l20_notes

l20_notes - Alternative views on gradient sensing: - Postma...

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Alternative views on gradient sensing: - Postma and van Haastert. ‘A diffusion-translocation model for gradient sensing by chemotactic cells.’ Biophys. J. 81 , 1314 (2001). - Levchenko and Iglesias. ‘Models of eukaryotic gradient sensing: applications to chemotaxis of amoeba and neutrophils’ Biophys. J. 82 , 50 (2002). Main point : - how to prevent cells to polarize ‘inreversibly’? 1
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P m k x m D dt dm m + = 1 2 2 D m ~ 1 µ m 2 s -1 (membrane protein. lipid) D m ~ 100 µ m 2 s -1 (cytosolic small molecule) For a second messenger to establish and maintain a gradient the dispersion range λ should be smaller than cell size Images removed due to copyright considerations. See Postma, M., and P. J. Van Haastert. " A diffusion-translocation model for gradient sensing by chemotactic cells." Biophys J. 81, no. 3 (Sep, 2001): 1314-23. m L s k k D m µ λ 10 1 1 1 1 = = = 2
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= + = r x R R k x P x P m k x m D dt dm R m * * 1 2 2 ) ( ) ( Second mesenger production in a gradient D m ~ 1 µ m 2 s -1 (membrane protein. lipid) D m ~ 100 µ m 2 s -1 (cytosolic small molecule) Diffusion flattens internal gradient Gain is < 1 (the larger D m the smaller the gain) How to amplify ? 3
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This note was uploaded on 11/11/2011 for the course BIO 7.344 taught by Professor Bobsauer during the Spring '08 term at MIT.

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l20_notes - Alternative views on gradient sensing: - Postma...

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