pset5_solns - Problem Set 5 Model Solutions Issued Due 100...

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Problem Set 5 Model Solutions 20.462J/3.962J Issued: 04/04/06 Spring 2006 Due: 04/13/06 100 points total 1. (50 points) Compare and contrast a natural extracellular matrix based on collagen fibers with a synthetic matrix formed by a covalent PEG-based hydrogel containing –APGL- peptide linkages sensitive to the enzyme collagenase—answer in brief paragraphs: a. Structurally, do these gels present the same barrier to cell movement/migration? A homogeneous covalent synthetic hydrogel will differ significantly in structure from a collagen fiber matrix. Collagen gels are typically formed via temperature-driven self- assembly of collagen triple helices into fibrils, and these fibrils can in turn assemble into fibers, which have cross-sections ranging from several hundred nanometers to 1 or 2 microns. These fibers, which can extend tens to hundreds of microns in the axial length, then form a gel by physical entanglement, with a mesh size which is often 100’s of nanometers and can be microns. In contrast, covalent gels form with the mesh size determined by the molecular weight between crosslinks, and because the mesh size is determined by such a molecular length scale, the mesh size rarely exceeds ~10 nm (the molecular weights required for larger mesh sizes are typically difficult to achieve in practice). Thus, a very different physical environment is presented to cells by these two structures. In addition, as a barrier to migration, collagen, because it is a physical network formed by
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This note was uploaded on 11/11/2011 for the course BIO 20.410j taught by Professor Rogerd.kamm during the Spring '03 term at MIT.

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pset5_solns - Problem Set 5 Model Solutions Issued Due 100...

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