s − 1 for amorphous InGaO 3 (ZnO) 5 (a-IGZO) TFTs. [ 15 ] The μ FE value is much higher than that of pentacene OTFTs. The research in fl exible electronics has focused on a-IGZO TFTs since then, especially in the fi eld of organic light emitting diodes (OLEDs). However, the fl exibility of amorphous semiconducting oxide TFTs is lower than OTFTs. An urgent requirement of fl exible electronics is to fi nd fl exible materials able to improve greatly the μ FE value of OTFTs.Here we present a pentacene OTFT made on a fl exible poly(ethylene terephthalate) (PET) plastic substrate with a very high μ FE value of 23.2 cm 2 V − 1 s − 1 in the saturation regime and a low operating voltage of -3 V. Silk fi broin was chosen as the gate dielectric and fabricated in thin fi lm form by a low-cost solution process at room temperature. The device performance is so high that the pentacene OTFTs outperform a-IGZO TFTs.Silk fi broin is one of the silk proteins emitted by the silkworm; silk fi broin forms the structural center of silk and sericin surrounds it. Silk fi broin is a natural biopolymer consisting of the repeated amino acid sequence of alternating Gly and Ala [ 16 ] ( Figure 1 a). The silk fi broin thin fi lm in our work is amorphous and its secondary structure is characterized by the Fourier transform infrared-attenuated total refl ection (FTIR-ATR) spectrum in Figure 1 b. The silk fi broin thin fi lm consists of turn (ca. 1666, ca. 1678, ca. 1690 cm − 1 ), random-coil (ca. 1642, ca. 1651 cm − 1 ), α -helix (ca. 1659 cm − 1 ), and hydrogen-bonded C = O (ca. 1704 cm − 1 ) according to the curve-fi tting results based on previously published FTIR-ATR data. [ 17 ] Silk fi broin has been used as a material fo...

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Molecular weight of silk fibroin

Cited by 20 publications

References 10 publications

Fractionation of the fibroin of Bombyx mori with alkali

Fractionation of the fibroin of Bombyx mori with alkali

Size exclusion chromatography for analyses of fibroin in silk: optimization of sampling and separation conditions

Flexible Organic Thin‐Film Transistors with Silk Fibroin as the Gate Dielectric

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