Design and analysis of random copolymers with antimicrobial activity

描述（由申请方提供）：病原性感染是对人类健康的持续威胁。对药物治疗的耐药性的快速发展产生了对新的抗感染剂的持续需求。拟议的研究重点是开发具有尼龙-3骨架的序列无规共聚物作为通用的廉价抗菌剂。我们将合成和表征各种各样的这些共聚物，旨在模拟天然宿主防御肽（HDPs）的活性，这些肽已在植物，动物和人类中发现。HDPs的显著之处在于其阻止革兰氏阴性和革兰氏阳性细菌生长的一般能力，同时使动物细胞基本上不受影响。细菌抵抗HDPs的相对无能通常归因于涉及细菌细胞膜降解的一般作用模式。 已知阳离子HDPs在与阴离子细胞膜结合时形成全局两亲性螺旋（在一侧上的疏水侧链，在相对侧上的带电和其它亲水侧链）。相比之下，感兴趣的尼龙-3共聚物含有阳离子和疏水侧链的随机序列;它们的长度也不同。初步工作表明，无规共聚物攻击膜形成不规则的两亲性表面结构，使尼龙-3骨干的灵活性。 几种无规尼龙-3共聚物具有与天然HDPs相媲美的抑菌特性;它们仅在高浓度下溶血性攻击红细胞。这项工作将获得更好的基本了解这些共聚物如何降解膜，以通知设计改进。该方法包括化学合成和通过单细胞荧光成像详细分析功能。合成方法能够控制平均共聚物长度以及疏水性、阳离子性和极性侧链的类型和百分比。对于每个单独的细胞，分析方法使得能够在细菌“症状”的发展与所吸收的抗微生物聚合物的量和细胞生长的停止的真实的时间中直接相关。初步工作将集中在E。coli和B.枯草芽孢杆菌作为代表性革兰氏阴性和革兰氏阳性菌种。可观察到的症状包括跨外膜（OM）易位、OM裂解、跨细胞质膜（CM）易位和CM裂解。同样的技术将确定“幸存者细胞”的特殊属性，这些细胞对攻击具有不同寻常的抵抗力。恢复正常生长培养基后的延时观察将揭示哪些短期症状足以杀死细胞，即阻止随后的恢复和生长。来自实验的详细机械数据将反馈到设计廉价有效的抗菌聚合物的努力中。 在这项工作中开发的新技术和概念将发现广泛的应用在所有的努力，设计涉及膜为基础的功能的抗菌剂。无规共聚物可以在抗真菌活性、抗疟原虫活性和肺表面活性剂活性的背景下找到应用。

DESCRIPTION (provided by applicant): Pathogenic infections represent a persistent threat to human health. The rapid development of resistance to drug therapies creates a continuing need for new anti-infective agents. The proposed research focuses on the development of sequence-random copolymers having a nylon-3 backbone as general, inexpensive antibacterial agents. We will synthesize and characterize a variety of these copolymers designed to mimic the activity of natural host-defense peptides (HDPs), which have been discovered in plants, animals, and humans. HDPs are remarkable for their general ability to halt growth of both Gram negative and Gram positive bacteria while leaving animal cells largely unaffected. The relative inability of bacteria to resist HDPs is usually attributed to a general mode of action involving degradation of bacterial cell membranes. Cationic HDPs are known to form globally amphipathic helices (hydrophobic side chains on one side, charged and other hydrophilic side chains on the opposite side) when they bind to anionic cell membranes. In contrast, the nylon-3 copolymers of interest contain a random sequence of cationic and hydrophobic side chains; they also vary in length. Preliminary work suggests that the random copolymers attack membranes by forming irregular amphipathic surface structures enabled by the flexibility of the nylon-3 backbone. Several of the random nylon-3 copolymers have bacteriostatic properties rivaling those of natural HDPs; they hemolytically attack red blood cells only at high concentration. This work will obtain a better fundamental understanding of how these copolymers degrade membranes in order to inform design improvements. The approach includes both chemical synthesis and detailed analysis of function by single-cell fluorescence imaging. The synthetic methodology enables control of mean copolymer length and the type and percentage of hydrophobic, cationic, and polar side chains. For each individual cell, the analytical methods enable direct correlation in real time of the development of bacterial "symptoms" with the amount of antimicrobial polymer absorbed and the halting of cell growth. The initial work will focus on E. coli and B. subtilis as representative Gram negative and Gram positive species. Observable symptoms include translocation across the outer membrane (OM), lysing of the OM, translocation across the cytoplasmic membrane (CM) and lysing of the CM. The same techniques will determine the special properties of "survivor cells" that are unusually resistant to attack. Time lapse observations after restoration of normal growth medium will reveal which short-term symptoms are sufficient to kill cells, i.e. to prevent subsequent recovery and growth. Detailed mechanistic data from the experiments will feed back into the effort to design cheap and effective antimicrobial polymers. The novel techniques and concepts developed in this work will find wide application in all efforts to design antimicrobial agents involving membrane-based functions. Random copolymers may find applications in the context of antifungal activity, antiplasmodial activity, and lung-surfactant activity as well.