Vasculogenesis is the de novo formation of a vascular network from individual endothelial progenitor cells occurring during embryonic development, organogenesis, and adult neovascularization. Vasculogenesis can be mimicked and studied in vitro using network formation assays, in which endothelial cells (ECs) spontaneously form capillary-like structures when seeded in the appropriate microenvironment. While the biochemical regulators of network formation have been well studied using these assays, the role of mechanical and topographical properties of the extracellular matrix (ECM) is less understood. Here, we utilized both natural and synthetic fibrous materials to better understand how physical attributes of the ECM influence the assembly of EC networks. Our results reveal that active cell-mediated matrix recruitment through actomyosin force generation occurs concurrently with network formation on Matrigel, a reconstituted basement membrane matrix regularly used to promote EC networks, and on synthetic matrices composed of electrospun dextran methacrylate (DexMA) fibers. Furthermore, modulating physical attributes of DexMA matrices that impair matrix recruitment consequently inhibited the formation of cellular networks. These results suggest an iterative process in which dynamic cell-induced changes to the physical microenvironment reciprocally modulate cell behavior to guide the formation and stabilization of multicellular networks.
Reasoning about organic chemistry reaction mechanisms requires engagement with multiple concepts and necessitates balancing the relative influence of different chemical properties. A goal of organic chemistry instruction is to support students with engaging in this type of reasoning. In this study, we describe our use of case comparison problems to elicit students’ reasoning about acyl transfer reaction mechanisms across a semester. Using an instrumental case study methodology, we analysed three students’ reasoning across three time points: in a pre-interview at the beginning of the semester, on their written responses to one implementation of an in-class scaffold activity, and in a post-interview near the middle of the semester. Through the theoretical lens of Hammer's resources framework, we analysed the resources that students activated when approaching the case comparison problems. We characterized how students used each resource to support their reasoning, alongside characterizing how students weighed the different resources they activated. Our findings indicate that the case comparison problems activated a number of resources for each student across the time points by encouraging students to relate the surface-feature differences between reactions with the associated underlying properties. Students generally used resources, such as resonance and steric effects, in similar ways to support their reasoning across the time points. The study also illustrates the range in students’ abilities to weigh multiple conceptual influences and how this ability might change across the semester. This case study has implications for future research exploring how students reason with multiple concepts and for instructors seeking to implement activities that support students’ reasoning with case comparison problems.
Teaching organic chemistry requires supporting learning strategies that meaningfully engage students with the challenging concepts and advanced problem-solving skills needed to be successful. Such meaningful learning experiences should encourage students to actively choose to incorporate new concepts into their existing knowledge frameworks by appealing to the cognitive, affective, and psychomotor domains of learning. This study provides a qualitative analysis of students’ meaningful learning experiences after completing three Writing-to-Learn (WTL) assignments in an organic chemistry laboratory course. The assignments were designed to appeal to the three domains necessary for a meaningful learning experience, and this research seeks to understand if and how the WTL assignments promoted students’ meaningful learning. The primary data collected were the students’ responses to open-ended feedback surveys conducted after each assignment. These responses were qualitatively analyzed to identify themes across students’ experiences about their meaningful learning. The feedback survey analysis was triangulated with interviews conducted after each assignment. The results identify how the assignments connected to students’ existing knowledge from other courses and indicate that assignment components such as authentic contexts, clear expectations, and peer review supported students’ meaningful learning experiences. These results inform how assignment design can influence students’ learning experiences and suggest implications for how to support students’ meaningful learning of organic chemistry through writing.
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