Browsing by Author "Slininger, Patricia J."

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    A Fiber-optic System for Measuring Single Excitation-Dual Emission Fluorescence Ratios in Real Time
    (Biotechnology progress, 1992) McCarthy, John F.; Magin, Richard L.; Kisaalita, William S.; Slininger, Patricia J.
    The development and subsequent evaluation of a fiber‐optic system for measuring single excitation—dual emission fluorescence ratios in real time is described. The design of the flashlamp excitation source, optics, electronics, and computer software is discussed. The dual emission pH sensitive fluorophore 1, 4‐dihydroxyphthalonitrile (1, 4‐DHPN) was used to test the performance of this system. The flexible design of this modular system permits the use of other single excitation—dual emission fluorophores by simply changing the appropriate optical filters. Upon a single 340–380‐nm excitation, pH‐sensitive emissions were monitored at 488 nm and 434 nm. The ratio of these emissions (488/434) was then computed in real time, for a 2 mM solution of 1, 4‐DHPN, while the pH was titrated over the range 5–9. The nonlinear, system‐dependent, calibration curve of pH versus the ratio of emission wavelengths was empirical fit by a fourth‐order polynomial (r2 = 0.995). Reliable pH measurements in the range 6–8 were obtained using concentrations of 1, 4‐DHPN as low as 50 μM. The standard deviation of pH measurements using a 1 mM solution of 1, 4‐DHPN, near neutral pH, was found to be approximately 0.1 pH unit
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    Defined media for optimal pyoverdine production by Pseudomonas fluorescens 2-79
    (Applied microbiology and biotechnology, 1993) Kisaalita, William S.; Slininger, Patricia J.; Bothast, Rodney J.
    Pseudomonas fluorescens strain 2-79 (NRRL-15132) produces a fluorescent yellow-green pyoverdine when cultured on Fe(III)-poor medium. When cultured on Fe(III)-rich medium, strain 2-79 produces an antibiotic, phenazine 1-carboxylic acid, which is effective in suppressing plant fungal diseases such as take-all of wheat. A 23 factorial design was used to examine pyoverdine production as a function of the presence or absence of Bacto casamino acids, purines-pyrimidines and vitamins in an iron-deficient medium. Amino acids were found to be an important factor (P=0.0002). A Plackett-Burman design was used to identity eight amino acids, out of the 19 present in casamino acids, that were responsible for the increased pyoverdine production: methionine, valine, isoleucine, tyrosine, proline, phenylalanine, glutamic acid, and glycine. Biomass was enhanced only by glutamic acid.