Studies on middle silkgland proteins of cocoon colour sex-limited silkworm (Bombyx mori L.) using two-dimensional polyacrylamide gel electrophoresis. (33/375)

Qualitative and quantitative differences in proteins expressed in the middle silkglands of male and female silkworm larvae that differ in silk colour were investigated by high resolution two-dimensional polyacrylamide gel electrophoresis (2-D PAGE), followed by computer assisted image analysis. About 1000 protein spots were resolved in both the sexes and most proteins were shown to be distributed in the area from 15 kDa to 70 kDa and pH 4-8. It was found that some proteins displayed higher expression in yellow cocoon, while two proteins were only expressed in female silkworm silkgland tissue through the comparison and analysis by two-D software. These proteins especially existed in female silkworm middle silkgland tissue of yellow cocoon. Furthermore, these proteins might be involved in the expression of cocoon colour phenotype  (+info)

Environmental mycological study and respiratory disease investigation in tussah silk processing workers. (34/375)

This study presents the results of an investigation of respiratory symptoms, pulmonary function and chest X-ray examinations, and analysis of antibodies to fungi of 197 tussah silk-processing workers and 40 control workers. An industrial hygiene survey and environmental mycological studies were also conducted. The dust concentrations in tussah silk processing workshops were less than 5.1 mg/m(3) on average, with a maximum of 7.8 mg/m(3) below the national health limit of 10 mg/m(3). Most dusts in all tussah silk processing workshops contained less than 1.2% silica. Numbers of isolated fungi in tussah silk processing workshops [755-6,544 cfu/m(3) (colony forming unit/m(3)), were significantly higher than those in control environments (63-472 cfu/m(3)). The prevalences of respiratory symptoms in tussah silk processing workers were higher than those in control workers. The prevalences of respiratory symptoms in exposed male non-smoking workers were 44.4% with chronic cough, and 38.9% with chronic phlegm respectively, which were significantly higher than those (12.5%, 12.5% respectively) in male non-smoking control workers (p<0.05). The prevalences in exposed male smoking workers were 42.9% with dyspnea, and 38.1% with chest tightness respectively, which were significantly higher than those (16.7%, 8.3% respectively) in male smoking control workers (p<0.01). The prevalences of respiratory symptoms in exposed female workers were 25.3% with chronic cough, 38.0% with chronic phlegm, 31.0% with dyspnea, and 29.1% with chest tightness respectively, which were significantly higher than those (10.0%, 10.0%, 10.0%, 5.0% respectively) in female control workers (p<0.01). Fifteen exposed workers often suffered from fever. Five X-rays were abnormal and four cases had nodular or patchy shadows. The prevalences of pulmonary function abnormalities in the exposed female group were significantly higher than those in control groups (p<0.01). The OD(450 nm) values for antibodies to fungi in tussah silk processing workers were significantly higher than those of control workers (p<0.05). The positive rates of anti-fungal antibodies in tussah silk-processing workers were also significantly higher than those of control workers (p<0.01). The results suggested that fungi might be one of the main allergens in respiratory diseases in the tussah silk processing workers.  (+info)

Stretching of supercontracted fibers: a link between spinning and the variability of spider silk. (35/375)

The spinning of spider silk requires a combination of aqueous environment and stretching, and the aim of this work was to explore the role of stretching silk fibers in an aqueous environment and its effect on the tensile properties of spider silk. In particular, the sensitivity of the spider silk tensile behaviour to wet-stretching could be relevant in the search for a relationship between processing and the variability of the tensile properties. Based on this idea and working with MAS silk from Argiope trifasciata orb-web building spiders, we developed a novel procedure that permits modification of the tensile properties of spider silk: silk fibers were allowed to supercontract and subsequently stretched in water. The ratio between the length after stretching and the initial supercontracted length was used to control the process. Tensile tests performed in air, after drying, demonstrated that this simple procedure allows to predictable reproduction of the stress-strain curves of either naturally spun or forcibly silked fibers. These results suggest that the supercontracted state has a critical biological function during the spinning process of spider silk.  (+info)

Macromolecular array patterns of silk gland secretion in social Hymenoptera larvae. (36/375)

The cocoon, produced by most holometabolous insects, is built with silk that is usually produced by the larval salivary gland. Although this silk has been widely studied in the Lepidoptera, its composition and macromolecular arrangement remains unknown in the Hymenoptera. The macromolecular array patterns of the silk in the larval salivary gland of some meliponids, wasps, and ants were analyzed with polarized-light microscopy, and they were compared with those of Bombyx mori (Lepidoptera). There is a birefringent secretion in the glandular lumen of all larvae, due to filamentous structural proteins that display anisotropy. The silk in the distal, middle and proximal regions of the secretory portion of Formicidae and Vespidae glands presented a lattice optical pattern. We found a different pattern in the middle secretory portion of the Meliponini, with a zigzag rather than a lattice pattern. This indicates that the biopolymer fibers begin their macromolecular reorganization at this glandular region, different from the Formicidae and the Vespidae, in which the zigzag optical pattern was only found at the lateral duct. Probably, the mechanism of silk production in the Hymenoptera is a characteristic inherited from a common ancestor of Vespoidea and Sphecoidea; the alterations in the pattern observed in the Meliponini could be a derived characteristic in the Hymenoptera. We found no similarity in the macromolecular reorganization patterns of the silk between the Hymenoptera species and the silkworm.  (+info)

Giant wood spider Nephila pilipes alters silk protein in response to prey variation. (37/375)

Recent studies have demonstrated that orb-weaving spiders may alter web structures, foraging localities or silk output in response to prey variations. In this study we conducted field surveys and food manipulations to examine whether orb-weaving spiders may also adjust the protein of silk to prey variations. A comparison of dragline silks collected from nine giant wood spider Nephila pilipes populations in Taiwan showed a spatial variation. The percentage of all amino acids (except alanine and glycine) exhibited significant differences among populations. A survey of prey composition also revealed a significant spatial variation among N. pilipes populations. To determine whether prey variation was responsible for silk protein variation, we fed N. pilipes with different types of prey (dipteran vs orthopteran) then compared the percentage of five major dragline amino acids and secondary structures. The results showed that dragline of N. pilipes fed with orthopteran prey contained significantly higher proline and glutamine but lower alanine. Congruent with this result were those from FTIR spectroscopy, which showed that dragline of N. pilipes fed with crickets exhibited significantly higher percentage of proline- and glutamine-containing beta turns, and lower percentage of alanine-containing beta sheet structures. Since the results of feeding manipulations showed that diet significantly affected the compositions of dragline silks, the observed spatial variation seemed to reflect the different types of prey these spiders had consumed. Results of this study thus indicated that orb-weaving spiders can alter dragline protein in response to prey variations.  (+info)

Egg case protein-1. A new class of silk proteins with fibroin-like properties from the spider Latrodectus hesperus. (38/375)

Spiders produce multiple types of silk that exhibit diverse mechanical properties and biological functions. Most molecular studies of spider silk have focused on fibroins from dragline silk and capture silk, two important silk types involved in the survival of the spider. In our studies we have focused on the characterization of egg case silk, a third silk fiber produced by the black widow spider, Latrodectus hesperus. Analysis of the physical structure of egg case silk using scanning electron microscopy demonstrates the presence of small and large diameter fibers. By using the strong protein denaturant 8 M guanidine hydrochloride to solubilize the fibers, we demonstrated by SDS-PAGE and protein silver staining that an abundant component of egg case silk is a 100-kDa protein doublet. Combining matrix-assisted laser desorption ionization tandem time-of-flight mass spectrometry and reverse genetics, we have isolated a novel gene called ecp-1, which encodes for one of the protein components of the 100-kDa species. BLAST searches of the NCBInr protein data base using the primary sequence of ECP-1 revealed similarity to fibroins from spiders and silkworms, which mapped to two distinct regions within the ECP-1. These regions contained the conserved repetitive fibroin motifs poly(Ala) and poly(Gly-Ala), but surprisingly, no larger ensemble repeats could be identified within the primary sequence of ECP-1. Consistent with silk gland-restricted patterns of expression for fibroins, ECP-1 was demonstrated to be predominantly produced in the tubuliform gland, with lower levels detected in the major and minor ampullate glands. ECP-1 monomeric units were also shown to assemble into higher aggregate structures through the formation of disulfide bonds via a unique cysteine-rich N-terminal region. Collectively, our findings provide new insight into the components of egg case silk and identify a new class of silk proteins with distinctive molecular features relative to traditional members of the spider silk gene family.  (+info)

Quasistatic and continuous dynamic characterization of the mechanical properties of silk from the cobweb of the black widow spider Latrodectus hesperus. (39/375)

Spider silks are among the strongest and toughest known materials, but investigation of these remarkable properties has been confined largely to orb-weaving spiders. We investigated the mechanical performance of silk from the cobweb-weaving spider Latrodectus hesperus. Both silk from the scaffolding region of the web and sticky gumfooted capture lines had material properties similar to the major ampullate silk that orb weavers use as the framework for their orb webs. Major ampullate fibers obtained from anaesthetized Latrodectus spiders were similar, but exhibited increased stiffness and reduced extensibility. Novel continuous dynamic analysis of the silks revealed that the loss tangent (tandelta) increased rapidly during the first 2-3% of extension and reached a maximum near the yield point of fibers. The loss tangent then rapidly declined at an ever-decreasing rate until failure. We suggest that these data support molecular models for the mechanics of spider silk. We also demonstrate that the addition of sticky aggregate glue to the ends of the gumfooted lines modulates their mechanical performance--reducing stiffness and increasing extensibility. The storage modulus of viscid regions of the gumfooted lines was much lower than dry regions. This may be explained by disruption of hydrogen bonding within the amorphous regions of the fibers due to hydration from the glue.  (+info)

Crystal structure of raw pure Mysore silk fibre based on (Ala-Gly)2-Ser-Gly peptide sequence using Linked-Atom-Least-Squares method. (40/375)

We have carried out crystal structure analysis of raw pure Mysore silk fibers belonging to Bombyx mori on the basis of model parameters of Marsh et al using Linked-Atom-Least-Squares technique. The intensity of all the reflections were computed employing CCP13 software. We observe that the molecular modification is essentially same as b-pleated structure with antipolar-antiparallel arrangements formed by hydrogen bonds. The essential differences observed in the structure are highlighted and discussed.  (+info)