Colloidal Mobility in Surfactant Films and its Application of the Shear Rheology of Protein Layers

在许多情况下，蛋白质吸附在空气-水或油-水界面上，并且在足够的浓度下，这种界面蛋白质可以形成具有显著弹性的层。这些层的机械行为通常是它们在当前和发展中技术中的实用性的关键，特别是那些与食品、生物医学和制药工业相关的技术。界面微观流变学，它使用胶体探针粒子询问在流体界面处的膜的机械性能，正在成为一个强大的方法来研究界面层。该提案描述了一组实验，将推进这种方法显着地提供新的见解胶体流动性的性质在接口，然后将利用这些见解，以获得新的理解的界面流变学的蛋白质layers.Intellectual优点：蛋白质层的流变特性的知识是至关重要的了解其形成和稳定性的基本方面，以及使其通过的技术应用。蛋白质层的研究可以进一步提供蛋白质变性，蛋白质-蛋白质相互作用和凝胶转变问题的独特视角。拟议的研究计划将是一项共同努力，涉及三名研究人员，他们具有良好的合作记录，并具有在这一领域取得实质性进展所需的互补专业知识。 拟议的研究的一个中心要素将是使用胶体探针与不同的几何形状，采用主动和被动的界面微观流变学测量。正如研究人员以前的工作所示，这种组合方法提供了一组互补信息，当自我一致地处理时，可以解决任何单一测量解释中的模糊性。其结果是洞察到粒子运动的性质在界面和该运动所暗示的主机层的界面流变学。在分析作用在被限制在界面层中的颗粒上的流体动力时，一个关键的近似是界面层的不可压缩性。通过实验确定这种近似的有效性范围以及当它分解时对颗粒流动性的影响将具有深远的影响，并将有助于巩固颗粒运动和界面流变学之间的联系，这是微观流变学方法的中心。因此，研究将开始的实验，调查的限制不可压缩性近似。通过对界面层中胶体阻力的深入了解，拟议的实验将解决蛋白质层流变学中的三个关键主题：（i）蛋白质溶液的表面粘度和动态表面张力的演变中的相关性，（ii）蛋白质和小分子表面活性剂的混合溶液的界面流变学，和（iii）比较机械性能的蔓延与吸附蛋白质层。更广泛的影响：通过表面活性剂层的一个关键属性，其不可压缩性的限制和后果的系统调查，研究将带来一系列问题，如界面处的多相流的相关问题。通过推进一种新的、高灵敏度的界面流变学方法，这项工作将有助于扩展界面科学的工具，可能影响材料、化学工程和生物科学的一系列领域。例如，作为微观流变技术，正在开发的测量方法需要比传统流变方法小得多的样品。因此，他们可以使可行的界面系统的机械特性，其中大的样品尺寸是不可能的或昂贵的合成。作为该计划的一部分，研究生和本科生将在一个高度跨学科的领域接受研究培训，这将为他们在学术界和工业界的职业生涯做好准备。与当地一所科学磁铁高中的合作将为巴尔的摩市的学生提供研究实习的机会。为了帮助促进妇女在科学和工程领域的进步，还将通过约翰霍普金斯大学的一项外联倡议-妇女在科学和工程领域的方案，招募女高中生参加这项研究。

1033985LehenyUnder many circumstances proteins adsorb at air-water or oil-water interfaces, and at sufficient concentration such interfacial proteins can form layers with pronounced elasticity. The mechanical behavior of such layers is often key to their utility in current and developing technologies, particularly those related to the food, biomedical, and pharmaceutical industries. Interfacial microrheology, which uses colloidal probe particles to interrogate the mechanical properties of films at fluid interfaces, is emerging as a powerful approach to investigate interfacial layers. This proposal describes a set of experiments that will advance this approach significantly by providing new insights into the nature of colloid mobility at interfaces and will then exploit these insights to gain new understanding of the interfacial rheology of protein layers.Intellectual Merit:Knowledge of the rheological properties of protein layers is crucial both for understanding fundamental aspects of their formation and stability, as well as for enabling their adoption for technological applications. The study of protein layers can further provide unique perspectives on issues of protein denaturation, protein-protein interactions, and gel transitions. The proposed research program will be a joint effort involving three Investigators with a strong record of collaboration and with the complementary expertise needed to make substantial progress in this area. A central element of the proposed research will be the use of colloidal probes with different geometries that are employed both in active and passive interfacial microrheology measurements. As previous work by the Investigators has shown, this combined approach provides sets of complementary information that, when treated self consistently, can resolve ambiguities in the interpretation of any single measurement. The result is insight into both the nature of particle motion at interfaces and the interfacial rheology of the host layers implied by that motion. A key approximation in the analysis of the hydrodynamic forces on a particle confined to an interfacial layer is the incompressibility of the layer. Determining experimentally the range of validity of this approximation and the impact on particle mobility when it breaks down would have far reaching implications, and would help solidify the connection between particle motion and interfacial rheology that is at the center of the microrheology approach. Hence, the research will begin with experiments that investigate the limits of the incompressibility approximation. Informed by the resulting insights into the drag on colloids in interfacial layers, the proposed experiments will then address three key topics in protein layer rheology: (i) correlations in the evolution of surface viscosity and dynamic surface tension of protein solutions, (ii) the interfacial rheology of mixed solutions of proteins and small molecule surfactants, and (iii) the comparative mechanical properties of spread versus adsorbed protein layers.Broader Impacts:Through systematic investigation of the limits and consequences of a key property of surfactant layers, their incompressibility, the research will bring to the fore an issue relevant to a range of problems, such as multiphase flows at interfaces. By advancing a new, high sensitivity approach to interfacial rheology, the work will help expand the tools of interfacial science, potentially impacting a range of fields within materials and chemical engineering and the biosciences. For example, as microrheological techniques, the measurement approaches being developed require far smaller samples than conventional rheological methods. Thus, they could make feasible mechanical characterization of interfacial systems where large sample sizes are impossible or prohibitively expensive to synthesize. As part of this program, graduate students and undergraduates will receive research training in a highly interdisciplinary field that will prepare them for careers in academia and industry. Collaboration with a local science magnet high school will provide Baltimore City students with opportunities for research internships. To help promote the advancement of women in science and engineering, female high school students will also be recruited through the Women in Science and Engineering Program, a Johns Hopkins University outreach initiative, to participate in the research.