Arsenic Mobility and Groundwater Extraction in Bangladesh

Biotechnology and Bioengineering, 1986

This article presents a method for determining the rate constant for deactivation and the internal distribution of immobilized enzyme. This method makes use of the parallel deactivation process in a diffusion-controlled regime, in which the internal activity profile behaves like a penetration front. This front basically traces through the initial active enzymatic profile, and one can determine the internal profile and the rate constant for deactivation from the experimentally observable bulk concentration versus time. This method is applied to the experimental data of the system of hydrogen-peroxide-immobilized catalase on controlled pore glass and Si-AI particles.

2004

The possibility of using synaptic plasma membrane (SPM) enzymes Na þ =K þ -ATPase and Mg 2þ -ATPase, isolated from rat brain, as a biological component of multi-response sensing system for detection of different compounds (alkaline and heavy metal salts, organic compounds) was studied. The method is based on the spectrophotometric determination of inorganic ortho-phosphate (P i ) that serves as a measure of the enzymatic activity in the presence of various analytes. The concentration of P i , liberated by enzyme catalysed hydrolysis of adenosinetriphosphate (ATP), was followed spectrophotometrically, by single exposure to analytes or in the mixture. P i was dose dependent on the analyte concentration. Alkaline elements (Na, K, Mg), heavy metals (Pb, Cd, Hg, Cu, Fe, Co, Zn), toxic organic compounds (pyridine, urea, chlorpyrifos), and some drugs (digoxin, gitoxin) showed diverse effects, inducing the inhibition or stimulation of the enzymes activity. Development of simple test method for simultaneous detection of the investigated analytes based on the variation of medium assay composition was discussed. metals and organic compounds are required . Because these pollutants are known to influence the activity of many enzymes, the development of respective detection systems becomes increasingly interesting . They usually use enzymes immobilized on solid support or simply enzyme assays in the water solution .

Tetrahedron Letters, 1996

A very low level of enzyme activity (10 -11 mol) has been detected using a PCR method following a vector hybridisation of a supported oligonucleotide. This methodology could be very useful for direct active catalytic antibody screening from a combinatorial library.

Mass spectrometry based technologies are promising as generalizable high-throughput assays for enzymatic activity. In one such technology, a specialized enzyme substrate probe is presented to a biological mixture potentially exhibiting enzymatic activity, followed by an in situ enrichment step using fluorous interactions and nanostructureinitiator mass spectrometry. This technology, known as Nimzyme, shows great potential but is limited by the need to synthesize custom substrate analogs. We describe a synthetic route that simplifies the production of these probes by fashioning their perfluorinated invariant portion as an alkylating agent. This way, a wide variety of compounds can be effectively transformed into enzyme activity probes. As a proof of principle, a chloramphenicol analog synthesized according to this methodology was used to detect chloramphenicol acetyltransferase activity in cell lysate. This verifies the validity of the synthetic strategy employed and constitutes the first reported application of Nimzyme to a non-carbohydrate-active enzyme. The simplified synthetic approach presented here may help advance the application of mass spectrometry to high-throughput enzyme activity determination.

Analytical Chemistry, 2011

Biosensors

The use of sensors in critical areas for human development such as water, food, and health has increased in recent decades. When the sensor uses biological recognition, it is known as a biosensor. Nowadays, the development of biosensors has been increased due to the need for reliable, fast, and sensitive techniques for the detection of multiple analytes. In recent years, with the advancement in nanotechnology within biocatalysis, enzyme-based biosensors have been emerging as reliable, sensitive, and selectively tools. A wide variety of enzyme biosensors has been developed by detecting multiple analytes. In this way, together with technological advances in areas such as biotechnology and materials sciences, different modalities of biosensors have been developed, such as bi-enzymatic biosensors and nanozyme biosensors. Furthermore, the use of more than one enzyme within the same detection system leads to bi-enzymatic biosensors or multi-enzyme sensors. The development and synthesis of...

Electroanalysis, 2000

A new method for enhancing the speci®city of enzyme electrodes in which the immobilized enzymatic layer is a relatively nonselective biocatalyst is reported. The approach is based on the use of an outer polymeric membrane doped with a substrate selective carrier that transports the target analyte selectively into the underlying enzyme layer. As an initial model for this concept, an amperometric enzyme electrode with enhanced selectivity for tryptophan is described. The sensor is prepared by coating a layer of L-amino acid oxidase (AAO) on the surface of a platinum working electrode and then covering this layer with an outer hydrophobic plasticized polyurethane (PU) ®lm containing the ditopic carrier, manganese(III)-4,5-di(3,5-di-t-butylsalicylideneimine)benzo-18-crown-6 tetraphenylborate (Mn(III)tBu-Salph-B18C6(BPh 4). Tryptophan is transported selectively from sample solution by the carrier into the L-amino acid oxidase layer, yielding production of hydrogen peroxide that can be detected amperometrically at the platinum electrode at 650 mV (vs. AgaAgCl reference electrode). The resulting enzyme electrode is shown to exhibit a dramatic increase in selectivity for tryptophan when compared to the amino acid response of an analogous enzyme electrode prepared with a nonselective outer dialysis membrane. Independent measurements of the PU-carrier membrane's substrate permselectivity using a diffusion cell correlate with the amperometric enzyme electrode results. The practical limitations of this approach for preparing enzyme electrodes (i.e., slower response times and reduced substrate¯uxes) are discussed, and potential solutions to these problems are proposed.

Topics in Catalysis

Access to secure water sources has become one of the biggest challenges for human sustainability. Climate change and associated droughts make it difficult to guarantee the usual water source and move to groundwater use or to the re-use of treated wastewater remains unviable due the lack on the capacity of monitoring water quality. Moreover, reusing treated wastewater from repositories near anthropogenic sources represents a risk of high concentrations of emerging contaminants. The strategies involve a higher risk of encountering toxic elements with a heavy burden on human and environmental health. New accessible and reliable tools are required to detect any hazard from the waterbodies in real time to ensure safe management and also to decrease mismanagement or ilegal water discharges. One of the available options is to look into enzyme-based biosensors that can detect toxic elements in the water. The proposed biosensors require sensible elements to be accessible and durable for their proper function. The present revision shows in first place, the actual need of real time monitoring due the different sources and effects of emergent pollutants. Secondly, describes how enzymes can be immobilized for its application in biosensors and the rol enzymes play as bioreceptor element in biosensing. Thirdly, describes the transduction methods that can be observed, and finally the actual application of enzyme biosensors for the detection of different toxic elements. According to the presented literature enzyme-based biosensors have been successfully applied for the detection of a wide number of pollutants reaching detection limits comparable to traditional methods such as up to 0.018 nM of mercury. Furthermore, laccase seems to be the more applied enzyme in literature, but positive results are not limited to this enzyme and other candidates have been explored showing good detection rate.

ASSAY and Drug Development Technologies, 2017

Adenosine monophosphate (AMP) is a key cellular metabolite regulating energy homeostasis and signal transduction. AMP is also a product of various enzymatic reactions, many of which are dysregulated during disease conditions. Thus, monitoring the activities of these enzymes is a primary goal for developing modulators for these enzymes. In this study, we demonstrate the versatility of an enzyme-coupled assay that quantifies the amount of AMP produced by any enzymatic reaction regardless of its substrates. We successfully implemented it to enzyme reactions that use adenosine triphosphate (ATP) as a substrate (aminoacyl tRNA synthetase and DNA ligase) by an elaborate strategy of removing residual ATP and converting AMP produced into ATP; so it can be detected using luciferase/luciferin and generating light. We also tested this assay to measure the activities of AMP-generating enzymes that do not require ATP as substrate, including phosphodiesterases (cyclic adenosine monophosphate) and Escherichia coli DNA ligases (nicotinamide adenine dinucleotide [NAD + ]). In a further elaboration of the AMP-Glo platform, we coupled it to E. coli DNA ligase, enabling measurement of NAD + and enzymes that use NAD + like monoadenosine and polyadenosine diphosphate-ribosyltransferases. Sulfotransferases use 3 0-phosphoadenosine-5 0-phosphosulfate as the universal sulfo-group donor and phosphoadenosine-5 0phosphate (PAP) is the universal product. PAP can be quantified by converting PAP to AMP by a Golgi-resident PAP-specific phosphatase, IMPAD1. By coupling IMPAD1 to the AMP-Glo system, we can measure the activities of sulfotransferases. Thus, by utilizing the combinations of biochemical enzymatic conversion of various cellular metabolites to AMP, we were able to demonstrate the versatility of the AMP-Glo assay.

Biotechnology and Bioengineering, 1992

In this article, the results from a theoretical and experimental investigation of enzyme immobilization in porous membranes are reported. A theoretical model of the immobilization process, which accounts for restricted diffusion of enzyme in the pores of the membrane, has been developed. The model predicts the effect of immobilization kinetics and time of immobilization on the enzyme distribution in the pores of the membrane. The immobilization of glucose oxidase and glucose oxidase-biotin conjugate on porous alumina membranes was experimentally investigated. Enzyme uptake data was correlated to the theory to determine the rate constant of immobilization and the distribution of the enzyme in the pore. Immobilization studies were carried out for enzyme adsorption and for enzyme attachment by covalent coupling. The distribution of enzyme was experimentally studied by assembling five membranes in the diffusion cell. Following immobilization, the membranes were separated and each was assayed for activity. The amount of active enzyme present in each membrane yielded a discrete distribution that compared well with that predicted by theory.