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从驱蛔中药楝属植物根皮提取的一种三萜化合物──川楝素是一个选择性地作用于突触前的神经肌肉传递阻遏剂。根据它作用的专一性和不可逆性推测，突触前末梢应存在着川楝素的结合位点。本工作利用３Ｈ－川楝素进行的结合实验表明，大鼠大脑皮层匀浆中存在川楝素的结合位点；３Ｈ－川楝素与结合位点复合物的平衡解离常数（ＫＤ）约为２．０×１０（－７）ｍｏｌ／Ｌ；皮层匀浆离心团粒（Ｐ２＇）的重悬液含川楝素结合位点约２．７×１０（－１２）ｍｏｌ／ｍｇ蛋白质；该结合位点的Ｈｉｌｌ系数为０．９７。研究还显示，Ｐ２＇重悬液经蔗糖密度梯度超离心得到的突触体组分是川楝素结合位点的富集亚细胞组分，其比结合活性是Ｐ２＇重悬液的２至３倍。
A triterpene compound extracted from the root bark of Medicinal Herba Azadirachtin ─ ─ Toosendanone is a neuromuscular transfer inhibitor that selectively acts on the presynaptic membrane. Based on the specificity and irreversibility of its role, it is speculated that there should be a binding site for toosendanin at the presynaptic terminals. The binding experiments using 3H-toosendanin showed that there was binding site of toosendanin in the homogenate of rat cerebral cortex. The equilibrium dissociation constant (KD) of 3H-toosendin and binding site complex Was 2.0 × 10 (-7) mol / L. The suspension of cortex homogenate pellet (P2 ’) contained about 2.7 × 10 (-12) mol / mg protein of toosendin-binding site. The Hill coefficient of the binding site is 0.97. The study also showed that the synaptosomal fraction of the P2 ’resuspension sucrose density gradient ultracentrifugation is the enriched subcellular fraction of the toosendin binding site with a specific binding activity ranging from 2 to 3 times.