The micro-structure of silk fibroin and the structural difference between silk surface and bulk were studied using a range of analytical techniques

microscopy

Fourier transform infra-red spectroscopy in ATR mode

analysis of amino acids composition and FuLin reagent analysis；The compositions and distribution of the amino acids in silk fibroin

especially the main aromatic amino acids (tyrosine) which plays an important role on the structure and properties of silk fibroin was studied

in order to reveal the relationship between silk structure and the intrinsic defect of silk fabrics such as yellowing

easy-crease

and color fastness．The results show that there is multiple-layers structure in natural silk fibroin

with higher crystallinity in the in-layer than out-layer；The acids with large side-chain such as Lys

His

Cys

Arg

Asp

Phe

Leu

Glu

Tyr are richer in the outer-layer

and the amino acids with small side-chain such as Gly．Ala and Ser are richer in the inner-layer of silk fibrions．