1. Department of Mathematics; Michigan State University, East Lansing; Michigan 48824
2. School of Medicine; Foshan University; Foshan Guangdong 528000 People's Republic of China
3. State Key Laboratory of Bioorganic Chemistry; Shanghai Institute of Organic Chemistry, Chinese Academy of Sciences; Shanghai 200032 People's Republic of China
4. Department of Electrical and Computer Engineering; Michigan State University; Michigan 48824
5. Department of Biochemistry and Molecular Biology; Michigan State University; Michigan 48824