Movement at the molecular level Diffusion:=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 [12=1 um, t-0.2 sec in cells [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: = 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. []1/2 =1 µm, t ~0.2 sec in cells []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
Elastic Brownian Ratchets and Tethered filaments Images removed due to copyright considerations See Mogilner, A and G. Oster Force generation by actin polymerization lI: the elastic ratchet and tethered filaments Biophys J.2003Mar;84(3):1591605 Brownian Actin filament tips fluctuate Some filaments are tethered
Elastic Brownian Ratchets and Tethered Filaments Images removed due to copyright considerations. See Mogilner, A. and G. Oster. "Force generation by actin polymerization II: the elastic ratchet and tethered filaments��." Biophys J. 2003 Mar;84(3):1591-605. Brownian: Actin filament tips fluctuate Some filaments are tethered 6
Actin Ruffles in Motile Cells
Actin Ruffles in Motile Cells 7
Supramolecular Springs Energy stored in chemical bonds which act as "latches Regulated by spasmin Calcium binding protein Images removed due to copyright considerations See Mahadevan L. and P. matsudaira Motility powered by supramolecular springs and ratchets. Science.2000Apr7;288(5463):95-100
Supramolecular Springs Energy stored in chemical bonds which act as “latches’ Regulated by Spasmin: Calcium binding protein Images removed due to copyright considerations. See Mahadevan, L. and P. Matsudaira. "Motility powered by supramolecular springs and ratchets." Science. 2000 Apr 7;288(5463):95-100. 8
Horseshoe Crab Sperm Uncoiling of an actin spring (unlike the echinoderm sperm-no polymerization!) Images removed due to copyright considerations See mahadevan L. and P. matsudaira Motility powered by supramolecular springs and ratchets Science.2000Apr7;288(5463)95-100
Horseshoe Crab Sperm Uncoiling of an actin spring (unlike the echinoderm sperm - no polymerization!) Images removed due to copyright considerations. See Mahadevan, L. and P. Matsudaira. "Motility powered by supramolecular springs and ratchets." Science. 2000 Apr 7;288(5463):95-100. 9
Molecular Motors Molecules that convert chemical energy into mechanical force Motors are specialized for specific tasks cell division cell movement organelle transport synthesis of ATP Most move unidirectionally along polymer filaments Coupled mechanical and chemical cycles(fuel)
Molecular Motors • Molecules that convert chemical energy into mechanical force • Motors are specialized for specific tasks: cell division cell movement organelle transport synthesis of ATP • Most move unidirectionally along polymer filaments • Coupled mechanical and chemical cycles (fuel) 10