Concentrations Of 2-mercaptoethanol Research Articles

Evaluation of DNA fragmentation in dog sperm using the sperm chromatin dispersion test.

The study's objective was to adapt the Sperm Chromatin Dispersion (SCD) protocol to evaluate sperm DNA fragmentation and implement a fragmentation control in dogs. Correlation between DNA status and routine sperm parameters was also analysed. To adapt the SCD, two different mercaptoethanol (ME) concentrations were assayed (2.5% and 5%) in fourteen ejaculates from seven dogs and semen incubation with 0.3M NaOH for 15min at room temperature was assayed as a control for sperm DNA fragmentation. Data were analysed using a Mann-Whitney test and either Pearson's or Spearman's correlation. The selected ME concentration to use in the SCD test was 5%, as it produced the largest DNA dispersion halo while preserving the core nucleus structure. Four DNA halo patterns were identified as follows: large dispersion halos, medium halos, small halos and nuclei without halos. Semen incubated with NaOH showed 100% sperm without halos (damaged DNA). A significant positive correlation was observed between sperm with fragmented DNA and sperm with coiled tails. Thus, it was possible to adapt the SCD protocol to evaluate dog sperm DNA fragmentation in raw semen without using a commercial kit and establish incubation with NaOH as a DNA fragmentation control. Only coiled tails showed correlation with DNA fragmentation.

Dithizone-functionalized C18 online solid-phase extraction-HPLC-ICP-MS for speciation of ultra-trace organic and inorganic mercury in cereals and environmental samples

A simple and efficient dithizone-functionalized solid-phase extraction (SPE) procedure, online coupled with high-performance liquid chromatography (HPLC)-inductively coupled plasma mass spectrometry, was developed for the first time for enrichment and determination of ultra-trace mercury (Hg) species (inorganic divalent Hg (Hg(II)), methylmercury (CH3Hg(II)) and ethylmercury (C2H5Hg(II)) in cereals and environmental samples. In the proposed method, functionalization of the commercial C18 column with dithizone, enrichment, and elution of the above Hg species can be completed online with the developed SPE device. A simple solution of 2-mercaptoethanol (1% (V/V)) could be used as an eluent for both the SPE and HPLC separation of Hg species, significantly simplifying the method and instrumentation. The online SPE method was optimized by varying dithizone dose, 2-mercaptoethanol concentration, and sample volume. In addition, the effect of pH, coexisting interfering ions, and salt effect on the enrichment was also discussed. Under the optimized conditions, the detection limits of Hg species for 5 mL water sample were 0.15 ng/L for Hg(II), 0.07 ng/L for CH3Hg(II), and 0.04 ng/L for C2H5Hg(II) with recoveries in the range of 85%–100%. The developed dithizone-functionalized C18 SPE column can be reused after a single functionalization, which significantly simplifies the enrichment step. Moreover, the stability of Hg species enriched on the SPE column demonstrated its suitability for field sampling of Hg species for later laboratory analysis. This environment-friendly method offers a robust tool to detect ultra-trace Hg species in cereals and environmental samples.

Determination of mercury species in seafood by liquid chrom tography - inductively coupled plasma mass spectrometry (LC-ICP-MS)

Liquid chromatography hyphenated with inductively coupled plasma mass spectrometry (LC­ICP­MS) was investigated to simultaneously determine three mercury species (mercury methyl mercury and ethyl mercury) in seafood samples. Important parameters such as organic solvents, flow rate of the mobile phase, 2­mercaptoethanol concentration, extraction time and temperature were optimized. The method was validated in term of the limit of detection, limit of quantitation, repeatability, and recovery meeting the AOAC performance requirements. The method has also been validated based on the analysis of certified standard samples DORM­4, then applied to determine three mercury species in 30 seafood samples. Results showed that the content of mercury species was below the maximum limit according to the QCVN 8­2 : 2011/BYT.

Photocatalytic and catalytic degradation of organic dye by uncapped and capped ZnS quantum dots

ZnS quantum dots were prepared with different concentrations of 2-mercaptoethanol as a capping agent by simple and fast co-precipitation method. The synthesized nanopowders were characterized using various analytical chemistry as well as image visualizing techniques to elucidate the changes in structure and shape of quantum dots. The lowest average estimated crystallite size of ZnS quantum dot was 4.2 nm that showed relevancy to 2-Mercaptoethanol amount. X-ray diffraction (XRD) confirmed purity of nanosized ZnS with cubic and rhombohedral crystalline structures. Upon capping increased absorption around 300 nm was recorded by UV–vis spectroscopy that suggests ZnS interaction with 2-mercaptoethanol. The surface morphology of capped ZnS showed nanorod shape with agglomeration of particles confirmed by field emission electron microscopy (FESEM). The presence of functional groups and strong chemical bonding at the interface of quantum dots was confirmed by fourier transform infrared spectroscopy (FTIR). However, thermal analysis revealed no decomposition till 200 °C evidenced by DSC-TGA that suggests its high temperature stability. Moreover, uncapped ZnS quantum dot showed extensive methylene blue (MB) dye degradation with maximum absorption peak (λmax) at 664 nm that suggests visible light activity. The synthesized ZnS quantum dots has strong potential to be used as effective dye degradation agents in textile, tanneries and leather industries.

Optimization Method for Proteomic Analysis of the Larva and Adult Tissues of Plutella xylostella (L.) (Lepidoptera: Plutellidae)

Plutella xylostella (L.) (Lepidoptera: Plutellidae), the major insect pest of cruciferous crops worldwide shows significant resistance to almost all classes of insecticides. In order to effectively prevent and manage the insecticidal resistance, it is crucial to understand the physiological adaptation of insects against insecticides. Identification of insect protein that interacting with insecticides and characterization of their modification in resistant strains can be done by using differential proteomics approach. This study focuses on optimizing a sensitive and rapid method for the extraction of high quality protein of both larva and adult tissues of P. xylostella to be used in two-dimensional gel electrophoresis. Five extraction methods were evaluated for protein concentration, yields and resolving patterns of one-dimensional and two-dimensional electrophoresis. The results showed that trichloroacetic acid/acetone extraction methods with two different concentrations of 2-mercaptoethanol produced the highest protein concentration and yield for both adult and larva tissues, respectively. Meanwhile, trichloroacetic acid/acetone with dithiothreitol extraction method gave better separation of spots and intensity for both larva and adult tissues compared to other methods tested. As such, we concluded that trichloroacetic acid/acetone with dithiothreitol successfully yielded high total protein concentration and good separation of two-dimensional electrophoresis gel spots in both adult and larva P. xylostella.

EVALUATION OF MONOLITHIC COLUMN FOR INORGANIC MERCURY AND METHYLMERCURY DETERMINATION IN FISH SAMPLE ANALYSIS

In the present work, the applicability of a monolithic column was evaluated for mercury speciation analysis in certified and real fish samples. The influence of the flow and composition of the mobile phase (2-mercaptoethanol concentration and methanol content) on the retention times of iHg and MeHg was evaluated. The optimal separation conditions were achieved for a mobile phase containing 5 % methanol and 0.02 % mercaptoethanol in acetate buffer (pH 5.0) at a flow rate of 1.6 ml min-1. Different extraction conditions were studied to analyze a certified reference material with the optimized methodology and the best results (93 % recovery) were obtained for microwave-assisted extraction with a mixture of HCl 6 M + NaCl 0.5 M. Finally, the proposed method was satisfactorily applied to real fish samples collected from different markets in the central region of Chile, presenting levels ranging from 0.73 – 3.4 mg kg-1.

Effect of particle size on activation energy and peak temperature of the thermoluminescence glow curve of undoped ZnS nanoparticles.

This paper reports the effect of particle size on the thermoluminescence (TL) of undoped ZnS nanoparticles. ZnS nanoparticles were prepared using a chemical precipitation method in which mercaptoethanol was used as the capping agent. The nanoparticles were characterized by X-ray diffraction, field emission gun-scanning electron microscopy and high-resolution transmission electron microscopy. When the concentrations of mercaptoethanol used are 0, 0.005, 0.01, 0.015, 0.025, 0.040 and 0.060 M, the sizes of the nanoparticles are 2.86, 2.81, 2.69, 2.40, 2.10, 1.90 and 1.80 nm, respectively. Initially, the TL intensity of UV-irradiated ZnS nanoparticles increases with temperature, attains a peak value Im for a particular temperature Tm, and then decreases with further increases in temperature. The values of both Im and Tm increase with decreasing nanoparticle size. Whereas the activation energy decreases slightly with decreasing nanoparticle size, the frequency factor decreases significantly as the nanoparticle size is reduced. The order of kinetics for the TL glow curve of ZnS nanoparticles is 2. Expressions are derived for the dependence of activation energy (Ea) and Tm on nanoparticle size, and good agreement is found between the experimental and theoretical results.

Optimization of Conditions for Extracting Muscle Protein from Grass Carp Using Response Surface Methodology

Protein is the major component of muscle tissue, in order to analyze change rule of the grass carp muscle protein during storage, the Plackett–Burman design and response surface methodology were employed to optimize its extraction conditions. The results showed that pH, SDS concentration and liquid-solid ratio were the significant factors influencing response, and the final combination of the optimized parameters was generated: pH, 8.3; liquid-solid ratio, 17:1; SDS concentration, 3.50%;beta mercaptoethanol concentration,0.3%; extraction temperature, 25 °C; extraction time, 1 h; ultrasonic time,15 min. And under these conditions, the protein extraction rate increased to 92.42%.

Optical studies of CdS:Mn nanoparticles

Cadmium sulphide nanoparticles were grown using a wet chemical method, by dissolving the reactants, cadmium chloride and sodium sulphide in water, in the presence of mercaptoethanol (ME), which was used as a capping agent. Manganese chloride was used to dope the nanoparticles. It was found that the particle size varied with different concentrations of ME. At higher concentrations of ME, smaller sized nanoparticles were synthesized. This method also reveals the high stability of nanoparticles in water. Nanoparticle properties were investigated using UV-vis absorption, photoluminescence spectroscopy, X-ray diffraction (XRD) and scanning electron microscopy (SEM) techniques. The particle sizes were measured by the XRD technique, SEM and optical absorption spectra and were in the range 2-6 nm.

Is vanadate reduced by thiols under biological conditions? Changing the redox potential of V(V)/V(IV) by complexation in aqueous solution.

Although dogma states that vanadate is readily reduced by glutathione, cysteine, and other thiols, there are several examples documenting that vanadium(V)-sulfur complexes can form and be observed. This conundrum has impacted life scientists for more than two decades. Investigation of this problem requires an understanding of both the complexes that form from vanadium(IV) and (V) and a representative thiol in aqueous solution. The reactions of vanadate and hydrated vanadyl cation with 2-mercaptoethanol have been investigated using multinuclear NMR, electron paramagnetic resonance (EPR), and UV-vis spectroscopy. Vanadate forms a stable complex of 2:2 stoichiometry with 2-mercaptoethanol at neutral and alkaline pH. In contrast, vanadate can oxidize 2-mercaptoethanol; this process is favored at low pH and high solute concentrations. The complex that forms between aqueous vanadium(IV) and 2-mercaptoethanol has a 1:2 stoichiometry and can be observed at high pH and high 2-mercaptoethanol concentration. The solution structures have been deduced based on coordination induced chemical shifts and speciation diagrams prepared. This work demonstrates that both vanadium(IV) and (V)-thiol complexes form and that redox chemistry also takes place. Whether reduction of vanadate takes place is governed by a combination of parameters: pH, solute- and vanadate-concentrations and the presence of other complexing ligands. On the basis of these results it is now possible to understand the distribution of vanadium in oxidation states (IV) and (V) in the presence of glutathione, cysteine, and other thiols and begin to evaluate the forms of the vanadium compounds that exert a particular biological effect including the insulin-enhancing agents, antiamoebic agents, and interactions with vanadium binding proteins.

Ultrasensitive detection of indoleamines by combination of nanoparticle-based extraction with capillary electrophoresis/laser-induced native fluorescence

For the first time, citrate-capped gold nanoparticles (citrate-AuNPs) have been used for the selective extraction of indoleamines – 5-hydroxytryptophan (5-HTP), tryptophan (Trp), tryptamine (TA), 5-hydroxytryptamine (5-HT), and 5-hydroxyindoleacetic acid (5-HIAA) – prior to their analysis by capillary electrophoresis/laser-induced native fluorescence (CE/LINF). The extinction spectra obtained for the citrate-AuNPs in the presence of indoleamines revealed that 5-HTP, 5-HT, and 5-HIAA were extracted mainly because of van der Waals interactions between the indole ring and the citrate-AuNPs (hydrophobic surface), while 5-HT and TA were extracted by electrostatic attractions between the amine group of the indoleamines and the citrate ligands adsorbed on the AuNP surface. The extracted indoleamines could be liberated from the AuNP surface by the addition of high concentrations of 2-mercaptoethanol (2-ME), which binds strongly to the AuNPs. The sensitivity of this method to indoleamines could be significantly enhanced by increasing the AuNP concentration, incubation time, and sample volume. Under optimal extraction and separation conditions, the combination of NP-based extraction and CE-LINF provided 48-, 4077-, 985-, 920-, and 4030-fold improvements in the limits of detection (signal-to-noise ratio of 3) for 5-HTP, Trp, TA, 5-HT, and 5-HIAA as compared to the analysis of five indoleamines by CE-LINF. In addition, this proposed method was successfully used for the determination of TA and 5-HT in urine.

Chain transfer agents in vinyl polymerizations photoinduced by bimolecular photoinitiators

The behavior of 2-mercaptoethanol and phenols as chain transfer agents in the polymerization of methyl methacrylate and acrylamide at 25 °C photoinitiated by bimolecular initiators based on xanthene dyes and aromatic ketones in the presence of amine was studied. Addition of millimolar concentrations of 2-mercaptoethanol or phenol to the methyl methacrylate polymerization reduced notably the polymer molecular weights, with minor changes of the polymerization rate. The photochemical behavior of the initiators in the polymerization media was analyzed. These studies allowed explaining the behavior of alkyl thiols and phenols as chain transfer agents in terms of the competition of the coinitiator and chain transfer agents to deactivate the triplet state of the photoinitiator, and the characteristics of the intermediates formed in the deactivation processes. Chain transfer constants were determined, and the values are similar to that obtained in the polymerization photoinduced by the α-cleavage of aliphatic azo compounds.

Development of a mild mercaptoethanol extraction method for determination of mercury species in biological samples by HPLC–ICP-MS

A mild, efficient and convenient extraction method of using 2-mercaptoethanol contained extractant solution combined with an incubator shaker for determination of mercury species in biological samples by HPLC–ICP-MS has been developed. The effects of the concentration of 2-mercaptoethanol, the composition of the extractant solution and the shaking time on the efficiency of mercury extraction were evaluated. The optimization experiments indicated that the quantitative extraction of mercury species from biological samples could be achieved by using 0.1% (v/v) HCl, 0.1% (v/v) 2-mercapoethanol and 0.15% (m/v) KCl extractant solution in an incubator shaker for shaking overnight (about 12 h) at room temperature. The established method was validated by analysis of various biological certified reference materials, including NRCC DOLT-3 (dogfish liver), IAEA 436 (tuna fish), IAEA MA-B-3/TM (garfish filet), IAEA MA-M-2/TM (mussel tissue), GBW 08193 (bovine liver) and GBW 08572 (prawn). The analytical results of the reference materials were in good agreement with the certified or reference values of both methyl and total mercury, indicating that no distinguishable transformation between mercury species had occurred during the extraction and determination procedures. The limit of detection (LOD) for methyl (CH 3Hg +) and inorganic mercury (Hg 2+) by the method are both as 0.2 μg L −1. The relative standard deviation (R.S.D.s) for CH 3Hg + and Hg 2+ are 3.0% and 5.8%, respectively. The advantages of the developed extraction method are that (1) it is easy to operate in HPLC–ICP-MS for mercury species determination since the extracted solution can be directly injected into the HPLC column without pH adjustment and (2) the memory effect of mercury in the ICP-MS measurement system can be reduced.

Catalytic activity and stability of anionic and cationic water soluble cobalt(II) tetraarylporphyrin complexes in the oxidation of 2-mercaptoethanol by molecular oxygen

The catalytic activity and stability of anionic cobalt(II) porphyrin complexes: 5,10,15,20-tetrakis(2,6-dichloro-3-sulfonatophenyl)porphyrinatocobalt(II), 5,10,15,20-tetrakis(2,4,6-trimethyl-3,5disulfonatophenyl)porphyrinatocobalt(II) and the cationic cobalt(II) porphyrin: 5,10,15,20-tetrakis[4-(diethylmethylammonio)phenyl]porphyrinatocobalt(II) tertraiodide have been investigated in the oxidation of 2-mercaptoethanol by dioxygen. All complexes were efficient catalysts for the auto-oxidation of 2-mercaptoethanol. The cationic cobalt(II) porphyrin has been found to be the most reactive catalyst. The rate of auto-oxidation of 2-mercaptoethanol catalysed by 5,10,15,20-tetrakis(2,4,6-trimethyl-3,5disulfonatophenyl)porphyrinatocobalt(II) has been found to increase with increasing the pH from 7 to 9 then decreased at higher pH. The rate constants of auto-oxidation reaction showed linear dependence on catalyst concentration and saturation kinetics in both 2-mercaptoethanol concentrations and dioxygen pressure. Anionic cobalt(II) porphyrin complexes showed higher stability than the cationic catalyst in repeat oxidation reactions. Immobilizing the anionic catalysts on ion exchange resin and supporting the cationic catalyst on clay mineral montmorillonite improved their stabilities towards oxidation.

The effect of thiol compounds on the autolysis of papain.

Incubation of papain with 3--17.5 mM dithiothreitol and dithioerythritol at pH 8.5 causes inactivation owing to autolysis. Such inactivation is not observed on incubation with equivalent concentrations of mercaptoethanol, cysteine or 2,3-dimercaptopropanol. The inactivation rate is independent of papain concentration within the range of 0.5--2% and is proportional to dithiothreitol concentration. This is in agreement with a sequence of two reactions: (Formula: see text) the first reaction being rate-limiting. S-Carboxymethyl-papain (I) and S-carboxamidomethyl-papain (II) were incubated with 18 mM dithiothreitol at pH 8.5 and, after stopping the reaction with iodoacetic acid, were subjected to gel electrophoresis. Electrophoretograms of both I and II exhibited a small new band attributable to a species with one disulphide bond reduced and carboxymethylated. The new band on II was more pronounced than that of I. It is argued that (Formula: see text) is a papain species with one reduced disulphide bond, sensitive to proteolytic attack by native papain.

Reductive Electron Injection into Duplex DNA by Aromatic Amines

An assay based on photoinduced reaction and subsequent cleavage of duplex DNA containing a bromodeoxyuridine ((Br)U) residue and an abasic site was developed to screen aromatic amines for their ability to initiate charge transfer by reductive electron donation. Two candidates, N,N,N',N'-tetramethyl-1,5-diaminonaphthalene (TMDN) and 1,5-diaminonaphthalene (DAN), expressed the desired activity, and an oligodeoxynucleotide-TMDN conjugate was subsequently prepared to identify additional variables affecting the efficiency of electron injection and transfer into DNA. This system demonstrated only mild sensitivity to molecular oxygen but was strongly inhibited by high concentrations of 2-mercaptoethanol. The nucleobase counter to the attached TMDN strongly modulated charge transfer as evident by a 60-fold decrease in reduction of the distal (Br)U when the counterbase A was substituted for C. An inverse relationship between this reduction and quenching of TMDN fluorescence by the counterbase was also discovered and is consistent with a competition between radical recombination and electron migration away from the initial site of its injection into DNA.

Nitric oxide and peroxynitrite promote complete disruption of the [4Fe-4S] cluster of recombinant human iron regulatory protein 1.

Iron regulatory protein 1 (IRP1) is a metalloprotein which regulates several proteins involved in mammalian iron homeostasis at a post-transcriptional level, by binding to specific mRNA sequences termed iron responsive elements (IREs). IRP1 exhibits two mutually exclusive activities, either aconitase or mRNA-binding protein, depending on the intactness of a versatile [4Fe-4S] cluster. Here we asked whether NO and peroxynitrite act directly on IRP1 and how they modify its functions. Recombinant human IRP1 was purified from Escherichia coli as a [4Fe-4S] cluster-containing protein, and exposed to 3-morpholinosydnonimine (SIN-1), which was used either as a peroxynitrite donor or as an NO donor when added with an excess of superoxide dismutase (SOD). We showed that, in both settings, IRP1 lost aconitase activity and iron concomitantly. Iron release reached 3.5-4 iron atoms per IRP1 molecule, proving that the Fe-S cluster was completely disrupted. An increase in IRP1 IRE-binding was observed upon the sequential addition of SIN-1/SOD and low concentrations of 2-mercaptoethanol, whereas SIN-1 alone induced a decrease in binding capacity which was not reversed by 2-mercaptoethanol, even at high concentrations. Moreover, nitrotyrosine adducts were detected on SIN-1-treated IRP1 by Western blot analysis.

Increasing membrane permeability of UV-modified poly(ether sulfone) ultrafiltration membranes

The use of the chain transfer agent, 2-mercaptoethanol, and ethanol cleaning was successful in producing hydrophilic membranes with higher permeabilities than the unmodified poly(ether sulfone) (PES) membrane. Permeabilities of dip-modified membranes were three to five times higher than with ethanol cleaning alone. Membrane permeability increased by 50% for dip-modified membranes in the presence of a low 2-mercaptoethanol concentration and by 20–200% when high 2-mercaptoethanol concentrations were used. From the lower degree of grafting (DG) achieved, it was inferred that the graft chain density and chain length decreased with increasing concentration of chain transfer agent. However, the observed rejection was severely reduced indicating that dip-modification caused considerable pore enlargement. This was not previously observed because non-grafted homopolymer may have been formed which effectively blocked the pores. It is speculated that ethanol cleaning removed the homopolymer because it wets and possibly swells the membrane pore structure. This indicated that it was not possible to dip-modify 50 kDa PES UF membranes using 300 nm lamps and a benzene filter without causing significant change to the pore structure. In addition, the combination of irradiation and N-vinyl-2-pyrrolidinone (NVP) caused a more severe loss of observed rejection than irradiation alone. The molecular weight cut-off (MWCO) of membranes irradiated and/or dip-modified with or without 2-mercaptoethanol was estimated to be between 50 and 100 kDa using a calibration curve for observed rejection versus membrane MWCO. The high hydrophilicity, high permeability, and low fouling character of membranes modified with 2-mercaptoethanol and cleaned with ethanol make them desirable for the filtration of larger proteins (>500 kDa) or for applications with smaller proteins in which high protein transmission is required.

Presence and features of fatty acyl-CoA binding activity in rat hepatic peroxisomes.

We studied the fatty acyl-CoA binding activity of rat liver peroxisomes. After subcellular fractionation of rat liver treated with or without clofibrate, a peroxisome proliferator, the binding activity with [1-(14)C]palmitoyl-CoA was detected in the light mitochondrial fraction in addition to the mitochondrial and cytosol fractions. After Nycodenz centrifugation of the light mitochondrial fraction, the binding activity was detected in peroxisomes. The peroxisomal activity depended on the incubation temperature and peroxisome concentration. The activity also depended on the concentration of 2-mercaptoethanol, and a plateau of activity was unexpectedly found at 2-mercaptoethanol concentrations from 20 to 40 mM. Clofibrate increased the total and specific activity of the fatty acyl-CoA binding of peroxisomes by 7.9 and 2.5 times compared with the control, respectively. In the presence of 20% glycerol at 0 degree C, approximately 90% of the binding activity was maintained for up to at least 3 wk. After successive treatment with an ultramembrane Amicon YM series, about 70% of the binding activity was detected in the M.W. 30,000-100,000 fraction. When the M.W. 30,000-100,000 fraction was added to the incubation mixture of the peroxisomal fatty acyl-CoA beta-oxidation system, a slight increase in the beta-oxidation activity was found. 2-Mercaptoethanol (20 mM) significantly activated the fatty acyl-CoA beta-oxidation system to 1.4 times control. After gel filtration of the M.W. 30,000-100,000 fraction, the peaks of fatty acyl-CoA binding protein showed broad elution profiles from 45,000 to 75,000. These results suggest that fatty acyl-CoA binding activity can be detected directly in peroxisomes and is increased by peroxisome proliferators. The high binding activity in the presence of higher concentrations of 2-mercaptoethanol indicates the importance of the SH group for binding. The apparent molecular weight of the binding protein may be from 45,000 to 75,000.

Inhibition kinetics of green crab ( Scylla serrata) alkaline phosphatase activity by dithiothreitol or 2-mercaptoethanol

Green crab ( Scylla serrata) alkaline phosphatase (EC 3.1.3.1) is a metalloenzyme which catalyzes the nonspecific hydrolysis of phosphate monoesters. Some pollutants in seawater affect the enzyme activity causing loss of the biological function of the enzyme, which affects the exuviating crab-shell and threatens the survival of the animal. The present paper studies the effects of thiohydroxyal compounds on the activity of green crab alkaline phosphatase. The results show that thiohydroxyal compounds can lead to reversible inhibition. The equilibrium constants have been determined for dithiothreitol (DTT) and mercaptoethanol (ME) binding with the enzyme and/or the enzyme-substrate complexes. The results show that both DTT and ME are non-competitive inhibitors. The kinetics of enzyme inactivation by ME at low concentrations has been studied using the kinetic method of the substrate reaction. The results suggest that at pH 10.0, the action of ME on green crab ALP is first quick equilibrium binding and then slow inactivation. The microscopic rate constants were determined for inactivation and reactivation. The rate constant of the forward inactivation ( k +0) is much larger than that of the reverse reactivation ( k −0). Therefore, when the ME concentration is sufficiently large, the enzyme is completely inactivated.