NMR Characterization of Native Liquid Spider Dragline Silk fromNephila edulis

Abstract

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.

Structure of silk by raman spectromicroscopy: From the spinning glands to the fibers

“…[73][74][75][76] The spectrum is also comparable to that obtained for the in vitro dissolution of recombinant MaSp1 and MaSp2 proteins. The conformation of the spinning dope that has flowed out of the gland is basically identical to the native silk contained in the sac of the gland, and is slightly affected by dehydration.…”

Diversity of Molecular Transformations Involved in the Formation of Spider Silks

“…secondary structures despite their different amino acid sequences. Major ampullate spidroins (MaSps) are known to be mostly unfolded in the gland, 24,25 but vibrational circular dichroism and NMR spectroscopies have clearly shown that they contain a significant amount of left-handed 3 1 -helices [also known as polyproline II (PPII) helices], which have been suggested to be important for the formation of β-sheets during the spinning process. 23 From the similarity of the Raman spectra of the Ma and Mi silks, it can be hypothesized that the Mi proteins also contain a significant amount of PPII helices.…”

Mollusk Shell Formation: A Source of New Concepts for Understanding Biomineralization Processes

“…[9] Furthermore, assemblies of chitin and silk in vitro do not provide either images or diffraction patterns any different from chitin alone, again implying that the silk fraction is not ordered. [18] Spider silk only becomes fibrillar and ordered during its extrusion from the silk gland. [17] It is thus relevant to note that spider silk in the silk gland is highly concentrated, hydrated, and not ordered.…”