Nephila

Figure 10 shows polarized spectra of two types of silks recorded by Raman spectromicroscopy the dragline silk (the lifeline) of the spider Nephila edulis and the cocoon silk of a wild silkworm Sarnia cynthia ricini. The position of the amide I band at 1,668-1,669 cm-1 for both threads is characteristic of the /i-sheet... 

Figure 10 Polarized spectra obtained by Raman microspectroscopy of (A) the dragline silk of the spider Nephila edulis and (B) the cocoon silk of the silkworm Sarnia cynthia ricini. Adapted with permission from Rousseau et al. [63]. Copyright 2004 American Chemical Society.

Tab.11.1 Spider silk proteins MaSpI, MaSpll and Flag from Nephila davipes.

Tab. 11.2 Mechanical properties of spider si materials. Ik from Nephila davipes com pared to other structural...

The first spinning experiments were performed with dissolved raw silk of the silkworm Bombyx mori [31] and the golden orb-weaver Nephila clavipes [32]. For this purpose a minimized wet-spinning apparatus was constructed [31]. The apparatus was capable of spinning fibers from solutions containing 10 mg of soluble protein. 

Raw silk was dissolved in hexafluoro-iso-propanol (HFIP) [17, 33]. A typical working concentration for spinning was 2.5% (w/v) silk fibroin in HFIP. The spinning solution was pressed through a small needle (0 80-250 pm) into a precipitation bath (methanol for Bombyx mori silk proteins and acetone for Nephila clavipes silk proteins) and the silk solution immediately precipitated as a fiber. The best performing fibers approached the maximum strength measured for native fibers of Bombyx mori, but did not achieve the mechanical properties of natural spider silk. 

Fig. 5. The effect of protein-protein interactions on Nephila edulis major ampullate circular dichroism spectra in solution. A change in secondary structure with increasing concentration is observed. At low concentration (minimal protein-protein interactions) silk proteins appear partially unfolded in solution. At higher concentration (higher protein-protein interactions) silk proteins refold into a helix-like structure, most likely a molten-like globule (from Dicko et al., 2004c). This final molten structure would facilitate local chain rearrangement while preserving the global structure for protein storage and transport. (Copyright 2004 American Chemical Society.)...

Fig. 6. Structural stability of major ampullate silk protein in constrained Nephila edulis. The graph shows a time series of circular dichroism spectra of major ampullate (MA) protein at 1% w/v in distilled water. The spiders prior to dissection were prevented from spinning, but fed and watered for at least 2 weeks. With time, the secondary structure of silk protein is becoming more and more disordered. The arrow indicates increasing time (days). Note that the amino acid composition of the silk protein was similar to that of a native N. edulis spider. Interestingly, silk protein extracted from the constrained spider did not respond to denaturing conditions (detergents, alcohols, pH, and salts Dicko et al, 2004a, 2005).

Chen, X., Knight, D. P., Shao, Z. Z., and Vollrath, F. (2002). Conformation transition in silk protein films monitored by time-resolved Fourier transform infrared spectroscopy Effect of potassium ions on Nephila spidroin films. Biochemistry 41, 14944-14950. 

Frische, S., Maunsbach, A. B., and Vollrath, F. (1998). Elongate cavities and skin-core structure in Nephila spider silk observed by electron microscopy. Journal of Microscopy 189, 64-70. 

Hronska, M., Van Beek, J. D., Williamson, P. T., Vollrath, F., and Meier, B. H. (2004). NMR characterization of native liquid spider dragline silk from Nephila edulis. Biomacromolecules 5, 834-839. 

Kovoor, J. (1986). L appareil sericigene dans les genres Nephila Leach et Nephilengys Koch Anatomie microscopique, histochimie affinites avec d autres Araneidae. Rev. Arachnol. 7, 15-34. 

Shao, Z., Hu, X. W., Frische, S., and Vollrath, F. (1999). Heterogeneous morphology of Nephila edulis spider silk and its significance for mechanical properties. Polymer 40, 4709-4711. 

Sirichaisit, J., Brookes, V. L., Young, R.J., and Vollrath, F. (2003). Analysis of structure/ property relationships in silkworm (Bombyx mori) and spider dragline (Nephila edulis) silks using Raman spectroscopy. Biomacromolecules 4, 387-394. 

Sponner, A., Schlott, B., Vollrath, F., Unger, E., Grosse, F., and Weisshart, K. (2005a). Characterization of the protein components of Nephila clavipes dragline silk. Biochemistry 44, 4727—1736. 

Nephila clavipes, silk from, 22 627, 628t, 632t, 633 Nephrotoxicity... 

From a defensive point of view, it was shown that sequestered PAs constitute an efficient protection against the orb-weaving spider Nephila clavipes, which liberates butterflies unharmed from its web. In this study, AT-oxides were shown to be more active than the corresponding free bases. This could be correlated with physicochemical properties of these molecules in interaction with the Nephila receptors. Moreover, there was a significant correlation between dosage and antipredator activity of PAs [160]. 

Nephila clavata E,V Males respond to pheromone from newly moulted females Miyashita and Hayashi, 1996... 

The small males of Nephila clavata cohabit with the much larger females in their web, and copulation takes place immediately after the final molt. Olfactometer tests showed that freshly molted females are much more attractive than older ones. Acetone extracts of the body surface of freshly molted females contained the active principle. Miyashita and Hayashi (1996) suggested that the volatile signal may originate from the molting fluid. 

Higgins, L.E., Townley, M. A., Tillinghast, E. K. and Rankin, M. A. (2001). Variation in the chemical composition of orb webs built by the spider Nephila clavipes (Araneae, Tetragnathidae). Journal of Arachnology 29 82-94. 

Miyashita, T. and Hayashi, H. (1996). Volatile chemical cue elicits mating behavior of cohabiting males of Nephila clavata (Araneae, Tetragnathidae). Journal of... 

Composition of the silk lipids of the spider Nephila clavipes. Lipids 36 637-647. 

Vasoconcellos-Neto, J. and Lewinsohn, T. M. (1984). Discrimination and release of unpalatable butterflies by Nephila clavipes, a neotropical orb-weaving spider. Ecological Entomology 9 337-344. 

Figure 12.3 Utetheisa ornatrix that were offered to the orb-weaving spider Nephila clavipes. The specimen on the right, rejected intact, was raised on one of its normal, pyrrolizidine alkaloid-containing food plants (Crotalaria mucronata). The one on the left, raised on an artificial diet devoid of alkaloid, was eaten. See also Figure 12.4. (From Eisner, 1982. American Institute of Biological Science.)...

Figure 12.4 Percent of prey item (Utetheisa, mealworms) remaining following attack by the orb-weaving spider Nephila davipes. Items were placed into individual webs with forceps (mealworms) or flipped from vials (Utetheisa).

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