Aaron E Albers

Publications of Aaron E Albers

• Driving oxygen coordinated ligand exchange at nanocrystal surfaces using trialkylsilylated chalcogenides.

  Authors: Marissa A Caldwell, Aaron E Albers, Seth C Levy, Teresa E Pick, Bruce E Cohen, Brett A Helms, Delia J Milliron

  Chemical communications (Cambridge, England). 01/2011; 47(1):556-8.

  A general, efficient method is demonstrated for exchanging native oxyanionic ligands on inorganic nanocrystals with functional trimethylsilylated (TMS) chalcogenido ligands. In addition, newlyA general, efficient method is demonstrated for exchanging native oxyanionic ligands on inorganic nanocrystals with functional trimethylsilylated (TMS) chalcogenido ligands. In addition, newly synthesized TMS mixed chalcogenides leverage preferential reactivity of TMS-S bonds over TMS-O bonds, enabling efficient transfer of luminescent nanocrystals into aqueous media with retention of their optical properties.

• Engineering of a synthetic electron conduit in living cells.

  Authors: Heather M Jensen, Aaron E Albers, Konstantin R Malley, Yuri Y Londer, Bruce E Cohen, Brett A Helms, Peter Weigele, Jay T Groves, Caroline M Ajo-Franklin

  Proceedings of the National Academy of Sciences of the United States of America. 10/2010; 107(45):19213-8.

  Engineering efficient, directional electronic communication between living and nonliving systems has the potential to combine the unique characteristics of both materials for advancedEngineering efficient, directional electronic communication between living and nonliving systems has the potential to combine the unique characteristics of both materials for advanced biotechnological applications. However, the cell membrane is designed by nature to be an insulator, restricting the flow of charged species; therefore, introducing a biocompatible pathway for transferring electrons across the membrane without disrupting the cell is a significant challenge. Here we describe a genetic strategy to move intracellular electrons to an inorganic extracellular acceptor along a molecularly defined route. To do so, we reconstitute a portion of the extracellular electron transfer chain of Shewanella oneidensis MR-1 into the model microbe Escherichia coli. This engineered E. coli can reduce metal ions and solid metal oxides ∼8× and ∼4× faster than its parental strain. We also find that metal oxide reduction is more efficient when the extracellular electron acceptor has nanoscale dimensions. This work demonstrates that a genetic cassette can create a conduit for electronic communication from living cells to inorganic materials, and it highlights the importance of matching the size scale of the protein donors to inorganic acceptors.

• Organelle-targetable fluorescent probes for imaging hydrogen peroxide in living cells via SNAP-Tag protein labeling.

  Authors: Duangkhae Srikun, Aaron E Albers, Christine I Nam, Anthony T Iavarone, Christopher J Chang

  Journal of the American Chemical Society. 03/2010; 132(12):4455-65.

  Hydrogen peroxide (H(2)O(2)) is a potent small-molecule oxidant that can exert a diverse array of physiological and/or pathological effects within living systems depending on the timing and locationHydrogen peroxide (H(2)O(2)) is a potent small-molecule oxidant that can exert a diverse array of physiological and/or pathological effects within living systems depending on the timing and location of its production, accumulation, trafficking, and consumption. To help study the chemistry and biology of this reactive oxygen species (ROS) in its native cellular context, we now present a new method for monitoring local, subcellular changes in H(2)O(2) levels by fluorescence imaging. Specifically, we have exploited the versatility of the SNAP-tag technology for site-specific protein labeling with small molecules on the surface or interior of living cells with the use of boronate-capped dyes to selectively visualize H(2)O(2). The resulting SNAP-Peroxy-Green (SNAP-PG) probes consist of appropriately derivatized boronates bioconjugated to SNAP-tag fusion proteins. Spectroscopic measurements of the SNAP-PG constructs confirm their ability to detect H(2)O(2) with specificity over other biologically relevant ROS. Moreover, these hybrid small-molecule/protein reporters can be used in live mammalian cells expressing SNAP-tag fusion proteins directed to the plasma membrane, nucleus, mitochondria, and endoplasmic reticulum. Imaging experiments using scanning confocal microscopy establish organelle-specific localization of the SNAP-tag probes and their fluorescence turn-on in response to changes in local H(2)O(2) levels. This work provides a general molecular imaging platform for assaying H(2)O(2) chemistry in living cells with subcellular resolution.

• A red-emitting naphthofluorescein-based fluorescent probe for selective detection of hydrogen peroxide in living cells.

  Authors: Aaron E Albers, Bryan C Dickinson, Evan W Miller, Christopher J Chang

  Bioorganic & medicinal chemistry letters. 08/2008;

  We report the synthesis, properties, and cellular application of Naphtho-Peroxyfluor-1 (NPF1), a new fluorescent indicator for hydrogen peroxide based on a red-emitting naphthofluorescein platform.We report the synthesis, properties, and cellular application of Naphtho-Peroxyfluor-1 (NPF1), a new fluorescent indicator for hydrogen peroxide based on a red-emitting naphthofluorescein platform. Owing to its boronate cages, NPF1 features high selectivity for hydrogen peroxide over a panel of biologically relevant reactive oxygen species (ROS), including superoxide and nitric oxide, as well as excitation and emission profiles in the far-red region of the visible spectrum (>600nm). Flow cytometry experiments in RAW264.7 macrophages establish that NPF1 can report changes in peroxide levels in living cells.

• Activity-based fluorescent reporters for monoamine oxidases in living cells.

  Authors: Aaron E Albers, Katherine A Rawls, Christopher J Chang

  Chemical communications (Cambridge, England). 12/2007;

  Monoamine Oxidase Reporters 1 and 2 (MR1 and MR2) are substrate-tethered activity probes that utilize a tandem amine oxidation/beta-elimination mechanism to detect MAO chemistry in vitro and inMonoamine Oxidase Reporters 1 and 2 (MR1 and MR2) are substrate-tethered activity probes that utilize a tandem amine oxidation/beta-elimination mechanism to detect MAO chemistry in vitro and in living cells directly and specifically without the need for additional enzymes or other activating reagents.

• A FRET-based approach to ratiometric fluorescence detection of hydrogen peroxide.

  Authors: Aaron E Albers, Voytek S Okreglak, Christopher J Chang

  Journal of the American Chemical Society. 09/2006; 128(30):9640-1.

  We report the synthesis, properties, and biological applications of Ratio-Peroxyfluor-1 (RPF1), a new ratiometric fluorescent reporter for hydrogen peroxide. RPF1 is comprised of a two-fluorophoreWe report the synthesis, properties, and biological applications of Ratio-Peroxyfluor-1 (RPF1), a new ratiometric fluorescent reporter for hydrogen peroxide. RPF1 is comprised of a two-fluorophore cassette, where the spectral overlap between coumarin donor and fluoran/fluorescein acceptor partners can be controlled by the chemoselective peroxide-mediated deprotection of boronic ester pendants on the acceptor dye. RPF1 features good selectivity for hydrogen peroxide over a variety of reactive oxygen species, including superoxide and nitric oxide, a ca. 8-fold increase in fluorescence intensity ratio (lambda517/lambda464) upon H2O2 reaction, and excitation and emission profiles in the visible region. Experiments with viable yeast mitochondria show that RPF1 can monitor and quantify endogenous production of H2O2, establishing the potential utility of this approach for probing peroxide biology in living systems.

• Boronate-based fluorescent probes for imaging cellular hydrogen peroxide.

  Authors: Evan W Miller, Aaron E Albers, Arnd Pralle, Ehud Y Isacoff, Christopher J Chang

  Journal of the American Chemical Society. 12/2005; 127(47):16652-9.

  The syntheses, properties, and biological applications of the Peroxysensor family, a new class of fluorescent probes for hydrogen peroxide, are presented. These reagents utilize a boronateThe syntheses, properties, and biological applications of the Peroxysensor family, a new class of fluorescent probes for hydrogen peroxide, are presented. These reagents utilize a boronate deprotection mechanism to provide high selectivity and optical dynamic range for detecting H2O2 in aqueous solution over similar reactive oxygen species (ROS) including superoxide, nitric oxide, tert-butyl hydroperoxide, hypochlorite, singlet oxygen, ozone, and hydroxyl radical. Peroxyresorufin-1 (PR1), Peroxyfluor-1 (PF1), and Peroxyxanthone-1 (PX1) are first-generation probes that respond to H2O2 by an increase in red, green, and blue fluorescence, respectively. The boronate dyes are cell-permeable and can detect micromolar changes in H2O2 concentrations in living cells, including hippocampal neurons, using confocal microscopy and two-photon microscopy. The unique combination of ROS selectivity, membrane permeability, and a range of available excitation/emission colors establishes the potential value of PR1, PF1, PX1, and related probes for interrogating the physiology and pathology of cellular H2O2.

• Screening mercury levels in fish with a selective fluorescent chemosensor.

  Authors: Sungho Yoon, Aaron E Albers, Audrey P Wong, Christopher J Chang

  Journal of the American Chemical Society. 11/2005; 127(46):16030-1.

  Societal concerns over toxic mercury accumulation in humans from fish and other dietary and environmental sources provide motivation to develop new tools and tactics for mercury detection in a wideSocietal concerns over toxic mercury accumulation in humans from fish and other dietary and environmental sources provide motivation to develop new tools and tactics for mercury detection in a wide range of laboratory and field settings. Here we report the synthesis, properties, and application of a selective and sensitive small-molecule chemosensor for fluorescence screening of mercury levels in fish. Mercuryfluor-1 (MF1) is a water-soluble, fluorescein-based reagent that features excellent selectivity for Hg2+ over competing analytes and the largest turn-on fluorescence response to date (>170-fold increase) for reporting this heavy metal ion in aqueous solution. Combining this chemoselective Hg2+ probe with a microwave digestion protocol provides a facile method for assaying mercury levels in fish samples with mercury concentrations spanning 0.1 to 8 ppm, a range well matched with the United States Environmental Protection Agency (U.S. EPA) standard for the maximum safe level of mercury in edible fish (0.55 ppm).