Efficient and highly selective copper(II) transport across a bulk liquid chloroform membrane mediated by lipophilic dipeptides
Efficient and highly selective copper(II) transport across a bulk liquid chloroform membrane mediated by lipophilic dipeptides
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DOI：
10.1021/jo9703257
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发表时间：
1997-08-08
影响因子：
3.6
通讯作者：
Tonellato, U
中科院分区：
文献类型：
--
作者：
Cleij, MC;Scrimin, P;Tonellato, U
合成了几种结构简单的N-单烷基化和-二烷基化二肽，由α-氨基酸甘氨酸，苯丙氨酸和亮氨酸，1-11，并研究了作为载体的运输Cu（II），Zn（II），和Ni（II）从水溶液的pH = 5.6的缓冲液源的0.1 M HCl接收相跨越散装氯仿膜。在此过程中，通过分析三个相中的金属离子浓度来跟踪质子驱动的易位。的运输效率取决于容易形成的中性络合物与铜（II）（肽基团和羧酸被去质子化）在源-氯仿界面和其中断的质子化在接收相：载体的亲脂性有利于金属离子的吸收，而不是释放。通过调节N-烷基链的长度和二肽部分的疏水性，观察到Cu（II）的相当显著的运输效率，在大多数情况下上级于工业萃取剂Kelex 100的运输效率。此外，使用L，L-和L，D-N-辛基-PheLeu作为载体，显着的非对映体效应中观察到的Cu（II）离子的吸收和释放的速率，虽然在整体传输速率的差异相互补偿。在所使用的条件下，载体在Zn（II）和Ni（II）的移位中的效率低得多，并且在Cu（II）的存在下，它们的传输效率显著下降，后者分别有利1.2 × 10（3）和> 10（4）的因子。如此高的选择性取决于在源相的pH值下，在其它过渡金属离子中只有Cu（II）能形成中性络合物。
Several structurally simple N-monoalkylated and -dialkylated dipeptides made of alpha-amino acids Gly, Phe, and Leu, 1-11, were synthesized and investigated as carriers for the transport of Cu(II), Zn(II), and Ni(II) from an aqueous pH = 5.6 buffer source to a 0.1 M HCl receiving phase across a bulk chloroform membrane. The proton-driven translocation was followed during the process by analyzing the metal ion concentrations in the three phases. The transport efficiency depends on the ease of formation of a neutral complex with Cu(II) (the peptide group and carboxylic acid being deprotonated) at the source-chloroform interface and on that of its disruption by protonation at the receiving phase: the carrier's Lipophilicity favors the metal ion uptake and not the release. By modulating the length of the N-alkyl chains and the hydrophobicity of the dipeptide moiety, a quite remarkable transport efficiency was observed for Cu(II), in most cases superior to that of the industrial extractant Kelex 100. Moreover, using L,L- and L,D-N-octyl-PheLeu as carriers, remarkable diastereomeric effects were observed in the rate of uptake and release of Cu(II) ion although the differences mutually compensate in the overall transport rate. Under the conditions used the carriers are much less effective in the translocation of Zn(II) and Ni(II) and their transport efficiency drops dramatically in the presence of Cu(II), the latter being favored by factors of 1.2 x 10(3) and > 10(4), respectively. Such very high selectivities depend on the fact that only Cu(II) among other transition metal ions Can form neutral complexes at the pH value of the source phase.