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PubMed2004

Anionic O --> alpha- and beta-vinyl carbamoyl translocation of 2-(O-carbamoyl) stilbenes.

[reaction: see text] New anionic oxygen to alpha- and beta-vinyl carbamoyl migration reactions, 17a and 26a-c --> 18 and 30a-c, proceed under LDA-mediated conditions leading stereoselectively to highly substituted stilbenes bearing electron-donating and -withdrawing substituents. Compounds 17a and 26a-c are prepared by combination of efficient, directed ortho metalation, Sonogashira, and Suzuki-Miyaura cross-coupling procedures.

Journal Article↗
PubMed2003

Water-soluble stilbene dendrimers.

The third generation of novel photo-responsive water-soluble stilbene dendrimer (trans- and cis-G3 WSD) undergoes unusual one-way trans-to-cis isomerization to give 100% of cis isomer at the photostationary state on UV irradiation in water.

Journal Article↗
PubMed2006

Stereoselective stilbene epoxidation over supported gold-based catalysts.

The gold reference catalyst Au/TiO(2) exhibits high activity in the stereoselective epoxidation of trans-stilbene in methylcyclohexane in the presence of 5 mol% TBHP, by taking part in a chain reaction involving the activation of molecular oxygen by a radical produced from methylcyclohexane.

Journal Article↗
PubMed1990

Identification and characterization of the major stilbene-disulphonate- and concanavalin A-binding protein of the porcine renal brush-border membrane as aminopeptidase N.

A 130 kDa glycoprotein (GP 130) was purified from porcine renal brush-border membranes by affinity chromatography using immobilized 4-acetamido-4'-isothiocyanostilbene-2,2'-disulphonate (SITS)- and concanavalin A-Sepharose. GP 130 was the major concanavalin A-binding protein in porcine renal brush-border membranes and also bound Ricinus communis (castor-bean) and wheat-germ agglutinins. Endo-beta-N-acetylglucosaminidase F reduced the molecular mass of GP 130 by 20 kDa as determined by SDS/PAGE, whereas endo-beta-N-acetylglucosaminidase H reduced the molecular mass by 5 kDa, showing that GP 130 contained both complex and high-mannose carbohydrate structures. Western-blot analyses using an antibody raised against GP 130 showed that it was localized to the brush-border membrane fraction and was present in a membrane fraction of the pig kidney cell line LLC-PK1. The N-terminal sequence and amino acid composition of GP 130 showed that GP 130 is similar to rat kidney zinc peptidase and human intestinal aminopeptidase N. GP 130 had aminopeptidase N enzymic activity and was inhibited by bestatin (Ki = 36 microM), 1,10-phenanthroline (Ki 30 microM), Zn2+ (Ki 26 microM), Cu2+ (Ki 260 microM), pre-incubation with EDTA and by a polyclonal antibody against GP 130. Bicarbonate and iodide blocked the binding of GP 130 to the SITS-affinity resin, showing that GP 130 has an anion-binding site. Neither these anions nor stilbene disulphonates affected the aminopeptidase N activity of GP 130.

4,4'-Diisothiocyanostilbene-2,2'-Disulfonic Acid↗
PubMed2006

Structure-property relationships for three-photon absorption in stilbene-based dipolar and quadrupolar chromophores.

Based on essential-state models for three-photon absorption (3PA), we have investigated the structure-property relationships for stilbene-based dipolar and quadrupolar chromophores. The emphasis lies on the evolution of the 3PA cross section with the degree of ground-state polarization. For dipolar systems, we find a dominant role played by Deltamu, which expresses the change in dipole moment between the ground state and the 3PA active excited state. Thus, the strategies usually applied to maximize the second-order polarizability beta are also applicable to optimize the 3PA cross section. For quadrupolar systems, the 3PA response is dominated by contributions from channels including various low-lying two-photon allowed states, which limits the applicability of essential-state models. Optimization strategies can be proposed but vary for different ranges of ground-state polarization.

Journal Article↗
PubMed1998

The effect of 4,4'-diisothiocyanato-stilbene-2,2'-disulfonate on CO2 permeability of the red blood cell membrane.

It has long been assumed that the red cell membrane is highly permeable to gases because the molecules of gases are small, uncharged, and soluble in lipids, such as those of a bilayer. The disappearance of 12C18O16O from a red cell suspension as the 18O exchanges between labeled CO2 + HCO3- and unlabeled HOH provides a measure of the carbonic anhydrase (CA) activity (acceleration, or A) inside the cell and of the membrane self-exchange permeability to HCO3- (Pm,HCO-3). To test this technique, we added sufficient 4, 4'-diisothiocyanato-stilbene-2,2'-disulfonate (DIDS) to inhibit all the HCO3-/Cl- transport protein (Band III or capnophorin) in a red cell suspension. We found that DIDS reduced Pm,HCO-3 as expected, but also appeared to reduce intracellular A, although separate experiments showed it has no effect on CA activity in homogenous solution. A decrease in Pm,CO2 would explain this finding. With a more advanced computational model, which solves for CA activity and membrane permeabilities to both CO2 and HCO3-, we found that DIDS inhibited both Pm,HCO-3 and Pm,CO2, whereas intracellular CA activity remained unchanged. The mechanism by which DIDS reduces CO2 permeability may not be through an action on the lipid bilayer itself, but rather on a membrane transport protein, implying that this is a normal route for at least part of red cell CO2 exchange.

4,4'-Diisothiocyanostilbene-2,2'-Disulfonic Acid↗
PubMed1996

Evaluation of the disodium salt of 4,4'-diamino-2,2'-stilbene disulfonic acid for estrogenic activity.

4,4'-Diamino-2,2'-stilbene disulfonic acid (DAS), a key intermediate in the synthesis of dyes and fluorescent whitening agents, has been purported to have weak estrogenic properties based on apparent structural similarity with diethylstibestrol (DES) and unsubstantiated reports of male reproductive dysfunction in an industrial setting. In weanling rats, high doses of DAS (300 mg/kg ip; 1000-3000 mg/kg oral) have been associated with modest increases in the uterus/body weight ratio (Smith & Quinn, 1992). In order to more directly and definitively determine if DAS possesses estrogenic activity, in vitro studies were conducted to establish its relative binding affinity to the human estrogen receptor (ER) in MCF-7 cells, a well-characterized breast cancer cell line. At concentrations approaching its solubility limit (10(-4) M), DAS failed to display [3H]-17beta-estradiol (E2) from the ER. In contrast, DES and E2 demonstrated characteristic competitive binding curves (50% displacement of 3H-E2 at 3.33 x 10(-9) and 1.33 x 10(-8) M, respectively). Parallel in vivo comparisons of DAS (10 or 30 mg/animal) and DES (1 or 3 microgram/animal) were also conducted to assess uterotropic effects. After three daily subcutaneous injections, DAS did not induce uterine weight gain. In contrast, DES consistently and markedly increased uterine weight and induced uterine water imbibition, with the latter effect being absent in DAS-treated rats. Under these experimental conditions, DAS was shown to possess negligible, if any, estrogenic activity, despite apparent structural similarity with known estrogens.

4-Acetamido-4'-isothiocyanatostilbene-2,2'-disulfo↗
PubMed1995

Mitochondrial enzyme-catalyzed oxidation and reduction reactions of stilbene estrogen.

We have demonstrated for the first time that mitoplasts (i.e. mitochondria without outer membrane) were able to convert stilbene estrogen (diethylstilbestrol, DES) to reactive metabolites, which covalently bind to mitochondrial (mt)DNA. Depending on the cofactor used, mitochondrial enzymes catalyzed the oxidation and/or reduction of DES. DES was oxidized to DES quinone by peroxide-supported mitochondrial enzyme. A Lineweaver-Burk plot of rate of formation of DES quinone at various substrate concentrations yielded a Km of 33 microM and Vmax of 39 nmol/mg protein/min. The oxidation of DES to DES quinone by mitochondria was drastically decreased by known inhibitors of cytochrome P450. DES quinone was reduced to DES by mitoplasts in the presence of NADH. The Km and Vmax for the DES quinone reduction in the absence of mitoplasts and NADH were 3.2 microM and 5.6 nmol respectively. The reduction of DES quinone to DES by mitoplasts was significantly inhibited by inhibitors of cytochrome b5 reductase and diaphorase. DES quinone was also reduced to DES by pure diaphorase, a mitochondrial reducing enzyme, in the presence of NADH. The Km and Vmax for the DES quinone reduction by diaphorase were 9.0 microM and 4.3 nmol respectively. Under reaction conditions similar to oxidation of DES to DES quinone by mitoplasts, it was observed that mitochondrial metabolic products of DES were able to covalently bind to mtDNA. These data provide direct evidence of mitochondrial enzyme-catalyzed oxidation and reduction reactions of DES. In the cell, activation of DES in the mitochondria (the organelle in which mtDNA synthesis, mtDNA repair and transcription systems are localized) is of utmost importance, because an analogous in vivo mitochondrial metabolism of DES through covalent modifications in mitochondrial genome may produce instability in the mitochondrial genome of the cells. These modifications may in turn play a role in the development of DES-induced hepatocarcinogenicity.

Animals↗
PubMed1995

Organ-specific inhibition of types I, II and III transcriptional activity in hamsters exposed to stilbene estrogen.

We have previously shown that stilbene estrogen (diethyl-stilbestrol, DES) covalently binds to nonhistone nuclear proteins both in vivo and in vitro. In this study, we demonstrate the differential effects of DES exposure on in organelle transcriptional activity in nuclei isolated from kidney (target organ of cancer) and liver (non target organ) of hamsters. Kidney RNA polymerase (RNA pol) I and III activities were significantly inhibited by 50% at days 8 and 15 of DES exposure compared to that of controls. Liver RNA pol I and III activities were only modestly inhibited (17 and 22%, respectively) by 2 and 8 days of DES exposure, respectively. However, longer exposure of DES to animals did not produce any significant effects on RNA pol I activity. The activity of RNA pol II was affected by DES exposure in both liver and kidney. DES treatment for two days resulted in an increase in RNA pol II activity in kidney. The enhanced enzyme activity was decreased to 50% of that of the control at 15 days of DES treatment. Unlike RNA pol I and III, RNA pol II activity in the liver was inhibited in a time-dependent fashion in response to DES exposure. To understand the mechanism of transcriptional inhibition by DES, we analyzed the effect of DES exposure on the expression of hepatic RNA pol II at both mRNA and protein levels and also phosphorylation of hepatic RNA pol II. The total amount of transcripts or protein contents of hepatic RNA pol II was not altered in response to DES exposure to hamster for 15 days. Total phosphorylation of hepatic RNA pol II was also not affected by 15 days DES exposure. However tyrosine phosphorylation of hepatic RNA pol II was lowered by 2.8-fold compared to that of control enzyme in response to DES exposure for 15 days. An inhibitory effect of DES on the total RNA polymerase activity in both kidney and liver nuclei in the presence of endogenous template was observed in vitro. No inhibitory effect of DES was observed in vitro on transcriptional activity in the presence of exogenously added DNA template. Based on these data it appears that the in vivo inhibition of transcription by DES may be due to alterations in chromatin template or the level of transcription regulating proteins and not due to decreased availability of the chromatin template and/or RNA polymerase. Whether DES related inhibition of transcriptional activity plays a role in the development of kidney cancer is not clear.

Animals↗
PubMed1987

Site-specific covalent binding of stilbene-type and steroidal estrogens to tubulin following metabolic activation in vitro.

Both the steroidal estrogen, 2-hydroxy estradiol, and the stilbene-type estrogen, diethylstilbestrol, bind covalently and selectively to the C-terminal domain of beta-tubulin after peroxidative activation in vitro. The binding probably has to be attributed to quinonoid metabolites, as estrogens such as estradiol and hexestrol, which are unable to form quinones under these conditions, fail to bind. Albumin is not simultaneously modified, demonstrating the selectivity of the binding. The observed protein binding is discussed with respect to estrogen-induced aneuploidy and neoplastic cell transformation.

Binding Sites↗
PubMed2003

Diallyl sulfide inhibits the oxidation and reduction reactions of stilbene estrogens catalyzed by microsomes, mitochondria and nuclei isolated from breast tissue of female ACI rats.

Previously, it has been demonstrated that microsomal, mitochondrial and nuclear enzymes isolated from the liver of male Sprague-Dawley rats catalyzed the oxidation of diethylstilbestrol (DES) to DES quinone. In the present study we have shown that diallyl sulfide (DAS) inhibits the oxidation of DES to DES quinone in all three subcellular fractions (microsomes, mitochondria and nuclei) isolated from breast tissue of female ACI rats. UV analysis of mitochondrial and microsomal fractions revealed that DAS decreased the rate of DES oxidation to DES quinone and DAS also decreased the rate in which DES quinone was reduced to DES. Lineweaver-Burk plots of the rate of DES quinone formation at various DES and DAS concentrations demonstrated that DAS inhibited the oxidation of DES and the reduction of DES quinone in a non-competitive fashion. In both microsomal and mitochondrial oxidation reactions the K(m) remained constant whereas the V(max) decreased with increasing DAS (0, 186 and 373 microM) concentrations (microsomes K(m) = 80 microM; V(max) = 5.56, 4.16 and 3.33 nmol/mg protein/min; mitochondria K(m) = 35.7 microM; V(max) = 3.45, 2.44 and 1.82 nmol/mg protein/min). Results were similar for reduction reactions. HPLC analysis revealed that a concentration of 186 microM DAS inhibited the mitochondrial, microsomal and nuclear oxidation by 27, 35 and 40%, respectively. A concentration of 373 microM DAS inhibited the mitochondrial, microsomal and nuclear oxidation by 50, 52 and 60% respectively. The data provide direct evidence that the breast tissue contain the metabolic machinery required to oxidize DES to reactive intermediates that may lead to genetic instability and cancer. This inhibition may play a role in the chemoprevention of stilbene estrogen-induced breast cancer.

Allyl Compounds↗
PubMed2006

Molecular basis of ergosterol-induced protection of grape against botrytis cinerea: induction of type I LTP promoter activity, WRKY, and stilbene synthase gene expression.

Type I lipid transfer proteins (LTPs) are basic, 9-kDa cystein-rich proteins believed to be involved in plant defense mechanisms. A 2,100-bp fragment containing the coding region of Vitis vinifera lipid transfer protein 1 (VvLTP1) and 1,420-bp of its promoter region was isolated by screening a grape genomic library. In silico analysis revealed several putative, defense-related, cis-regulatory elements such as W- and MYB-boxes, involved in the binding of WRKY and MYB transcription factors, respectively. The 5'-truncated versions of the VvLTP1 promoter were generated, cloned in front of the beta-glucuronidase (GUS) reporter gene, and introduced in tobacco plants and grapevine cell suspensions using Agrobacterium spp. Single MYB- and the W-boxes identified on the 0.250-kbp fragment were sufficient to induce GUS activity in transgenic tobacco plants after transient expression of MYB and WRKY. Ergosterol, a nonspecific fungal elicitor, induced GUS activity in transgenic grapevine cell suspensions transformed with the 1,420- and 750-bp promoter containing a palindromic arrangement of two W-boxes but not the 650- or 250-bp fragment, where only one W-box was present. Moreover, ergosterol triggered WRKY, VvLTP1, and stilbene synthase gene expression in grape plantlets and enhanced protection against Botrytis cinerea. The molecular basis of ergosterol-induced protection is discussed.

Acyltransferases↗
PubMed1982

Plasmalemma Chloride Transport in Chara corallina: Inhibition by 4,4'-Diisothiocyano-2,2'-Disulfonic Acid Stilbene.

Chloride transport, presumably via a Cl(-)-2H(+) co-transport system, was investigated in Chara corallina. At pH 6.5, the control influx (3.1 picomoles per centimeter(2) per second) was stimulated 4-fold by an 18-hour Cl(-) starvation. The stimulated influx was inhibited to 4.7 picomoles per centimeter(2) per second after a 60-minute pre-exposure to 0.5 millimolar 4,4'-diisothiocyano-2,2'-disulfonic acid stilbene (DIDS). This compares with a nonsignificant inhibition of the control under similar conditions. At 2 millimolar DIDS, both stimulated and control influx were inhibited to values of 1.1 and 2.2 picomoles per centimeter(2) per second, respectively; in all cases, DIDS inhibition was reversible. Over the pH range 4.8 to 8.5, the control and DIDS-inhibited influx showed only slight pH sensitivity; in contrast, the stimulated flux was strongly pH dependent (pH 6.5 optimum). Inasmuch as changes in pH alter membrane potential, N-ethylmaleimide was used to depolarize the membrane; this had no effect on Cl(-) influx. A transient depolarization of the membrane (about 20 millivolts) was observed on restoration of Cl(-) to starved cells. The membrane also depolarized transiently when starved cells were exposed to 0.5 millimolar DIDS, but the depolarization associated with Cl(-) restoration was inhibited by a 40-minute pretreatment with DIDS. Exposure of control cells to DIDS caused only a small hyperpolarization (about 7 millivolts). DIDS may have blocked Cl(-) influx by inhibiting the putative plasmalemma H(+)-translocating ATPase. Histochemical studies on intact cells revealed no observable effect of DIDS on plasmalemma ATPase activity. However, DIDS application after fixation resulted in complete inhibition of ATPase activity.The differential sensitivity of the stimulated and control flux to inhibition by DIDS may reflect an alteration of transport upon stimulation, but could also result from differences in pretreatment. The stimulated cells were pretreated with DIDS in the absence of Cl(-), in contrast to the presence of Cl(-) during pretreatment of controls. The differential effect could result from competition between Cl(-) and DIDS for a common binding site. Our histochemical ATPase results indicate that Cl(-) transport and membrane ATPase are separate systems, and the latter is only inhibited by DIDS from the inside of the cell.

Journal Article↗
PubMed1984

Anion-Sensitive, H-Pumping ATPase of Oat Roots : Direct Effects of Cl, NO(3), and a Disulfonic Stilbene.

To understand the mechanism and molecular properties of the tonoplast-type H(+)-translocating ATPase, we have studied the effect of Cl(-), NO(3) (-), and 4,4'-diisothiocyano-2,2'-stilbene disulfonic acid (DIDS) on the activity of the electrogenic H(+)-ATPase associated with low-density microsomal vesicles from oat roots (Avena sativa cv Lang). The H(+)-pumping ATPase generates a membrane potential (Deltapsi) and a pH gradient (DeltapH) that make up two interconvertible components of the proton electrochemical gradient (Deltamuh(+)). A permeant anion (e.g. Cl(-)), unlike an impermeant anion (e.g. iminodiacetate), dissipated the membrane potential ([(14)C]thiocyanate distribution) and stimulated formation of a pH gradient ([(14)C]methylamine distribution). However, Cl(-)-stimulated ATPase activity was about 75% caused by a direct stimulation of the ATPase by Cl(-) independent of the proton electrochemical gradient. Unlike the plasma membrane H(+)-ATPase, the Cl(-)-stimulated ATPase was inhibited by NO(3) (-) (a permeant anion) and by DIDS. In the absence of Cl(-), NO(3) (-) decreased membrane potential formation and did not stimulate pH gradient formation. The inhibition by NO(3) (-) of Cl(-)-stimulated pH gradient formation and Cl(-)-stimulated ATPase activity was noncompetitive. In the absence of Cl(-), DIDS inhibited the basal Mg,ATPase activity and membrane potential formation. DIDS also inhibited the Cl(-)-stimulated ATPase activity and pH gradient formation. Direct inhibition of the electrogenic H(+)-ATPase by NO(3) (-) or DIDS suggest that the vanadate-insensitive H(+)-pumping ATPase has anion-sensitive site(s) that regulate the catalytic and vectorial activity. Whether the anion-sensitive H(+)-ATPase has channels that conduct anions is yet to be established.

Journal Article↗
PubMed1985

Characterization of 4,4'-Diisothiocyano-2,2'-disulfonic Acid Stilbene Inhibition of 3-Phosphoglycerate-Dependent O(2) Evolution in Isolated Chloroplasts : Evidence for a Common Binding Site on the C(4) Phosphate Translocator for 3-Phosphoglycerate, Phosphoenolpyruvate, and Inorganic Phosphate.

3-Phosphoglycerate (PGA)-dependent O(2) evolution by mesophyll chloroplasts of the C(4) plant, Digitaria sanguinalis L. Scop. (crabgrass), was inhibited by micromolar levels of 4,4'-diisothiocyano-2,2'-disulfonic acid stilbene (DIDS). As little as 1.8 micromolar DIDS added to the assay medium (containing 0.7 millimolar PGA) resulted in 80 to 100% inhibition of O(2) evolution. The extent of inhibition of O(2) evolution observed was dependent on various factors including: pH, concentration of DIDS to relative chlorophyll, concentration of PGA, and the time of addition of DIDS to the chloroplasts relative to addition of PGA.Preincubation of crabgrass chloroplasts with micromolar levels of DIDS, followed by washing to remove any nonirreversibly bound DIDS, inhibited PGA-dependent O(2) evolution. Protection against this inhibition was afforded by preincubating the chloroplasts with various substrates before adding DIDS. For example, if the chloroplasts were first incubated with 8.3 millimolar PGA, phosphoenolpyruvate (PEP) or inorganic phosphate before adding 42 micromolar DIDS, the percentage of inhibition was decreased from 100% (without any substrate) to 0, 54, and 67%, respectively. 2-Phosphoglycerate caused a slight decrease in the inhibition (about 10%) and glucose-6-phosphate had no protective effect. If the chloroplasts were pretreated with DIDS initially, the inhibition could not be overcome by PGA, suggesting that DIDS acts as an irreversible inhibitor. Micromolar levels of DIDS also inhibited PGA dependent O(2) evolution by isolated chloroplasts of the C(3) plant barley. As with crabgrass, preincubation with PGA or inorganic phosphate resulted in a decrease in the DIDS inhibition, but PEP was very ineffective compared to the C(4) chloroplasts.Oxalacetate-dependent O(2) evolution and its stimulation by the uncoupler, NH(4)Cl, were unaffected by the addition of DIDS to crabgrass mesophyll chloroplasts. Furthermore, preincubation of the chloroplasts with DIDS (up to 65 micromolar) had no inhibitory effect on the extractable activity of NADP glyceraldehyde-3-P dehydrogenase and phosphoglycerate kinase. Inhibition by DIDS was interpreted to be at the substrate binding site of the phosphate translocator. The data further suggest that in C(4) crabgrass chloroplasts, PEP is transported on a carrier which also transports PGA.

Journal Article↗