NMR Lateral Diffusion Measurements in Biomembranes

核磁共振（NMR）光谱学已经彻底改变了扩散的测量，因为引入了脉冲场梯度（PFG）NMR扩散技术，该技术现在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，由于膜环境的固有挑战，PFG NMR扩散方法的贡献相当小。 这些包括宽的NMR共振线、差的分辨率和大范围的扩散速率，扩散速率可以从“快速”扩散的小药物分子到“缓慢”扩散的大锚定膜蛋白变化几个数量级。 膜内的这种“横向”扩散是构成膜的蛋白质、脂质和其他生物分子的基本性质，对于适当的膜功能至关重要，并且可以揭示迄今未被认识的结构-功能关系的关键方面。 我们已经介绍了几种新的方法，克服了许多固有的障碍，在膜的NMR扩散测量。 这里提出的研究计划的主要目标是利用这些方法在几个重要的生物膜现象的调查。 特别是，我们将研究跨膜α-螺旋肽之间的关联的能量，目的是了解这种关联发生的不同方式的能量层次。 此外，我们将研究膜中的结构域，这些结构域是具有不同组成和功能的长寿命区域，但其特征仍然很差，了解得更少。 最后，我们将继续完善我们的新模型膜系统，这是一个混合的脂质双层支持的“智能”聚合物水凝胶球，并表现出特别的优势，作为扩散和其他基础和应用研究的模型系统。

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.