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Role of Diffusion in Cells
Bio311
con2nued…
Bibliography Books • Random Walks in Biology‐ Berg • Biological Physics of the Developing Embryo‐ Forgacs & Newman • Molecular Biology of the Cell‐ Alberts, et al. Papers 1. A. M. Turing, (1952) Phil. Trans. R. Soc. B237, 37 2. Sinha DK, et al. (2008) Biophys J. 95, p5432 3. H. Meinhardt et al. (2001) PNAS 98, 14202 4. Meacci G. et al. (2006) Phys Biol. 3, p255 5. Loose M, et al (2008) Science, 320, p789 6. Kaláb P, et al. Nature.(2006) 440, p697 7. Athale et al. (2008) Science, 322, p1243
Diffusion based transport Transcrip2on compartments (TCs) dynamics affected by chroma2n structure
Uridine 5’‐triphosphate (UTP) labelling
RNA polymerase II
Chroma2n compac2on
Sinha DK, et al. (2008) Biophys J. 95, p5432
Outline
The role of diffusion in cells
• Transport • Pabern forma2on/Cellular geometry
• Signaling
Mobility of TCs affected by Local DNA packing
Sinha DK, et al. (2008) Biophys J. 95, p5432
Different Modes of Mobility
Measure of anomalous diffusion
normal 0.8<α<1.2
Sub‐diffusion α<0.8
Super‐diffusion α>1.2
Independent of size Sinha DK, et al. (2008) Biophys J. 95, p5432
Finding the Centre in E. coli
Z‐ring
Division
Polymeriza2on
Septa2on
Centre finding
Forma2on of a ring of FtsZ
1. Min inhibi2on of FtsZ 2. Nucleoid Occlusion
Finding the Centre
The Min cycle MinC inhibits FtsZ polymeriza2on
Meacci G. et al. (2006) Phys Biol. 3, p255
Diffusion Reac2on Paberns
Loose M, et al (2008) Science, 320, p789
Min protein waves. MinD (1 μM), doped with 20% Bodipy‐labeled MinD (green), MinE (1 μM), doped with 10% Alexa647‐labeled MinE (red).
Scale bar is 50 μm, frames are 9 s apart
MinE MinD Merge
Signalling Protein Diffusion‐Reac2on Gradients
Visualizing the RanGTP Gradient using FRET
Gradient Range
Role in Spindle Assembly
Athale et al. (2008) Science, 322, p1243
Conclusions
Role of Diffusion in 1. Transport 2. Pabern forma2on/geometry
3. Signalling gradients
Complex mechanisms combined‐ not in isola2on
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