1. BNLMSState Key Laboratory for Structural Chemistry of Unstable and Stable Species, Peking-Tsinghua Center for Life Sciences, College of Chemistry and Molecular EngineeringPeking University Beijing 100871 P. R. China
2. Center for Quantitative Biology, Peking-Tsinghua Center for Life Sciences, Academy for Advanced Interdisciplinary StudiesPeking University Beijing 100871 P. R. China
3. State Key Laboratory for Protein and Plant Gene ResearchPeking-Tsinghua Center for Life Sciences, College of Life SciencesPeking University Beijing 100871 P. R. China
4. National Plant Gene Research Center Beijing 100101 P. R. China