Chemical and Physical Properties of Sulfated Silk Fabrics

Abstract

Silk fabrics were treated with chlorosulphonic acid in pyridine for different times. The amount of sulfur bound to silk increased during the first 2 h of reaction and then reached a plateau. The amino acidic pattern of sulfated silk remained essentially unchanged for short reaction times (< or =2 h). Longer reaction times resulted in drastic changes in the concentration of Asp, Glu, and Tyr. Surface morphology and texture of silk fabrics changed upon sulfation. Warp and weft yarns became progressively thinner, and deposits of foreign material appeared on the fiber surface. Changes were more evident at longer reaction times (> or =2 h). Spectroscopic analyses performed by FT-IR and FT-Raman showed the appearance of new bands attributable to various vibrations of sulfated groups. The IR bands at 1049 and 1014 cm-1, due to organic sulfate salts, were particularly intense. Bands assigned to alkyl sulfates and sulfonamides appeared in the 1300-1180 cm-1 range. Organic covalent sulfates displayed a weak but distinct IR band at 1385 cm-1. Both IR and Raman spectra revealed that silk fibroin mainly bound sulfates through the hydroxyl groups of Ser and Tyr, while involvement of amines could not be proved. Changes observed in the amide I and II range indicated an increase of the degree of molecular disorder of sulfated silk. Accordingly, the I850/I830 intensity ratio between the two Tyr bands at 850-830 cm-1 increased from 1.41 to 1.52, indicating a more exposed state of Tyr residues in sulfated silk. TGA, DSC, and TG analyses showed that sulfated silk attained a higher thermal stability. A thermal transition attributable to sulfated silk fibroin fractions appeared at about 260 degrees C in the DSC thermograms.

Spectroscopic Characteristics of Carbon Dots (C-Dots) Derived from Carbon Fibers and Conversion to Sulfur-Bridged C-Dots Nanosheets

“…5b, region E), which is assigned to the SO 2 asymmetrical stretching of covalent sulfonates. 30,[32][33][34] The spectra in Fig. 5 were normalized to the band around 1435 cm À1 (identified by an asterisk), which is present in all spectra and can be assigned to C=C bonding.…”

Quantification of perchloroethylene residues in dry‐cleaned fabrics

“…The latter seems unlikely. Raw silk fibers produced by the Bombyx mori silkworm are composed primarily of two proteins: an outer coating of sericin, and fibroin [25]. The former has adherent properties and the latter is a fibrous protein primarily composed of the amino acids Gly, Ser, and Ala [25].…”

“…Raw silk fibers produced by the Bombyx mori silkworm are composed primarily of two proteins: an outer coating of sericin, and fibroin [25]. The former has adherent properties and the latter is a fibrous protein primarily composed of the amino acids Gly, Ser, and Ala [25]. The approximately 50% Gly composition enables tight packing of silk fibers, while hydrogen bonding between the backbone and Ser side chains affords significant tensile strength [25].…”

“…The former has adherent properties and the latter is a fibrous protein primarily composed of the amino acids Gly, Ser, and Ala [25]. The approximately 50% Gly composition enables tight packing of silk fibers, while hydrogen bonding between the backbone and Ser side chains affords significant tensile strength [25]. This tight packing and sequestration of hydrophilic Ser residues in hydrogen bonding, coupled with the sericin coating, might explain silk's resistance to PCE absorption.…”

Antheraea assama Silk Fibroin‐Based Functional Scaffold with Enhanced Blood Compatibility for Tissue Engineering Applications

“…[20,22] Briefly, the scaffold was suspended in 5 mL of chlorosulfonic acid/pyridine solution (1:6) and heated at 80 8C for 2 h. Next, the scaffolds were incubated in isopropanol and then acetone at 55 8C for about 1 h to remove residual reagents and, finally, washed with distilled water and dried under vacuum at 37 8C. For biocompatibility studies the pristine and sulfated scaffolds were sterilized by autoclaving.…”