Departments of †Chemistry & Biochemistry and ‡Biology, §Center for Nanoscience, University of Missouri-St. Louis , St. Louis, Missouri 63121, United States.
Acc Chem Res. 2013 Dec 17;46(12):2824-33. doi: 10.1021/ar400026x. Epub 2013 Jun 5.
In this Account, we describe the development of several diverse families of synthetic, membrane-active amphiphiles that form pores and facilitate transport within membrane bilayers. For the most part, the compounds are amphiphiles that insert into the bilayer and form pores either on their own or by self-assembly. The first family of synthetic ion channels prepared in our lab, the hydraphiles, used crown ethers as head groups and as a polar central element. In a range of biophysical studies, we showed that the hydraphiles formed unimolecular pores that spanned the bilayer. They mediated the transport of Na(+) and K(+) but were blocked by Ag(+). The hydraphiles are nonrectifying and disrupt ion homeostasis. As a result, these synthetic ion channels are toxic to various bacteria and yeast, a feature that has been used therapeutically in direct injection chemotherapy. We also developed a family of amphiphilic heptapeptide ion transporters that selected Cl(-) >10-fold over K(+) and showed voltage dependent gating. The formed pores were approximately dimeric, and variations in the N- and C-terminal anchor chains and the acids affected transport rates. Surprisingly, the longer N-terminal anchor chains led to less transport but greater Cl(-) selectivity. A proline residue, which is present in the ClC protein channel's conductance pore, proved to be critical for Cl(-) transport selectivity. Pyrogallol[4]arenes are macrocycles formed by acid-catalyzed condensation of four 1,2,3- trihydroxybenzenes with four aldehydes. The combination of 12 hydroxyl groups on one face of the macrocycle and four pendant alkyl chains conferred considerable amphiphilicity to these compounds. The pyrogallol[4]arenes inserted into bilayer membranes and conducted ions. Based on our experimental evidence, the ions passed through a self-assembled pore comprising four or five amphiphiles rather than passing through the central opening of a single macrocycle. Pyrogallol[4]arenes constructed with branched chains are also amphiphilic and active in membranes. The pyrogallol[4]arene with 3-pentyl sidechains formed a unique nanotube assembly and functioned as an ion channel in bilayer membranes. Finally, we showed that dianilides of either isophthalic or dipicolinic acids, compounds which have been extensively studied as anion binders, can self-assemble to form pores within bilayers. We called these dianilides tris-arenes and have shown that they readily bind to phosphate anions. These structures also mediated the transport of DNA plasmids through vital bilayer membranes in the bacterium Escherichia coli and in the yeast Saccharomyces cerevisiae . This transformation or transfection process occurred readily and without any apparent toxicity or mutagenicity.
在本专题介绍中，我们描述了几种不同的合成膜活性两亲分子的发展，这些分子能够形成孔并促进膜双层内的物质运输。在大多数情况下，这些化合物是插入双层的两亲分子，它们可以自行形成孔，也可以通过自组装形成孔。我们实验室制备的第一类合成离子通道，水通道，使用冠醚作为头基和极性中心元素。在一系列生物物理研究中，我们表明水通道形成了跨越双层的单分子孔。它们介导 Na(+)和 K(+)的运输，但被 Ag(+)阻断。水通道是非整流的，会破坏离子内环境平衡。因此，这些合成离子通道对各种细菌和酵母具有毒性，这一特性已在直接注射化疗中得到应用。我们还开发了一类两亲七肽离子转运体，它们对 Cl(-)的选择性是 K(+)的 10 倍以上，并表现出电压依赖性门控。形成的孔大约是二聚体，N-和 C-末端锚链以及酸的变化会影响运输速率。令人惊讶的是，较长的 N-末端锚链导致运输减少，但 Cl(-)选择性增加。脯氨酸残基存在于 ClC 蛋白通道的电导孔中，被证明对 Cl(-)运输选择性至关重要。邻苯三酚[4]芳烃是由四个 1,2,3-三羟基苯在酸催化下缩合四个醛形成的大环。大环一侧的 12 个羟基和四个悬挂的烷基链组合赋予这些化合物相当大的两亲性。邻苯三酚[4]芳烃插入双层膜并传导离子。根据我们的实验证据，离子通过一个由四个或五个两亲分子自组装形成的孔而不是通过单个大环的中心开口穿过。带有支链的邻苯三酚[4]芳烃也是两亲的，并在膜中具有活性。带有 3-戊基侧链的邻苯三酚[4]芳烃形成独特的纳米管组装体，并在双层膜中充当离子通道。最后，我们表明，间苯二甲酸或二吡啶酸的二酰亚胺，这些化合物作为阴离子结合物已经得到了广泛的研究，可以自组装形成双层内的孔。我们称这些二酰亚胺为三芳基，并表明它们很容易与磷酸阴离子结合。这些结构还介导了 DNA 质粒通过细菌大肠杆菌和酵母酿酒酵母的重要双层膜的运输。这种转化或转染过程很容易发生，而且没有明显的毒性或致突变性。
