Tran Helen, Gael Sarah L, Connolly Michael D, Zuckermann Ronald N
Molecular Foundry, Lawrence Berkeley National Laboratory.
J Vis Exp. 2011 Nov 2(57):e3373. doi: 10.3791/3373.
Peptoids are a novel class of biomimetic, non-natural, sequence-specific heteropolymers that resist proteolysis, exhibit potent biological activity, and fold into higher order nanostructures. Structurally similar to peptides, peptoids are poly N-substituted glycines, where the side chains are attached to the nitrogen rather than the alpha-carbon. Their ease of synthesis and structural diversity allows testing of basic design principles to drive de novo design and engineering of new biologically-active and nanostructured materials. Here, a simple manual peptoid synthesis protocol is presented that allows the synthesis of long chain polypeptoids (up to 50mers) in excellent yields. Only basic equipment, simple techniques (e.g. liquid transfer, filtration), and commercially available reagents are required, making peptoids an accessible addition to many researchers' toolkits. The peptoid backbone is grown one monomer at a time via the submonomer method which consists of a two-step monomer addition cycle: acylation and displacement. First, bromoacetic acid activated in situ with N,N'-diisopropylcarbodiimide acylates a resin-bound secondary amine. Second, nucleophilic displacement of the bromide by a primary amine follows to introduce the side chain. The two-step cycle is iterated until the desired chain length is reached. The coupling efficiency of this two-step cycle routinely exceeds 98% and enables the synthesis of peptoids as long as 50 residues. Highly tunable, precise and chemically diverse sequences are achievable with the submonomer method as hundreds of readily available primary amines can be directly incorporated. Peptoids are emerging as a versatile biomimetic material for nanobioscience research because of their synthetic flexibility, robustness, and ordering at the atomic level. The folding of a single-chain, amphiphilic, information-rich polypeptoid into a highly-ordered nanosheet was recently demonstrated. This peptoid is a 36-mer that consists of only three different commercially available monomers: hydrophobic, cationic and anionic. The hydrophobic phenylethyl side chains are buried in the nanosheet core whereas the ionic amine and carboxyl side chains align on the hydrophilic faces. The peptoid nanosheets serve as a potential platform for membrane mimetics, protein mimetics, device fabrication, and sensors. Methods for peptoid synthesis, sheet formation, and microscopy imaging are described and provide a simple method to enable future peptoid nanosheet designs.
类肽是一类新型的仿生、非天然、序列特异性杂聚物，它们抗蛋白水解，具有强大的生物活性，并能折叠成高阶纳米结构。类肽在结构上与肽相似，是聚N-取代甘氨酸，其侧链连接在氮原子上而非α-碳原子上。它们易于合成且结构多样，这使得对基本设计原则进行测试成为可能，从而推动新型生物活性和纳米结构材料的从头设计与工程化。在此，我们展示了一种简单的手动类肽合成方案，该方案能够以极高的产率合成长达50聚体的长链类肽。仅需基本设备、简单技术（如液体转移、过滤）以及市售试剂，这使得类肽成为许多研究人员工具包中易于获取的补充工具。类肽主链通过亚单体法一次生长一个单体，该方法由两步单体添加循环组成：酰化和取代。首先，用N,N'-二异丙基碳二亚胺原位活化的溴乙酸酰化树脂结合的仲胺。其次，伯胺对溴化物进行亲核取代以引入侧链。重复这两步循环，直至达到所需的链长。这个两步循环的偶联效率通常超过98%，能够合成长达50个残基的类肽。由于数百种易于获得的伯胺可直接并入，采用亚单体法可实现高度可调、精确且化学性质多样的序列。由于其合成灵活性、稳定性以及在原子水平上的有序性，类肽正成为纳米生物科学研究中一种通用的仿生材料。最近已证明，单链、两亲性、富含信息的类肽可折叠成高度有序的纳米片。这种类肽是一个36聚体，仅由三种不同的市售单体组成：疏水、阳离子和阴离子单体。疏水性苯乙基侧链埋于纳米片核心，而离子性胺基和羧基侧链排列在亲水面上。类肽纳米片可作为膜模拟物、蛋白质模拟物、器件制造和传感器的潜在平台。文中描述了类肽合成、片层形成和显微镜成像的方法，为未来类肽纳米片设计提供了一种简单方法。
