NMR Lateral Diffusion Measurements in Biomembranes

自从脉冲场梯度(PFG)核磁共振扩散技术被引入以来，核磁共振波谱已经使扩散测量发生了革命性的变化，该技术现在被常规地应用于许多化学和生物系统和情况，并取得了巨大的成功。然而，在生物膜中，无论是模型还是真实的生物膜，由于膜环境的内在挑战，PFG核磁共振扩散方法的贡献相当小。这些问题包括较宽的核磁共振共振线、较差的分辨率和较大的扩散速率范围，这些扩散速率可以按数量级变化，从“快速”扩散的小药物分子到“缓慢”扩散的大的锚定膜蛋白。这种膜内的“横向”扩散是构成膜的蛋白质、脂类和其他生物分子的基本性质，对膜的正常功能至关重要，并可以揭示迄今尚未认识的结构-功能关系的关键方面。我们介绍了几种新的方法来测量膜中的核磁共振扩散，这些方法克服了许多固有的障碍。这里提出的研究计划的主要目标是利用这些方法来研究几个重要的生物膜现象。特别是，我们将研究跨膜α-螺旋肽之间的相互作用的能量，目的是了解这种相互作用发生的不同方法的能量等级。此外，我们还将研究膜中的结构域，这些结构域具有不同的组成和功能，但仍未得到很好的描述，更不用说了解了。最后，我们将继续改进我们的新模型膜系统，它是支撑在“智能”聚合物水凝胶球上的脂质双层的混合体，作为扩散和其他基础和应用研究的模型系统显示出独特的优势。

Nuclear magnetic resonance (NMR) spectroscopy has revolutionized the measurement of diffusion, since the introduction of the pulsed field gradient (PFG) NMR diffusion technique, which is now routinely applied in a multitude of chemical and biological systems and situations with enormous success. However, in biological membranes, whether model or real, the PFG NMR diffusion method has contributed considerably less, due to the inherent challenges of the membrane environment. These include broad NMR resonance lines, poor resolution, and the large range of diffusion rates which can vary by orders of magnitude from "fast" diffusing small drug molecules, to "slow" diffusing large anchored membrane proteins. Such "lateral" diffusion within membranes is a fundamental property of the proteins, lipids and other biomolecules of which membranes are constituted, is critical for proper membrane functioning, and can reveal key aspects of structure-function relations hitherto unrecognized. We have introduced several new approaches to NMR diffusion measurements in membranes that overcome many of the inherent barriers. The primary objectives of the research program proposed here are to exploit these approaches in the investigation of several important biomembrane phenomena. In particular, we will investigate the energy of the associations between transmembrane alpha-helical peptides with the goal of understanding the energy hierarchy of the different means by which such associations occur. Also, we will examine domains in membranes, which are long-lived regions of distinct composition and function, but which remain poorly characterized, much less understood. Finally, we will continue to refine our new model membrane system, which is a hybrid of a lipid bilayer supported on a "smart" polymer hydrogel sphere, and which exhibits particular advantages as a model system for diffusion and other fundamental and applied studies.