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PubMedDate not supplied

Variability in the mechanical properties of spider silks on three levels: interspecific, intraspecific and intraindividual.

The mechanical characteristics of dragline silks collected from a range of spiders drawn from the Argiopidae, Tetragnathidae, Theridiidae and Pisauridae displayed significant inter- and intraspecific differences. Dragline silks of the same species could show considerable variability probably dependent upon spider condition: starvation, for example, lead to decreased breaking elongation in Nephila edulis. Environmental conditions such as reeling speed affected silk properties such that (i) breaking elongation decreased, (ii) breaking stress increased and (iii) Young's modulus increased with increasing reeling speed. However, N. edulis and Araneus diadematus responded differently to the reeling speed treatments suggesting differences in basic silk properties.

Animals↗
PubMedDate not supplied

Structure and function of the silk production pathway in the spider Nephila edulis.

Our observations on the major ampullate gland of the spider Nephila edulis indicate that the exceptionally tough and strong core and coat composite structure of the dragline thread is formed by the co-drawing of two feedstocks through a single die. The cuticle that lines the gland's duct has the structure of an advanced hollow fibre dialysis membrane and is thought to facilitate a rapid removal of water and change in ionic composition involved in the spinning process. A structure previously termed the 'valve' is thought to advance the broken thread and act as a pump to restart spinning after the accidental internal rupture of a thread. Together, these observations indicate that the spider silk production pathway is highly optimised for the production of silk threads and shows considerable biomimetic potential.

Animals↗
PubMedDate not supplied

Spider (Araneus diadematus) cocoon silk: a case of non-periodic lattice crystals with a twist?

Transmission electron microscopy was used to investigate the supramolecular structure of Araneus diadematus (garden spider) cocoon silk. Electron diffraction patterns contain features which are consistent with the presence of non-periodic lattice crystals, i.e. highly frustrated crystalline regions as identified previously in the major ampullate silk (MAS, dragline) of Nephila clavipes spiders. The diffraction patterns further suggest that crystals in A. diadematus cocoon silk may be twisted parallel to the chain direction, offering a potential explanation for the lower tensile stiffness of this fibre relative to MAS.

Amino Acid Sequence↗
PubMed1988

Wound care of spider and snake envenomations.

Venomous bites and stings are numerous but severe local tissue damage is uncommon. Venoms may be simple substances or complex mixtures of many poorly characterized components whose interactions are still not fully understood. The best studied example of a dermonecrotic venom is that produced by the brown recluse spider (Loxosceles reclusa). Rattlesnake envenomation also causes significant wound injuries. Many spider and snake envenomation management modalities are controversial and the evidence is mounting against the use of a number of these treatments.

Animals↗
PubMed2002

Spider webs as environmental indicators.

Analysis of spider webs from limestone arches in New South Wales, Australia showed levels of lead and zinc to be several times higher at Jenolan Caves than reference sites at Abercrombie and Wombeyan Caves. The high concentrations at Jenolan were attributed to emissions from motor vehicles that travel through the arch. Analysis of water-soluble ions in webs from Jenolan and Abercrombie Caves showed large differences between the sites, which could be explained by differences in the geology and biology of the cave environments. Spider webs proved useful indicators of environmental chemistry and undoubtedly have applications beyond the cave environments studied here.

Animals↗
PubMed1998

Inhibitory actions of synthesised polyamine spider toxins and their analogues on Ca2+-activated Cl- currents recorded from cultured DRG neurones from neonatal rats.

The whole cell variant of the patch clamp technique was used to investigate the actions of polyamine spider toxins and their analogues on high voltage-activated Ca2+ currents and Ca2+-activated Cl- currents (I(Cl(Ca))). The actions of synthesised FTX (putative natural toxin from the American funnel web spider), sFTX-3.3, Orn-FTX-3.3, Lys-FTX-3.3, and argiotoxin-636 on cultured dorsal root ganglion neurones from neonatal rats were investigated. Synthesised FTX (1 microM) inhibited I(Cl(Ca)) but did not inhibit high voltage-activated Ca2+ currents. In contrast, sFTX-3.3 (10 microM) inhibited both high voltage-activated Ca2+ currents and the associated I(Cl(Ca)) in near equal proportions. Argiotoxin-636 (1-10 microM) inhibited I(Cl(Ca)) evoked by Ca2+ entry through voltage-activated channels and by intracellular photorelease of Ca2+ from a caged precursor DM-nitrophen. This data indicates that synthesised FTX and argiotoxin-636 directly inhibit Ca2+-activated Cl- channels. In conclusion, the potency of polyamines as non-selective inhibitors of Ca2+ channels and Ca2+-activated Cl- channels is in part determined by the presence of a terminal arginine and this may involve an interaction between terminal guanidino groups and Ca2+ binding sites.

Animals↗
PubMedDate not supplied

Computer-delivered modeling of exposure for spider phobia: relevant versus irrelevant exposure.

Spider phobic subjects (n = 45) completed 3 x 40 minute computer-delivered treatment sessions. Questionnaire ratings of phobic severity were completed pre- and posttreatment (n = 45) and 6-12 month follow-up (n = 38). The program used interactive animations to model self-exposure treatment methods. Subjects were randomized to one of three treatment groups (n = 15), each receiving a different version of the program. These treatment conditions were relevant exposure with feedback (REF), relevant exposure with no feedback (RENoF), or irrelevant exposure with feedback (IEF). Relevant exposure modeled exposure to spiders, irrelevant exposure to elevators. All groups showed significant phobic improvement following the treatment, as measured on a variety of instruments. Learning on the programs was demonstrated by a significantly increased performance (time taken to reach a target score) within each group across the three computer treatment sessions. Outcome was not significantly affected either relevance of exposure or the manipulation of the onscreen feedback. Subjects' report of exposure treatment undertaken at home correlated positively with phobic improvement.

Adult↗
PubMedDate not supplied

Visual function: how spiders find the right rock to crawl under.

Animals that go on hunting expeditions face the problem of finding the way home at the end of the day. A group of hunting spiders has now been added to the list of animals that use the celestial pattern of polarized light as a compass to navigate with, and explains an old conundrum of spider eye anatomy.

Animals↗
PubMedDate not supplied

Purification and characterization of five cuticular proteins from the spider Araneus diadematus.

Urea-extractable proteins have been purified from the cephalothoracic cuticle of mature Araneus diadematus spiders. Two-dimensional gel electrophoresis showed at least 12 major proteins, with pIs between 4.5 and 8.5. Five proteins were purified and their primary structure determined, using a combination of mass spectrometry and Edman degradation. Based on the amino acid sequence the proteins can be divided into two groups, both characterized by hydrophobic regions dominated by Ala, Pro and Val. Sequence similarity was observed between all the spider cuticle proteins and a number of proteins from other arthropod cuticles. Although the similarity seemed to be confined only to a region in the central part of the molecules, it does link these very distantly related species.

Amino Acid Sequence↗
PubMed1997

Brown recluse spider bite: a case study.

The case of a young man with a chronic, resistant, and unpredictable wound is described. The wound is believed to have been caused by the bite of a brown recluse spider. This article presents a brief overview of the potential sequelae of brown recluse spider bite and a pictorial review of this young man's wound during a 22-month period.

Adult↗
PubMed2005

A spider toxin that induces a typical effect of scorpion alpha-toxins but competes with beta-toxins on binding to insect sodium channels.

Delta-palutoxins from the spider Paracoelotes luctuosus (Araneae: Amaurobiidae) are 36-37 residue long peptides that show preference for insect sodium channels (NaChs) and modulate their function. Although they slow NaCh inactivation in a fashion similar to that of receptor site 3 modifiers, such as scorpion alpha-toxins, they actually bind with high affinity to the topologically distinct receptor site 4 of scorpion beta-toxins. To resolve this riddle, we scanned by Ala mutagenesis the surface of delta-PaluIT2, a delta-palutoxin variant with the highest affinity for insect NaChs, and compared it to the bioactive surface of a scorpion beta-toxin. We found three regions on the surface of delta-PaluIT2 important for activity: the first consists of Tyr-22 and Tyr-30 (aromatic), Ser-24 and Met-28 (polar), and Arg-8, Arg-26, Arg-32, and Arg-34 (basic) residues; the second is made of Trp-12; and the third is made of Asp-19, whose substitution by Ala uncoupled the binding from toxicity to lepidopteran larvae. Although spider delta-palutoxins and scorpion beta-toxins have developed from different ancestors, they show some commonality in their bioactive surfaces, which may explain their ability to compete for an identical receptor (site 4) on voltage-gated NaChs. Yet, their different mode of channel modulation provides a novel perspective about the structural relatedness of receptor sites 3 and 4, which until now have been considered topologically distinct.

Alanine↗
PubMed2006

Spider egg case core fibers: trimeric complexes assembled from TuSp1, ECP-1, and ECP-2.

Spider silk proteins are well-known for their extraordinary mechanical properties, displaying remarkable strength and toughness. In this study, matrix-assisted laser desorption ionization (MALDI) tandem time-of-flight (TOF) mass spectrometry (MS/MS) and reverse genetics were used to isolate a new cDNA sequence that encodes for a protein assembled into egg case silk from the black widow spider, Latrodectus hesperus. Analysis of the primary sequence of this protein reveals approximately 52% identity to the egg case protein 1 (ECP-1) fibroin-like family member. On the basis of the similarity in the primary sequence and expression pattern, we have named this factor egg case protein 2 (ECP-2). Alignments of ECP-1 and ECP-2 demonstrate highly conserved N termini, with 16 Cys residues found within the first 153 amino acids. Traditional ensemble repeats found within reported fibroins were poorly represented in the primary sequence of ECP-2, but scattered blocks of polyalanine were present, along with a C terminus rich in GA repeats. Reverse transcription quantitative PCR analysis showed that ECP-2 is predominantly expressed in the tubuliform gland. Relative to ECP-1, ECP-2 mRNA levels were determined to be >2-fold higher. MALDI MS/MS analysis of peptide fragments generated from the large-diameter core fiber after enzymatic digestion and acid hydrolysis demonstrated the presence of a fiber that is trimeric in nature, containing tubuliform spidroin 1 (TuSp1), ECP-1, and ECP-2. We also report an additional primary sequence for TuSp1, demonstrating that TuSp1 contains two Cys residues within a nonrepetitive N-terminal region. In combination with the distinctive protein architectures of ECP-1 and ECP-2, along with their co-localization with TuSp1 in the core fiber, our findings suggest that ECP-1 and ECP-2 play important structural roles in the egg case silk fiber.

Amino Acid Motifs↗
PubMed2001

Comparison of the spinning of selachian egg case ply sheets and orb web spider dragline filaments.

Liquid crystal spinning appears to be widespread in the animal kingdom, utilizing protein dopes to give materials with a range of different secondary structures including beta-pleat, alpha-helix and collagen-fold. Here we seek to identify the essential design features used in natural liquid crystal spinning by comparing the spinning of two very different materials: the egg case wall of Selachians (dogfish, rays, and their allies) and the dragline silk of orb web spiders. The fish extrudes a "sea and island" composite in which the islands consist of flat ribbons of carefully orientated collagen and the sea, small quantities of an amorphous matrix. Dragline silk filaments are largely constructed from spidroin, a beta protein and have a skin and core structure together with two to three coats. The essential design features common to both systems appear to be the following: (i) intracellular co-storage of a hexagonal columnar liquid crystalline component and a peroxidase within the same secretory vesicles; (ii) luminal storage of a highly concentrated liquid crystalline dope; (iii) use of a dope containing immiscible droplets; (iv) hyperbolic extrusion dies; (v) control of pH and water content of the dope; (vi) preorientation of dope molecules before assembly into fibrils; (vii) combination of extrusion die, treatment/coating bath, and solvent recovery plant within a single microminiaturized device; (viii) slow natural spinning rates. The most important difference is that spiders produce a tough material by unfolding and hydrogen-bonding their silk dope molecules while Selachian fish do it by covalently cross-linking the molecules without unfolding them.

Animals↗
PubMedDate not supplied

NMR characterization of native liquid spider dragline silk from Nephila edulis.

Solid spider dragline silk is well-known for its mechanical properties. Nonetheless a detailed picture of the spinning process is lacking. Here we report NMR studies on the liquid silk within the wide sac of the major ampullate (m.a.) gland from the spider Nephila edulis. The resolution in the NMR spectra is shown to be significantly improved by the application of magic-angle spinning (MAS). From the narrow width of the resonance lines and the chemical shifts observed, it is concluded that the silk protein within the wide sac of the m.a. gland is dynamically disordered throughout the molecule in the sense that each amino acid of a given type senses an identical environment, on average. The NMR data obtained are consistent with an isotropic liquid phase.

Animals↗
PubMedDate not supplied

Study of protein conformation and orientation in silkworm and spider silk fibers using Raman microspectroscopy.

Raman microspectroscopy has been used for the first time to determine quantitatively the orientation of the beta-sheets in silk monofilaments from Bombyx mori and Samia cynthia ricini silkworms, and from the spider Nephila edulis. It is shown that, for systems with uniaxial symmetry such as silk, it is possible to determine the order parameters P2 and P4 of the orientation distribution function from intensity ratios of polarized Raman spectra. The equations allowing the calculation of P2 and P4 using polarized Raman microspectroscopy for a vibration with a cylindrical Raman tensor were first derived and then applied to the amide I band that is mostly due to the C=O stretching vibration of the peptide groups. The shape of the Raman tensor for the amide I vibration of the beta-sheets was determined from an isotropic film of Bombyx mori silk treated with methanol. For both the Bombyx mori and Samia cynthia ricini fibroin fibers, the values of P2 and P4 obtained are equal to -0.36 +/- 0.03 and 0.19 +/- 0.02, respectively, even though the two types of silkworm fibroins strongly differ in their primary sequences. For the Nephila edulis dragline silk, values of P2 and P4 of -0.32 +/- 0.02 and 0.13 +/- 0.02 were obtained, respectively. These results clearly indicate that the carbonyl groups are highly oriented perpendicular to the fiber axis and that the beta-sheets are oriented parallel to the fiber axis, in agreement with previous X-ray and NMR results. The most probable distribution of orientation was also calculated from the values of P2 and P4 using the information entropy theory. For the three types of silk, the beta-sheets are highly oriented parallel to the fiber axis. The orientation distributions of the beta-sheets are nearly Gaussian functions with a width of 32 degrees and 40 degrees for the silkworm fibroins and the spider dragline silk, respectively. In addition to these results, the comparison of the Raman spectra recorded for the different silk samples and the polarization dependence of several bands has allowed to clarify some important band assignments.

Animals↗
PubMedDate not supplied

Analysis of the conserved N-terminal domains in major ampullate spider silk proteins.

Major ampullate silk, also known as dragline silk, is one of the strongest biomaterials known. This silk is composed of two proteins, major ampullate spidroin 1 (MaSp1) and major ampullate spidroin 2 (MaSp2). Only partial cDNA sequences have been obtained for these proteins, and these sequences are toward the C-terminus. Thus, the N-terminal domains have never been characterized for either protein. Here we report the sequence of the N-terminal region of major ampullate silk proteins from three spider species: Argiope trifasciata, Latrodectus geometricus, and Nephila inaurata madagascariensis. The amino acid sequences are inferred from genomic DNA clones. Northern blotting experiments suggest that the predicted 5' end of the transcripts are present in fibroin mRNA. The presence of more than one Met codon in the N-terminal region indicates the possibility of translation of both a long and a short isoform. The size of the short isoform is consistent with the published, cDNA based, N-terminal sequence found in flagelliform silk. Analyses comparing the level of identity of all known spider silk N-termini show that the N-terminus is the most conserved part of silk proteins. Two DNA sequence motifs identified upstream of the putative transcription start site are potential silk fibroin promoter elements.

Amino Acid Sequence↗
PubMed2006

An essential role for the C-terminal domain of a dragline spider silk protein in directing fiber formation.

We have employed baculovirus-mediated expression of the recombinant A. diadematus spider dragline silk fibroin rADF-4 to explore the role of the evolutionary conserved C-terminal domain in self-assembly of the protein into fiber. In this unique system, polymerization of monomers occurs in the cytoplasm of living cells, giving rise to superfibers, which resemble some properties of the native dragline fibers that are synthesized by the spider using mechanical spinning. While the C-terminal containing rADF-4 self-assembled to create intricate fibers in the host insect cells, a C-terminal deleted form of the protein (rADF-4-DeltaC) self-assembled to create aggregates, which preserved the chemical stability of dragline fibers, yet lacked their shape. Interestingly, ultrastructural analysis showed that the rADF-4-DeltaC monomers did form rudimentary nanofibers, but these were short and crude as compared to those of rADF-4, thus not supporting formation of the highly compact and oriented "superfiber" typical to the rADF-4 form. In addition, using thermal analysis, we show evidence that the rADF-4 fibers but not the rADF-4-DeltaC aggregates contain crystalline domains, further establishing the former as a veritable model of authentic dragline fibers. Thus, we conclude that the conserved C-terminal domain of dragline silk is important for the correct structure of the basic nanofibers, which assemble in an oriented fashion to form the final intricate natural-like dragline silk fiber.

Animals↗
PubMed2006

Volume constancy during stretching of spider silk.

The characterization of silk properties requires a reliable measurement of stress-strain curves from tensile tests, which calls for a detailed analysis of what is considered the cross section of the sample and how it varies during the experiments. Here, spider silk fibers from the major ampullate gland (MAS) of Argiope trifasciata spiders are tensile tested, and the cross-sectional area is measured under different strained configurations. It has been found that the fiber volume remains practically constant during stretching, and deformation proceeds homogeneously in all the fibers. The conservation of volume is validated independently of the type of fiber and the strain level. This result, applied to compute true stress-strain curves for different MAS fibers, shows that the description of their properties depends noticeably on which set of tensile parameters is chosen (true or engineering), and that engineering values could lead to misinterpretation of experiments that combine results from different strain ranges.

Animals↗