一种新型高价锰取代的多金属氧酸盐合成、结构及性质研究

在含有MnⅡ的夹心型多金属氧酸盐水溶液中加入强氧化剂KMnO4,制得一种新型的含有MnⅢ的多金属氧酸盐K5Na3[{MnⅢ(H2O)}2(WO)(H2O) (AsW9O33)2]·18H2O (KNa-1).该化合物的多阴离子结构是基于2个B-α-[AsW9]三缺位Keggin型构筑单元,中间夹着2个{MnⅢ(H2O)}和1个{WⅥO}片段而构成的夹心式构型.对KNa-1进行了变温磁化率测定并采用双核MnⅢ簇为模型进行了拟合,并对该化合物进行了电化学分析.结果表明:KNa-1 中的2个MnⅢ中心存在弱的反铁磁相互作用;化合物中的MnⅢ离子具有不可逆的氧化还原过程.     

Feedback inhibition of calcineurin and Ras by a dual inhibitory protein Carabin

Feedback regulation of adaptive immunity is a fundamental mechanism for controlling the overall output of different signal transduction pathways, including that mediated by the T-cell antigen receptor (TCR). Calcineurin and Ras are known to have essential functions during T-cell activation. However, how the calcineurin signalling pathway is terminated in the process is still largely unknown. Although several endogenous inhibitors of calcineurin have been reported, none fulfils the criteria of a feedback inhibitor, as their expression is not responsive to TCR signalling. Here we identify an endogenous inhibitor of calcineurin, named Carabin, which also inhibits the Ras signalling pathway through its intrinsic Ras GTPase-activating protein (GAP) activity. Expression of Carabin is upregulated on TCR signalling in a manner that is sensitive to inhibitors of calcineurin, indicating that Carabin constitutes part of a negative regulatory loop for the intracellular TCR signalling pathway. Knockdown of Carabin by short interfering RNA led to a significant enhancement of interleukin-2 production by antigen-specific T cells in vitro and in vivo. Thus, Carabin is a negative feedback inhibitor of the calcineurin signalling pathway that also mediates crosstalk between calcineurin and Ras.