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PubMed2006

Palatability of macroalgae that use different types of chemical defenses.

This study compared algal palatability and chemical defenses from subtropical green algae that may use different types of defense systems that deter feeding by the rock-boring sea urchin Echinometra lucunter. The potential defense systems present include (1) the terpenoid caulerpenyne and its activated products from Caulerpa spp., and (2) dimethylsulfoniopropionate (DMSP)-related defenses in Ulva spp. Secondary metabolites from these chemical groups have been shown to deter feeding by various marine herbivores, including tropical and temperate sea urchins. Live algal multiple-choice feeding assays and assays incorporating algal extracts or isolated metabolites into an artificial diet were conducted. Several green algae, including Ulva lactuca, Caulerpa prolifera, and Cladophora sp., were unpalatable. Nonpolar extracts from U. lactuca deterred feeding, whereas nonpolar extracts from C. prolifera had no effect on feeding. Polar extracts from both species stimulated feeding. Caulerpenyne deterred feeding at approximately 4% dry mass; however, dimethyl sulfide and acrylic acid had no effect at natural and elevated concentrations. E. lucunter is more tolerant than other sea urchins to DMSP-related defenses and less tolerant to caulerpenyne than many reef fish. Understanding the chemical defenses of the algae tested in this study is important because they, and related species, frequently are invasive or form blooms, and can significantly modify marine ecosystems.

Animals↗
PubMed1992

The use of a spectrophotometric assay to study the interaction of S-adenosylmethionine synthetase with methionine analogues.

We have developed a continuous spectrophotometric assay for S-adenosylmethionine synthetase and, using this assay, have examined the interaction of five potential inhibitors with the E. coli enzyme. S-Vinylhomocysteine and S-allylhomocysteine were found to be substrates, while S-(methanethio)cysteine and S-(methanethio)homocysteine were found to be competitive inhibitors. S-Cyanohomocysteine is neither a substrate nor an inhibitor.

Bacterial Proteins↗
PubMed1984

The role of tryptophan residues in heparin-antithrombin interactions.

A single tryptophan residue on antithrombin has been modified with dimethyl-(2-hydroxy-5-nitrobenzyl)sulfonium bromide. This alteration led to a 500-fold reduction in the heparin-dependent acceleration of thrombin-modified antithrombin interactions, as well as a 10-fold decrease in the avidity of the modified protease inhibitor for mucopolysaccharide. Preincubation of antithrombin with the octasaccharide binding domain of heparin prior to treatment with dimethyl-(2-hydroxy-5-nitrobenzyl) sulfonium bromide was able to suppress modification of the critical tryptophan and preserve the functional capacities of the protease inhibitor. Fluorescence quenching experiments indicated that the modifiable tryptophan groups of antithrombin were exposed to the solvent environment. Based upon these data, it was proposed that the loss of "heparin cofactor" activity of antithrombin must be predominantly due to an inability of the modified protease inhibitor to undergo a conformational transition required for mucopolysaccharide-dependent "activation" of the macromolecule.

Antithrombins↗
PubMed1979

Structure of 2-hydroxy-5-nitrobenzylated carboxypeptidase A.

Bovine pancreatic carboxypeptidase A (EC 3.4.12.2) was treated with dimethyl (2-hydroxy-5-nitrobenzyl)sulfonium chloride at pH 7.5, resulting in a preparation which consisted primarily of a monohydroxynitrobenzylated derivative of the enzyme. Samples of the hydroxynitrobenzylated enzyme were subjected to tryptic digestion and to cyanogen bromide cleavage, and resulting peptides were isolated chromatographically. One tryptic hydroxynitrobenzyl-containing peptide was isolated; its amino acid composition was that of the N-terminal tryptic segment of carboxypeptidase Agamma (residues 8--35). Likewise, CNBr cleavage of the hydroxynitrobenzylated enzyme revealed that the hydroxynitrobenzyl group resided in the N-terminal fragment, FN (residues 8--22). Neither of these hydroxynitrobenzylated peptides contains Trp, the amino acid residue which is characteristically the site of hydroxynitrobenzylation in proteins, and each was found to contain approximately one less Asx than the corresponding native peptide. Both dansylation and automated Edman degradation procedures revealed that the N-terminal Asn of carboxypeptidase Agamma had been modified by hydroxynitrobenzylation of the enzyme. Thus the sulfonium salt reacts with carboxypeptidase A in the same manner as that established earlier for 2-hydroxy-5-nitrobenzyl bromide (Radhakrishnan, T.M., Bradshaw, R.A., Deranleau, D.A. and Neurath, H. (1970) FEBS Lett. 7, 72--76). Such reactivity of the alpha-amino group presumably reflects its unique location with respect to Trp residues in the tertiary structure of the enzyme.

Amino Acid Sequence↗
PubMed1984

Stereochemical course of the biosynthesis of 1-aminocyclopropane-1-carboxylic acid. I. Role of the asymmetric sulfonium pole and the alpha-amino acid center.

The substrate stereospecificity of 1- aminocyclopropane -1-carboxylic acid synthase, a pyridoxal phosphate-containing enzyme, from the pericarp tissue of Lycopersicon esculentum (tomatoes) was studied using the various stereoisomers of S-adenosylmethionine (AdoMet) at both the sulfonium pole and the amino acid center. The data indicate that only the naturally occurring isomer (-)Ado-L-Met acts as substrate (Km = 20 +/- 5 microM). Both (+/-)Ado-D-Met and (+)Ado-L-Met were inactive as substrates. The (+)Ado-L-Met (Ki = 15 +/- 5 microM) was found to be a potent inhibitor of ACC synthase whereas (+/-)Ado-D-Met (Ki = 70 +/- 20 microM) was less active as an inhibitor. This active isomer has the (S) configuration at both the sulfur and the alpha-carbon of the amino acid portion of AdoMet.

Amino Acids↗
PubMed1989

Rapid oxidative-elimination of the terminal base from model deoxynucleotide esters.

The 5'-isopropyl esters of 2'-deoxycytidylate, 2'-deoxyadenylate, 2'-deoxyguanylate and 2'-deoxythymidylate were synthesized and used as model substrates to demonstrate that the 3'-terminal deoxynucleoside can be rapidly removed by combined 3'-hydroxyl oxidation and beta-elimination. Trifluoroacetyloxy-dimethylsulfonium ion oxidation of the free 3'-hydroxyl group gave almost 80% yields of the free purine and pyrimidine bases in less than 5 minutes reaction at -80 degrees C.

Acetic Anhydrides↗
PubMed1992

Temperature- and concentration-dependence of compatibility of the organic osmolyte beta-dimethylsulfoniopropionate.

The effects of the organic osmolyte beta-dimethylsulfoniopropionate (DMSP) on the structural stability of three model proteins were examined to determine whether DMSP, like the structurally similar solute dimethyl sulfoxide (DMSO), is compatible with native protein structure at low, but not elevated, temperatures. DMSP stabilized phosphofructokinase under conditions of cold-induced denaturation. Thus, DMSP, like DMSO, may be an effective protein cryoprotectant. However, DMSP was not an effective stabilizer of protein structure under conditions of heat denaturation. Whereas low (0.2 M) concentrations of DMSP stabilized lactate dehydrogenase against inactivation at 50 degrees C, higher DMSP concentrations were ineffective. DMSP favored the denaturation of glutamate dehydrogenase at all DMSP concentrations tested. DMSP may be a compatible osmotic solute only under conditions of moderate temperature and low, yet physiological, concentrations. The mechanistic basis of DMSP's temperature- and concentration-dependent effects and the possible roles played by adaptation temperature and severity of osmotic stress in the evolutionary selection of organic osmolytes are discussed.

Dimethyl Sulfoxide↗
PubMed1994

Suppressive effects of IPD-1151T (suplatast-tosilate) on induction of mast cells from normal mouse splenocytes.

The influence of IPD-1151T (suplatast-tosilate) on murine mast cell induction was examined by in vitro cell culture. Splenocytes from BALB/c mice suspended in RPMI-1640 medium supplemented with interleukin-3 were cultured in the presence or absence of IPD-1151T. Half of the total volume of the medium was changed every 4-5 days. The number of mast cells increased with culture time and reached a peak on the 16th day when the cells were cultured without IPD-1151T. However, the growth of mast cells from the splenocyte culture was dose dependently inhibited by IPD-1151T. Furthermore, IPD-1151T inhibited the proliferation of mast cell progenitor cells, IC-2, but not that of splenocytes or mature mast cells.

Animals↗
PubMed1995

Down-regulation of Th2 cell-mediated murine peritoneal eosinophilia by antiallergic agents.

Local eosinophilia has been linked to the pathogenesis of the inflammatory aspect of allergic diseases. The present study found that co-injection of D10G4.1 (D10) cells, a murine Th2 clone, with conalbumin (CA) into the peritoneal cavity of AKR/J mice increased the number of peritoneal eosinophils. The accumulation of eosinophils reached a maximum level at 24 to 48 hr and was accompanied by a marked increase in the number of neutrophils and a minor increase in the number of mononuclear cells. D10-induced peritoneal eosinophilia was suppressed by administration of either anti-IL-4 and anti-IL-5 monoclonal antibodies in an additive manner or by cyclosporin A (CsA). Interestingly, suplatast tosilate (IPD-1151T), known to be antiallergic agent capable of suppressing IgE synthesis and chemical mediator release, but not disodium cromoglycate, selectively suppressed eosinophil accumulation. Taken together with the observation that CsA and IPD-1151T suppressed IL-4 and IL-5 production by CA-stimulated D10 cells in vitro, the present results strongly suggest that agents capable of down-regulating Th2 cell cytokine production may attenuate allergic inflammation by impairing the recruitment of eosinophils that is mediated by Th2 cells.

Animals↗
PubMed1984

Conformational integrity of human alpha-thrombin.

It is known that storage at pH 6 stabilizes thrombin against inactivation. In order to determine whether structural changes accompany this stabilization, the conformation of human alpha-thrombin at pH 6.0 and 7.5 was investigated by chemical modification, difference spectroscopy, circular dichrosim, and thermal stability. It was shown that the CD spectra at the 230-200 nm peptide transition were indistinguishable at the two pH values, indicating no differences in the secondary structure as also indicated by the thermal stability of the enzyme at pH 6.0, 7.4 and 8.3. However, differences were observed in the 300-250 nm aromatic transition suggesting some changes in the microenvironment of the aromatic chromophores. Solvent perturbation in 20% ethylene glycol and 20% dimethylsulfoxide showed that at pH 7.5, 4.3 +/- 0.3 tryptophan and 8.6 +/- 0.4 tyrosine residues were exposed and accessible to the solvent whereas at pH 6.0 these values were 3.6 +/- 0.1 tryptophan and 7.8 +/- 0.4 tyrosine residues. At pH 7.5, 6.0 +/- 0.5 tryptophan residues were found reactive toward dimethyl-(2-hydroxy-5-nitrobenzyl)sulfonium bromide while 2.5 +/- 0.3 were found reactive at pH 6.0. Accompanying these structural changes were ultraviolet absorption and CD spectral changes with transition midpoints at pH 6.45 characteristic of histidine ionization. These spectral changes were lost when alpha-thrombin was modified by diethylpyrocarbonate but not by N-alpha-tosyl-L-Lysinechloro-methyl ketone. It is concluded that a second histidine residue, not the active site His-43, is associated with the pH dependent conformational changes at pH 6.0. The ionization of this histidine residue and the accompanying conformational changes could explain the reduced catalytic efficiency and stability of alpha-thrombin at pH 6.

Circular Dichroism↗
PubMed1996

Binding of 2-hydroxy-5-nitrobenzyl alcohol to rat alpha class glutathione S-transferases; evidence for binding at tryptophan 21.

2-Hydroxy-5-nitrobenzyl alcohol (HNB) was prepared from dimethyl(2-hydroxyl-5-nitrobenzyl)sulfonium bromide (HNBB). HNB binds to glutathione S-transferases (GSTs) 1-2 and 2-2 with moderate affinity at a site separate from 1-anilino-8-naphthalenesulfonate (ANS). Intrinsic fluorescence due to Trp-21 is strongly quenched by HNB binding but there is no effect on catalytic activity. There appear to be two HNB binding sites per dimer in each GST isoenzyme. We suggest that HNB binds directly at Trp-21 of each subunit and that previously reported quenching of intrinsic fluorescence in these proteins upon ligand binding may be due to indirect structural effects rather than direct binding at this residue.

Anilino Naphthalenesulfonates↗
PubMed2004

Alkylation of protein disulfide isomerase by the episulfonium ion derived from the glutathione conjugate of 1,2-dichloroethane and mass spectrometric characterization of the adducts.

The reactivity of the episulfonium ion derived from S-(2-chloroethyl)glutathione (CEG), the glutathione conjugate of 1,2-dichloroethane, with the catalytic sites of protein disulfide isomerase (PDI) was investigated. The two cysteine residues of the two active sites of PDI are expected to be the major targets of alkylation. PDI was incubated with equimolar to 100-fold excess CEG. The activity of PDI was irreversibly inhibited with a concurrent loss of two thiols; however, PDI oxidative refolding activity was not completely inhibited. With mass spectrometry, sequencing PDI identified one alkylation event on each of the N-terminal cysteine residues in the two active site peptides. PDI appears robust and able to maintain some activity by steric constraint. We have established that the episulfonium ion of CEG can adduct PDI and may have important toxicologic significance for 1,2-dichloroethane toxicity.

Alkylation↗
PubMed2006

Adsorption behaviors of L-arginine from aqueous solutions on a spherical cellulose adsorbent containing the sulfonic group.

An investigation was conducted regarding the adsorption and desorption of L-arginine from aqueous solutions with a new spherical cellulose adsorbent containing the sulfonic group. The adsorption of L-arginine on the adsorbent was time, pH, initial concentration of L-arginine and temperature dependent. The adsorption process followed the Langmuir adsorption isotherm, and was endothermic (DeltaH =24.66 KJ/mol). Almost 100% L-arginine adsorbed on the adsorbent could be recovered with a 2.0 mol/L NH4OH or 2.0 mol/L NH4Cl aqueous solution. After 25 and 40 cycles of adsorption and desorption, the decrease in adsorption capacity reached to 4.9% and 20.3%, respectively.

Adsorption↗
PubMed2005

Synthesis of C-5-thioglycopyranosides and their sulfonium derivatives from 1-C-(2'-oxoalkyl)-5-S-acetylglycofuranosides.

1-C-(2'-oxoalkyl)-5-S-acetylglycofuranosides of L-arabinose, D-ribose, and D-xylose were converted to 1-C-(2'-oxoalkyl)-5-thioglycopyranosides by base treatment. The transformation was achieved through beta-elimination to an acyclic alpha,beta-conjugated aldehyde (ketone or ester), followed by an intramolecular hetero-Michael addition by the 5-thiol group. The cycloaddition was highly stereoselective in favor of an equatorial 1-C-substitution. The resultant C-5-thioglycopyranosides were further converted to the sulfonium salts by treatment with cyclic sulfate and methyl iodide. Two sulfonium isomers were obtained due to the presence of both S-axial and S-equatorial substitutions. We observed that the chemical shifts of both C-1 and C-5 in the S-axial substituted sulfonium sugars are always shifted up-field (5-10 ppm) in comparison to those in the S-equatorial substitutions (deltaC 49-53 ppm vs 42-45 ppm at C-1 and 37-42 ppm vs 32-35 ppm at C-5), which provides an easy way for determination of the stereochemistry.

Furans↗
PubMed2006

Facile synthesis of sulfonium ion derivatives of 1,5-anhydro-5-thio-L-fucitol as potential alpha-L-fucosidase inhibitors.

Five sulfonium ion derivatives with 1,5-anhydro-5-thio-L-fucitol as a core structure were efficiently synthesized as potential alpha-L-fucosidase inhibitors. The key unit, the tri-O-benzyl derivative of L-fucitol, was readily synthesized from methyl alpha-D-mannopyranoside. Alkylation with methyl iodide or 5-methoxycarbonyl-1-pentyl iodide in acetonitrile containing AgBF4 afforded the corresponding alkylated sulfonium tetrafluoroborates. Alternatively, ring opening of three 1,3-cyclic sulfates in 1,1,1,3,3,3-hexafluoro-2-propanol (HFIP) containing K2CO3 afforded the corresponding zwitterionic sulfonium sulfates.

Enzyme Inhibitors↗
PubMed2004

Trimethylsulfonium hydroxide as derivatization reagent for the chemical investigation of drying oils in works of art by gas chromatography.

A procedure for the determination of fatty acids (FA) and glycerol in oils has been developed. The method includes a derivatization step of the FAs into their methyl esters or a transesterification of the triacylglycerols with trimethylsulfonium hydroxide (TMSH), respectively. The analysis is carried out by gas chromatography with parallel flame ionization and mass spectrometric detection. The parameters involved in the transesterification reaction were optimized. Only the stoichiometric ratio of TMSH:total FA amount showed a significant influence on the reaction yield. Relative standard deviations for 10 replicates were below 3% for all FAs studied and their linearity range was 0.5-50 mmol/L, when using heptadecanoic acid as an internal standard. The final procedure was rapid and required little sample handling. It was then tested on fresh oil samples and presented satisfying results, in agreement with previous works.

Art↗
PubMed2006

7. Control of allergic airway inflammation through immunomodulation.

Among the asthma clinical trials published over the last several years, a unique subset has focused on novel means for inhibiting the airway inflammation that is believed to cause airway obstruction in many patients. Such interventions, broadly considered here as immune-modifying or immunomodulatory therapies, include several new drugs (omalizumab, suplatast tosilate, anti-cytokine antibodies, soluble receptors, and recombinant cytokines) and bacterial extracts. In this chapter we review the major findings with these clinical trials and indicate which have changed the management of asthma, which have not, and those that deserve further study.

Anti-Allergic Agents↗