title: Chemical modification of silk sericin in lithium chloride/dimethyl sulfoxide solvent with 4-cyanophenyl isocyanate.
abstract: This paper reports chemical modification of silk sericin in LiCl/dimethyl sulfoxide (DMSO) solvent with 4-cyanophenyl isocyanate. Sericin is a highly hydrophilic protein secreted by Bombyx mori, serving as a protein glue in a cocoon. LiCl/DMSO was found to be a good solvent of sericin and useful for homogeneous modification of its abundant hydroxyl groups under nonaqueous condition. Fourier transform infrared (FTIR) analysis of the modified sericins revealed that 4-cyanophenyl groups were incorporated into sericin molecules mainly through urethane linkages. Several characteristics of the modified sericins such as solubility characteristic, hygroscopic property, and thermal stability were investigated. Secondary structure analysis using FTIR spectra suggested that formation of strong intermolecular hydrogen bonds was inhibited by the modification that is probably attributable to the incorporation of bulky 4-cyanophenyl groups. These results demonstrate that chemical modification of sericin using LiCl/DMSO solvent markedly alters its characteristics.
authors.affiliation: New Silk Materials Laboratory, Insect Biotechnology and Sericology Department, National Institute of Agrobiological Sciences, 1-4-8 Gohda, Okaya, Nagano 394-0021, Japan. teramoto@nias.affrc.go.jp
authors.forename: Hidetoshi
authors.initials: H
authors.lastname: Teramoto
authors.forename: Ken-ichi
authors.initials: K
authors.lastname: Nakajima
authors.forename: Chiyuki
authors.initials: C
authors.lastname: Takabayashi
mesh_terms: D000818:Animals; D012831:Bombyx / Q000737:chemistry / Q000235:genetics; D002850:Chromatography, Gel / Q000379:methods; D004121:Dimethyl Sulfoxide / Q000737:chemistry*; D019476:Insect Proteins / Q000737:chemistry*; D017953:Isocyanates / Q000737:chemistry*; D018021:Lithium Chloride / Q000737:chemistry*; D015394:Molecular Structure; D009154:Mutation; D047030:Sericins / Q000737:chemistry*; D012995:Solubility; D012997:Solvents / Q000737:chemistry*; D017550:Spectroscopy, Fourier Transform Infrared / Q000379:methods
chemical_list: C496055:4-cyanophenyl isocyanate; D019476:Insect Proteins; D017953:Isocyanates; D047030:Sericins; D012997:Solvents; D018021:Lithium Chloride; D004121:Dimethyl Sulfoxide