RESUMEN
Bacterial aerotaxis is a rapid response towards or away from oxygen. Here we report on the use of computer-assisted motion analysis coupled to flash photolysis of caged oxygen to quantify aerotactic responses in bacteria. The caged compound (mu-peroxo)(mu-hydroxo)bis[bis(bipyridyl) cobalt(III)] perchlorate liberates molecular oxygen upon irradiation with near-UV light. A mixture of cells and the caged oxygen compound was placed in a capillary tube and challenged by discrete stimuli of molecular oxygen produced by photolysis. We then recorded the rate of change of direction (rcd) as an estimate of tumble frequency in response to liberated oxygen and measured the signal processing (excitation) times in Bacillus subtilis, Bacillus halodurans and Escherichia coli. This computer-assisted caged oxygen assay gives a unique physiological profile of different aerotaxis transducers in bacteria.
Asunto(s)
Fenómenos Fisiológicos Bacterianos , Oxígeno/metabolismo , Bacillus subtilis/crecimiento & desarrollo , Bacillus subtilis/metabolismo , Sitios de Unión , Escherichia coli/crecimiento & desarrollo , Escherichia coli/metabolismo , Movimiento , Mutación , Fotoquímica , Fotólisis , Espectrofotometría UltravioletaRESUMEN
We have developed a method for time-lapse video photography and line scanning of optical densities for analysis of aerotactic responses of Halobacterium salinarum. This automated digital technique, along with line scan analysis of selected frames, gives a unique profile of the aerotactic migration of halobacterial cells.
Asunto(s)
Halobacterium salinarum/fisiología , Microscopía por Video , Aire , Acción Capilar , Procesamiento de Imagen Asistido por Computador/métodos , Movimiento (Física) , Factores de TiempoRESUMEN
Graphene's single atomic layer of sp(2) carbon has recently garnered much attention for its potential use in electronic applications. Here, we report a memory application for graphene, which we call graphene flash memory (GFM). GFM has the potential to exceed the performance of current flash memory technology by utilizing the intrinsic properties of graphene, such as high density of states, high work function, and low dimensionality. To this end, we have grown large-area graphene sheets by chemical vapor deposition and integrated them into a floating gate structure. GFM displays a wide memory window of â¼6 V at significantly low program/erase voltages of ±7 V. GFM also shows a long retention time of more than 10 years at room temperature. Additionally, simulations suggest that GFM suffers very little from cell-to-cell interference, potentially enabling scaling down far beyond current state-of-the-art flash memory devices.