In our previous study, we have proposed a lamellar structure for Ala-Gly repeated copoly meric peptide, a model for crystalline region of Bombyx mori silk fibroin Here, we propose the structure of (AGSGAG)(5) with silk II form which is a more mimic of the crystalline region of B mori silk fibroin than (AG)(15) The local structure for each Ala residue was determined from C-13 CP/MAS NMR spectra of 10 different [3 C-13]Ala (AGSGAG)(5) peptides differing in their C-13 labeling positions The highest field peak for the Ala C beta carbon (16 7 ppm) assigned to a distorted beta turn structure and/or random coil changes significantly depending on the C-13 labeling position In addition, the fractions of the random coil and/or distorted beta-turn component of each Ser residue were determined by REDOR experiments from the C-13-N-15 atomic distances of five versions of the above peptide with different [1 C-13]Gly Ser [N-15]Gly positions By combining the structural information of Ala and Ser residues from solid state NMR, with statistical mechanical calculation previously used for (AG)(15), the probable lamellar structures of (AGSGAG)(5) in the solid state are proposed The models of two turns in the central part of the sequence of (AGSGAG)(5) consist of approximately 8-12 amino acids The effect of the introduction of Ser residue on the local structure of Ala-Gly copolymeric peptides is also discussed on the basis of the evidence from C-13 solid state spin lattice relaxation experiments