1. Department of ChemistrySchool of ScienceBeijing Technology and Business University Beijing 100048 P. R. China
2. Department of NeurosurgeryBeijing Neurosurgical InstituteChina National Clinical Research Center for Neurological DiseasesBeijing Tian Tan HospitalCapital Medical University Beijing 100050 P. R. China
3. Institute of ChemistryChinese Academy of Sciences Beijing 100190 P. R. China