Influence of CO2 on the micro-structural properties of spider dragline silk: X-ray microdiffraction results.
The mechanical properties of spider dragline fibres are altered by CO(2) exposure under anaesthetizing conditions during the spinning process. In order to relate these macroscopic changes to a microscopic model, the extrusion of dragline silk was studied by synchrotron radiation microdiffraction. A brief exposure of a female Nephila senigalensis spider to CO(2 )results after an incubation time of less than 7 min in the extrusion of a thread (two fibres) swollen with water. The data are interpreted for a model of crystalline beta-sheet domains containing nanofibrils, which reinforce a network of protein chains. The protein network absorbs water, leaving the nanofibrils unaffected. A continuous flow of CO(2) results in a co-extrusion of a dragline thread and an isotropic silk fraction, which probably has a glycine-rich sequence. Long CO(2) exposure reduces the axial alignment of nanofibrils, presumably due to a partial destruction of the amorphous network.
Riekel
Christian
C
European Synchrotron Radiation Facility, BP 220, 38043 Grenoble Cedex, France. riekel@esrf.fr
Rössle
Manfred
M
Sapede
Daniel
D
Vollrath
Fritz
F
D000818:Animals; D002245:Carbon Dioxide / Q000494:pharmacology*; D019476:Insect Proteins / Q000187:drug effects / Q000648:ultrastructure*; D047011:Silk; D013112:Spiders; D014961:X-Ray Diffraction / Q000379:methods
D019476:Insect Proteins; D047011:Silk; D002245:Carbon Dioxide