Abstract: The present invention intends to provide an assay system using split luciferase that has a remarkably high detection sensitivity. In an embodiment, binding of mutually binding first and second proteins is detected by preparing a first fusion protein comprising the first protein fused with a peptide having the amino acid sequence of amino acid SEQ ID NO: 1 and a second fusion protein comprising the second protein fused with a peptide having an amino acid sequence selected from the group consisting of amino acid SEQ ID NOS: 2 to 6, and allowing the first fusion protein to bind with the second fusion protein to form a complex, and detecting luminescence emitted from the complex.

Abstract: The present invention relates to a polyester composition excellent in transparency, thermal stability, and flavor retention or excellent in transparency, thermal stability, flavor retention and gas barrier properties, which is obtained by blending a partially aromatic polyamide to a thermoplastic polyester, and also relates to a packaging material comprising the same. The polyester composition of the invention preferably contains an alkali metal atom in an amount of 0.1 to 300 ppm and phosphorus atom in an amount of 5 to 200 ppm. Further, it is preferable that the Color-L value of the molded article obtained by injection molding of the polyester composition of the invention at a molding temperature of 290° C. is 80.0 or more and the haze thereof is 20% or less. As the partially aromatic polyamide, an m-xylylene group-containing polyamide is preferable.