William Charles Neely

Specific and selective biosensor for Salmonella and its detection in the environment

The specific and selective detection of Salmonella typhymurium based on the use of a polyclonal antibody immobilized by the Langmuir-Blodgett method on the surface of a quartz crystal acoustic wave device was demonstrated in liquid samples. These biosensors were selective to S. typhymurium in the presence of large concentrations of Escherichia coli O157:H7. They were also specific to S. typhymurium since bacteria preincubated with free antibody produced no signal. Dark-field and electron microscopy showed that two different antibodies, polyvalent somatic O and flagellar H7, were immobilized on the sensor surface producing two distinct attachments of bacteria at the liquid-solid interface. The somatic O antibody exhibits a rigid, binding, while the flagellar H7 antibody forms a flexible connection allowing a large degree of freedom. When the attachment of bacteria was rigid and strong, the responses of the acoustic wave sensors correlated with changes in the mass of bacteria present at the liquid-solid interface. In contrast, when attachment was flexible, the sensor signals were inversely proportional to the additional mass of bound bacteria. This difference is probably determined by the interfacial viscoelasticity and by acoustic and electromagnetic coupling. The signals of environmentally aged sensors with either predominantly rigid or flexible positioning of bacteria were correlated with changes in mass at the liquid-solid interface. Sensors with O or H type of binding could be used for analytical purposes.

Mechanism of killing of spores of Bacillus anthracis in a high-temperature gas environment, and analysis of DNA damage generated by various decontamination treatments of spores of Bacillus anthracis, Bacillus subtilis and Bacillus thuringiensis

To determine how hydrated Bacillus anthracis spores are killed in a high‐temperature gas environment (HTGE), and how spores of several Bacillus species including B. anthracis are killed by UV radiation, dry heat, wet heat and desiccation.

Phage Fusion Proteins As Bioselective Receptors For Piezoelectric Sensors

Departments of Biological Sciences , Chemistry and Biochemistry , Anatomy, Physiology and Pharmacology , and Pathobiology , Auburn AL 36849 Author for correspondence: Tel. 707-423-7422; Fax 707-423-7267; e-mail: eric.olsen@travis.af.mil; current address: Clinical Investigations Facility, David Grant Medical Center, Travis Air Force Base, CA 94535 The views expressed in this article are those of the author, and do not reflect the official policy or position of the United States Air Force, Department of Defense, or the U.S. Government.

Infrared spectroscopy at high pressure: Interaction of CO with oxidized Rh/Al2O3

Infrared spectroscopy was used to study the interaction of CO with preoxidized Rh/Al{sub 2}O{sub 3} catalyst films in a high-pressure cell reactor. An infrared band near 2,125 cm{sup {minus}1}, which had previously been assigned to a Rh{sup 2+}CO species and to one band component of an asymmetric Rh(CO){sub 3} species by two different laboratories, is now assigned to Rh{sup 2+}CO. This work demonstrates that gas-phase contributions from infrared-active species with high extinction coefficients can be eliminated from surface contributions, even at high pressures of the gas.

Phage Langmuir monolayers and Langmuir-Blodgett films.

Stable, insoluble Langmuir monolayer films composed of Staphylococcus aureus-specific lytic bacteriophage were formed at an air-water interface and characterized. The phage monolayer was very strong, withstanding a surface pressure of ∼40 mN/m at 20 °C. The surface pressure-area (Π-A) isotherm possessed a shoulder at ∼7 × 10(4)nm(2)/phage particle, attributed to a change in phage orientation at the air-water interface from horizontal to vertical capsid-down/tail-up orientation as surface pressure was increased. The Π-A-dependence was accurately described using the Volmer equation of state, assuming horizontal orientation to an air-water interface at low surface pressures with an excluded area per phage particle of 4.6 × 10(4)nm(2). At high pressures phage particles followed the space-filling densely packed disks model with a specific area of 8.5 × 10(3)nm(2)/phage particle. Lytic phage monolayers were transferred onto gold-coated silica substrates from the air-water interface at a constant surface pressure of 18 mN/m by Langmuir-Blodgett method, then dried and analyzed by scanning electron microscopy (SEM) and ellipsometry. Phage specific adsorption (Γ) in Langmuir-Blodgett (LB) films measured by SEM was consistent with that calculated independently from Π-A isotherms at the transfer surface pressure of 18 mN/m (Γ=23 phage particles/μm(2)). The 50 nm-thickness of phage monolayer measured by ellipsometer agreed well with the horizontal phage average size estimated by SEM. Surface properties of phage Langmuir monolayer compare well with other monolayers formed from nano- and micro-particles at the air-water interface and similar to that of classic amphiphiles 1,2-diphytanoyl-sn-glycero-3-phosphocholine (phospholipid) and stearic acid.

Plasma etching and patterning of CVD diamond at <100°C for microelectronics applications

Abstract Oxidation resistance of diamond is an important characteristic to be considered in high-temperature microelectronics and other applications. We have tested the stability of CVD diamond by exposing it to Ground State Atomic Oxygen (GSAO, O) at a temperature of 74°C. Polycrystalline diamond is quite stable at this temperature using O. We have also tested the stability of diamond using Excited State Atomic Oxygen (ESAO, O*). Initially, CVD diamond was exposed to O* for 15 min at 63°C, and diamond etching was observed. We have also carried out the experiments at different time intervals such as 30 and 45 min. The etching rate of the polycrystalline diamond using O* is ≈ 0.2–0.25 m/min at 63°C. We have successfully patterned the diamond (polycrystalline and single crystal) using a Ni mask by exposing the sample to O* for a longer time. O* etched the diamond uniformly in all the directions of the diamond crystal as opposed to the molecular oxygen. Stability of the single crystal diamond has been tested using O* by using Ni mask material. We were able to etch the single crystal diamond (type IIa, 100 orientation) quite uniformly. The etching rate of single crystal diamond using O* was observed to be 0.3 m/min.

Solvent effects on amphotericin B monolayers

Monolayers of the antifungal antibiotic amphotericin B undergo the liquid expanded/liquid condensed state transition if spread from chloroform/methanol solvent. The transition disappeared after a long spreading time. The presence of the transition may be due to the retention of solvent and/or the presence of metastable aggregates of amphotericin B.

Assembly of cadmium stearate and valinomycin molecules assists complexing of K+ in mixed Langmuir-Blodgett films

The incorporation of valinomycin molecules into cadmium stearate multilayers increased complexation of valinomycin with potassium ions and potassium permeability of the multilayers. Valinomycin-cadmium stearate mixed Langmuir-Blodgett multilayers were exposed to aqueous solutions of KCl, NaCl and KClNaCl mixtures in a concentration range of 0.001–100 mM. The current responses of the multilayers indicated a significant dependence on the K+ concentration but not on the Na+ concentration. A marked preference for K+ over Na+ was observed in mixed ion solutions even when the concentration of Na+ exceeded the concentration of K+ by the factor of 100000. The K+Na+ selectivity was dependent on the concentration of valinomycin in mixed monolayers and was highest at about 9 mol% of valinomycin, at which point the antibiotic molecules were completely surrounded by cadmium stearate molecules. This information may be useful for understanding of fundamental properties of molecular assemblies and antibiotic/cell membrane interactions.

Versatile Dewar Assembly for Use with a Commercial Spectrofluorometer

A dewar assembly suitable for use on the Farrand Mark I spectrofluorometer and similar instruments not normally equipped with a conventional dewar-type cryostat is described. The assembly is simple to construct and will accept either conventional round quartz dewars or square quartz dewars. A simple dewar arrangement has been developed to use on the Farrand Mark I spectrofluorometer. The dewar method makes rapid low temperature fluorescence and phosphoresence measurements possible. Rapid low temperature polarization measurements can be made with a square dewar modification.

Modification of a Commercial Instrument for Low Temperature Absorption

Many authors have noted the importance of low temperature absorption spectra and have described various attachments to obtain these with commercial instruments. These attachments vary widely in expense, temperature capabilities, construction time, alignment problems, purpose, applicability to specific instruments, ease of use, and in many other ways. The present modification appears to be superior to most of the reported methods for low temperature absorption measurements between room temperature and -180°C. It requires only minor modifications of the Farrand spectrofluorometer (Mark I) with the cryogenic accessories. A modification of this design could be used in other spectrometers.