Glycoproteins and skin‐core structure in Nephila clavipes spider silk observed by light and electron microscopy

Abstract

Summary: Microscopical imaging of natural, unstressed draglines or of untreated bulk samples showed two types or threads with diameters of either ~ 1-2 µm or 4-5 µm, which could be identified as products of the minor or major ampullate glands. The threads had a circular profile in serial cross sections and are surrounded by a thin outer layer of a different material within the section. Such fibrillar configurations were also found in untreated threads or in the same serial sections of transmission electron microscopy (TEM) samples by means of the special technique of laser scanning microscopy. In TEM slides, numerous cavities with the same circular profile were detectable, and the length of these cavities is variable from 40-300 nm. The threads are oriented parallel and twisted around themselves to construct a double thread. In the interface between the two single threads, bridge-like structures are prominent. The single untreated thread consists of cylindrical fibers with a diameter of approximately 1-1.5 µm. Apparently more than eight fibers are within a thread and each fiber is composed of a great number of fibrils with a diameter of about 150 nm. The surface of threads is coated with a characteristic layer ~150-250 nm thick that contains glycoproteins. These were demonstrated for the first time by labeling with concanavalin A lectin-gold complex and are dependent on the diameter and length of the thread. The same substances could also be detected inside the single thread. The skin can be removed completely or partially by mechanical treatment, or by washing with phosphatebuffered saline or trypsin.

Recombinant Spider Silks—Biopolymers with Potential for Future Applications

“…Schematic representation of the hierarchical structure of a spider MA silk fiber. On the macroscopic level, the skin-core structure can be recognized [106] and on the sub-microscopic level, the presence of the aligned fibrils has been shown [107]. The nanoscopic structure is represented by poly-Ala -sheet crystals aligned with the fiber axis and embedded in the amorphous phase, comprising GPGXX and GGX ensemble repeats [108,109].…”

Parasitoid suppression and life-history modifications in a wolf spider following infection by larvae of an acrocerid fly

“…1C; Sponner et al 2007). For instance, major ampullate threads are surrounded by sheaths of glycoproteins and lipids (Frische et al 1998;Augsten et al 2000). Internally, the core of the thread may be arranged into nanofibrils or contain elongate cavities that may distribute energy and help to prevent crack propagation as energy is propagated longitudinally rather than in the plane of the crack (Li et al 1994;Frische et al 1998).…”

Do habitat features affect the composition of silk proteins by Namibian arid-adaptedAriadnaspiders (Araneae: Segestriidae)?

“…Until now, in-depth studies have concerned the orb web spiders belonging to the genera Nephila (Andersen 1970;Hinman & Lewis 1992;Frische et al 1998;Higgins & Rankin 1999;Vollrath & Knight 1999;Augsten et al 2000;Schulz 2001;Gaines & Marcotte 2008;Lefèvre et al 2008), Araneus (Andersen 1970;Beckwitt & Arcidiacono 1994) and Argiope (Craig et al 2000;Blackledge & Hayashi 2006;Opell et al 2009). …”