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Recent research in the field of nanometer-scale electronics has focused on the operating principles of small-scale devices and schemes to realize useful circuits. In contrast to established "top-down" fabrication techniques, molecular self-assembly is emerging as a "bottom-up" approach for fabricating nanostructured materials. Biological macromolecules,(More)
pH sensing is crucial for survival of most organisms, yet the molecular basis of such sensing is poorly understood. Here, we present an atomic resolution structure of the periplasmic portion of the acid-sensing chemoreceptor, TlpB, from the gastric pathogen Helicobacter pylori. The structure reveals a universal signaling fold, a PAS domain, with a molecule(More)
Imaging membrane dynamics is an important goal, motivated by the abundance of biochemical and biophysical events that are orchestrated at, or by, cellular membranes. The short length scales, fast timescales, and environmental requirements of membrane phenomena present challenges to imaging experiments. Several technical advances offer means to overcome(More)
The two-dimensional fluidity of lipid bilayers enables the motion of membrane-bound macromolecules and is therefore crucial to biological function. Microrheological methods that measure fluid viscosity via the translational diffusion of tracer particles are challenging to apply and interpret for membranes, due to uncertainty about the local environment of(More)
Cellular membranes exhibit a variety of controlled curvatures, with filopodia, microvilli, and mitotic cleavage furrows being only a few of many examples. Coupling between local curvature and chemical composition in membranes could provide a means of mechanically controlling the spatial organization of membrane components. Although this concept has surfaced(More)
In recent years three powerful optical imaging techniques have emerged that provide nanometer-scale information about the topography of membrane surfaces, whether cellular or artificial: intermembrane fluorescence resonance energy transfer (FRET), fluorescence interference contrast microscopy (FLIC), and reflection interference contrast microscopy (RICM).(More)
Lipid bilayers provide the structural framework for cellular membranes, and their character as two-dimensional fluids enables the mobility of membrane macromolecules. Though the existence of membrane fluidity is well established, the nature of this fluidity remains poorly characterized. Three-dimensional fluids as diverse as chocolates and cytoskeletal(More)
I introduce an algorithm for subpixel localization of imaged objects based on an analytic, non-iterative calculation of the best-fit radial symmetry center. This approach yields tracking accuracies that are near theoretical limits, similarly to Gaussian fitting, but with orders-of-magnitude faster execution time, lower sensitivity to nearby particles and(More)
Most materials freeze when cooled to sufficiently low temperature. We find that magnetic dipoles randomly distributed in a solid matrix condense into a spin liquid with spectral properties on cooling that are the diametric opposite of those for conventional glasses. Measurements of the nonlinear magnetic dynamics in the low-temperature liquid reveal the(More)
We introduce a simple intermembrane junction system in which to explore pattern and structure formation by membrane-bound proteins. The junction consists of a planar lipid bilayer to which one species of protein (an IgG antibody) is bound, forming a 2D, compressible fluid. Upon the adhesion of a second lipid bilayer, the formerly uniformly distributed(More)