Waveform generation by enzymatic oscillators

The control of cell chemistry is being investigated through a multipronged approach combining the techniques of physics, chemistry, and biology with the development of electronic instrumentation and the application of analog and digital computers. An example of such metabolic control phenomena is provided by biological oscillators involving enzymatic reactions. These oscillators, which may exist in nearly every kind of cell and even in several forms in a single cell, reveal basic instabilities in biochemical reactions and metabolic control that may be of significance to health and disease. In addition, the high-frequency oscillations observed in simple enzyme systems may be models for the longer-period rhythms that regulate the activities of nearly all biological systems.     

Inhibition of Escherichia coli O157:H7 and Clostridium sporogenes in spinach packaged in modified atmospheres after treatment combined with chlorine and lactic acid bacteria

Abstract: Implementation of modified atmospheric packaging (MAP) into retail produce is a less commonly practiced method due to differences among commodities and the potential growth of anaerobes. Pathogens including Escherichia coli O157:H7 have been responsible for spinach outbreaks across the United States. In this study, hurdles, including those currently used with produce safety, such as MAP and chlorine, were combined with lactic acid bacteria (LAB) to inhibit pathogens. Spinach was coinoculated with E. coli O157:H7 and Clostridium sporogenes, a surrogate for C. botulinum, and treated with water or a hurdle that included water, chlorine, and LAB. Spinach from treatments were packaged in air (traditional), oxygen (80% O₂, 20% CO₂), or nitrogen (80% N₂, 20% CO₂) and stored in a retail display case for 9 d at 4 to 7 °C. The hurdle inhibited E. coli O157:H7 and C. sporogenes compared to controls with reductions of 1.43 and 1.10 log (P < 0.05), respectively. The nitrogen atmosphere was outperformed by air and oxygen in the reduction of E. coli O157:H7 (P < 0.05) with a decrease of 0.26 and 0.15 logs. There were no significant differences among the 3 atmospheres on C. sporogenes survival. Relative to these hurdles, we also chose to evaluate the potential benefits of LAB in pathogen control. The survival of LAB in interventions demonstrates implementation of LAB into produce could control pathogens, without damaging produce or altering organoleptic properties. Practical Application: The goal of our work was to identify methods that could reduce food‐borne pathogens in packaged spinach products. Using current industry techniques in combination with unique methods, such as the use of beneficial bacteria, our research identified whether harmful microorganisms could be eliminated. Our data demonstrate that specific packaging conditions with beneficial bacteria can help eliminate or reduce the survival of E. coli O157:H7 and C. sporogenes (a model for C. botulinum) in produce.     

A Time-Sharing Instrument for Direct Readout of Oxidation-Reduction States in Intracellular Compartments of Cardiac Tissue

Internal fluorochromes and chromophores afford the possibility of a continuous, nondestructive readout of biochemical information from complex systems such as intact organs. An instrument has been constructed which allows simultaneous observation of fluorescence emission from reduced pyridine nucleotides [NAD(P)H] and certain oxidized flavoproteins together with dual wavelength absorption measurements of cytochrome b. The instrument is applied to a preparation of perfused frog heart. The kinetic responses of the three parameters to oxygen, nitrogen, and 2-mM amytal are observed. Flavoprotein and cytochrome b show a delayed reduction in response to a transition from O2 to N2.NAD(P)H shows an early small reduction which can be attributed to the interaction of a cytoplasmic pool with oxidases located in peroxisomes and the endoplasmic reticulum. Addition of amytal to the oxygenated perfusate produces a small additional oxidation of cytochrome b.     

Experimental and computational design tools for industrial drying processes: Challenges in process-limit prediction

The coating and drying of inks and slurries are important steps to manufacture a plethora of products. Drying processes, particularly, comprise energy-intensive steps that affect product cost and quality. Prior work has highlighted failures of various multicomponent diffusivity models to conserve mass in dryer modeling and challenges in predicting process limits given variability in published values of key thermodynamic parameters. Herein, we develop a computational model and benchtop drying experiments to investigate these concerns for drying polymer-laden coatings. Model predictions of process limits in a single-zone drying oven demonstrate that published variability in Flory–Huggins parameter yields large variations in predicted operating temperatures above which blistering occurs. This indicates that caution should be exercised when choosing approaches to obtain or predict the Flory–Huggins parameter, and that both benchtop drying experiments and a set of additional experiments, such as sorption experiments, are needed to fully characterize and optimize a given drying process.