Single-molecule studies of hyaluronic acid

非技术：该奖项由加州大学圣巴巴拉分校材料研究部生物材料项目颁发，旨在研究在盐和其他与这种聚合物结合的分子存在的情况下，透明质酸（透明质酸，HA）的大小、形状和溶液性质。透明质酸（HA）是一种巨大的聚合物分子，它定义了人体许多空间的结构和力学，如组织水合作用、伤口愈合、某些生物界面的润滑，并有助于定义关节和功能的力学。此外，透明质酸正在积极研究用于生物材料的应用，特别是作为细胞/组织工程基质的功能化透明质酸凝胶。透明质酸的这些功能依赖于其聚合的随机游走结构，该结构受溶液条件的调节，包括盐浓度、其他生物聚合物的拥挤以及HA结合分子的存在。因此，从生物学和化学的角度来看，对透明质酸构象和溶液行为的微观基础有一个详细的了解是非常重要的。这些建议的研究有望使人们更好地了解HA的各种生物学作用，并允许基于HA的生物材料的合理工程。此外，实施该项目将产生各种重要的更广泛的影响，包括加强大学/国家实验室伙伴关系，以及在具有良好长期潜力的跨学科科学领域培养本科和研究生水平的年轻科学家。国际传播和科学交流是该项目的组成部分，这些独特的活动对于实现科学的广泛影响非常重要。技术：透明质酸（HA）是一种存在于几乎所有哺乳动物组织中的多糖。透明质酸的特点是阴离子电荷密度大，构象灵活，由于多种氢键相互作用而具有多态性。这些特征，连同它与某些配体的关联，导致它定义细胞外空间的力学和粘弹性特性，如细胞周围基质、玻璃体和滑液。透明质酸在临床应用和作为生物材料用于制造细胞和组织生长的凝胶基质方面具有进一步的兴趣。在所有这些生物和生物材料的应用中，都需要彻底了解透明质酸的微观结构和功能，特别是包括机械性能及其与主导渗透和粘弹性性能的离子效应的关系。在之前的NSF项目中，该研究人员已经建立了低力单分子弹性测量是了解复杂溶液中聚电解质结构的有力工具。在这里，“低力”意味着张力足够小，可以允许链中的循环、随机行走结构；这样的力是标准力谱法无法得到的，因为它只能得到近乎直链的结构。低作用力允许对弱、远距离相互作用的敏感性，从而量化对透明质酸的生物和生物材料功能至关重要的影响，如静电排斥、直接和水介导的氢键和自我回避。在这里，提出的研究是应用低力方法来严格检查HA的溶液介导的构象和力学性能。本研究将通过以下两个目标进行。在目标1中，将研究通过静电筛选、水结构（使用超/宇宙性盐）和有溶剂的情况下调制的透明质酸构象。在目标2中，将研究特定生物配体对HA构象的影响，重点是引起肿胀和交联效应的蛋白多糖。国际传播和科学交流在实现科学的更广泛影响方面具有独特和重要的意义，是该奖项的一部分。

Non-technical: This award by the Biomaterials program in the Division of Materials Research to University of California-Santa Barbara is to study the size, shape and solution properties of hyaluronic acid (hyaluronan, HA) in the presence of salts and other molecules that binds with this polymer. Hyaluronan, or hyaluronic acid (HA), is a huge polymer molecule that defines the structure and mechanics of many spaces in the human body such as tissue hydration, wound healing, lubrication of certain biological interfaces, and helps to define the mechanics of joints and functionality. Further, HA is under active investigation for use in biomaterials applications, notably functionalized HA gels that act as cell/tissue engineering substrates. These functions of HA rely on its polymeric, random-walk structure, which is modulated by solution conditions, including salt concentration, crowding by other biological polymers, and the presence of HA-binding molecules. It is thus of basic importance, for both biological and chemical reasons, to have a detailed understanding of the microscopic basis of HA conformation and solution behavior. The proposed studies are expected to lead to a better understanding of HA's various biological roles, as well as to permit rational engineering of HA-based biomaterials. Further, carrying out this project would have a variety of important broader impacts, including strengthening university/national lab partnerships, and training young scientists, at both undergraduate and graduate levels in an interdisciplinary scientific area with excellent long-term potential. International dissemination and scientific exchanges are parts of this project, and these unique activities are important in achieving scientific broader impacts. Technical: Hyaluronic acid (HA) is a polysaccharide present in nearly all mammalian tissues. HA is characterized by a large anionic charge density, conformational flexibility, and polymorphism due to a variety of hydrogen-bonding interactions. These features, along with its association with certain ligands, lead it to define the mechanical and viscoelastic properties of extracellular spaces, such as the pericellular matrix, eye vitreous, and synovial fluid. HA is of further interest for clinical applications, and as a biomaterial used to create gel substrates for cell and tissue growth. In all these biological and biomaterials applications, there is a common need for a thorough understanding of HA's microscopic structure and functions, particularly including mechanical properties and their relation to the ionic effects that dominate osmotic and viscoelastic properties. With the prior NSF project, this researcher has established that low-force single-molecule elasticity measurements are powerful tools to understand polyelectrolyte structure in complex solutions. Here, 'low force' means tensions small enough to permit looped, random-walk structure in the chain; such forces are inaccessible to standard force spectroscopy approaches that only access nearly-straight chain configurations. Low forces permit sensitivity to weak, long range interactions, and thus quantification of the effects that are key to HA's biological and biomaterials functions, such as electrostatic repulsion, direct and water-mediated hydrogen bonding, and self-avoidance. Here, the proposed studies are to apply the low-force approach to a rigorous examination of HA's solution-mediated conformational and mechanical properties. This research will proceed through the following two goals. In goal 1, HA conformation will be studied as modulated by electrostatic screening, water structure (using chao/kosmotropic salts), and in the presence of crowders. In goal 2, the effects of specific biological ligands on HA conformation will be studied, with emphasis on proteogylcans that cause swelling and crosslinking effects. International dissemination and scientific exchange that are unique and important in the context of achieving broader impact of the sciences are part of this awards.