1. Pharmaceutical Analysis Laboratory, School of Pharmaceutical Sciences; Sun Yat-sen University; 132 Waihuan Road East Guangzhou 510006 China
2. The Center for Cellular and Structural Biology; Sun Yat-sen University; 132 Waihuan Road East Guangzhou 510006 China
3. Kornberg Group, School of Pharmaceutical Sciences; Sun Yat-sen University; 132 Waihuan Road East Guangzhou 510006 China