Silk Polymer Models for Structure-Function Relationships

智力优点-丝蛋白是一个有用的模型系统，用于研究新的功能特性，从疏水聚合物在水溶液中。 绢丝纤维令人印象深刻的机械性能取决于对蚕和蜘蛛腺体结构发育的不寻常控制，所有这些都是通过控制水含量结合适当的顺序化学来实现的。 我们的目标是了解丝蛋白组装的机理基础，通过控制丝溶液中的水含量，作为一种新的和改进的处理选择疏水性聚合物一般的路线。 这一见解对以下方面具有强烈的影响：（a）从丝工程化的新材料，以及（B）模拟丝的新聚合物化学/序列，因为设计（化学序列）必须考虑加工环境以及功能结果。 将进行系统的调查，通过渗透胁迫，以及随后的过渡和结构和形态特征诱导通过化学和机械因素的蛋白质浓度高的丝凝胶的形成和结构特征。 具体而言，将追求以下目标：（a）通过系统地控制水含量来比较含水系统中的结构发展，包括来自蚕腺体的天然凝胶和重构蚕丝之间的比较;以及（B）研究特定环境因素（例如，pH、二价阳离子、温度）对不同含水量下结构和形态发展的速率和性质的影响。 为了解决这些问题，将使用光谱技术来表征模型材料（傅里叶变换红外，FTIR;拉曼），散射技术（宽和小角X射线散射，WAXS/SAXS;小角光散射，SALS）和成像技术（原子力显微镜，AFM;扫描电子显微镜，SEM;光学椭圆偏振法;微分干涉对比显微术，DIC）以评估各种长度尺度下的形态和结构。 这些评估将允许静态丝凝胶的相图的制定。 然后，近似纤维形成的步骤，应力（使用拉伸变形和剪切）的结构演变和相应的力学性能的重组丝绸的影响将被研究。 计划中的研究建立在实验室最近发现的丝蛋白的溶液行为和控制这种行为的基础上。 更广泛的影响-拟议的实验代表了一个跨学科的方法来研究这种独特的聚合物，包括生物化学家（大卫卡普兰）和物理学家（佩吉Cebe）。 参与的研究生和本科生将在研究过程中从这两个角度获得直接的见解，同时也为聚合物科学和工程的新方向做出贡献。 研究方法和成果将以多种方式出口到课堂环境中，以供更广泛的学生使用，包括本科和研究生课程中的讲座模块，本科生研究实验室经验的窗口，以及聋人和听力受损学生的具体计划。

Intellectual Merit - Silk proteins are a useful model system for the study of novel functional properties derived from hydrophobic polymers in aqueous systems. The impressive mechanical properties of spun silk fibers rest with the unusual control of structure development in glands in silkworms and spiders, all achieved through control of water content in combination with appropriate sequence chemistry. The objective is to understand the mechanistic basis for silk protein assembly, through control of water content in silk solutions, as a route to new and improved processing options for hydrophobic polymers in general. This insight has strong implications for: (a) new materials engineering from silks, and (b) for new polymer chemistries/sequences that mimic silk in that the designs (chemical sequences) must consider processing environments as well as functional outcomes. A systematic investigation will be undertaken into the formation and structural features of silk gels containing high concentrations of protein achieved via osmotic stress, and subsequent transitions and structural and morphological features induced through chemical and mechanical factors. Specifically, the following aims will be pursued: (a) to compare structure development in aqueous systems by systematic control of water content, including comparisons between native gels from silkworm glands and reconstituted silkworm silk; and, (b) to study the role of specific environmental factors (e.g., pH, divalent cations, temperature) on rates and nature of structure and morphology development at different water contents. To address these questions, model materials will be characterized using spectroscopic techniques (Fourier Transform infrared, FTIR; Raman), scattering techniques (wide and small angle X-ray scattering, WAXS/SAXS; small angle light scattering, SALS), and imaging techniques (atomic force microscopy, AFM; scanning electron microscopy, SEM; optical ellipsometry; differential interference contrast microscopy, DIC) to assess morphologies and structures at a variety of length scales. These assessments will permit the formulation of phase diagrams for quiescent silk gels. Then, to approximate the step of fiber formation, the effects of stress (using tensile deformation and shear) on structure evolution and the corresponding mechanical properties of reconstituted silks will be studied. The planned studies build off the recent discoveries from the lab on the solution behavior of silk proteins and control of this behavior. %%%Broader Impact - The proposed experiments represent an interdisciplinary approach to the study of this unique polymer, including a biochemist (David Kaplan) and a physicist (Peggy Cebe). The graduate and undergraduate students involved will gain direct insight from both perspectives during their research, while also contributing to new directions in polymer science and engineering. The research approaches and outcomes will be exported into classroom settings in a number of ways for a broader audience of students including lecture modules in both undergraduate and graduate courses, windows on research laboratory experiences for undergraduate students, and specific programs for deaf and hearing impaired students.