Molecules 2011, 16, 1544-1558; doi:10.3390/molecules16021544 molecules ISSN 1420-3049 www.mdpi.com/journal/molecules Article Identification and Characterization of Three Novel Small Interference RNAs That Effectively Down-Regulate the Isolated Nucleocapsid Gene Expression of SARS Coronavirus Ying-Li Cao, Ying Wang, Rong Guo, Fan Yang, Yun Zhang, Shu-Hui Wang and Li Liu * Department of Microbiology, Institute of Basic Medical Sciences, Chinese Academy of Medical Sciences & School of Basic Medicine, Peking Union Medical College, Beijing 100005, China * Author to whom correspondence should be addressed; E-Mail: