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  Biological matter in microfluidic environment - from single molecules to self-assembly

Köster, S. (2006). Biological matter in microfluidic environment - from single molecules to self-assembly. PhD Thesis, Georg-August-Universität, Göttingen.

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Item Permalink: http://hdl.handle.net/11858/00-001M-0000-002C-7EDE-5 Version Permalink: http://hdl.handle.net/11858/00-001M-0000-002C-7EDF-3
Genre: Thesis

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 Creators:
Köster, Sarah1, Author              
Affiliations:
1Group Dynamics of biological matter, Department of Dynamics of Complex Fluids, Max Planck Institute for Dynamics and Self-Organization, Max Planck Society, ou_2063313              

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 Abstract: The interior as well as the exterior of cells is governed by networks composed of fi- brous proteins. The mesh size of these networks is on the order of micrometers and therefore distinguishes microfluidics as an excellent tool to gain insight into principal mechanisms of single molecule behavior, on the one hand, and the interplay and self-assembly of the network constituents, on the other hand. Here, we present new results derived from biomimetic investigations of two different systems, namely single molecule experiments on actin, one of the most important intracellular proteins, and in situ observation of the fibril formation of collagen I, the most abundant extracellular protein. The use of microfluidic channels fabricated by means of soft photolithography as the principle tool for our experiments enables us to manipulate the molecules via confining wall potentials and hydrodynamic flow fields, analyze their mechanical behavior, and observe time and spatially resolved reactions. Furthermore, microfluidics is very well suited for combination with different observation methods such as fluorescence microscopy, polarized light microscopy, and X-ray microdiffraction. Analyzing single fluctuating actin filaments under the influence of confinement yields a thorough characterization of the mechanics of the system. The biomacromolecules are observed by means of fluorescence microscopy. We find that the behavior of the biopolymers depends on their contour length L and the influence of the microfluidic environment. The confining energy is considered as a parabolic wall potential. Thus, we succeed to remarkably well describe the competition between bending energy and confining energy. Moreover, the results are consistent with Monte Carlo simulations and with scaling laws for the deflection length λ and the segment distribution in the channels. The experiments on collagen I give insight into the dynamic evolution of the hierarchical organization of native collagen fibrils. We use a hydrodynamic focusing and diffusive mixing device to establish a stable pH-gradient within the microfluidic channels. Therefore, we are able to perform non-equilibrium measurements in the laminar flow and observe different stages of the self-assembly process at different positions within the same system. We characterize the system on a microscopic length scale by availing the birefringent properties of collagen. Additionally, using X-ray microdiffraction the dynamic formation of critical subunits of collagen fibrils can be observed. Furthermore, we demonstrate that finite element method simulations provide a good description of our experimental results regarding diffusive phenomena, influence of the solution viscosity on the flow profile, and pH distribution. The experiments presented here elucidate the principle understanding of the studied biological systems and furthermore show the ability of microfluidic tools to advance the diverse field of life science.

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Language(s): eng - English
 Dates: 2006-06-13
 Publication Status: Accepted / In Press
 Pages: x, 127
 Publishing info: Göttingen : Georg-August-Universität
 Table of Contents: -
 Rev. Method: -
 Degree: PhD

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