1. Research Institute of Biological Resources, National Institute of Bioscience and Human-Technology, 1-1-1 Higashi, Tsukuba, Ibaraki 305-8566, Japan
2. Corresponding author: email: y.tokiwa@aist.go.jp
3. Konan Chemical Ind. Company, Ltd., Osaka 569-0066, Japan
4. Polymer Research Department, Toyobo Research Center Company, 1-1, Katata 2-Chome, Otsu, Shiga 520-0292, Japan