Microscopy of DNA in dilute polymer solutions

The mechanism of separation of DNA in polymer solutions is not well understood. In this paper we use epifluorescence videomicroscopy to investigate the dynamic behavior of DNA electrophoresing through dilute polymer solutions. DNA collides with polymer obstacles, which cause the conformation of DNA to change from the globular, random coil conformation it takes in free solution. There are two main types of DNA-polymer collisions: U-shape collisions and brief collisions. In U-shape collisions, the DNA collides with a polymer obstacle, extends into a U-shape, and then slides around the polymer obstacle like a pulley. There are occasionally multiple entanglement points, causing the DNA to take more complex conformations, such as W-shapes. In the brief collision process, the DNA collides with a polymer obstacle and begins to extend but then collapses back into its globular conformation before a full U-shape is formed. The frequency of these interactions increases as the DNA size increases, and it also increases when the polymer size or concentration increases. These data support the transient entanglement coupling mechanism of separation of DNA, which states that entanglements between DNA and polymer molecules result in the separation of DNA.     

The gnd gene encoding a novel 6-phosphogluconate dehydrogenase and its adjacent region of Actinobacillus actinomycetemcomitans chromosomal DNA

Integrin alpha IIb beta 3 is necessary for platelet thrombus formation by virtue of its ability to bind fibrinogen and von Willebrand factor in a regulated fashion and to mediate platelet aggregation. Moreover, alpha IIb beta 3 transduces inward signals in response to ligand binding which promote cytoskeletal reorganization and other post-ligand binding events. Anchorage and signaling through alpha IIb beta 3 appear to be controlled by interactions of intracellular proteins with the cytoplasmic tails of alpha IIb and/or beta 3. The cytoplasmic tails and associated cytoskeletal components may function as a scaffold or nucleation site for the assembly of enzymes, substrates and adaptor molecules into a signaling complex. Identification of the components of this signaling complex and characterization of their dynamic interactions should lead to insights into the molecular basis of platelet activation defects and may provide a rationale for the development of new anti-thrombotic drugs.