国家自然科学基金81060140;海南省自然科学基金30838;海南省科技计划081009;海南医学院科研启动基金2011011;It is supported by National Nature Science Fund81060140;Nature Science Fund of Hainan Province30838;Science and Technology Planning of Hainan Province081009;Initiative Fund for Science Research of Hainan Medical College2011011