SIMULATING MEMBRANE PERMEATION BY CATIONIC PEPTIDES

这个子项目是许多研究子项目中的一个 由NIH/NCRR资助的中心赠款提供的资源。子项目和 研究者（PI）可能从另一个NIH来源获得了主要资金， 因此可以在其他CRISP条目中表示。所列机构为 研究中心，而研究中心不一定是研究者所在的机构。 二十年前发现的高电荷的膜穿透肽改变了质膜是不可渗透屏障的看法。这对物理有机化学家提出了一个重要的挑战：在吸收和渗透过程中，静电力和vdW力之间的相互作用是如何调节的？细胞穿透肽（CPP）以及脂质和溶剂分子的哪些结构和动力学特征发生改变，以允许亲水肽穿过膜的疏水核心？此外，许多报告记录了CPP跨膜运输不同大小亲水性货物的能力。因此，CPP被研究用于各种应用，包括用于基于蛋白质的疫苗的开发、细胞凋亡和细胞增殖的研究、胰岛细胞的移植、氧化应激障碍的治疗、肿瘤的免疫治疗和炎症的调节。核酸、抗体和成像剂的递送是CPP的一些其他应用。很明显，CPP-膜相互作用的物理化学数据对于设计新的和更有效的载体至关重要。然而，在积累的生物和生物物理宏观数据相反，CPP膜相互作用的基本化学信息是稀缺的。因此，目前对CPP如何结合并随后穿过脂质双层的原子水平理解是有限的。为了填补这一空白，我们设计了一个研究计划，旨在表征CPP吸收和膜渗透的结构和热力学原理。我们的研究将使用第一性原理计算，基于分子动力学模拟和自由能计算，以揭示阳离子电荷含量和CPP的两亲性，以及膜电位和抗衡离子的作用。这项研究将分三个阶段进行。在项目期的第一阶段，我们将探索CPP的哪些特性是膜吸收的原因。为此，我们将比较富含精氨酸、富含赖氨酸和两性肽的双层结合特性。第二阶段将着重于阐明膜转位的机制，重点是膜电位和反离子的作用。最后一个阶段涉及货物交付。研究结果将通过揭示CPP-膜相互作用的结构和能量决定因素，建立CPP膜吸收和渗透的物理和化学原理，从而为未来的应用导向研究奠定坚实的基础。

This subproject is one of many research subprojects utilizing the resources provided by a Center grant funded by NIH/NCRR. The subproject and investigator (PI) may have received primary funding from another NIH source, and thus could be represented in other CRISP entries. The institution listed is for the Center, which is not necessarily the institution for the investigator. The discovery of highly charged membrane penetrating peptides two decades ago has changed the perception that the plasma membrane is an impermeable barrier. This presented an important challenge for physical organic chemists: how does the interplay between electrostatics and vdW forces is modulated during uptake and permeation? Which structural and dynamical features of the cell penetrating peptides (CPPs), and of the lipid and solvent molecules, alter to allow a hydrophilic peptide to cross a hydrophobic core of membrane? Furthermore, numerous reports documented the capability of CPPs to transport hydrophilic cargo of varying sizes across membranes. CPPs are therefore being investigated for a variety of applications, including for the development of protein-based vaccines, the study of apoptosis and cell proliferation, transplantation of Islet cells, treatment of oxidative stress disorders, immunotherapy of tumors, and regulation of inflammation. Delivery of nucleic acids, antibodies, and imaging agents are some of the other applications of CPPs. It is apparent that physicochemical data on CPP-membrane interactions is vital for the design of novel and more effective vectors. However, in contrast to the accumulated biological and biophysical macroscopic data, information on the basic chemistry of CPP-membrane interactions is scarce. As a result, atomic-level understanding of how CPPs bind to and subsequently cross lipid bilayers is currently limited. In order to fill this void, we devised a research program that aims at characterizing the structural and thermodynamic principles underlying CPP uptake and membrane permeation. Our research will use first-principles computations, based around molecular dynamics simulations and free energy calculations, to unravel the roles of cationic charge content and amphiphiliciy of CPPs, and of membrane potential and counterions. The study will be carried out in three stages. In the first stage of the project period, we will probe which characteristics of CPPs are responsible for membrane uptake. To this end, we will compare the bilayer binding properties of arginine-rich, lysine-rich and amphipatic peptides. The second stage will focus on deciphering the mechanism of membrane translocation, with emphasis on the roles of membrane potential and counterions. The last stage concerns cargo delivery. The results will establish the physical and chemical principles of membrane uptake and permeation of CPPs by delineating the structural and energetic determinants of CPP-membrane interactions, thus laying a solid foundation for future applications-oriented studies.