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A New Generation of Ca2+ Indicatorsw ith Greatly Improved Fluorescence Properties* Posted: 02 Jan 2012 02:05 AM PST A New Generation of Ca2+ Indicatorsw ith Greatly Improved Fluorescence Properties* Grzegorz Grynkiewicz$, Martin Poenie, and Roger Y. TsienB From the Department of Physiology-Anatomy, Uniuersitoyf California, Berkeley, California9 4720 Abstract: A new family of highly fluorescent indicators has been synthesized for biochemical studies of the physiological role of cytosolic free Ca2+. The compounds combine an 8-coordinate tetracarboxylate chelating site with stilbene chromophores. Incorporation of the ethylenic linkage of the stilbene into a heterocyclic ring enhances the quantum efficiency and photochemical stability of the fluorophore. Compared to their widely used predecessor, "quina," the new dyes offer up to 30-fold brighter fluorescence, major changes in  wavelength not just intensity upon Ca2+ binding, slightly lower affinities for Ca2+, slightly longer wavelengths of excitation, and considerably improved selectivity for Ca2+ over other divalent cations. These properties, particularly the wavelength sensitivity to Ca2+, should make these dyes the preferred fluorescent indicators for many intracellular applications, especially in single cells, adherent cell layers, or bulk tissues. Sources: THE JOURNAOLF BIOLOGICAL CHE MISTRY

Analysis and simulation of digital electron holograms from Polymer latexes Posted: 01 Jan 2012 02:05 PM PST Analysis and simulation of digital electron holograms from Polymer latexes Y.C. Wang, T.M. Chou and M. Libera* Department of Chemical, Biochemical and Materials Engineering, Stevens Institute of Technology, Hoboken, NJ Abstract This paper describes procedures being developed to quantitatively measure mean inner potential and use such data in holographic image simulations of polymer microstructure. Results from holographic imaging experiments are presented using polymer latexes whose spherical geometry leads to a simple relation between specimen thickness and lateral position in a phase image. Success with this approach demands accurate determination of the center and radius in the image of a latex sphere. These parameters are found via a least-squares fit to experimental image data. Recursive methods to enhance the accuracy of the measured Φo values are being developed based on characteristic features in difference images generated using an experimental phase image and a simulated phase image calculated from experimentallyderived center, radius, and data. Key Words: Latex sphere, multi-phase polymer microstructure, styrene-butadiene-styrene triblock copolymer, transmission electron holography, phase-contrast imaging, electron-optical refractive index, mean inner potential, simulation of phase image, least-squares fit, spherical geometry. Sources: Scanning Microscopy Vol. 11, 1997 (Pages 427-436)

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