用原子力显微镜和单层膜技术研究短杆菌肽D与卵磷脂混合物的界面性质(英文)

短杆菌肽是一种被广泛研究的细胞膜中的多肽．其与磷脂之间的相互作用以及其在磷脂单层膜中的构象还不十分清楚．研究发现短杆菌肽Ｄ在卵磷脂单层膜中有自发形成聚集体的趋势，而且聚集体的形状依赖于短杆菌肽Ｄ在膜中的浓度．当浓度特别低时，聚集体很大；随着浓度的增加，聚集体逐渐变高但面积逐渐变小．特别是当短杆菌肽Ｄ的摩尔百分率达到１０％时，聚集体几乎形成圆锥型     

Mechanisms of valence selectivity in biological ion channels

Transmembrane ion channels play a crucial role in the existence of all living organisms. They partition the exterior from the interior of the cell, maintain the proper ionic gradient across the cell membrane and facilitate signaling between cells. To perform these functions, ion channels must be highly selective, allowing some types of ions to pass while blocking the passage of others. Here we review a number of studies that have helped to elucidate the mechanisms by which ion channels discriminate between ions of differing charge, focusing on four channel families as examples: gramicidin, ClC chloride, voltage-gated calcium and potassium channels. The recent availability of high-resolution structural data has meant that the specific inter-atomic interactions responsible for valence selectivity can be pinpointed. Not surprisingly, electrostatic considerations have been shown to play an important role in ion specificity, although many details of the origins of this discrimination remain to be determined. Received 4 September 2005; received after revision 17 October 2005; accepted 2 November 2005