Abstract: The present invention provides a cell-free protein synthesis method characterized by a cell-free protein synthesis reaction solution that is weakly reducing and suitable for protein folding, performing a weakly reducing synthesis reaction, and preferably performing a translation reaction with the further addition of a substance catalyzing a disulfide bond exchange reaction at the beginning of the translation reaction. This method allows for proper formation of intramolecular disulfide bonds in the protein and efficiently provides protein having substantially the same function as the original protein. Specifically, it provides antibody protein that binds specifically to an antigen.

Abstract: The present invention provides a single chain antibody that retains its original specific binding activity with an antigen, and a labeled single chain antibody in which a labeling substance is bound to the single chain antibody. Specifically, the labeled single chain antibody of the present invention can be produced by linking a labeling substance to a linker part of a single chain antibody. The antibody is produced using a wheat embryo-derived cell-free protein synthesis system, and production is carried out in a low reductive state that allows an intramolecular disulfide bond to be retained. Further, bonding the antibody to a solid phase via the labeling substance enables production of an immobilized single chain antibody as well as a method for analyzing an antigen-antibody reaction using the immobilized single chain antibody.

Abstract: The present invention provides a cell-free protein synthesis method characterized by a cell-free protein synthesis reaction solution that is weakly reducing and suitable for protein folding, performing a weakly reducing synthesis reaction, and preferably performing a translation reaction with the further addition of a substance catalyzing a disulfide bond exchange reaction at the beginning of the translation reaction. This method allows for proper formation of intramolecular disulfide bonds in the protein and efficiently provides protein having substantially the same function as the original protein. Specifically, it provides antibody protein that binds specifically to an antigen.