Interfacial Microrheology of Protein Layers using Magnetic Nanowire Probes

使用磁性纳米线探针进行蛋白质层的界面微流变学

• 批准号: 0651666
• 负责人: Robert Leheny
• 金额: $ 20.71万
• 依托单位: Johns Hopkins University
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 2007
• 资助国家: 美国
• 起止时间: 2007-04-15 至 2010-03-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=0651666&HistoricalAwards=false
• 关键词: Interfacial; Microrheology; Protein; Layers; using

Leheny / Johns Hopkins / 0651666The tendency for proteins to adsorb at air-water or oil-water interfaces and to create stiffinterfacial layers is vital to many current and developing technologies, particularly those related to the food, biomedical, and pharmaceutical industries. Further, the process of protein-layer formation provides a unique perspective on issues of protein denaturation, protein-protein interactions, and the gel transition. This proposal describes experiments to apply a new, high sensitivity approach to characterizing the interfacial shear rheology of protein layers by employing magnetic nanowires confined at the interface as active microrheology probes.Intellectual Merit: A key difference between proteins adsorbed at interfaces and conventional small-molecule surfactants is the propensity of the proteins to form layers that are strongly viscoelastic. In many circumstances, this mechanical behavior can lead to superior properties, such as in stabilizing emulsions and foams. Consequently, knowledge of the rheological properties of protein layers is crucial both for understanding fundamental aspects of their formation and stability as well as for adopting them for technological application. Based on geometric considerations, the proposed microrheology approach using wire-shaped probes is naturally suited for measuring the shear rheology of nanometer-scale fluid films, and the nanowires should be significantly more sensitive than existing interfacial shear rheology techniques. The basis of the approach involves characterizing the drag experienced by nanowires confined to the air-water interface at which protein layers form as the wires are rotated by precise magnetic torques. Recent theory has predicted fundamental changes to the hydrodynamic behavior of an anisotropic object, such as a wire-shaped particle, when it is confined to such a thin film. Clarifying experimentally the validity of these predictions and their range of applicability would have far-reaching implications. Such clarification will also be necessary for a proper quantitative interpretation of the proposed interfacial rheology experiments on protein layers. The magnetic nanowires are an ideal system to investigate these theoretical ideas, and the project will include experiments to test the predictions. With the rotational drag on nanowires in films understood, the approach will then be applied to interfacial shear rheology studies of two protein layer systems (i) lysozyme solutions at low concentration for which layer formation is characterized by an extended induction period and (ii) films formed from solutions of lactoglobulin and small molecule surfactants for which the mechanical properties of the protein layer are highly sensitive to the presence of the surfactant. These systems are selected for thecompelling scientific problems they present and for the opportunities to uncover significant new phenomena through the proposed experimental approach. However, an additional objective of the proposed experiments will be to establish more generally the technique of microrheology with magnetic nanowires as an important tool for studying the mechanical properties of interfacial systems.Broader Impacts: As part of this project, a female high school student will be recruited from the Women in Science and Engineering (WISE) Program, a Johns Hopkins outreach initiative, to participate in the research. The broader impacts of the project will also include research training and education for a graduate student and an undergraduate student. In addition, the work will provide potentially significant impact to both the research on and the technology based on interfacial proteins layers, particularly with regard to systems with mesoscale heterogeneity that cannot be accessed with current techniques and to materials for which small sample quantity is currently a limiting factor. Stiff interfacial layers are vital to many current and developing technologies, particularly those related to the food, biomedical, and pharmaceutical industries.

Leheny / Johns霍普金斯/0651666蛋白质吸附在空气-水或油-水界面并产生硬界面层的趋势对许多当前和发展中的技术至关重要，特别是那些与食品、生物医学和制药工业相关的技术。此外，蛋白质层形成的过程提供了一个独特的视角，蛋白质变性，蛋白质-蛋白质相互作用和凝胶转变的问题。该提案描述了实验应用一种新的，高灵敏度的方法来表征的界面剪切流变学的蛋白质层，通过采用磁性纳米线限制在界面作为主动microrheology probes.Intellectual优点：蛋白质吸附在界面和传统的小分子表面活性剂之间的一个关键区别是蛋白质的倾向，形成层，是强烈的粘弹性。在许多情况下，这种机械行为可以导致上级性能，例如在稳定乳液和泡沫方面。因此，了解蛋白质层的流变特性对于理解其形成和稳定性的基本方面以及将其用于技术应用都是至关重要的。基于几何的考虑，所提出的微流变学方法，使用线形探针自然适合于测量纳米级流体膜的剪切流变学，纳米线应该比现有的界面剪切流变学技术更敏感。该方法的基础涉及表征纳米线所经历的阻力，该纳米线被限制在空气-水界面处，当纳米线被精确的磁力矩旋转时，在该界面处形成蛋白质层。最近的理论已经预测了各向异性物体的流体动力学行为的根本变化，例如线状颗粒，当它被限制在这样的薄膜中时。通过实验澄清这些预测的有效性及其适用范围将产生深远的影响。这样的澄清也将是必要的一个适当的定量解释建议的界面流变学实验蛋白质层。磁性纳米线是研究这些理论想法的理想系统，该项目将包括测试预测的实验。了解了薄膜中纳米线的旋转阻力后，然后将该方法应用于两种蛋白质层系统的界面剪切流变学研究：（i）低浓度的溶菌酶溶液，其层形成的特征在于延长的诱导期，和（ii）由乳球蛋白和小分子表面活性剂的溶液形成的膜，的表面活性剂。选择这些系统是因为它们提出了复杂的科学问题，并有机会通过拟议的实验方法发现重大的新现象。然而，一个额外的目标，拟议的实验将是建立更普遍的技术与磁性纳米线作为一个重要的工具，用于研究界面system.Broader影响的机械性能：作为这个项目的一部分，一名女高中生将被招募从科学和工程（WISE）计划，约翰霍普金斯外展倡议，参加研究。该项目的更广泛影响还将包括研究生和本科生的研究培训和教育。此外，这项工作将提供潜在的重大影响的研究和技术的基础上的界面蛋白质层，特别是关于系统的中尺度异质性，不能用目前的技术和材料的小样本量目前是一个限制因素。刚性界面层对许多当前和发展中的技术至关重要，特别是那些与食品、生物医学和制药行业相关的技术。