Facile Method for Monitoring Inhibition of Anaerobic Spore Outgrowth

A device is presented for the laboratory monitoring of spore outgrowth under controlled temperature and anaerobic conditions. Alterations in pH, redox potential, headspace composition, and optical density are followed as the activated spores grow out into vegetative cells. An interlock system allows the addition of test solutions or the removal of medium under anaerobic conditions. The device may also be used for rapid (<4 h) chemical inhibition studies or adapted for temperature injury studies of aerobic or anaerobic cells. Data on outgrowth of Clostridium sporogenes and inhibition by nitrite solutions are presented.     

A device for the measurement of residual chemical shift anisotropy and residual dipolar coupling in soluble and membrane-associated proteins

Residual dipolar coupling (RDC) and residual chemical shift anisotropy (RCSA) report on orientational properties of a dipolar bond vector and a chemical shift anisotropy principal axis system, respectively. They can be highly complementary in the analysis of backbone structure and dynamics in proteins as RCSAs generally include a report on vectors out of a peptide plane while RDCs usually report on in-plane vectors. Both RDC and RCSA average to zero in isotropic solutions and require partial orientation in a magnetic field to become observable. While the alignment and measurement of RDC has become routine, that of RCSA is less common. This is partly due to difficulties in providing a suitable isotopic reference spectrum for the measurement of the small chemical shift offsets coming from RCSA. Here we introduce a device (modified NMR tube) specifically designed for accurate measurement of reference and aligned spectra for RCSA measurements, but with a capacity for RDC measurements as well. Applications to both soluble and membrane anchored proteins are illustrated.     

Method for automated extraction and purification of nucleic acids and its implementation in microfluidic system

A method and a microfluidic device for automated extraction and purification of nucleic acids from biological samples have been developed. The method involves disruption of bacterial cells and/or viral particles by combining enzymatic and chemical lysis procedures followed by solid-phase sorbent extraction and purification of nucleic acids. The procedure is carried out in an automated mode in a microfluidic module isolated from the outside environment, which minimizes contact of the researcher with potentially infectious samples and, consequently, decreases the risk of laboratory-acquired infections. The module includes reservoirs with lyophilized components for lysis and washing buffers; a microcolumn with a solid-phase sorbent; reservoirs containing water, ethanol, and water-ethanol buffer solutions for dissolving freeze-dried buffer components, rinsing the microcolumn, and eluting of nucleic acids; and microchannels and valves needed for directing fluids inside the module. The microfluidic module is placed into the control unit that delivers pressure, heats, mixes reagents, and flows solutions within the microfluidic module. The microfluidic system performs extraction and purification of nucleic acids with high efficiency in 40 min, and nucleic acids extracted can be directly used in PCR reaction and microarray assays.     

Microfabricated devices in biotechnology and biochemical processing

In the past few years, interdisciplinary science and technologies have converged to create exciting challenges and opportunities, which involve a new generation of integrated microfabricated devices. These new devices are referred to as 'lab-on-a-chip' or Micro Total Analysis Systems. Their development involves both established and evolving technologies, which include microlithography, micromachining, Micro Electro Mechanical Systems technology, microfluidics and nanotechnology. This review summarizes the key device subject areas and the basic interdisciplinary technologies, and gives a better understanding of how these technologies can be used to provide appropriate technical solutions to fundamental problems. Important applications for this novel 'synergized' technology in chemical and biotechnological processing, in addition to the application of simulation methods in the development of microfabricated devices, will also be discussed.     

D-value determinations are an inappropriate measure of disinfecting activity of common contact lens disinfecting solutions

Determination of a D value for specific test organisms is a component of the efficacy evaluation of new contact lens disinfecting solutions. This parameter is commonly defined as the time required for the number of surviving microorganisms to decrease 1 logarithmic unit. The assumption made in establishing a D value is that the rate of kill exhibits first-order kinetics under the specified conditions. Such exponential kill rates are seen with thermal contact lens disinfection system. A comparison of the death rate kinetics for a variety of chemical contact lens disinfecting solutions was undertaken to ascertain the suitability of D-value determination for these chemical disinfectants. The active agents of these different solutions included hydrogen peroxide, thimerosal, chlorhexidine, tris(2-hydroxyethyl)tallow ammonium chloride, thimerosal, polyaminopropyl biguanide, and polyquaternium-1. The solutions were challenged with 10(6) CFU of either Pseudomonas aeruginosa, Serratia marcescens, or Staphylococcus hominis per ml, and survival rate was determined. This study clearly demonstrates the nonlinear nature of the inactivation curves for most contact lens chemical disinfecting solutions for the challenge organisms. D-value determination is, therefore, an inappropriate method of reporting the biocidal activity of these solutions.     

D-value determinations are an inappropriate measure of disinfecting activity of common contact lens disinfecting solutions.

Determination of a D value for specific test organisms is a component of the efficacy evaluation of new contact lens disinfecting solutions. This parameter is commonly defined as the time required for the number of surviving microorganisms to decrease 1 logarithmic unit. The assumption made in establishing a D value is that the rate of kill exhibits first-order kinetics under the specified conditions. Such exponential kill rates are seen with thermal contact lens disinfection system. A comparison of the death rate kinetics for a variety of chemical contact lens disinfecting solutions was undertaken to ascertain the suitability of D-value determination for these chemical disinfectants. The active agents of these different solutions included hydrogen peroxide, thimerosal, chlorhexidine, tris(2-hydroxyethyl)tallow ammonium chloride, thimerosal, polyaminopropyl biguanide, and polyquaternium-1. The solutions were challenged with 10(6) CFU of either Pseudomonas aeruginosa, Serratia marcescens, or Staphylococcus hominis per ml, and survival rate was determined. This study clearly demonstrates the nonlinear nature of the inactivation curves for most contact lens chemical disinfecting solutions for the challenge organisms. D-value determination is, therefore, an inappropriate method of reporting the biocidal activity of these solutions.     

用铁蛋白合成纳米粒子的研究进展

铁蛋白是一种生物储铁蛋白 ,其储存铁的特性和储存铁在生物体内的特殊形态 ,通过相对温和、简便的生物、化学、物理过程 ,可合成多种具有特异的力、热、光、电、磁等特性的纳米粒子 ,并可用来构建纳米级的分子器件     

A Simple Automatic Apparatus for the Concentration of Macromolecular Solutions

An apparatus for the concentration of macromolecular solutions is described in detail. It features automatic volume control and is inexpensive and simple to fabricate. The basis for the device is negative pressure dialysis.     

An automated in‐gel digestion/iTRAQ‐labeling workflow for robust quantification of gel‐separated proteins

Simple protein separation by 1DE is a widely used method to reduce sample complexity and to prepare proteins for mass spectrometric identification via in‐gel digestion. While several automated solutions are available for in‐gel digestion particularly of small cylindric gel plugs derived from 2D gels, the processing of larger 1D gel‐derived gel bands with liquid handling work stations is less well established in the field. Here, we introduce a digestion device tailored to this purpose and validate its performance in comparison to manual in‐gel digestion. For relative quantification purposes, we extend the in‐gel digestion procedure by iTRAQ labeling of the tryptic peptides and show that automation of the entire workflow results in robust quantification of proteins from samples of different complexity and dynamic range. We conclude that automation improves accuracy and reproducibility of our iTRAQ workflow as it minimizes the variability in both, digestion and labeling efficiency, the two major causes of irreproducible results in chemical labeling approaches.     

Kinetic measurements of protein conformation in a microchip

This paper presents a microchip-based system for collecting kinetic time-based information on protein refolding and unfolding. Dynamic protein conformational change pathways were studied in microchannel flow using a microfluidic device. We present a protein-conserving approach for quantifying refolding by dynamically varying the concentration of the chemical denaturants, guanidine hydrochloride and urea. Short diffusion distances in the microchannel result in rapid equilibrium between protein and titrating solutions. Dilutions on the chip were tightly regulated using pressure controls rather than syringe-based flow, as verified with extensive on-chip tracer dye controls. To validate this protein assay method, folding transition experiments were performed using two well-characterized proteins, human serum albumin (HSA) and bovine carbonic anhydrase (BCA). Transition events were monitored through fluorescence intensity shifts of the protein dye 8-anilino-1-naphthalenesulfonic acid (ANS) during dilutions of protein from urea or guanidine hydrochloride solutions. The enzymatic activity of refolded BCA was measured by UV absorption through the conversion of p-nitrophenyl acetate (p-NPA). The microchip protein refolding transitions using ANS were well-correlated with conventional plate-based experiments. The microfluidic platform enables refolding studies to identify rapidly the optimal folding strategy for a protein using small quantities of material.     

An automated device for the preparation of complex reagent mixtures

A microcomputer-controlled device was built that automatically prepares small volumes of mixtures of up to eight reagents. The operation of the system is fast, flexible, and reliable, thus making possible the routine use of experimental protocols that require large numbers of small volume reagent samples, each having a different composition. In particular, the software we developed for this device handles the preparation of three-antibody staining solutions to be used in triple labeling immunofluorescent flow cytometry experiments that involve only two fluorochromes. In this role, the device is known as an “Immunofluorescence Tomograph.”     

An automated device for the preparation of complex reagent mixtures. The immunofluorescence tomograph

A microcomputer-controlled device was built that automatically prepares small volumes of mixtures of up to eight reagents. The operation of the system is fast, flexible, and reliable, thus making possible the routine use of experimental protocols that require large numbers of small volume reagent samples, each having a different composition. In particular, the software we developed for this device handles the preparation of three-antibody staining solutions to be used in triple labeling immunofluorescent flow cytometry experiments that involve only two fluorochromes. In this role, the device is known as an "Immunofluorescence Tomograph."     

An opto-electronic sediment detector and its use in the chemical micro-profiling of lakes

SUMMARY. A device for detecting (with minimum disturbance) the sediment-water interface in lakes is described. It is based on a commercially available slotted 'opto-switch' incorporating a light emitting diode and a phototransistor. The design of an audible and visual indicator is given. Possible uses are discussed and an example of chemical micro-profiling near to the sediment with the aid of the device is reported.     

Enhancing Science Teaching through Performing Marbling Art Using Basic Solutions and Base Indicators

Basic solutions are an indispensable part of our daily life. Basic solutions are commonly used in industries such as the textile industry, oil refineries, the fertilizer industry, and pharmaceutical products. Most cleaning agents, such as soap, detergent, and bleach, and some of our foods, such as chocolate and eggs, include bases. Bases are the fundamental concepts of chemistry. Indicators are chemical compounds that can be added to solution to determine whether it is a base or not. This article describes an activity whose primary aim is to teach base indicators to preservice elementary teachers. In this activity, the authors turned the traditional art of marbling into something achievable with the chemical substances that are the basic solutions and base indicators found in nearly all chemistry laboratories. Therefore, this activity can be called chemical marbling. The preservice elementary teachers learned the base indicators and basic solutions throughout this activity. The purpose of the study is not only to teach the science concepts to the preservice elementary teachers with fun but also to promote the development of their attitudes toward science, creativity, and aesthetic feelings. Suggestions stress that chemical marbling might be a good tool to acquire the preservice elementary teachers’ cognitive and affective learning outcomes.     

A triaxial-measurement shear-test device for soft biological tissues

A novel shear-test device for soft biological tissue, capable of applying simple shear deformations simultaneously in two orthogonal directions while measuring the resulting forces generated in three axes, is described. We validated the device using a synthetic gel, the properties of which were ascertained from independent tensile and rotational shear tests. Material parameters for the gel were fitted using neo-Hookean analytical solutions to the independent test data, and these matched the results from the device. Preliminary results obtained with rat septal myocardium are also presented to demonstrate the feasibility of the apparatus in determining the shear characteristics of living tissue.     

Interactions of myoglobin with urea and some alkylureas. I. Solvation in urea and alkylurea solutions

The interactions of myoglobin with urea, methyl-, N,N'-dimethyl- and ethylurea in aqueous solutions were studied by density measurements. From the densities at constant chemical potential and constant molality, the partial specific volumes of myoglobin in these solutions as well as the extent of preferential binding of urea and alkylurea to myoglobin were determined. It has been found that water and not the denaturant is preferentially bound in urea solutions and alkylurea solutions up to 4 M so that the Gibbs free energy of myoglobin, i.e., its chemical potential in a denaturant solution, is larger than in water. This behavior of myoglobin is different from that of other globular proteins for which preferential binding of urea has been found. It appears that preferential hydration of myoglobin is due to its high content of ionic groups.     

Classification and stability of global inhomogeneous solutions of a macroscopic model of cell motion

Many micro-organisms use chemotaxis for aggregation, resulting in stable patterns. In this paper, the amoeba Dictyostelium discoideum serves as a model organism for understanding the conditions for aggregation and classification of resulting patterns. To accomplish this, a 1D nonlinear diffusion equation with chemotaxis that models amoeba behavior is analyzed. A classification of the steady state solutions is presented, and a Lyapunov functional is used to determine conditions for stability of inhomogenous solutions. Changing the chemical sensitivity, production rate of the chemical attractant, or domain length can cause the system to transition from having an asymptotic steady state, to having asymptotically stable single-step solution and multi-stepped stable plateau solutions.     

A microfluidic device to establish concentration gradients using reagent density differences

Microfabrication has become widely utilized to generate controlled microenvironments that establish chemical concentration gradients for a variety of engineering and life science applications. To establish microfluidic flow, the majority of existing devices rely upon additional facilities, equipment, and excessive reagent supplies, which together limit device portability as well as constrain device usage to individuals trained in technological disciplines. The current work presents our laboratory-developed bridged μLane system, which is a stand-alone device that runs via conventional pipette loading and can operate for several days without need of external machinery or additional reagent volumes. The bridged μLane is a two-layer polydimethylsiloxane microfluidic device that is able to establish controlled chemical concentration gradients over time by relying solely upon differences in reagent densities. Fluorescently labeled Dextran was used to validate the design and operation of the bridged μLane by evaluating experimentally measured transport properties within the microsystem in conjunction with numerical simulations and established mathematical transport models. Results demonstrate how the bridged μLane system was used to generate spatial concentration gradients that resulted in an experimentally measured Dextran diffusivity of (0.82 ± 0.01) × 10(-6) cm(2)/s.     

Bifurcation analysis of nonlinear reaction-diffusion equations—I. Evolution equations and the steady state solutions

A model nonlinear network involving chemical reactions and diffusion is studied. The time evolution and bounds on the steady state solutions are analyzed. Spatially ordered solutions of the equations of the dissipative structure type are found by bifurcation theory. These solutions are calculated analytically and their qualitative properties are discussed.     

Combination of microdialysis and Glucosensor permits continuous (on line) s.c. glucose monitoring in a patient operated device: I. In vitro evaluation.

A device for continuous glucose monitoring in fluids was obtained by combining the microdialysis technique with a measuring flow chamber of the "Glucosensor Unitec Ulm" using the GOD method for determining amperometrically blood glucose profiles. The in vitro experiments demonstrate that the relative recovery of glucose by this device is inversely related to the flow rate of the microdialysis perfusion fluid, which, in turn, is inversely related to the response time of the device. The glucose signal increases linearly with the area of the microdialysis working membrane (r = 0.98), and with the glucose concentrations of the standard solutions (r greater than 0.95). The variation coefficient for repeated measurements is below 8%. The accuracy of the device as demonstrated by mean measuring deviation ranges between 1 and 3.8%.