Movie 3.1 Neutrophil Chase (Referenced in Figure 3.3)
This classic movie was made by David Rogers at Vanderbilt University in the 1950s. It shows a neutrophil (a type of white blood cell) chasing a bacterium through a field of red blood cells in a blood smear. After pursuing the bacterium around several red blood cells, the neutrophil finally catches up to and engulfs its prey. In the human body, these cells are an important first line of defense against bacterial infection. The speed of rapid movements such as cell crawling can be most easily measured by the method of direct observation.Courtesy of the estate of David Rogers, Vanderbilt University.
Movie 3.2 Early Embryonic Cell Division (Referenced in Figure 3.16)
This video shows the remarkable synchrony of the early embryonic cell divisions for the clawed frog Xenopus laevis. About 25 frog eggs were fertilized simultaneously in this petri dish, and then filmed over the first dozen rounds of cell division. Each cell division cycle takes about 25 minutes in real time. Not only do all the cells in each embryo divide simultaneously, but the entire dish of embryos maintains essentially the same clock time over several hours after fertilization.
Movie 3.3 Eukaryotic Cell Division (Referenced in Figure 3.21)
This video sequence shows some of the events of the eukaryotic cell cycle, for an individual mammalian cell growing in tissue culture. This living cell is observed using differential interference contrast microscopy. At the start of the video sequence, the DNA has finished replication, the chromosomes have condensed, and they have all lined up in the middle of the cell. Shortly after the video starts playing, the chromosomes split into two equal groups, and move to opposite sides of the cell. Then the cell undergoes cytokinesis, dividing into two daughter cells. Courtesy of Aaron Straight, Stanford University School of Medicine.
Movie 3.4 Myosin Steps (Referenced in Figure 3.33)
In this experiment, a single fluorescent molecule was attached to one of the two actin-binding motor heads on a molecule of myosin V. As the motor protein steps along the actin filament, the fluorescent spot changes its location by discrete steps. For this particular motor protein, each step is about 72 nanometers, corresponding to movement of only a few pixels in the video. Courtesy of Paul Selvin, University of Illinois Champaign-Urbana
Movie 10.1 DNA Packaging (Referenced in Figure 10.19)
This animation illustrates the packaging of DNA into the capsid head of bacteriophage phi-29. From cryo-electron microscopy, it appears that the DNA is packaged as a series of near-concentric hoops inside the rigid phage capsid. Experiments using optical traps can precisely measure the rate of DNA packaging as a linear strand is pulled into the phage capsid by the portal motor. Initially the rate is very fast, but it slows as the DNA accumulates inside. This slowing is thought to be due to the increasing stored elastic energy of the packed DNA, which must be overcome by the portal motor to complete packaging. Courtesy of Eric Keller, Geordie Martinez, and Michael Dalby of Stylus LLC, Kensington, CA.
Movie 10.2 DNA Twist Elasticity Experiment (Referenced in Figure 10.37)
This experiment was designed to measure the twist modulus of DNA. A double-stranded DNA molecule (which is not visible here) has been stretched between two large beads, shown at the top and bottom of the video frame. The upper large bead is attached to a micropipette, and the lower large bead is held in an optical trap. Then, a smaller bead was attached to a specific location on the DNA molecule. Before the start of the movie, the pipette was twisted to build up torsional strain in the DNA, while the central bead was held in place using fluid flow. When the fluid flow was halted, the DNA was free to rotate to relieve the torsional strain. The rapidly twirling central bead now acts as a marker enabling measurement of the speed of DNA untwisting. This data can be used to measure the twist elasticity of a single molecule. Supplementary movie from: Bryant Z, Stone MD, Gore J, Smith SB, Cozzarelli NR, Bustamante C. 2003. "Structural transitions and elasticity from torque measurements on DNA." Nature. 424(6946): 338-341.
Movie 11.1 Force-Induced Tether Formation (Referenced in Figure 11.25)
This experiment was designed to measure the amount of force required to pull a membrane tether from a spherical vesicle. This large phospholipid vesicle was made by including a small fraction of biotinylated lipid molecules, so that an avidin-coated bead could be tightly bound to the surface. The bead was then pulled away from the vesicle using an optical trap. The force on the bead increases suddenly when the tether is formed, and then remains fairly constant as the tether is extended. Courtesy of Heun Jin Lee, California Institute of Technology
Movie 11.2 Cell Compartments Tomography (Referenced in Figure 11.38)
The precise three-dimensional shapes of all the membrane-enclosed organelles within a cultured cell can be painstakingly reconstructed using electron tomography. Here, we see the region surrounding the Golgi apparatus in an insulin-secreting cell. First, electron tomography is used to generate a stack of virtual slices through the cell, each only 3.8 nm thick. Next, the outline of each individual organelle is traced through every slice. Here, a single cisterna of the Golgi stack is colored red. It is also possible to trace microtubules and ribosomes in these high-resolution images. Finally, the outlines of every organelle, vesicle, microtubule and ribosome are reassembled by the computer into a complete three-dimensional model. This emphasizes the complexity of membrane structures, and also the incredibly dense packing of things within the cell.Marsh BJ, Mastronarde DN, Buttle KF, Howell KE, McIntosh JR. 2001. "Organellar relationships in the Golgi region of the pancreatic beta cell line, HIT-T15, visualized by high resolution electron tomography." Proc Natl Acad Sci U S A. 98(5):2399-2406.
Movie 13.1 Transport Within a Nerve Cell (Referenced in Figure 13.05)
In nerve cells, passive diffusion is insufficient to transport large membrane-enclosed organelles down the length of the axon, which can range in length from under one millimeter to over a meter. Rapid directed transport in these cells is accomplished by molecular motors, which bind to organelles and walk along microtubules. In this video, the microtubule-rich cytoplasm from the inside of a squid giant axon has been squirted out onto a microscope slide. The microtubules and numerous membraneous organelles of various sizes can be readily seen using differential interference contrast microscopy on a standard light microscope. This video shows movement of organelles along the microtubules in real time.
Movie 15.1 Keratocyte (Referenced in Figure 15.2)
This video sequence shows a single fish skin cell moving across the field of view. The cell body, containing the nucleus and all the membraneous organelles, is at the left side. The large, broad, flat lamellipodium that pulls the cell forward to the right is filled with a dense network of actin filaments.Courtesy of Kinneret Keren, Technion—Israel Instute of Technology
Movie 15.2 Listeria (Referenced in Figure 15.3)
The intracellular bacterial pathogen <i>monocytogenes</i> is able to move around inside of host cells by inducing the local assembly of host cell actin filaments at its surface. In this video, a mammalian epithelial cell was infected by the bacteria in tissue culture about four hours before the movie was made. The bacteria have replicated in the host cell, and the many descendants of the initial infecting bacteria are now moving rapidly throughout the cell, visible as small black oblongs. Remarkably, only a single protein from the bacterium is necessary and sufficient to direct this kind of movement. On the right, we can see a small polystyrene bead that has been coated with the bacterial protein ActA. It has been dropped into a cytoplasmic extract that contains actin and actin-associated proteins from the host cell. On the left, we can see the fluorescent signal from labeled actin forming a comet tail that pushes the bead through the cytoplasmic extract. These artificial particles move at the same rate as real bacteria under the same conditions. Courtesy of Julie Theriot, Stanford University School of Medicine, Daniel Portnoy, University of California, Berkeley, and Lisa Cameron, University of Melbourne
Movie 16.1 Gliding Motility Assay with Myosin (Referenced in Figure 16.9)
This video sequence shows fluorescently labeled actin filaments gliding on a surface coated with the motor protein myosin II. Each actin filament moves in only one direction, as the orientation of the motor protein steps are dictated by the structural asymmetry of the actin filament. This movement requires the addition of ATP. Courtesy of James Spudich, Stanford University
Movie 16.2 Kinesin Bead (Referenced in Figure 16.10)
In this experiment, small glass beads have been coated with the microtubule-associated motor protein, kinesin. Microtubules bound to the surface of the glass slide can be seen using differential interference contrast microscopy. As the movie plays, a single bead covered with kinesin lands on a microtubule near the center of the video frame. The bead travels for several micrometers along the microtubule, from right to left, before dissociating from the microtubule and moving away by Brownian motion. This video shows kinesin-driven movement of the bead in real time. Courtesy of Jonathon Howard, Dresden University of Technology.
Movie 16.3 Transport of Pigment Granules (Referenced in Figure 16.41)
Some fish and frogs can change their colors depending on their mood. They accomplish this trick by using hormones to regulate the activity of motor proteins that move pigment-containing vesicles within their skin cells. In this video sequence, cultured skin cells from a black tetra fish are stimulated with adrenaline. This causes rapid activation of a dynein motor attached to the pigment granules, and drives the pigment granules to collect in the center of the cell. When this happens all over the fish, it appears to turn a lighter color.Courtesy of Gary Borisy, Northwestern University. Supplementary movie from: Rodionov VI, Borisy GG. 1998. "Self-centering in cytoplasmic fragments of melanophores." Mol Biol Cell. 9(7):1613-1615.