Browsing by Author "Griffiths, Peter R."

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Binding of Metal Ions by Extracellular Polymers of Biofilm Bacteria
(1988-11) Geesey, Gill G.; Jang, Larry K.; Jolley, John G.; Hankins, Michael R.; Iwaoka, Teika; Griffiths, Peter R.
Exopolymers which anchor sessile bacteria to metallic surfaces exhibit the capacity to bind copper ions with high affinity. Ionized carboxyl groups on the polymers appear to participate in cupric ion binding. Formation of complexes between the polymers and cupric ions results in the release of protons from the polymer molecule. Attenuated total reflectance Fourier transform infrared spectroscopy showed that polymers composed of acidic polysaccharides promote ionization and deterioration of metallic copper surfaces. X-ray photoelectron spectroscopy studies revealed that the ionic state of the surface-derived copper varied depending on the type of acidic polysaccharide that was in contact with the surface. The results suggest that exopolymers elaborated by adherent bacteria can enhance corrosion of the surfaces with which they are associated.
Characterization of interfacial phenomena occurring during exposure of a thin copper film to an aqueous suspension of an acidic polysaccharide
(1987-12) Geesey, Gill G.; Iwaoka, Teika; Griffiths, Peter R.
A Fourier transform infrared spectrometer equipped with a cylindrical internal reflection element was used to sample the solidâ€”liquid interface of a metallic copper film submerged in an aqueous acidic polysaccharide solution. The presence of a polysaccharide absorption band at 1050 cmâˆ’1 in a water-subtracted spectrum supported previous spectroscopic data indicating polymer accumulation at the surface of the film. Firm binding of the polysaccharide to the surface after a 17-day exposure period was demonstrated by the retention of the 1050-cmâˆ’1 absorption band in spectra obtained after gentle rinsing of the film surface with polymer-free water. The sampling technique also provided evidence which suggests that acidic polysaccharides, including the firmly bound exopolymers produced by adherent cells of a freshwater sediment bacterium, promoted deterioration of the copper film. Internal reflection Fourier transform infrared spectroscopy appeared to be a useful, nondestructive method to study the sorption of biomolecules to a solid metal surface submerged in an aqueous medium.
Comparison of the amide i/ii intensity ratio of solution and solid-state proteins samples by transmission, attenuated total reflectance, and diffuse reflectance spectrometry
(1993-05) Ishida, Kenneth P.; Griffiths, Peter R.
The absolute and relative differences in amide I and amide II band intensities of albumin, β-lactoglobulin, and myoglobin as measured by attenuated total reflection infrared (ATR-IR) spectrometry, transmission of aqueous solutions, and KBr disks and diffuse reflectance (DR) spectrometry are compared. The amide I/II intensity ratios of the proteins sampled by ATR, DR, and transmission spectrometry of KBr disks were similar and were significantly different from the intensity ratios of the proteins in solution. The absolute amide II band intensity of dissolved proteins did not vary significantly with changes in pH. The difference in amide I/II intensity ratios between solution and adsorbed proteins was attributed to differences in secondary and possible tertiary structure. The thickness of each protein film was estimated with the use of the absorptivities calculated from the amide II band intensities of the KBr disk spectra. pH had a significant influence on the thickness of the adsorbed films. Differences in film thickness were attributed to a difference in the orientation of the protein molecules at the surface of the germanium internal reflection element.
Copper Coated Cylindrical Internal Reflection Elements for Investigating Interfacial Phenomena
(1986-09) Iwaoka, Teika; Griffiths, Peter R.; Kitasako, J. T.; Geesey, Gill G.
Techniques for coating thin copper films on the surface of cylindrical germanium internal reflection elements are described. These films were then characterized in an aqueous environment. The expected exponential relationship between the depth of penetration of the evanescent wave into water and the thickness of the copper film was verified experimentally. The stability of vacuum-deposited copper coatings was strong enough that the internal reflection element could be exposed to an aqueous solution of a polysaccharide for more than 40 h. The weak adhesion of polysaccharides to copper surfaces was studied spectroscopically.
Role of Bacterial Exopolymers in the Deterioration of Metallic Copper Surfaces
(1986) Geesey, Gill G.; Mittelman, M. W.; Iwaoka, Teika; Griffiths, Peter R.