Study on peptides passing through cell membranes by the electrostatic interaction.

血脑屏障（blood-brain barrier，BBB）是一种高度选择性的膜屏障，调节血液中物质向脑实质的转运。近年来，我们成功地利用细胞膜上的阴离子位点与阳离子配体之间的静电相互作用，通过吸附介导的胞吞转运（AMT）将合成肽转运到脑内。例如，合成的阳离子肽MeTyr-Arg-MeArg-D-Leu-NH（CH_2）_8（OO 1-C8）通过AMT机制被高度转运通过BBB。本研究中，我们制备了一种荧光标记肽001-C8-NBD（NBD：5-硝基苯并-3-氧杂-2，4-二唑），通过测量荧光OO 1-C8-NBD的跨上皮转运，以及通过活体的可视化三维分析，接下来，我们合成了促酪激素释放激素（TRH）和镇痛肽kyotorphin（KYO）类似物，其中引入了辛二胺（Oda=C8）和NBD残基;这些肽被设计为具有适合的阳离子和亲脂性，这是通过AMT机制进行BBB转运所需要的。到目前为止，我们研究了TRH-C8-NBD通过被动转运机制而不是AMT机制通过BBB，而KYO-C8-NBD不通过BBB。这一事实表明，我们需要重新考虑通过BBB的肽的设计。此外，我们制备了三种含对硼苯丙氨酸的二肽，它们将用于肿瘤细胞的中子俘获治疗。

The blood-brain barrier (BBB) is a highly selective membranous barrier regulating the transport of substances in blood into the brain parenchyma. Recently we succeeded to open away to deliver synthetic peptides into the brain by the adsorptive-mediated transcytosis (AMT) which is based on the electrostatic interaction between the cationic ligands and the anionic sites on the cell membranes. For example, a synthetic cationic peptide MeTyr-Arg-MeArg-D-Leu-NH(CH_2)_8 termed OO1-C8 was highly transported through the BBB via the AMTmechanism. In the present research project, we prepared a fluorescence-labeled peptide 001-C8-NBD (NBD : 5-nitrobenzo-3-oxa-2, 4-diazole) which was successfully applied to elucidate and visualize the process of AMT in Caco-2 cells by measuring the transepithelial transport of fluorescent 0O1-C8-NBD, as well as by visual three-dimentional analysis of living, nonfixed cells by confocal laser microscopy.We next synthesized both the tyrotropic hormone releasing hormone (TRH) and an analgesic peptide kyotorphin (KYO) analogs in which the octanediamine (Oda=C8) and NBD residues were introduced ; these peptides were designed as possessing suitable cationic and lipophilic character requiring for the BBB transport by the AMT mechanism. So far we examined, TRH-C8-NBD was transported through the BBB by the passive transport mechanism but not the AMT mechanism, while KYO-C8-NBD did not pass through the BBB.This fact suggests that we need to reconsider for the design of the peptides passing through the BBB.Furthermore, we prepraed three kinds of p-boronophenylalanine containing dipeptides which will be applied to the elucidation of neutron capture therapy of cancer cells.