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Recently, silk fibroin has been widely attended for its biomedical material applications, because of its excellent properties such as strength, flexibility, biocompatibility and permeability (Altman et al., 2003). Compared with the silk fibroin from silkworm, spider fibroin has higher strength and stronger toughness, but its resource is limited. So people have tried to synthesize the spider fibroin using genetic recombination method to obtain the spider fibers (Fukushima, 1998; Heslot, 1998; Zhou et al., 2001). Shao et al. (Shao & Vollrath, 2002) demonstrated that although the amino acid sequence of Bombyx mori silkworm fibroin is different from that of spider fibroin, by controlling the process of the silkworm spinning, the high strength of the silk fiber as that of the spider fiber can be gained. The investigations indicate that there are the correlations among spinning process, secondary structure and mechanical properties of the silk fibroin. The environment of the silkworm spinning is changed during the process, such as shearing strength (Chen et al., 2001; Shao & Vollrath, 2002; Terry et al., 2004), pH (Magoshi et al., 1996; Xie et al., 2004; Zhou et al., 2004; Zong et al., 2004), concentration of metal ions (Li et al., 2001; Ruan et al., 2008; Zhou et al., 2004; Zong et al., 2004) and concentration of the silk fibroins (Magoshi et al., 1996; Terry et al., 2004), etc. Therefore, studying the environment effects on the silk fibroin conformation is benefit to understand the silkworm spinning mechanism, and helpful to synthesize artificially the silk fibroin or spidroin and fabricate the high performance silk fiber to meet the requirements of the biomaterial usages. The methods used to investigate the silk fibroin mainly include X-ray diffraction (XRD) (Lv et al., 2005; March et al., 1955; Qiao et al., 2009; Takahashi et al., 1999; Saitoh et al., 2004; Sinsawat et al., 2002), electron diffraction (ED) (He et al., 1999), infrared (IR) (Chen et al., 2001; Mo et al., 2006), nuclear magnetic resonance (NMR) (Yao et al., 2004; Zhao et al., 2001) and so on. Among them, nuclear magnetic resonance spectroscopy is very effective to characterize the molecular chain structures of the biopolymers (Du et al., 2003; Li et al., 2008). Asakura et al. analyzed the crystal structures of 40 proteins and their NMR chemical shifts, and established the correlation of Ala, Ser, and Gly residues between 13C chemical shifts of C┙, C┚ atoms and the dihedral angels of  and  of the peptide chains, which are very useful to determine the protein structure by NMR method (Asakura et al., 1999). The

Environment-Induced Silk Fibroin Conformation Based on the Magnetic Resonance Spectroscopy