Featured Research
Click on an image for an explanation of the research it represents.
 A dominant mutation in the adenomatous polyposis coli tumor suppressor gene causes mitotic abnormalities in human cells. The microtubule (red) spindle has not properly segregated all the chromosomes (blue), as seen by the kinetochore positive (green) chromosomes left at the midzone.
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 The position of the nucleus in the cell plays many important roles in development. Here we show dorsal epidermal nuclei migrating to a new position in a C. elegans embryo. Green shows the cell-cell boundaries and DAPI stained nuclei are blue. Antibodies against UNC-83 (red) localize to the nuclear envelope of these migrating nuclei. UNC-83 is required for these and other nuclear migration events. For more information, please contact the Starr lab.
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 The image shows the potentially lethal scorpion Parabuthus with a drop of highly toxic venom. We identify peptide toxins from such venoms by LC coupled to a hybrid electrospray-time of flight mass spectrometer and study their effect on vertebrate and insect cells. We express insect specific toxins in baculoviruses as green approaches to insect pest control. Mammal specific toxins are used as probes to study the vertebrate nervous system and potential pharmaceutical leads.
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 Root tip of the plant Medicago truncatula stained with a specific dye for nitric oxide. Nitric oxide is an attractant to plant parasitic nematodes and probably other organisms that interact with roots.
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ATP sulfurylase catalyzes the adenylyl group transfer of ATP onto inorganic sulfate to produce adenosine 5-phosphosulfate (APS). This is the first step in the biological assimilation of inorganic sulfate. In fungi, ATP sulfurylase is an oligomer composed of six identical subunits, and is allosterically regulated by PAPS, the product of APS kinase. Shown here are the conformational changes seen in the ATP sulfurylase hexamer upon binding the allosteric inhibitor PAPS, which results in decreased enzyme activity.
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Our lab studies the structure of proteins containing WD repeats, a ~40 amino acid motif found in approximately 1-2% of all eukaryotic proteins. Despite the striking regularity and similarity of these propeller-like structures, they function in very divergent cellular processes. Clockwise from the upper left, Bub3, a mitotic checkpoint regulator; Ski8, a protein mediating nonstop mRNA degradation; Aip1, a protein involved in actin depolymerization and Sif2, functioning in histone deacetylation.
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Alphavirus represents one of the best known model systems of macromolecular assembly in the context of studying virus-cell interaction. The RNA genome (red) is packaged into a nucleocapsid (orange for the capsid proteins), which is surrounded by a lipid bilayer (green) with transmembrane spike proteins (blue). One of the key questions is how the viral proteins drive the assembly reactions through the cytoplasm (left), and how the nucleocapsids bud out from the cellular membrane in forming a mature virion with lipid envelop, capable of further infections. Our research interest is to determine the conformations of the virus and the cellular compartments at the various stages of life cycle. This would help us to understand the mechanism of virus functions as well as the design of anti-viral drugs more effectively.
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The image is of a DNA catenane produced by RecQ helicase and DNA topoisomerase III, in the presence of SSB protein. Atomic force microscopy was used to visualize the DNA, which had been coated with RecA protein to enhance resolution and thereby facilitate tracing of the path followed by the duplex DNA strands.
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 Model used in Artyom Kopp's laboratory.
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