June 22, 2008
June 22, 2008
June 25, 2008
13.1348.1 - 13.1348.11
Using microtubules to illustrate polymer properties
Microtubules are a biopolymer, which assembles in vitro within minutes via noncovalent interactions from thousands of tubulin proteins at a temperature of 37 degrees Celsius. The large size (25 nm in diameter and several micrometers in length) and stiffness of these tubular, hollow polymers enables the imaging of individual, fluorescently labeled microtubules by fluorescence microscopy. We have utilized microtubules to create a stimulating laboratory, for undergraduate students which illustrates basic polymer concepts using commercially available compounds.
By imaging and analyzing a population of microtubules, students can directly determine molecular weight distributions and the degree of polymerization. Polymerization parameters, such as initial monomer concentration, temperature, and polymerization time, as well as post- polymerization processing conditions (such as shearing) can be varied, and their effect on the microtubule population can be directly observed.
Based on the assessment of the first group of students conducting this laboratory, we propose that a microtubule-based laboratory is a valuable addition to the curriculum of MSE and BME students specializing in polymers and biomaterials, since it enables striking demonstrations of polymer science and bioengineering principles.
At our institution, a 3-credit, semester long, senior level course “Physical Properties of Polymers” is accompanied by a laboratory section. In this section, an introductory polymerization laboratory where the students polymerized Nylon 6,6 and Poly- methylmethacrylate (PMMA) is followed by five laboratories focusing on rheology, surface energy, viscosity, gel permeation chromatography (GPC), and mechanical properties.
Based on our extensive experience 1-3 in working in vitro with microtubules (biopolymer structures which self-assemble from the protein tubulin) we perceived an opportunity to design a novel laboratory focused on the illustration of basic polymer properties using microtubules as examples. We primarily aimed to enhance the students’ intuitive grasp of concepts such as molecular weight distribution, Brownian motion, and post-polymerization processing. Due to the increasing interest of engineers in biological systems, this laboratory would also complement the traditional study of synthetic polymers with the investigation of a biopolymer having central functions in eukaryotic cells.
Microtubules are a unique polymer for our purposes due to their large size 4, 5. With a length of several micrometers and a diameter of 25 nm these tubular structures are thousand-fold larger compared to synthetic linear polymer chain such as polyethylene. Conjugation of fluorescent molecules to the tubulin subunits at a ratio of approximately one-to-one results in bright structures which can be readily imaged with a modern fluorescence microscope. Since the spatial resolution of the optical microscope is on the order of 200 nm, the length of individual
Jeune, Y., & Hess, H. (2008, June), Using Microtubules To Illustrate Polymer Properties Paper presented at 2008 Annual Conference & Exposition, Pittsburgh, Pennsylvania. https://peer.asee.org/4147
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