Physics of Polymers under Nanoscopic Confinement: a Single Molecule Study
S.l. : s.n.
Number of pages
RU Radboud Universiteit, 09 juni 2016
Promotores : Rowan, A.E., Christianen, P.C.M., Maan, J.C. Co-promotor : Engelkamp, H.
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Physicist Masoumeh Keshavarz studied the thermal motion of a fluorescently labelled, individual “reporter” polymer molecule, surrounded and entangled by a gel of similar but unlabelled polymers. Owing to their extreme length and stiffness, it is possible to follow the shape and the motion of the reporter in time using wide-field fluorescence microscopy. The real time movies thus obtained showed a restricted motion for long polymers as they move back and forth along their long axis in a snake-like fashion within a tube defined by the entangled network of transient neighbouring chains. Using advanced, home-made image analysis techniques, she was able to determine the polymer trajectories at the nano-scale for a large number of polymer lengths, concentrations and stiffnesses. With this, a wealth of information became available, such as the characteristic times of the polymer motion, the Rouse and disentanglement time, as well as many interesting scaling laws. The diameter of the tube was extracted and a harmonic profile was observed for the tube i.e. the confining potential the test chain feels from the entangled neighbouring chains. This new, local, nanoscale technique can now be used for studying much more complex systems, such as biological cells, where molecular individualism, crowdedness and heterogeneity are important but hinder more traditional, bulk studies.
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