Electron diffraction studies on Indian silk

Abstract

SynopsisThe lateral order factor of four Indian varieties of silk, viz., Mulberry, Tasar, Eri, and Muga, were determined by electron diffraction technique and compared with that determined by x-ray diffraction. The profiles of the 002 and 201 reflections in Mulberry were better resolved by the electron diffraction technique. INTRODUCTIONStructure investigation of silk fibroin has been carried out by many workers using different techniques such as x-ray diffraction,1,2 infrared spectroscopy,3 amino acid a n a l y~i s ,~ and electron microscopy.5.6 Detailed x-ray diffraction studies by Marsh et al.1.7 and Warwicker2 have established that fibroin has a parallel P-type structure. The unit cell proposed by these workers is orthorhombic. Magoshi et al.8.9 have studied the a-p transition of regenerated silk obtained from the glands of mature silkworms. Recently, studies have been made on synthetic poly(a-amino acids) using x-ray and electron diffraction techniqueslOJ1 to elucidate elaborately with models the structure of silk fibroin. However, electron diffraction has not been used extensively for structure investigation of the silk fibroin. In this paper, we report the electron diffraction results obtained for different varieties of Indian silk. EXPERIMENTAL MaterialsMulberry (Bombyx mori), Tasar or Tussah of India (Antheraea mylitta), Eri (Philosamia Cynthia ricini), and Muga (A. assamensis) silks were used for the studies. Mulberry silk yarn was degummed by treating with textile soap a t 100°C for 1 hr with a materia1:liquor ratio of 1:50. The sample was washed with hot and cold water and finally dried under vacuum. The wild silk yarns were degummed by treating with textile soap in the presence of washing soda (0.5 gh.) a t 100°C for 1 hr with a materiakliquor ratio of 1:50. The sample was rinsed with hot and cold water. The degumming was repeated.12 * Part of this work was presented a t the XIth Annual Conference of EMS1 held a t Madras, India, Equipment and ProcedureThe electron diffraction technique employed was essentially the same as that described by Paralikar and Betrabet.'" The silk filaments were thoroughly beaten in a high-speed laboratory blender. A drop of diluted slurry of silk fragment was placed on uncoated 400-mesh copper grid and dried at room temperature. A Hitachi HU 11E electron microscope was used. The experimental conditions were, in brief use of liquid nitrogen throughout the experiment to cool the specimen, accelerating potential of 75 kV with extremely lowbeam current, and exposure time of 5 sec. Before examining the silk specimen, a grid supporting thin film of A1 was inserted in the microscope and the microscope was preset in the diffraction mode and focused to get a sharp typical A1 pattern. This served two purposes. The camera constant could be determined and scanning of grids supporting silk specimen in the bright-field transmission mode was avoided, thereby minimizing to the utmost any degradation owing to the electron beam. Then grid supporting the A1 film was replaced by the grid su...

Effect of silk nano‐disc dispersion on mechanical, thermal, and barrier properties of poly(lactic acid) based bionanocomposites

“…X‐ray diffraction patterns along with characteristic lattice planes for Muga silk, fabricated CSNs, PLA, and PLA/CSN bionanocomposites with different CSN loadings are shown in Figure (f). Muga silk consists of both amorphous and crystalline parts of silk, the crystallinity value for Muga silk is about 57% which closely matched with the reported values of 60% . CSN show the presence of three distinct peaks at 16.8°, 20.2°, and 23.9° representing the orthorhombic β‐sheet crystal structure with (002), (201), and (003) lattice planes, respectively .…”

“…Muga silk consists of both amorphous and crystalline parts of silk, the crystallinity value for Muga silk is about 57% which closely matched with the reported values of 60% . CSN show the presence of three distinct peaks at 16.8°, 20.2°, and 23.9° representing the orthorhombic β‐sheet crystal structure with (002), (201), and (003) lattice planes, respectively . The diffraction patterns for the acid‐derivatized CSNs shows the presence of β‐sheet structure similar to initial fibroin precursor used (degummed muga fibers) suggesting that hydrolysis using different acids did not alter the inherent silk structure.…”

Investigation of amino acid composition in the crystalline region of silk fibroin

“…Silk yarn was degummed by the method described earlier. 5 The partial acid hydrolysis was carried out using hydrochloric acid of different concentration, as reported earlier. 6 The residue obtained after partial acid hydrolysis has been called as "hydrofibroin or hydrolysate.…”

Modification of Silk Yarn with β‐Cyclodextrin Nanoparticles: Preparation, Characterization, and Natural Dyeing Properties

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