Browsing by Author "Ridgley, Devin M."

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    Design and Construction of Large Amyloid Fibers
    Ridgley, Devin M.; Rippner, Caitlin M. W.; Barone, Justin R. (MDPI, 2015-04-16)
    Mixtures of “template” and “adder” proteins self-assemble into large amyloid fibers of varying morphology and modulus. Fibers range from low modulus, rectangular cross-sectioned tapes to high modulus, circular cross-sectioned cylinders. Varying the proteins in the mixture can elicit “in-between” morphologies, such as elliptical cross-sectioned fibers and twisted tapes, both of which have moduli in-between rectangular tapes and cylindrical fibers. Experiments on mixtures of proteins of known amino acid sequence show that control of the large amyloid fiber morphology is dependent on the amount of glutamine repeats or “Q-blocks” relative to hydrophobic side chained amino acids such as alanine, isoleucine, leucine, and valine in the adder protein. Adder proteins with only hydrophobic groups form low modulus rectangular cross-sections and increasing the Q-block content allows excess hydrogen bonding on amide groups that results in twist and higher modulus. The experimental results show that large amyloid fibers of specific shape and modulus can be designed and controlled at the molecular level.
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    Field survey of Drosophila suzukii (Matsumura) and Zaprionus indianus Gupta (Diptera: Drosophilidae) in Maui, Hawaii
    Willbrand, Brittany N. (Virginia Tech, 2019-04-18)
    Drosophila suzukii (Matsumura) and Zaprionus indianus Gupta (Diptera: Drosophilidae) are notable agricultural pests of soft-skinned fruits. Efficient field surveying is vital in an integrated pest management program. A survey to identify D. suzukii populations was conducted in four localities in Maui County among seven host-plants. During the survey, adult Z. indianus specimens were collected at all four localities in traps positioned in six of the seven host plants, suggesting that this previously unreported exotic species may already be well-established. Though there are currently no species-specific attractants available for D. suzukii or Z. indianus, characterization of attractant specificity by species and understanding how attractant efficacy varies with time is needed to advance development. A modification of the deli-cup trap was used and five attractants (brown rice vinegar, apple cider vinegar, red wine, brown rice vinegar plus red wine, apple cider vinegar plus red wine) were deployed in cherimoya in Kula, Maui, Hawaii. This investigation includes the first reported use of brown rice vinegar as an olfactory attractant in the United States and the results suggest that it may have higher specificity in the field capture of D. suzukii than apple cider vinegar, red wine, and apple cider vinegar with red wine. No significant differences were observed in attractant specificity for the field capture of Z. indianus. To examine attractant efficacy over time with and without a preservative, traps were maintained daily in cherimoya. The results suggest that attractants up to seven days old had a significant effect on mean field captures of D. suzukii and non-target drosophilids. Inclusive of all attractants and field ages, The addition of 1% boric acid (w/v) to the attractant solution increased the total field captures of D. suzukii by 44%, but no effect was observed for non-target drosophilids. These investigations enhance our current understanding of attractant specificity, which is the first step towards identifying selective compounds for a species-specific attractant. Furthermore, the first report of Z. indianus in Hawaii highlights the importance of examining interspecies interactions between endemic and invasive drosophilids and the need for the establishment of economic thresholds for vinegar fly pests.
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    Genetically Encoded Self-Assembly of Large Amyloid Fibers
    Ridgley, Devin M.; Freedman, Benjamin G.; Lee, Parker W.; Barone, Justin R. (The Royal Society of Chemistry, 2014-01-14)
    “Functional” amyloids are found throughout nature as robust materials. We have discovered that “template” and “adder” proteins cooperatively self-assemble into micrometer-sized amyloid fibers with a controllable, hierarchical structure. Here, Escherichia coli is genetically engineered to express a template protein, Gd20, that can initiate self-assembly of large amyloid fibrils and fibers. Through atomic force microscopy (AFM) we found that expression of Gd20 produces large amyloid fibrils of 490 nm diameter and 2–15 _m length. Addition of an extracellular adder protein, myoglobin, continues self-assembly to form amyloid tapes with widths of [similar]7.5 _m, heights of [similar]400 nm, and lengths exceeding 100 _m. Without myoglobin the amyloid fibrils are metastable over time. When myoglobin is present, the amyloid fiber continues self-assembling to a width of [similar]18 _m and height of [similar]1 _m. Experimental results demonstrate that large amyloid fibers with a tailored stiffness and morphology can be engineered at the DNA level, spanning four orders of magnitude.