Facilitated Phospholipid Flip-Flop Using Synthetic Steroid-Derived Translocases
摘要:
Cholate esters with phenylurea groups at the 7alpha- and 12alpha-positions are highly effective promoters of phosphatidylcholine translocation across vesicle and cell membranes. The urea groups are essential for strong binding of the highly polar phosphate portion of the phosphocholine headgroup and apparently cannot be replaced by simple amide, alcohol, or amine moieties. NMR and UV studies show that these synthetic translocases have very weak affinity for phosphatidylethanolamine and phosphatidylserine.
High-Affinity Anion Binding by Steroidal Squaramide Receptors
作者:Sophie J. Edwards、Hennie Valkenier、Nathalie Busschaert、Philip A. Gale、Anthony P. Davis
DOI:10.1002/anie.201411805
日期:2015.4.7
Exceptionally powerful anionreceptors have been constructed by placing squaramide groups in axial positions on a steroidal framework. The steroid preorganizes the squaramide NH groups such that they can act cooperatively on a bound anion, while maintaining solubility in nonpolar media. The acidic NH groups confer higher affinities than previously‐used ureas or thioureas. Binding constants exceeding 1014 M−1
通过将方酰胺基团放置在类固醇框架的轴向位置,构建了异常强大的阴离子受体。该类固醇预先组织方酰胺 NH 基团,以便它们可以协同作用于结合的阴离子,同时保持在非极性介质中的溶解度。酸性 NH 基团比以前使用的脲或硫脲具有更高的亲和力。通过采用克拉姆萃取程序的变型,已经测量了氯仿中四乙基铵盐的超过10 14 M -1的结合常数。这些受体还作为单层囊泡中的跨膜阴离子载体进行了研究。不同寻常的是,它们的活性与阴离子亲和力不相关,因此表明阴离子载体设计中结合强度的上限。