RESUMEN
Three-dimensional structures of actin bundles formed with polycations were observed by using transmission electron microtomography and atomic force microscopy. We found, for the first time, that the cross-sectional morphology of actin bundles depends on the polycation species and ionic strength, while it is insensitive to the degree of polymerization and concentration of polycation. Actin bundles formed with poly-N-[3-(dimethylamino)propyl] acrylamide methyl chloride quaternary show a ribbon-like cross-sectional morphology in low salt concentrations that changes to cylindrical cross-sectional morphology with hexagonal packing of the actin filaments in high salt concentrations. Contrastingly, actin bundles formed with poly-L-lysine show triangular cross-sectional morphology with hexagonal packing of the actin filaments. These variations in cross-sectional morphology are discussed in terms of anisotropy in the electrostatic energy barrier.
Asunto(s)
Actinas/química , Imagenología Tridimensional , Poliaminas/química , Citoesqueleto de Actina/química , Actinas/análisis , Animales , Imagenología Tridimensional/métodos , Estructura Molecular , Pectinidae , Poliaminas/análisis , PolielectrolitosRESUMEN
Bioluminescence imaging reveals the long-term dynamics of individual gene expression in a single cell. However, methods for simultaneously imaging multiple gene expression patterns have been unknown to date. Here, we constructed a dual-path optical luminescence imaging system using a two-color reporter system and could simultaneously track two gene expression patterns for several days in a single cell.
Asunto(s)
Expresión Génica , Mediciones Luminiscentes/métodos , Imagen Molecular/métodos , Proteínas Recombinantes de Fusión/análisis , Animales , Ritmo Circadiano/genética , Genes Reporteros , Luciferasas , Ratones , Células 3T3 NIH , Proteínas Recombinantes de Fusión/genética , TransfecciónRESUMEN
We developed a novel in situ method for the control of F-actin assembly by using a synthetic photoresponsive polycation. The photoresponsive polycation mainly comprises a water-soluble cationic monomer and also contains a small amount of the monomer of a triphenylmethane leucohydroxide derivative (20 mol %), which is a well-known photochromic molecule that can be cationized in aqueous solution by ultra violet (UV) irradiation, thereby causing an increase in the total charge on the photoresponsive polycation. Thus, by exposure to UV radiation in aqueous solution, F-actin and the photoresponsive polycation start assembling into F-actin/photoresponsive polycation complexes of various morphologies such as bundles, coils, and networks, depending upon the concentrations of both the F-actin and salt. Further, localized UV irradiation can be applied in order to control the local formation of F-actin/photoresponsive polycation complexes. Thus, this technique provides a novel method for the spatiotemporal control of F-actin assembly and can be applied to investigate the unknown characteristics of F-actin.