Abstract: The spider dragline silks have attracted many interests for their marvelous comprehensive mechanical properties in the past few decades. However,the application of such an excellent material is extraordinarily restricted due to the difficulty of collection. Therefore,many attempts have been made in order to obtain spider silk fibers,in which the artificial spinning was thought to be most practical. Unfortunately,till now the properties of artificial silk fibers still cannot compare with the natural one. We think the reason for poor artificial silk fibers may be the only consideration of pure silk protein spinning solution and industrial spinning condition in the artificial spinning process. We know the spider spinning process in a bioprocess,therefore we think it is necessary to consider its biological environment. In this article,we found the potassium content was much higher in Nephila dragline silk than in its spinning dope by means of ICP-MS. We also found the addition of KCl into Nephila spidroin solution made it become turbid. The electron microscope observation revealed the nanofibril formation in the solution and the turbidimetry showed the turbidity declined about 1 h later indicating the precipitation of spidroin aggregation from the solution. Moreover,the conformation transition from random coil/helical to β-sheet was monitored with FTIR and Raman spectroscopy when the Nephila spidroin membranes were immersed in KCl solution. In conclusion,all the experimental results suggest that potassium may have a special effect in the spinning process of spider Nephila.

Key words: Conformation transition, ICP-MS, Turbidimetry, Nephila silk protein