Movement at the molecular level Diffusion:<rp2>=6Dt(D≈6πμa) Typical numbers 10 nm protein in water D=10-10 m2/s Image removed due to in cells D=10-12 m /s(D=10-14 m2/s lipids) copyright considerations [<r2>12=1 um, t-0.2 sec in cells [<r2>12=10 um, t-20 sec in cell Slow and isotropic How to generate fast vectorial motion Axonal transport of organelles in giant squids 22803BEH410-10.537J
Movement at the Molecular Level Diffusion: <r2> = 6 D t (D≈6 π µ a) Typical numbers: Image removed due to 10 nm protein in water D= 10-10 m2/s ….in cells D= 10-12 m2/s (D= 10-14 m2/s lipids) copyright considerations. [<r2>]1/2 =1 µm, t ~0.2 sec in cells [<r2>]1/2 =10 µm, t ~20 sec in cells Slow and isotropic. How to generate fast vectorial motion ? Axonal transport of organelles in giant squids 2/28/03 BEH 410-10.537J 1
Directed(Vectorial) Molecular Movement Polymerization Living polymerization of actin/microtubules Springs Conformational changes of molecules Motor proteins nucleotide(atP)hydrolysis: chemical energy-> work Pumps Hydrolysis of ATP Create concentration gradients
Directed (Vectorial) Molecular Movement Polymerization: Living polymerization of actin/microtubules Springs: Conformational changes of molecules Motor Proteins: nucleotide (ATP) hydrolysis: chemical energy -> work Pumps: Hydrolysis of ATP Create concentration gradients 2
Actin Comets Propelling Listeria Listeria monocytogenes moving in PtK2 cells These pathogenic bacteria grow directly in the host cell cytoplasm The phase-dense streaks behind the bacteria are the actin-rich comet tails Actin-based motility is also used in cellular motility; this cell is using it's cytoskeleton to crawl toward the lower right-hand corner. Speeded up 150X over real time Julie Theriot dan Portnoy
Actin Comets Propelling Listeria Listeria monocytogenes moving in PtK2 cells These pathogenic bacteria grow directly in the host cell cytoplasm. The phase-dense streaks behind the bacteria are the actin-rich comet tails. Actin-based motility is also used in cellular motility; this cell is using it's cytoskeleton to crawl toward the lower right-hand corner. Speeded up 150X over real time. --Julie Theriot & Dan Portnoy 3
Actin is Transiently Tethered to the bacteria Images removed due to copyright considerations See Cameron, L.A., T. M. Svitkina, D. Vignjevic, J. A. Theriot, and G. G Borisy Dendritic organization of actin comet tails. Curr biol.2001Jan23:11(2):130 Noireaux et al.(2000): it takes about 10 picoN to separate the actin from the comet
Actin is Transiently Tethered to the Bacteria Images removed due to copyright considerations. See Cameron, L.A., T. M. Svitkina, D. Vignjevic, J. A. Theriot, and G. G. Borisy. "Dendritic organization of actin comet tails." Curr Biol. 2001 Jan 23;11(2):130-5. Noireaux et al. (2000): it takes about 10 picoN to separate the actin from the comet… 4
Images removed due to copyright considerations See Kuo. S. c and J. L. McGrath Steps and fluctuations of Listeria monocytogenes during actin-based motility Nature.2000oct26;407(6807):10269 Steps of 5. 4nm
Images removed due to copyright considerations. See Kuo, S. C and J. L. McGrath. "Steps and fluctuations of Listeria monocytogenes during actin-based motility��." Nature. 2000 Oct 26;407(6807):1026-9. Steps of 5.4nm 5