Spiders can produce up to seven different types of silks or glues with different mechanical properties. Of these, flagelliform (Flag) silk is the most elastic, and aciniform (AcSp1) silk is the toughest. To produce a chimeric spider silk (spidroin) Flag R-AcSp1 R , we fused one repetitive module of flagelliform silk from Araneus ventricosus and one repetitive module of aciniform silk from Argiope trifasciata. The recombinant protein expressed in E. coli formed silk-like fibers by manual-drawing. CD analysis showed that the secondary structure of Flag R-AcSp1 R spidroin remained stable during the gradual reduction of pH from 7.0 to 5.5. The spectrum of FTIR indicated that the secondary structure of Flag R-AcSp1 R changed from α-helix to β-sheet. The conformation change of Flag R-AcSp1 R was similar to other spidroins in the fiber formation process. SEM analysis revealed that the mean diameter of the fibers was around 1 2 μm, and the surface was smooth and uniform. The chimeric fibers exhibited superior toughness (33.1 MJ/m 3) and tensile strength (261.4 MPa). This study provides new insight into design of chimeric spider silks with high mechanical properties.

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