1. Division of Mass Spectrometry, Korea Basic Science Institute, 804-1 Yangcheong-Ri, Ochang-Myun, Cheongwon-Gun 363-883, Republic of Korea, GRAST, Chungnam National University, Daejeon 305-764, Republic of Korea, and Daejeon-KRIBB-FHCRC Research Cooperation Center, KRIBB, 111 Gwahangno, Yuseong-gu, Daejeon 305-806, Republic of Korea