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PubMed1973

Investigations of the structural function of the J chain in human immunoglobulin M.

Human IgM molecules were treated with Na(2)SO(3) or mercaptoethylamine in concentrations ranging from 2 to 14mm or 2 to 22mm respectively. The dissociation of IgM to IgM(s) varied from 0% to 100%. At the intermediate concentrations of either reagent the amount of freed J chains was less than expected. In an attempt to find an explanation for this, IgM was partially dissociated to IgM(s) with mercaptoethylamine. The IgM(s) isolated by gel filtration was divided according to the ascending and descending portions of the elution curve. These portions were treated with 24mm-mercaptoethylamine and analysed for the presence of J chains. Only the ascending portion contained free J chains. Thus, after mild reduction where not all the IgM molecules are dissociated to IgM(s), some J chains remain covalently attached to some IgM(s) molecules although most of the J chains are freed. It was concluded that the J chain could serve as a ;hitch' for IgM(s) molecules forming intact IgM.

Animals↗
PubMed1993

Preparation of antigen-binding monomeric and half-monomeric fragments from human monoclonal IgM antibodies against colorectal cancer-associated antigens.

The large size of human IgM monoclonal antibodies (MAbs) may impede the tumor-localizing capacity. A procedure is described for the preparation of antigen-binding monomeric (IgMm) and half-monomeric (IgM1/2m) fragments from two human IgM MAbs, COU-1 and D4213. The fragments retained binding activity against colon carcinoma. Six different reducing reagents (dithiothreitol, 2-mercaptoethanol, 2-mercaptoethylamine, L-cysteine, metabisulphite, ascorbic acid) were investigated over a range of concentrations, pHs, and incubation periods. The reduced IgM preparations were alkylated with iodoacetamide and fractionated by high-performance gel permeation chromatography. The fractions were directly collected on ELISA plates coated with extracts of colon cancer cells. Antigen-binding IgMm and IgM1/2m fragments were obtained after treatment with mercaptoethanol, mercaptoethylamine, metabisulphite, and cysteine. IgMm and IgM1/2m fragments were also obtained after dithiothreitol treatment. These fragments were, however, nonreactive. The pH during the reduction was important for optimal yields of the fragments. The fragments obtained with 2-mercaptoethanol and mercaptoethylamine were most effective in binding to the cancer cell extract. The association constants per binding site for intact, monomeric, and half-monomeric COU-1 were by competitive inhibition assays estimated at 1.5 x 10(8) M-1, 3.1 x 10(8) M-1 and 4.0 x 10(6) M-1, respectively. The reduction of human IgM MAbs to IgMm and IgM1/2m fragments may facilitate the tumor localization when these are used in the diagnosis and therapy of cancer patients.

Alkylation↗
PubMed1973

Production of a noncovalently bonded pentamer of immunoglobulin M: relationship of J chain.

Human immunoglobulin M was reduced with concentrations of 2-mercaptoethylamine chosen so that approximately 40% of the immunoglobulin M was reduced to 7S subunits. Under these conditions, which selectively cleave intersubunit disulfides, J chain was released. The 7S subunits of immunoglobulin M so produced did not contain J chain. The high-molecular-weight immunoglobulin M remaining after treatment with 2-mercaptoethylamine had a sedimentation coefficient of 18.0 S and molecular weight of 1 million, and dissociated in 4 M guanidine into subunits similar in size to the 7S subunits. J chain was found in the 18.0S, noncovalently linked immunoglobulin M from which it was released only after more complete reduction with 10 mM dithiothreitol. The results are consistent with the hypothesis that J chain participates in the formation of the intersubunit linkages. However, it need not necessarily be directly involved in all of the intersubunit disulfides. It may play an important role in modulating the assembly of immunoglobulin M subunits, perhaps by inducing conformational changes that lead to noncovalent interactions between the subunits.

Chemical Phenomena↗
PubMed2002

Novel method for linking CdS nanoparticles at liquid-liquid interface.

Liquid-liquid interface of water-hexane provides a unique reaction environment in which CdS nanoparticles capped with mercaptoethylamine could be linked together to form a homodimer with a divalent acid chloride, sebacoyl chloride. Prior to the reaction, mercaptoethylamine-capped CdS in aqueous solution was purified by dialysis and freeze-drying. The observation with a transmission electron microscope suggested the formation of a homodimer of CdS nanoparticles.

Letter↗
PubMed2005

Study on the immobilization of anti-IgG on Au-colloid modified gold electrode via potentiometric immunosensor, cyclic voltammetry, and electrochemical impedance techniques.

The immobilization of anti-IgG on Au-colloid modified gold electrodes has been investigated. A cleaned gold electrode was first immersed in a mercaptoethylamine (AET) solution, and then gold nanoparticles were chemisorbed onto the thiol groups of the mercaptoethylamine. Finally, anti-IgG was adsorbed onto the surface of the gold nanoparticles. Potentiometric immunosensor, cyclic voltammetry, and electrochemical impedance techniques were used to investigate the immobilization of anti-IgG on Au colloids. In the impedance spectroscopic study, an obvious difference of the electron transfer resistance between the Au-colloid modified electrode and the bare gold electrode was observed. The cyclic voltammogram tends to be more irreversible with increased anti-IgG concentration. Using the potentiometric immunosensor, the proposed technique is based on that the specific agglutination of antibody-coated gold nanoparticles, averaging 16 nm in diameter, in the presence of the corresponding antigen causes a potential change that is monitored by a potentiometry. It is found that the developed immunoagglutination assay system is sensitive to the concentration of IgG antigen as low as 12 ng mL(-1). Experimental results showed that the developed technique is in satisfactory agreement with the ELISA method, and that gold nanoparticles can be used as a biocompatible matrix for antibody or antigen immobilization.

Biocompatible Materials↗
PubMed1999

Resveratrol, melatonin, vitamin E, and PBN protect against renal oxidative DNA damage induced by the kidney carcinogen KBrO3.

Free radical scavengers can protect against the genotoxicity induced by chemical carcinogens by decreasing oxidative damage. The protective effect of the antioxidants melatonin, resveratrol, vitamin E, butylated hydroxytoluene and 2-mercaptoethylamine, and the spin-trapping compound alpha-phenyl-N-tert-butyl nitrone (PBN) against oxidative DNA damage was studied in the kidney of rats treated with the kidney-specific carcinogen potassium bromate (KBrO3). KBrO3 was given to rats previously treated with melatonin, resveratrol, PBN, vitamin E, butylated hydroxytoluene, or 2-mercaptoethylamine. Oxidative damage to kidney DNA was estimated 6 hours afterwards by measuring 8-oxo-7,8-dihydro-2'-deoxyguanosine (oxo8dG) referred to deoxyguanosine (dG) by means of high performance liquid chromatography with electrochemical-coulometric and ultraviolet detection. Levels of oxo8dG in the renal genomic DNA significantly increased by more than 100% after the KBrO3 treatment. This increase was completely abolished by the treatment with resveratrol and was partially prevented by melatonin, PBN and vitamin E. Resveratrol and PBN also prevented the increase in relative kidney weight induced by KBrO3. These results show that various different antioxidants and a free radical trap, working in either the water-soluble or the lipid-soluble compartments, can prevent the oxidative DNA damage induced in the kidney by the carcinogen KBrO3.

Animals↗
PubMed2006

Effects of bismuth contamination on the growth and activity of soil microorganisms using thiols as model compounds.

The present study was undertaken to obtain information about the effects of Bi contamination on soil microbial growth and activity using a series of Bi complexes with thiol compounds, including mercaptoethanol, thioglycerol, mercaptoethylamine, thioglycolic acid, thiomallic acid, reduced glutathione, 2-mercaptopropionic acid, and L-cysteine. We found that Bi complexes with mercaptoethanol, thioglycerol, and mercaptoethylamine, all of which showed lipophilicity, markedly inhibited bacterial growth in 1/10 TSB liquid media in both Eutric Cambisol (brown forest soil) and Eutric Fluvisol (brown lowland soil), with relative CFU of less than 2% at 50 micro M Bi and 6% at 25 micro M Bi. However, none of the Bi-thiols, including Highly lipophilic complexes, at 200 micro M Bi in rosebengal agar medium inhibited fungal growth, possibly because fungi have a metabolic system that protects against Bi uptake or detoxifies Bi compounds. When soil was contaminated experimentally with Bi-thiol, these complexes suppressed soil dehydrogenase activity, particularly in brown forest soil, which contains large amounts of easily decomposable organic matter. These results indicate that the effects of Bi on soil microbes may depend on mutual reactions with organic matter in the environment.

Bacteria↗
PubMed1981

Cysteine and growth inhibition of Escherichia coli: threonine deaminase as the target enzyme.

Cysteine has been shown to inhibit growth in Escherichia coli strains C6 and HfrH 72, but not M108A. Growth inhibition was overcome by inclusion of isoleucine, leucine, and valine in the medium. Isoleucine biosynthesis was apparently affected, since addition of this amino acid alone could alter the inhibitory effects of cysteine. Homocysteine, mercaptoethylamine, and mercaptoethanol inhibited growth to varying degrees in some strains, these effects also being prevented by addition of branched-chain amino acids. Cysteine, mercaptoethylamine, and homocysteine were inhibitors of threonine deaminase but not transaminase B, two enzymes of the ilvEDA operon. Cysteine inhibition of threonine deaminase was reversed by threonine, although the pattern of inhibition was mixed. These results suggest a relationship between the growth-inhibitory effects of cysteine and other sulfur compounds and the inhibition of isoleucine synthesis at the level of threonine deaminase.

Cysteine↗
PubMed1975

[The enzymatic hydrolysis of cell wall applied to yeasts classification (author's transl)].

The rigid structure of yeast cell wall may be a taxonomic criterion. Using the Helix pomatia juice (with mercaptoethylamine hydrochloride) as a polyenzymatic system, we have always obtained protoplasts from ascomycetous yeasts and never from basidiomycetous yeasts tested. Then, we have applied this enzymatic analysis to the Fungi imperfecti yeasts and, according to this test, separated genus looking like basidiomycetous behaviour: Trichosporon, Pityrosporum, Rhodotorula, Cryptococcus and non fermentative Candida (group II). Oppositely, we have put together the Fungi imperfecti yeasts looking like ascomycetous behaviour: Kloeckera, Trigonopsis, Brettanomyces and fermentative Candida (group I). With the second lytic system made of mercaptoethylamine-HCl and beta-(1-3)-D-glucanase, we have selected ascomycetous yeasts giving protoplasts: Saccharomycoidea with genus Saccharomyces, Kluyveromyces, Pichia, Hansenula, Citeromyces, Debaryomyces; we have joined Saccharomycodes and Hanseniaspora to this second group. The other ascomycetous yeasts studied did not give protoplasts with the definite lytic system made of purified beta-(1-3)-D-glucanase and thiol. These results seem to demonstrate that the structure of cell wall can act as an important taxonomic criterion.

Ascomycota↗
PubMed1982

Model reactions for CoA transferase involving thiol transfer. Anhydride formation from thiol esters and carboxylic acids.

Rate and equilibrium constants were determined for anhydride formation from the thiol esters p-nitrophenyl thiosuccinate (PTS) and N-acetyl-S-succinyl-beta-mercaptoethylamine, and from p-nitrophenyl thioacetate in the presence of substituted acetates. These thiol esters undergo thiol transfer reactions through rate-determining anhydride formation that are models for the enzymic reaction catalyzed by CoA transferase. The same value of beta nuc approximately equal to 1.0 for the nucleophilic reactions of substituted acetates with p-nitrophenyl thioacetate and with enzyme-CoA supports the anhydride mechanism for the enzymic reactions. The bimolecular reaction of succinyl-CoA with enzyme is 10(13) times faster than the nonenzymic reaction of acetyl-CoA with acetate; the intramolecular reaction of bound substrate is accelerated by a factor of kcat/kN - 10(11) M. The nonenzymic intramolecular reaction of PTS is faster than the nucleophilic reaction of acetate with acetyl-CoA by a similar factor of 4.5 X 10(10) M, of which 6 X 10(5) M is caused by intramolecularity and 7 X 10(4) by the increased chemical reactivity of PTS compared to acetyl-CoA. The enzyme may utilize binding energy to increase the reaction rate by making the reaction intramolecular (decreasing the requirement for loss of entropy) and by destabilizing the bound substrate relative to the transition state in an analogous manner. An identical rate increase of 6 X 10(5) M from intramolecularity was observed for the reaction of N-acetyl-S-succinyl-beta-mercaptoethylamine compared with the corresponding acetate. The rate increase in the intramolecular reaction of PTS reflects more favorable values of T delta S identical = 5.0 +/- 1.4 kcal mol-1 and -delta H identical to = 2.9 +/- 1.3 kcal mol-1 compared with the bimolecular reaction.

Acyltransferases↗
PubMed1964

ISOLATION AND PROPERTIES OF INTACT MITOCHONDRIA FROM SPHEROPLASTS OF YEAST.

Duell, E. A. (Western Reserve University, Cleveland, Ohio), Sakae Inoue, and Merton F. Utter. Isolation and properties of intact mitochondria from spheroplasts of yeast. J. Bacteriol. 88:1762-1773. 1964.-Functionally intact mitochondria can be obtained in good yields by osmotic disruption of spheroplasts formed from yeast by treatment with an enzyme mixture from the snail digestive tract. The useful range of this method is extended greatly by pretreatment of the yeast cells with 2-mercaptoethylamine and ethylene-diaminetetraacetate. The concentration of the yeast suspension can be increased greatly, the incubation period can be shortened considerably, and the requirement for log-phase cells is obviated. Mitochondria prepared by this method have been compared with those obtained by mechanical disruption in terms of respiratory control, specific activity on a wide range of oxidizable substrates, heterogeneity during centrifugation, and structures observed by electron microscopy. In all cases, the mitochondria obtained from spheroplasts appear to be much less damaged by the preparative procedures.

Centrifugation↗
PubMed1984

Effects of radioprotectors on the cAMP and cGMP systems.

The sulphur-containing radioprotectors mercaptoethylamine (MEA), aminoethylisothiourea (AET), 2- aminothiazoline , 4-oxo-2- aminothiazoline , and S-S-3- oxapentane -1,5- diisothiourea , and the radioprotective biogenic amines serotonin, histamine, and dopamine, caused the elevation of cAMP content and intensified the rate of cAMP-dependent protein phosphorylation in tissues of animals following intraperitoneal injection at radioprotective doses. Biogenic amines stimulated the adenylate cyclase activity in membrane preparations from liver, spleen, and small-intestine mucosa; sulphur-containing radioprotectors caused no such effects. None of the radioprotectors affected cAMP and cGMP phosphodiesterases in vitro. AET and MEA inhibited guanylate cyclase in vitro, whereas serotonin and dopamine stimulated the enzyme. A biphasic change in the level of cGMP was observed in tissues after the administration of MEA and AET (more than 2-fold fall by 1-3 min after the administration of drug and 1.4-fold rise after 15-20 min); serotonin and dopamine caused a slow rise in the cGMP level; the cAMP/cGMP ratio in liver showed biphasic changes in level during the 20 min following injection of serotonin. The data obtained support the conclusion that the action of radioprotectors on cellular metabolism in animals may be mediated by the cAMP system. The reciprocal regulation of radioresistance by cAMP and cGMP is unlikely to exist.

Adenylyl Cyclases↗
PubMed1985

Structural requirements for specific inhibition of microsomal aminopeptidase by mercaptoamines.

L-Leucinthiol, a synthetic derivative of mercaptoethylamine with a hydrophobic side chain, was recently reported to be a potent inhibitor of microsomal aminopeptidase. The structural features necessary for interaction of mercaptoamines with this enzyme have now been explored more systematically. Optimal binding requires a primary amine linked to the mercapto group via two carbon atoms. Only a substituent with L-configuration at the 1 position increased the affinity toward the enzyme. The high degree of specificity and other evidence suggest that the mode of binding of these inhibitors is similar to that of substrates. Comparison of leucinthiol with other amino compounds suggest that the mercapto group makes a much greater contribution to the binding than the hydrophobic side chain. L-Leucinthiol is fairly specific for aminopeptidase although some inhibition of thermolysin and carboxypeptidase A is observed.

Aminopeptidases↗
PubMed1985

Cystine depletion by WR-1065 in cystinotic cells. Mechanism of action.

Cystinotic leucocytes and skin fibroblasts incubated with the aminothiol N-(2'-mercaptoethyl)-1,3-propanediamine (WR-1065) exhibited substantial intralysosomal cystine depletion within 2 hr. Wr-2721, the thiol phosphorylated derivative of WR-1065, did not lower cystinotic leucocyte cystine in 1 hr but depleted cystinotic fibroblasts of cystine after 21 hr. Concentrations of cysteamine (beta-mercaptoethylamine) equimolar with those of WR-1065 depleted cystine more rapidly than did WR-1065, but the extent of cystine depletion by WR-1065 approached that for cysteamine when longer periods of incubation or higher concentrations were used. Cystine depletion by WR-1065 was slower for leucocyte lysosomal granular fractions than for whole leucocytes. L-[35S]Cystine-labeled fibroblasts exposed to WR-1065 exhibited new compounds not seen when cells were incubated without WR-1065: WR-1065-cysteine, cysteamine-cysteine and cysteamine-glutathione mixed disulfides. L-[35S]Cystine-loaded lysosome-rich granular fractions from cystinotic leucocytes incubated with WR-1065 formed WR-1065-cysteine mixed disulfide but no cysteamine-cysteine mixed disulfide. We suggest that WR-2721 is dephosphorylated intracellularly to the free thiol, WR-1065, which subsequently is converted to cysteamine by an unknown route. Intracellular cysteamine then enters the lysosome and reacts with free cystine to form cysteamine-cysteine mixed disulfide and cysteine which move into the cytosol and the incubation medium where they participate in further interchange reactions with free thiols present there, namely WR-1065 and glutathione.

Amifostine↗
PubMed1980

A general and mild procedure for the purification of rabbit Fab' antibodies.

A mild procedure for the purification of rabbit Fab' antibodies is described. A small column of normal goat IgG-Sepharose 4B (3 cm x 5mm) was saturated with F(ab')2 prepared from rabbit anti-goat IgG, and anti-goat IgG Fab was eluted from the column by splitting the disulfide bond in the hinge of the F(ab')2 molecule using 10 or 12 mM 2-mercaptoethylamine at pH 7. The recovery of anti-goat IgG Fab' in the eluate was about 35% of anti-goat IgG F(ab')2 bound to the column, and the purity of anti-goat IgG Fab' eluted was more than 90%. This procedure may be applicable to most kinds of rabbit IgG antibodies and useful for various immunoassays.

Animals↗
PubMed1995

Solid phase synthesis of bifunctional antibodies.

Bifunctional antibodies were prepared using the principle of solid-phase synthesis. The two Fab' fragments were chemically linked together via a bismaleimide crosslinking reagent. The F(ab')2 fragments from intact IgG were prepared using an immobilized pepsin column. Goat, mouse and human antibodies were digested completely within 4 h. The F(ab')2 fragments thus produced did not contain any IgG impurities. The Fab' fragments were produced by reducing the inter-heavy chain disulfide bonds using 2-mercaptoethylamine. The use of the solid-phase reactor in the preparation of the bifunctional antibodies eliminated many of the time-consuming separation steps between the fragmentation and conjugation steps. This procedure facilitates the automation of the bifunctional antibody preparation and the rapid optimization of reaction conditions.

Animals↗
PubMed1978

A possible combination of hypoxic cell sensitizer with an oxic protector: implications for radiotherapy.

This paper discusses the results of experiments using γ-rays and a hypoxic sensitizer metronidazole (MET) and also a well-known protector, mercaptoethylamine (MEA), individually and in combination, on the survival of the yeast S. cerevisiae BZ 34. MET (5mM) gave a hypoxic enhancement ratio (ER) of 1·3. MEA (5mM, 10mM) gave a dose-modifying factor (DMF) of 1·9 and 2·3 respectively for euoxic cells. However, the DMFs for hypoxic cells were 1·0 and 1·1 for 5 and 10mM concentrations of MEA. A combination of 5mM MEA and 5mM MET gave a DMF of 2·0 for euoxic cells and the ER remained at 1·3 for hypoxic cells. The "effective" oxygen enhancement ratios were 2·3 and 1·7 for the control and the sensitizer respectively. In the combination this value was equal to or even slightly less than 1. All DMF, ER and OER values were derived from D(0) values of the survival curves. The values based on 10% survival are almost equal to those derived from D(0) values. All the survival curves gave the same extrapolation number, showing that the chemicals individually or in combination were truly dose-modifying.These results indicate that protectors such as MEA could be preferentially protecting euoxic cells, and that combining such "oxic protectors" with a hypoxic sensitizer could result in protecting euoxic cells while the sensitization of hypoxic cells was not much reduced. The implications of our results for radiotherapy are discussed. It appears that the use of nontoxic oxic protectors may be a useful adjuvant in overcoming the hypoxic-cell problem in radiotherapy.

Dose-Response Relationship, Drug↗