基金Acknowledgments We thank Dr Boja Emily S (NHLBI, NIH, USA) for expert technical assistance in mass spectrometry analyses, and our colleagues Drs Bin Lu, Zhao-Qiu Wu for helpful comments. This work was supported by a National Basic Research Program grant from the Ministry of Science and Technology of China (G2003CB515401), National Science Fund for Distinguished Young Scholar from the National Natural Science Foundation of China (30425002) and a fund supported by the "100 Talents Project" of Chinese Academy of Sciences (J-G Liu).