Silk fibroin fiber

Arai, T., Freddi, G., Innocenti, R., and Tsukada, M. "Biodegradation of Bombyx mori silk fibroin fibers and films".. Appl. Polym. Sci. 91(4), 2383-2390 (2004). 

Lock, R.L."Process for Making Silk Fibroin Fibers". US 5171505 [P] (1992). 

Matsumoto, K., Uejima, H., Iwasaki, T., Sano, Y., and Sumino, H. "Studies on regenerated protein fibers 3. Production of regenerated silk fibroin fiber by the self-dialyzing wet spinning method". J. Appl. Polym. Sci. 60(4), 503-511 (1996). 

Meechaisue, C., Wutticharoenmongkol, P., Waraput, R., Huangjing, T., Ketbumrung, N., Pavasant, P., and Supaphol, P. "Preparation of electrospun silk fibroin fiber mats as bone scaffolds A preliminary study". Biomed. Mater. 2(3), 181-188 (2007). 

Wang, H., Shao, H.L., and Hu, X.C. "Structure of silk fibroin fibers made by an electrospinning process from a silk fibroin aqueous solution". J. Appl. Polym. Sci. 101(2), 961-968 (2006). 

Li et al. [83] fabricated silk fibroin fiber scaffolds containing bone morphogenetic protein 2 (BMP-2) and/or nanoparticles of hydroxyapatite (nHAp) by electrospinning. These scaffolds were used in vitro to study bone formation from hMSCs. The results showed that the incorporation of BMP-2 and/or nHAp into silk... 

To extract information on molecular orientation distribution from experimental data, the most widely known technique, the Legendre moment expansion approach can be taken. In this section, this approach will be discussed first, followed by methods to elucidate atomic resolution details of the structures of ordered polymers with orientation-dependent NMR interactions, such as those from chemical shielding, dipole-dipole and quadrupolar coupling. Then, solid-state NMR studies of the torsion angles of the peptide backbone of highly ordered silk fibroin fiber, a protein that has been studied extensively as a model for fibrous proteins, will be described. 

Fig. 8.5. Solid-state N NMR spectra obtained from the oriented [ N]Gly silk fibroin fiber sample. Spectra were observed with the fiber axis both (A) parallel and (B) perpendicular to the magnetic field. The best-fit simulated line shapes are superimposed on the experimental spectra. Parameters for spectral simulation were found from error analysis as a function of ap and Pf(C).

Figure 8.8 shows the solid-state NMR spectra (solid line) obtained from blocks of oriented natural abundance silk fibroin fiber, Poly(p-pheny-... 

Fig. 23.8. Solid-state C NMR spectra of an oriented block of [T CJGly silk fibroin fibers as a function of the angles between the oriented fiber axis and Bo-...

Fujiwara et al. [69] applied solid-state NMR to a structural study on oriented [l- C]Ala silk fibroin fiber from B. mori. They found that the Euler angles obtained from the simulated lineshapes of the Ala carbonyl group are slightly different from that of a typical anti parallel j8-sheet, [30] raising questions concerning the accuracy of the current models for silk II structure. However, our data are in agreement with the X-ray diffraction model within experimental error. 

In order to use solid-state NMR for atomic coordinate determinations, the angle of the C H bond vector relative to the fiber axis was determined for [2,2- H2]Gly and [3,3,3- H3]Ala labeled silk fibroin fibers from B. mori with quadrupole echo NMR spectroscopy [65]. This structural information... 

Fig. 23.9. (A) quadrupole echo spectrum of (A) an oriented block and (B) unaligned silk fibroin fiber of [2,2- H2]Gly-labeled samples.

Figure 23.9(A) shows the quadrupole echo spectrum of an oriented block of [2,2- H2]Gly labeled silk fibroin fibers when the fiber axis was set parallel to the magnetic field direction. The quadrupole echo spectrum, Fig. 23.9(B), of unaligned [2,2- H2]Gly labeled silk fibroin fiber is also observed as a powder pattern. Both spectra are split into doublets, which give the value of the quadrupole splitting, Avq as 117.8 kHz for the [2,2- H2]Gly site the values are the same in each case. The full rigid-lattice width of about 126 kHz should be observed when the motion is frozen [72]. Thus, it is concluded that the motion of the methylene groups of the Gly residue is almost frozen at room temperature, which is in agreement with the prediction from the intermolecular hydrogen bonding network in the silk fibroin backbone chain with an antiparallel /3-sheet conformation.

The quadrupole splitting, Ai q of 117.8 kHz observed for the oriented block of [2,2- H2]Gly labeled silk fibroin fiber is the same as the value in the spectrum of an unaligned sample as shown in Fig. 23.9(B). Therefore, if the latter quadrupole splitting is used to provide a value of the proportionality constant, (3/4)e qQ/h, which describes the relationship between the quadrupole splitting and the angle CD (the angle of the C H bond vector of Gly relative to the fiber axis) > CD is calculated as 90°. By taking into account an... 

The solid-state NMR spectrum of an oriented block of the [3,3,3- HsjAla labeled silk fibroin fiber was also observed. The quadrupole splitting, Avq, is 39.8 kHz and is the same as the value in the spectrum of the unaligned sample. This is the same as the case of the [2,2- H2]Gly labeled silk fibroin fiber. The smaller value of the quadrupole splitting for the Ala site indicates the presence of three-fold fast rotation about the Ca-C/3 axis [50, 72]. This... 

Fig. 23.10. Experimental and calculated solid-state NMR spectra of an ordered block of [2,2- H2]Gly-labeled silk fibroin fibers as a function of the angle between the fiber axis and Bq.

A restricted (<, ifi) region for Gly in the Ramachandran map (-180° > 0°, 0° > i/r> 180°) was obtained as the overlap of each region obtained experimentally from the NH, NC, CN, and CO bond orientations as described above. The quadrupole echo spectrum of the oriented [2,2- HaJGly labeled silk fibroin fiber yields an angle, 0 = 90 2°, for the C H2 bond vector of Gly residue relative to the fiber axis. A further narrow... 

Dynamic NMR studies of the silk fibroin from silkworms have been reviewed. The chain dynamics of B. ntori and S.c. ricini silk fibroins in aqueous solution were studied to determine the relaxation parameters spin-lattice relaxation time, nuclear Overhauser enhancement and line width. - C NMR observations were also made to study the chain dynamics of silk fibroin stored in the silk gland of living silkworms. The chain dynamics of the B. mori and S.c. ricini silk fibroin fiber were studied with "H and C solid-state NMR. The solid-state NMR spectra of S.c. ricini silk fibroins showed a gradual and monotonic slowdown of the overall molecular motions leading to molecular aggregation. The chain dynamics of silk fibroin absorbed solvent were detected by H and C solid-state NMR methods, and also using an NMR imaging method. ESR approaches were applied to the dynamic studies of Tyr side-chain in the silk fibroin. 

Fig. 5. C CP/MAS NMR spectra of B. rnori (a) and S.c. ricini (b) silk fibroin fibers in the solid state.

Fig. 10. Temperature dependence of H spin-lattice relaxation times, T of B. mori silk fibroin fiber, film, powder, and the cry,stalline fraction powder, in a dry system.

Fig. 13. Observed (a) and simulated (b) -H NMR powder pattern of l2,2- H2jGly labeled silk fibroin fiber from S, mori.

Dynamic of [2,2- H2]Gly residue of B. mori silk fibroin fiber were analyzed from solid state NMR powder pattern as shown in Fig. 13. 

A H NMR study of [3,3,3- H3]Ala labeled B. mori silk fibroin fiber has been carried out by Asakura et al. and Fig. 14 shows the H NMR powder pattern of [3,3,3- H3 Ala labeled B. mori silk fibroin. 

Chutipakdeevong, J., Ruktanonchai, U.R., and Supaphol, P. (2013) Process optimization of electrospun silk fibroin fiber mat for accelerated wound healing. J. Appl Polym. Sci., 130, 3634-3644. 

Nakazawa Y, Sato M, Takahashi R, Aytemiz D, Takabayashi C, Tamura T, Enomoto S, Sata M, Asakura T. Development of small diameter vascular grafts based on silk fibroin fibers from Bombyx mori for vascular regeneration. J. Biomat. Set Polym. Ed. 22 195-206,2011. 

Zhang, F., Lu, Q., Yue, X., Zuo, B., Qin, M., Li, F., Kaplan, D.L., Zhang, X., 2015. Regeneration of high-quality silk fibroin fiber by wet spinning from CaCl2-formic acid solvent. Acta Biomaterialia 12, 139—145. 

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