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At least 19 recordsLinked to original sources
PubMed2004

Sulfation of silk sericin and anticoagulant activity of sulfated sericin.

Silk sericin extracted from a cocoon was sulfated by chlorosulfonic acid. Sulfation of sericin was confirmed by FT-IR and the reaction efficiency was calculated as 44.9%. 1H-NMR suggested that sulfation mainly occurred at serine residues in the sericin molecule. The sulfated sericin was separated in three fractions by gel-filtration chromatography using Sephacryl S-200. The sulfate group content and amino-acid composition of each fraction were almost identical, while the anticoagulant activity differed for each fraction of sulfated sericin. Higher anticoagulant activity was observed for the higher-molecular-mass fraction. The anticoagulant activity of sulfated sericin was estimated at 1/10 to 1/20 of heparin.

Animals↗
PubMed2004

Characterization of sericin powder prepared from citric acid-degraded sericin polypeptides of the silkworm, Bombyx Mori.

Acid-degraded sericin powder (AC-SP) was prepared from aqueous solution containing citric acid-degraded sericin polypeptides of Bombyx mori. The morphological and biochemical properties of AC-SP were compared with those of alkali-degraded sericin powder (AL-SP) and hot-water degraded sericin powder (HW-SP). Based on an SEM analysis, AC-SP showed a thin film structure of 10-100 microm with good dispersity while AL-SP and HW-SP had a much larger thin film structure (<500 microm). The extract of AC-SP showed stronger trypsin inhibitor activity due to cocoon shell trypsin inhibitor (CSTI-IV) than that of HW-SP. The extract of AL-SP showed no CSTI-IV activity. It was found that AC-SP was a trypsin inhibitor complex powder and that the release of CSTI-IV from AC-SP depended on pH and ion strength. Similar powder materials were obtained when such organic acids as tartaric acid and succinic acid were used. These results suggest that the acid-degraded sericin polypeptides work as a protein matrix to which CSTI-IV may bind ionically.

Animals↗
PubMed1997

Structure and organization of the Bombyx mori sericin 1 gene and of the sericins 1 deduced from the sequence of the Ser 1B cDNA.

The sericin 1 primary transcript of the silkworm Bombyx mori is differentially spliced via a tissue- and developmentally-regulated process. From a middle silk gland cDNA library, we have elucidated the sequence of one of the four mRNAs, the 4.0 kb Ser1B mRNA. Determination of alternative or constitutive exons and intron-exon boundaries allowed us to establish the nine exon-eight intron structure of the Ser1 gene. From these and previous data, it was possible to deduce the sequence of the sericins 1 and to predict the secondary structure and physiochemical properties of the different regions of the proteins.

Alternative Splicing↗
PubMed2005

Preparation of silk protein sericin as mitogenic factor for better mammalian cell culture.

We previously reported that sericin small (sericin-S), with a molecular weight that ranges from 5 to 100 kDa, is a cell culture supplement used to accelerate cell proliferation. In this study, a novel preparation method for sericin and several applications of sericin were examined. Sericin large, prepared under nonhydrolyzing conditions and ranging from 50 to 200 kDa, also accelerated cell proliferation, but its effects were inferior to those of sericin-S. Additional sericin preparations with various molecular weights that were differentially hydrolyzed were also tested but none of them was significantly superior to sericin-S, and neither were several recombinant sericin peptides. Sericin-S successfully accelerated the proliferation of hybridoma cells in various serum-free media, implying the mitogenic effect of sericin is independent from media. We also demonstrated that sericin-S successfully induced the proliferation of CTLL-2, an established T lymphocyte cell line, under IL-2 starvation conditions. These results indicate that sericin, particularly sericin-S, improves serum-free mammalian cell culture.

Animals↗
PubMed2006

Interfacial behavior of fatty-acylated sericin prepared by lipase-catalyzed solid-phase synthesis.

Fatty-acylated sericin {1:0.7 molar ratio of sericin (Mr 18,700) to oleic acid} was prepared by lipase-catalyzed solid-phase synthesis in n-hexane containing oleic acid to endow sericin with interfacial properties. Acylation with oleic acid was confirmed by 1H-NMR. The fatty-acylated sericin exhibited superior emulsifying activity index and emulsion stability in the presence of 0-0.5 M NaCl, in a temperature range of 30-80 degrees C and pH range of 2-7, as compared with the control sericin. The fatty-acylated sericin (1:0.4 molar ratio) prepared by using low-molecular-weight sericin (Mr 5,000) also exhibited superior emulsifying properties. The affinity of the fatty-acylated sericin to a hydrophobic surface as evaluated by a biomolecular interaction analyzer was about twice as much as that of the control sericin. The fatty-acylated sericin showed retarded water vaporization, similar to the control sericin, indicating good retention of moistness, and was adsorbed four times as much to defatted wool with little desorption as compared with the control sericin.

Acylation↗
PubMed2001

Cryoprotective effect of the serine-rich repetitive sequence in silk protein sericin.

The silk proteins, fibroin and sericin, are produced in the silk gland of Bombyx mori, and hydrophilic sericin envelops fibroin with successive sticky layers in the formation of a cocoon. To study the biological functions of sericin, we focused on the serine-rich sericin peptide consisting of 38 amino acids, which is a highly conserved and internally repetitive sequence of a sericin protein. The corresponding gene was chemically synthesized, and the PCR-amplified gene was ligated to oligomerize sericin peptide and fused at the amino terminus to a His-tagged and proteolytic cleavage sequence in an inducible expression vector. When the dimers of sericin peptides were overexpressed in Escherichia coli, the transformants showed a prominent increase in cell viability after freezing in medium. Further, the purified dimeric sericin peptide from E. coli was found to be effective in protecting lactate dehydrogenase from denaturation caused by freeze-thaw. Both of these protective effects against freezing stress in cells and proteins were also observed with sericin hydrolysate. These results indicate that this unique sericin peptide, like sericin, has a high cryoprotective activity and will be valuable as a new biomaterial for industrial use.

Amino Acid Sequence↗
PubMedDate not supplied

Silk protein, sericin, suppresses DMBA-TPA-induced mouse skin tumorigenesis by reducing oxidative stress, inflammatory responses and endogenous tumor promoter TNF-alpha.

This study was conducted to assess protective effect of an antioxidant protein, sericin, on tumor promotion in the 7,12-dimethylbenz (alpha) anthracene (DMBA)-initiated and 12-O-tetradecanoylphorbol 13-acetate (TPA)-promoted mouse skin tumorigenesis model. In experiment 1, sericin was applied topically to DMBA-initiated female ICR mouse skin at the doses of 2.5 and 5 mg twice per week for 16 weeks, 30 min prior to each promotion treatment with TPA. The protective effect of sericin was evident in terms of significant reduction in tumor incidence and tumor multiplicity at the doses of 2.5 and 5 mg per application, compared to the control group without receiving sericin. The expression of tumor necrosis factor (TNF)-alpha protein and the level of 4-hydroxynonenal (4-HNE) in normal epidermis were significantly reduced in both sericin treatment groups. In experiment 2, sericin at the dose of 5 mg was applied topically to the dorsal mouse skin 30 min before application of a TPA, and the same doses of TPA and sericin were applied twice at an interval of 24 h. Sericin treatment inhibited double TPA treatment-induced morphological changes reflecting inflammatory response, including leukocyte infiltration, hyperplasia and cell proliferation. Furthermore, sericin treatment significantly suppressed the elevation in 4-HNE level and elevated expressions of c-fos, c-myc and cyclooxygenase-2 (COX-2) in normal epidermis induced by double application of TPA. The results suggest that sericin possesses protective effect against tumor promotion in mouse skin by suppressing oxidative stress, inflammatory responses and TNF-alpha.

9,10-Dimethyl-1,2-benzanthracene↗
PubMed2003

Cloning, expression, and assembly of sericin-like protein.

Recombinant sericin proteins of different molecular masses (17.4, 31.9, and 46.5 kDa), based on the 38-amino acid repetitive motif of native sericin, were cloned, expressed, and purified. The recombinant sericin self-assembled during dialysis (starting concentration of 2.5 mg/ml) forming twisted fibers. Circular dichroism and Fourier transform infrared spectroscopy studies demonstrated protein conformational transitions occurred from random coil to beta-sheets during the dialysis. Congo red-stained recombinant sericin fibrils exhibited apple-green birefringence, indicating long-range order in the array of beta-sheets. Biosynthetic sericin has a high content of polar amino acids (e.g. > 40 mol % serine), leading to a beta-sheet conformation formed by hydrogen bonding via polar zipper interactions. Analysis of recombinant sericin sequence using Mandel-Gutfreund's (Mandel-Gutfreund, Y., and Gregoret, L. M. (2002) J. Mol. Biol. 323, 453-461) definition of polar and non-polar amino acids showed that the hydrophobicity pattern resembles the most frequent pattern of amyloidogenic proteins, polar amino acid aggregates (PPPPP). Many beta-proteins and peptides are designed to study amyloidogenesis using a polar/non-polar alternating pattern (PNPNPN). Sericin-like proteins or peptides provide an alternative model in terms of hydrophobicity pattern with which to explore questions related to beta-sheet formation and amyloidogenesis. The glue-like property of sericin is attributed to the hydrogen bonding between serine residues of sericin with serine residues in the fibroin structural components of silk fiber.

Amino Acid Motifs↗
PubMed2006

Tyrosinase-catalyzed grafting of sericin peptides onto chitosan and production of protein-polysaccharide bioconjugates.

The capability of Agaricus bisporus tyrosinase to catalyze the oxidation of tyrosine residues of silk sericin was studied under homogeneous reaction conditions, by using sericin peptides purified from industrial wastewater as the substrate. Tyrosinase was able to oxidize about 57% of sericin-bound tyrosine residues. The reaction rate was higher than with silk fibroin, but lower than with other silk-derived model peptides, i.e. tryptic and chymotryptic soluble peptide fractions of silk fibroin, suggesting that the size and the molecular conformation of the substrate influenced the kinetics of the reaction. The concentration of tyrosine in oxidized sericin samples decreased gradually with increasing the enzyme-to-substrate ratio. The average molecular weight of sericin peptides significantly increased by oxidation, indicating that cross-linking occurred via self-condensation of o-quinones and/or coupling with the free amine groups of lysine and, probably, with sulfhydryl groups of cysteine. The high temperature shift of the main thermal transitions observed in the differential scanning calorimetry curves confirmed the formation of peptide species with higher molecular weight and higher thermal stability. Fourier transform-infrared spectra of oxidized sericin samples showed slight changes related to the loss of tyrosine and formation of oxidation products. Oxidized sericin peptides were able to undergo non-enzymatic coupling with chitosan. Infrared spectra provided clear evidence of the formation of sericin-chitosan bioconjugates under homogeneous reaction conditions. Spectral changes in the NH stretching region seem to support the formation of bioconjugates via the Michael addition mechanism.

Agaricus↗
PubMed2006

Effect of the silk protein sericin on the production of adenovirus-based gene-therapy vectors.

Adenoviral vectors are extensively used as gene-delivery vehicles in gene therapy. They are usually produced by HEK-293 cell (human embryonic kidney-293 cell) culture, which requires specially formulated serum-free medium, the cost of which is considerable or by supplementation with FBS (fetal bovine serum). The risk of infectious diseases such as BSE (bovine spongiform encephalopathy) and endogenous retrovirus derived from cattle is a serious concern. The present study reports the use of sericin protein derived from silkworm (Bombyx mori) as an effective supplement instead of FBS. Without FBS, HEK-293 cells significantly proliferated in the presence of 0.025-0.4% sericin, especially at 0.1%, but the effect was inferior to that of FBS. When a lower titre [MOI (multiplicity of infection) 0.03] of adenoviral vector pAxCAiLacZ was used as the inoculum, HEK-293 cells in the presence of 0.1% sericin produced a nearly 3-fold higher vector titre than culture in the presence of 5% (v/v) FBS. However, when a higher vector titre (MOI 3.7) was used as the inoculum, HEK-293 cells in the presence of sericin produced a slightly higher vector titre than in the presence of FBS, which might suggest that HEK-293 cells produce a maximum amount when a higher vector titre is used as the inoculum. These increases in vector production with sericin were confirmed by LacZ (beta-galactosidase reporter gene) activity assay. Supplementation with sericin decreased lactate dehydrogenase activity, an indicator of cell death, suggesting that sericin improved cell survival; hence, prolonging the culture period might be one of the reasons for increased vector production. On the basis of these results, sericin peptide seems to be a potent and effective alternative supplement for production of adenoviral vectors without such risks as BSE and retrovirus.

Adenoviridae↗
PubMed1982

Structural analysis of sericin genes. Homologies with fibroin gene in the 5' flanking nucleotide sequences.

Two closely related mRNAs (11.0 and 9.6 kilobases long) for sericin, a cocoon protein other than fibroin, were isolated from the middle silk gland of Bombyx mori. They were shown to be specifically accumulated in this particular part of the gland. Nine genomic clones complementary to the mRNAs were isolated from the recombinant phage library of Bombyx DNA. They represent two structurally similar genomic segments, and contain the 5' end and its surrounding region of sericin gene. We have identified at least 5 exons in then, and the intervening coding junctions were determined at nucleotide level. The two genomic segments differ mainly in the 5' flanking as well as in the intervening sequences and may represent alleles of a sericin locus. DNA sequence analysis of an exon has revealed an internally repetitive unit of 114 base pairs. From an internally repetitive unit of 114 base pairs. From an open frame of the repetitive DNA sequence, a peptide consisting of 38 amino acids abundant in serine was deduced. We propose the peptide represents a repetitive unit of a sericin protein. The probable site of initiation of sericin gene transcription in vivo has been identified at the nucleotide level that also turned out to be the 5' end of mature sericin mRNA. There exist strong homologous regions in the sericin and fibroin genes at their corresponding 5' flanking sequences. A possible involvement of the homologous sequences around -111 and -186 for the concerted expression of the sericin and fibroin genes in the silk glands is discussed.

Amino Acid Sequence↗
PubMedDate not supplied

Chemical modification of silk sericin in lithium chloride/dimethyl sulfoxide solvent with 4-cyanophenyl isocyanate.

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.

Animals↗
PubMedDate not supplied

Molecular orientation behavior of silk sericin film as revealed by ATR infrared spectroscopy.

This paper reports the structure-dependent molecular orientation behavior of sericin, an adhesive silk protein secreted by silkworm, Bombyx mori. Although application of sericin as a biomaterial is anticipated because of its unique characteristics, sericin's physicochemical properties remain unclear, mainly because of its vulnerability to heat or alkaline treatment during separation from fibroin threads. This study employed intact sericin obtained from fibroin-deficient mutant silkworm to investigate the relationship between molecular orientation and the secondary structure of sericin. Sericin films were artificially stretched after moistening with aqueous ethanol of various concentrations. The resulting molecular orientation was analyzed using polarized infrared spectroscopy. These analyses indicated that formation of aggregated strands among extended sericin chains induced by ethanol treatment is the key to generating molecular orientation. Strong intermolecular hydrogen bonds are inferred to allow aggregated strands' stretching-force transmission, thereby causing molecular orientation.

Animals↗
PubMed2001

Supplemental silk protein, sericin, suppresses colon tumorigenesis in 1,2-dimethylhydrazine-treated mice by reducing oxidative stress and cell proliferation.

This study was done to discover the underlying mechanism of the inhibitory effect of sericin against colon tumorigenesis. Mice were fed a diet with 30 g/kg sericin for 115 d, and given a weekly injection of 1,2-dimethylhydrazine (10 mg/kg body weight) for the initial 10 wk. Dietary supplemental sericin caused a 62% reduction in the incidence of colonic adenoma (P<0.05), but did not affect the incidence of colonic adenocarcinoma. Sericin intake significantly reduced the number of colon adenomas. Consumption of sericin significantly reduced the BrdU labeling index of colonic proliferating cells and the expression of colonic c-myc and c-fos. The levels of colonic 8-hydroxydeoxyguanosine, 4-hydroxynonenal, and inducible nitric oxide synthase protein were significantly suppressed by sericin. The results suggest that dietary sericin suppresses the development of colon tumors by reducing oxidative stress, cell proliferation, and nitric oxide production.

1,2-Dimethylhydrazine↗
PubMed2005

Preparation of elastic silk sericin hydrogel.

This paper reports a preparation method for silk sericin hydrogel using the Sericin-hope silkworm, whose cocoons consist almost exclusively of sericin. Sericin solution, prepared from Sericin-hope cocoons, contains intact sericin and forms elastic hydrogels with the addition of ethanol. The sericin hydrogel can be prepared without crosslinking by chemicals or irradiation and might be usable as a naturally occurring biomaterial.

Amides↗
PubMed2002

Applications of natural silk protein sericin in biomaterials.

Silk sericin is a natural macromolecular protein derived from silkworm Bombyx mori. During the various stages of producing raw silk and textile, sericin can be recovered for other uses. Also, sericin recovery reduces the environmental impact of silk manufacture. Sericin protein is useful because of its properties. The protein resists oxidation, is antibacterial, UV resistant, and absorbs and releases moisture easily. Sericin protein can be cross-linked, copolymerized, and blended with other macromolecular materials, especially artificial polymers, to produce materials with improved properties. The protein is also used as an improving reagent or a coating material for natural and artificial fibers, fabrics, and articles. The materials modified with sericin and sericin composites are useful as degradable biomaterials, biomedical materials, polymers for forming articles, functional membranes, fibers, and fabrics.

Journal Article↗
PubMed2004

Immobilization of L-asparaginase on the microparticles of the natural silk sericin protein and its characters.

The natural silk sericin recovered from Bombyx mori silk waste by the degumming processing in the high-temperature and high-pressure is a macromolecular protein. Amino acid composition and molecular weight range of the sericin protein as a vector for enzyme immobilization were investigated. The silk sericin protein with different molecular mass from 50 to 200 kDa was poorly soluble microparticles with an average size of about 10 microm. Anti-leukemic enzyme L-asparaginase (L-ASNase) was covalently conjugated on the microparticles of the sericin protein. The immobilized L-ASNase on the natural support by cross-linking with glutaraldehyde maintained 62.5% of the original activity of the enzyme. The Km of sericin-conjugates was 8 times lower than that of native L-ASNase. The bioconjugation of L-ASNase widened the optimum reactive temperature range of the enzyme. The immobilized L-ASNase showed significantly higher stability when the temperature raised to 40-50 degrees C, it also showed preferable resistance to trypsin digestion as compared with native enzyme. The results are discussed regarding the possible explanations of sericin-induced enzyme stability, as well as the possible applications of immobilized L-ASNase research.

Adsorption↗