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PubMed1983

Assay method for myeloperoxidase in human polymorphonuclear leukocytes.

A simple assay method for measuring myeloperoxidase (MPO) has been developed. MPO is found in polymorphonuclear leukocytes and is important as a bactericidal agent in the presence of H2O2 and halide ions. This improved assay method is based on work of Andrews and Krinsky using tetramethylbenzidine (TMB) a noncarcinogenic substrate. By assaying MPO under optimal conditions of TMB at 1.6 mM, H2O2 concentration of 0.3 mM, pH 5.4, and incubation temperature of 37 degrees C, sensitivity of MPO measurements increased eightfold in comparison with the original TMB method. A method has been established to determine absorbance at 655 nm of the reaction mixture by incubation for 3 min and then stopping the reaction by the addition of pH 3.0 buffer. An attempt was also made to raise the sensitivity by using 3,3'-dimethyoxybenzidine (DMB), a carcinogenic substrate. The improved TMB method was 34 times more sensitive than the DMB method.

Benzidines↗

PubMed1985

Ultrastructure of transganglionic HRP transport in cat trigeminal system.

The ultrastructure of transganglionic transport of horseradish peroxidase (HRP) from the inferior alveolar (IA) nerve to the brainstem is being studied in the cat. The IA nerve was soaked in an HRP solution and following a two-day survival the animal was perfused transcardially with a paraformaldehyde-glutaraldehyde solution. The tissue was immediately dissected and postfixed for 1-3 h in perfusate. Sections of 75 micron thickness were cut with a Vibratome and reacted utilizing tetramethyl benzidine (TMB) as the chromagen. Optimum results for electron microscopy were obtained by osmication in a pH 6.0, 1% osmium tetroxide solution for 45 min at 45 degrees C, followed by rapid dehydration and embedment in Epon. The resulting HRP-TMB reaction product was characterized and identified ultrastructurally in ganglion cells, peripheral and central axons and in brainstem terminals. The HRP-TMB reaction product varied in density but had consistent crystalline-like laminations of a repeating unit and characterized by a membrane 4-5 nm in diameter. Some of the HRP-TMB reaction product found in terminals and axons was below the limit of resolution of the light microscope.

Animals↗

PubMed1987

Glutathione conjugate formation without N-demethylation during the peroxidase catalysed N-oxidation of N,N',N,N'-tetramethylbenzidine.

The mechanism of peroxidative N-dealkylation of alkylamines proceeds via one-electron oxidation to the iminium cation which reacts with water to give the N-hydroxymethyl derivative which decomposes to formaldehyde and the N-demethylated product. This reaction is normally inhibited by glutathione by reduction of the cation radical with subsequent formation of oxidized glutathione (GSSG) with oxygen uptake. It was found that the horseradish peroxidase catalyzed N-demthylation of N,N,N',N'-tetramethylbenzidine (N4-TMB) in the presence of glutathione leads to the formation of water-soluble metabolites identified by high field nuclear magnetic resonance (NMR) and fast atom bombardment (FAB) mass spectrometry as 3,3'-(diglutathion-S-yl) and 2,2'-(diglutathion-S-yl)-N4-TMB. Smaller amounts of (monoglutathion-S-yl)-N4-TMB were also found. Only trace amounts of GSSG were formed and no oxygen uptake was observed. Electron spin resonance (ESR) spectrometry in the presence of 5,5-dimethyl-1-pyrroline-N-oxide (DMPO) did not indicate the presence of a DMPO-glutathionyl adduct. These results indicate that glutathione inhibited the N-demethylation of N4-TMB under the described reaction conditions not by reduction of the cation radical but by conjugate formation. The mechanism of N-demethylation must involve removal of two successive electrons to give the benzoquinone-diimine which undergoes rearrangement to the iminium cation followed by reaction with water.

Benzidines↗

PubMed1990

Assay of the human leukocyte enzymes myeloperoxidase and eosinophil peroxidase.

Conditions were optimized for measuring the activity of myeloperoxidase (MPO) and the eosinophil peroxidase (EPO) with tetramethylbenzidine (TMB) as the substrate. Detergents caused a small increase in the measured activity of the purified enzymes and were required when isolated neutrophils or eosinophils were assayed. Sharp concentration optima were observed with both ionic and non-ionic detergents. Activity was also influenced by halide ions. Bromide or iodide caused up to a 7-fold increase in EPO activity and a 1.5-fold increase in MPO activity. The effect of bromide is notable because the bromide-containing detergent CETAB is often used to extract the enzymes for assay and purification. Stimulation by bromide or iodide was consistent with peroxidase-catalyzed oxidation of the halides to hypohalous acids (HOBr and HOI), which oxidized TMB. MPO catalyzes the oxidation of chloride to hypochlorus acid (HOCl), which also oxidized TMB, but chloride up to 20 mM had little effect on the assay. Both MPO and EPO catalyze thiocyanate oxidation, but the product (HOSCN) was a poor oxidant for TMB, and thiocyanate inhibited the measured activities. Stimulation by bromide or iodide could be used to facilitate detection of EPO and to distinguish between MPO and EPO. Activities could also be distinguished based on the greater sensitivity of EPO to inhibition by thiocyanate, azide, aminotriazole, and dapsone. Methods reported here may prove useful for measuring leukocyte influx into inflamed tissues, detecting MPO or EPO deficiencies, and measuring enzyme synthesis and secretion.

Amitrole↗

PubMed1988

Effect of alteration of nerve terminal Ca2+ regulation on increased spontaneous quantal release of acetylcholine by methyl mercury.

Agents known to disrupt intraterminal Ca2+ buffering, N,N-dimethylamino-8-octyl-3,4,5-trimethoxybenzoate (TMB-8), 25 microM; caffeine, 7.5 mM; N,N-bis(3,4-dimethoxyphenethyl)-N-methylamine (YS035), 180 microM; ouabain, 200 microM; and dantrolene, 50 microM, were tested for the ability to alter effects of methyl mercury (MeHg) on spontaneous quantal release of acetylcholine (ACh) at the rat neuromuscular junction. In particular, we sought to determine whether any of the above agents could prevent the MeHg-induced increase of spontaneous release of ACh, an effect measured electrophysiologically as increased frequency of miniature end-plate potentials (MEPPs). MEPPs were recorded continuously from myofibers of the rat hemidiaphragm using conventional, intracellular recording techniques during pretreatment with an inhibitor of Ca2+ regulation and subsequently with the inhibitor plus MeHg (100 microM). When given alone, caffeine and ouabain, which release Ca2+ from the smooth endoplasmic reticulum and mitochondria, respectively, increased MEPP frequency in a biphasic manner. Following pretreatment, concomitant application of MeHg with caffeine or ouabain increased MEPP frequency after a brief latent period to peak values of 53 and 92 Hz, respectively. TMB-8 and dantrolene, putative inhibitors of Ca2+ release from smooth endoplasmic reticulum, differed in their effects on MEPP frequency; TMB-8 alone decreased MEPP frequency to approximately 10% of drug-free control, whereas dantrolene did not significantly alter control MEPP frequency. Subsequent concomitant application of MeHg with TMB-8 or dantrolene increased MEPP frequency to peak values of 40 and 100 Hz after 17 and 30 min, respectively. YS035, a putative inhibitor of mitochondrial uptake and release of Ca2+, decreased MEPP frequency to less than 10% of control after 15 min when given alone. Application of MeHg following YS035 pretreatment failed to increase MEPP frequency for up to 90 min. YS035 did not mask a MeHg effect by blocking postsynaptic sensitivity to ACh or preventing its release since subsequent treatment with La3+ (2 mM) after YS035 had abolished spontaneous release, increased MEPP frequency within 5 min. Thus, of the five inhibitors of nerve terminal Ca2+ regulation tested, only YS035 prevented the stimulatory action of MeHg on MEPP frequency. Results of the present study suggest that release of Ca2+ from nerve terminal mitochondria contributes to the increased MEPP frequency caused by MeHg while release of Ca2+ from smooth endoplasmic reticulum may not.

Acetylcholine↗

PubMed1981

Effects of extracellular Ca2+ and the intracellular Ca2+ antagonist 8-(n,n-diethylamino)octyl-3,4,5-trimethoxybenzoate on rabbit platelet conversion of arachidonic acid into thromboxane.

The regulatory role of Ca2+ on the conversion of arachidonic acid (AA) into thromboxane B2 (TXB2) was examined in washed rabbit platelets, whose secretory processes are known to have requirements for extracellular Ca2+. Varying the extracellular free Ca2+ [Caf2+] concentration from less than 10(-8) M to 10(-3) M had no significant effect on the synthesis of immunoreactive TXB2 by rabbit platelets incubated with 1-4 microM AA. On the other hand, 8-(N,N-diethylamino)octyl-3,4,5-trimethoxybenzoate (TMB-8), a putative antagonist of intracellular Ca2+ movement, inhibited AA-stimulated synthesis of TXB2 in a concentration dependent manner--an effect which could be partially overcome by increasing the AA concentration. The TMB-8 inhibition could not be reversed by increasing the [Ca2+f]. Studies examining platelet metabolism of 14C-AA and 14C-prostaglandin H2 demonstrated that TMB-8 inhibited platelet cyclooxygenase, but not thromboxane synthetase. These studies demonstrate the absence of a requirement for [Ca2+f] but suggest the presence of a TMB-8 sensitive intracellular Ca2+ pool in the rabbit platelet synthesis of TXB2 from AA.

Animals↗

PubMed1993

The tungstate-stabilized tetramethylbenzidine reaction for light and electron microscopic immunocytochemistry and for revealing biocytin-filled neurons.

A peroxidase reaction product that can be easily distinguished from standard diaminobenzidine (DAB) reaction products is needed for pre-embedding electron microscopic double-antibody labelling studies. Benzidine dihydrochloride (BDHC) and gold-substituted silver peroxidase reactions are unsatisfactory for double labelling because they lack sensitivity and reliability and/or compromise ultrastructure. We show here that light and electron microscopic immunocytochemistry can be done with a modification of the tungstate-stabilized tetramethylbenzidine (TMB) reaction (Weinberg and Van Eyck 1991) which yields a crystalline reaction product. With this method, we have obtained excellent immunolabelling for a variety of antigens, including tyrosine hydroxylase, enkephalin, serotonin, Fos protein and retrogradely transported cholera toxin B subunit (CTB). The TMB-tungstate reaction is useful for ultrastructural double labelling because the crystals contrast well with the amorphous product of diaminobenzidine reactions. The TMB-tungstate reaction is more sensitive and reliable for immunocytochemistry than the benzidine dihydrochloride reaction and gives better ultrastructure than the gold-substituted silver peroxidase reaction. We also show that neurons filled with biocytin by intracellular injection can be visualized with TMB-tungstate for either light (LM) or electron (EM) microscopy.

Animals↗

PubMed1988

Thermally-induced activities of the mesencephalic reticulospinal and rubrospinal neurons in the rat.

Unit activities of 226 midbrain reticulospinal (mRfS) and non-mRfS neurons and 238 rubrospinal (RbS) and non-RbS neurons were investigated during changes in temperatures of midbrain (Tmb), preoptic and anterior hypothalamus (Thyp) and skin (Ts) in the urethane-anesthetized rat. Responsiveness to Tmb, Thyp and Ts were found in 43.5%, 41.6% and 51.5% of neurons of midbrain reticular formation (mRf), and in 35.2%, 32.7% and 17.6% of neurons of red nucleus (Rb). Higher incidence of responsiveness to remote temperatures was found among Tmb responsive neurons than Tmb unresponsive neurons in both mRf and Rb. The mRf contains significantly greater numbers of neurons having such multiple thermal responsiveness and also of neurons which were activated by falls in temperatures (cold-responsive neurons) than the Rb. These characteristics were more conspicuously seen among mRfS neurons, showing a high degree of convergence of cold signals from different sites of body. On the other hand, RbS neurons did not differ from non-RbS neurons regarding thermal characteristics and showed no particular combinations of responsiveness to temperatures of different sites. Microinjection of procaine and glutamate into the mRf just dorsolateral to the Rb, but not into the Rb, decreased and increased cold-induced increase in EMG activity and shivering without changes in cardiovascular and respiratory parameters and pilomotor activity. The results suggest that mRfS neurons are involved in the control of thermoregulatory muscle tone and shivering.

Action Potentials↗

PubMed1990

A new chromogen for use in HRP-tract tracing and double-label immunocytochemistry.

A new chromogen, Indophane Blue (IB) was tested for use in HRP-tract tracing and double-label immunocytochemistry. Although TMB was slightly more sensitive and delineated individual labeled fibers better than IB in tract-tracing experiments, there were two advantages to using IB over TMB. First, the IB reaction could be performed at a pH of 6.0, rather than the pH of 3.3 required for TMB, resulting in much better preservation of tissue. Second, there was no crystalline artifact as has been observed with TMB. In the double-label immunocytochemistry experiments, the combination of diaminobenzidine for the first chromogen and IB as the second, provided excellent contrast.

Animals↗

PubMed2006

Heterogeneity and tissue specificity of tropomyosin isoforms from four species of bivalves.

Heterogeneity and tissue specificity of tropomyosin isoforms obtained from four species of bivalves (Scapharca broughtonii (ark shell), Mytilus galloprovincialis (mussel), Atrina pectinata (surf clam) and Crassostrea gigas (Pacific oyster)), were examined. Tropomyosins were extracted from translucent and opaque portions of posterior adductor muscle, respectively, and cardiac muscle of each bivalve. There were two tropomyosin isoforms in the ark shell, the surf clam and the Pacific oyster. They were designated as TMa and TMb. In the ark shell, TMa was the common isoform and TMb was specific for the opaque portion of the adductor muscle. In the surf clam, TMb was the common isoform present in all tissues. TMa was found only in the translucent portion of muscle. In the Pacific oyster, TMb was the major component in both portions of adductor muscle and TMa was the major component in cardiac muscle, although both tropomyosins were included in all tissues. The mussel had only one tropomyosin.

Animals↗

PubMed1996

Allosteric regulation of the binding of [3H]acetylcholine to m2 muscarinic receptors.

Muscarinic receptors of the m2 subtype expressed in Chinese hamster ovary cells were labeled with [methyl-3H]acetylcholine([3H]ACh), and the rate of dissociation in the presence and absence of several compounds known to exert allosteric effects on labeled antagonist binding was observed. At 25 degrees C, [3H]ACh bound to the receptors with a Kd of 1.2 nM and dissociated with a half-time of 1.6 min. This binding was sensitive to appropriate concentrations of guanine nucleotide and the muscarinic antagonist N-methylscopolamine (NMS). Gallamine, tetrahydroaminoacridine, physostigmine, obidoxime, and 3,4,5-trimethoxybenzoic acid 8-(diethylamino)octyl ester (TMB-8) all inhibited the binding of [3H]ACh and all slowed the rate of dissociation of [3H]ACh in a concentration-dependent manner. However, the nature of some of the allosteric effects differed from previous studies that used other labeled ligands. In particular, TMB-8, which is very effective in slowing the dissociation of the antagonist [3H]NMS, had much weaker effects on the dissociation of [3H]ACh. Furthermore, TMB-8 was able to partially reverse the stronger effects of gallamine on the dissociation of [3H]ACh, consistent with the possibility that TMB-8 and gallamine share a common site on the receptor. In summary, the binding of ACh to muscarinic receptors is subject to allosteric regulation, and assays using [3H]ACh may be especially useful in the evaluation of potential allosteric regulators of muscarinic systems.

Acetylcholine↗

PubMed2002

Functional modulation of a peroxygenase cytochrome P450: novel insight into the mechanisms of peroxygenase and peroxidase enzymes.

Cytochrome P450(BSbeta) is a peroxygenase that catalyzes the alpha- or beta-hydroxylation of myristic acid by utilizing H(2)O(2). The wild-type enzyme not only hydroxylated myristic acid, but oxidized 3,5,3',5'-tetramethylbenzidine (TMB), a peroxidase substrate, in a myristic acid-dependent reaction. Study of inhibition of hydroxylation of myristic acid by TMB indicates these two substrates compete for the same highly reactive intermediate during the course of their respective reactions. When deuterated myristic acid was used as a substrate to decrease hydroxylation activity, the rate of TMB oxidation increased. This increased rate of TMB oxidation was greatly enhanced when the R242K mutant enzyme bound with deuterated myristic acid was used. These results suggest that there are critical structural elements at the distal active site which determine whether this enzyme acts as a peroxygenase or a peroxidase.

Bacillus subtilis↗

PubMed1997

Brain aging in a sample of normal Egyptians cognition, education, addiction and smoking.

The impact of duration of education, cannabis addiction and smoking on cognition and brain aging is studied in 211 normal Egyptian volunteers with mean age 46.4+/-3.6 years (range: 20-76 years). Subjects were classified into two groups: Gr I (non-addicts) with 174 subjects, mean age 49.9+/-3.8 years (range 20-76 years), smokers and non-smokers, educated and non-educated and Gr II (cannabis addicts) with 37 subjects, mean age 43.6+/-2.6 years (range 20-72 years) all smokers, educated and non-educated. Outcome measures included the Paced Auditory Serial Addition test (PASAT) for testing attention and the Trailmaking test A, and B (TMa and TMb) for testing psychomotor performance. Age correlated positively with score of Trailmaking test (TMb) in the non-addict group and in the addict group (TMa and TMb). Years of education correlated negatively with scores of Trialmaking test (TMb) in the non-addict group (Gr I) but not the addict group (Gr II). However, in both groups mean scores of the Trailmaking test (TMa) were significantly lower in subjects with a primary level of education than those with higher levels of education. No significant difference was detected between male smokers and nonsmokers of Gr I (non-addicts) regarding any of the neuropsychological tests. Yet, smokers and the non-educated group had poorer attention compared to non-smokers of the same group. Cannabis addicts (Gr II) had significantly poorer attention than non-addict normal volunteers (Gr I). It is concluded that impairment of psychomotor performance is age related whether in normal non-addicts or in cannabis addicts. A decline in attention was detected in cannabis addicts and has been considered a feature of pathological aging. Education in early life as well as the duration of education are neuroprotectors for brain aging more so in the non-addict than addict group. Though cigarette smoking per se has no effect on cognitive abilities in normal aging, it becomes evident that its association with lack of education impairs attention.

Adult↗

PubMed1996

Volume regulation and the efflux of amino acids from cells in incubated slices of rat cerebral cortex. II. Dependence on Ca2+ ions.

The efflux of gamma-aminoisobutyric acid (GABA) and L-glutamate from pre-loaded cells in rat cerebral cortical slices has been studied during interventions designed to affect the availability of intracellular Ca2+ during hyposmotic swelling and membrane depolarization due to raised extracellular K+. Calmodulin-dependent acceleration of amino acid efflux in hyposmotic media, with cell swelling less than would be predicted on the basis of perfect osmometric behaviour (see Ref. [1]), was unaffected by Ca-ionophore in the presence of external Ca2+ or by the omission of external Ca2+, but was suppressed by pre-exposure of slices to thapsigargin (2 microM), which is reported to deplete cytosolic Ca2+, and by TMB-8 (0.5 mM), which blocks release of Ca2+ from internal stores. TMB-8 also led to significant cell swelling. The effects of TMB-8 were reversed by Ca-ionophore. Raised external K+ (54 mM) led to accelerated amino acid efflux which required calmodulin activation and was blocked by (i) omission of external Ca2+, (ii) the voltage-sensitive Ca2+ channel blocker nifedipine (1 microM), (iii) the anion transport inhibitor DIDS (25 microM for GABA, 100 microM for L-glutamate, see Ref. [1]), and (iv) the -SH group acetylator N-ethylmaleimide. TMB-8 was without effect in high K+ media. These results suggest that while enhanced amino acids efflux probably occurs through the same population of Ca/calmodulin-dependent, DIDS-sensitive pathways following hyposmotic shock or membrane depolarization, the source of Ca2+ ions required for the activation of these pathways may depend upon which of these acceleratory stimuli is applied.

4,4'-Diisothiocyanostilbene-2,2'-Disulfonic Acid↗

PubMed1999

The Telemedicine benchmark--a general tool to measure and compare the performance of video conferencing equipment in the telemedicine area.

In this paper, we describe the 'Telemedicine Benchmark' (TMB), which is a set of standard procedures, protocols and measurements to test reliability and levels of performance of data exchange in a telemedicine session. We have put special emphasis on medical imaging, i.e. digital image transfer, joint viewing and editing and 3D manipulation. With the TMB, we can compare the aptitude of different video conferencing software systems for telemedicine issues and the effect of different network technologies (ISDN, xDSL, ATM, Ethernet). The evaluation criteria used are length of delays and functionality. For the application of the TMB, a data set containing radiological images and medical reports was set up. Considering the Benchmark protocol, this data set has to be exchanged between the partners of the session. The Benchmark covers file transfer, whiteboard usage, application sharing and volume data analysis and compression. The TMB has proven to be a useful tool in several evaluation issues.

Benchmarking↗

PubMed1994

Ceramic bracket bonding: a comparison of shear, tensile, and torsional bond strengths of ceramic brackets.

The purpose of this study was to evaluate whether shear, tensile, or torsional forces were best suited for debonding ceramic brackets. Four commercially available ceramic brackets were evaluated. The brackets included both polycrystalline and monocrystalline types with either chemical or mechanical retention in the bracket bases. The ceramic brackets were bonded to one hundred and twenty bovine teeth, using Concise. The brackets were stressed until bond or bracket failure occurred with either shear, tensile, or torsional forces on the Instron machine. The maximum bond strength and the site of bond failure was recorded. Starfire TMB brackets fractured 30% of the time during shear debonding, whereas, Quasar 1000, Lumina, and Transcend 2000 brackets exhibited no bracket fractures. The shear bond strengths of Quasar 1000 brackets were significantly higher than Starfire TMB brackets. Starfire TMB was the only bracket type that exhibited no bracket fractures with tensile force. Tensile bond strengths were not significantly different between the four bracket types. In torsion, Lumina was the only bracket type that did not exhibit any bracket failures. Shear and tensile bond strengths of chemically retained brackets were not significantly different than mechanically retained brackets. Torsional bond strength of chemically retained brackets was significantly higher than mechanically retained brackets. The results suggest Quasar 1000, Lumina, and Transcend 2000 are best removed with shear or tensile forces. Starfire TMB is best removed with tensile forces.

Animals↗

PubMed2003

The effect of etanercept and infliximab on the production of tumour necrosis factor alpha, interferon-gamma and GM-CSF in in vivo activated intestinal T lymphocyte cultures.

BACKGROUND/AIMS: Infliximab (Ifx) is effective in the treatment of Crohn's disease (CD) and rheumatoid arthritis (RA), etanercept (Eta) in RA but not in CD. The mechanisms underlying these clinical differences are not fully understood, but this knowledge could be valuable to identify responders and develop new treatments. This study compares Eta and Ifx in vitro regarding transmembrane tumour necrosis factor alpha (tmb-TNF-alpha) expression and interferon-gamma (IFN-gamma), TNF-alpha and granulocyte macrophage colony stimulating factor (GM-CSF) production in intestinal T lymphocytes. METHODS: T lymphocyte cultures were established from biopsies from 10 CD patients and three healthy controls. The cytokine production and the expression of tmb-TNF-alpha were measured in the presence of Ifx/Eta. RESULTS: Eta and Ifx downregulated the production of IFN-gamma and GM-CSF in colonic T lymphocytes from CD patients and healthy controls. Both drugs bound tmb-TNF-alpha on activated T lymphocytes besides neutralising TNF-alpha, Eta less efficiently than Ifx (406 pg/ml (337-475); 133 pg/ml (119-147); p=0.004). TNF-alpha was detectable with the present assay in cell lines cultured in the presence of excess Eta. CONCLUSIONS: We have established that Eta is just as efficient as Ifx in downregulating IFN-gamma and GM-CSF production in vitro and Eta bound to tmb-TNF-alpha. However, Eta bound the TNF-alpha molecule, important in CD, less efficiently than Ifx.

Antibodies, Monoclonal↗

PubMedDate not supplied

[Peroxidase-catalyzed oxidation of 3,3',5,5'-tetramethylbenzidine in the presence of 2,4-dinitrosoresorcinol and polydisulfide derivatives of resorcinol and 2,4-dinitrosoresorcinol].

A comparative study of the kinetics of peroxidase-catalyzed oxidation of 3,3',5,5'-tetramethylbenzidine (TMB) in the presence of 2,4-dinitrosoresorcinol (DNR), its polydisulfide derivative [poly(DNRDS)], and resorcinol polydisulfide [poly(RDS)], substances that competitively inhibit the formation of TMB conversion product, was carried out. The inhibition constants, Ki for DNR, poly(DNRDS), and poly(RSD) were determined at 20 degrees C and pH 6.4 to be 110, 13.5, and 0.78 microM, respectively. The stoichiometric coefficients of inhibition were calculated to be 0.38 and 76 for poly(DNRDS) and poly(RDS), respectively. In the pH range 6.4-7.0, the initial rates of the peroxidative oxidation of TMB, and its mixtures with DNR and poly(DNRDS) and the Ki value for poly(RDS) substantially decreased with increasing pH. The kinetic parameters of poly(RDS) (Ki 0.22-0.78 microM and f76) suggest that it is the most efficient inhibitor of peroxidase oxidation of TMB: in micromolar concentrations, it completely stops this process and can be used in EIA.

Benzidines↗