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PubMed2000

In vitro antiproliferative activity of isothiocyanates and nitriles generated by myrosinase-mediated hydrolysis of glucosinolates from seeds of cruciferous vegetables.

A comparison of the effect of isothiocyanates and nitriles derived from some glucosinolates, namely, epi-progoitrin, sinalbin, glucotropaeolin, glucocheirolin, and glucoraphenin, on human erythroleukemic in vitro cultured cells was studied. Many studies have in fact evidenced that a consumption of vegetable containing glucosinolates could reduce the development of colorectal cancer. In the experimental conditions used, the production of isothiocyanates and nitriles from glucosinolates is almost quantitative as confirmed by HPLC or GC-MS analysis. The obtained results demonstrated that in general nitriles are considerably less potent than the corresponding isothiocyanates in inhibiting cancer cell growth. Particularly, the isothiocyanates inhibitory activity on K562 cells growth is higher in the case of products derived from epi-progoitrin, glucotropaeolin, glucoraphenin, and glucocheirolin; while for nitriles the higher activity in inhibiting K562 cells growth is showed by sinalbin-derived product. Considering the antiproliferative activity found for isothiocyanates and nitriles, further studies will be aimed to the possible application of glucosinolate-derived products as chemopreventive cancer agents for the reduction of colorectal cancer.

Brassicaceae↗
PubMed2001

4-(Methylthio)-3-butenyl isothiocyanate, a principal antimutagen in daikon (Raphanus sativus; Japanese white radish).

The antimutagenic activity of n-hexane extracts from eight strains of daikon (Raphanus sativus; Japanese white radish) have been examined using the UV-induced mutation assay of Escherichia coli B/r WP2. A correlation was found between the potency of antimutagenicity and the amount of 4-(methylthio)-3-butenyl isothiocyanate (MTBITC) in their n-hexane extracts. Because the pure MTBITC also showed antimutagenicity, MTBITC is presumably the active antimutagen principle in n-hexane extracts of daikon. Among the eight strains of daikon studied, Aokubi, the improved common strain in Japan, contained 71.0 micromol of MTBITC in 100 g of fresh daikon. In contrast, Karami and Momoyama, which are original wild strains, contained much more MTBITC (363.5 and 168.0 micromol/100 g, respectively). In addition, phenethyl isothiocyanate was found in a lesser amount (5-33 nmol/100 g) in eight strains of daikon, and allyl isothiocyanate and benzyl isothiocyanate were not detectable in any strains (<3 nmol/100 g). The amount of total isothiocyanate in grated daikon was 7.0 times higher than that in cut daikon measured after 30 min of cooking. Through eating habits, humans might be able to consume substantial amounts of the antimutagen MTBITC from dishes using the grated form of wild strains of daikon. Therefore, it is possible to substantially increase the intake of the antimutagenic ingredient of daikon (i.e., MTBITC) by changing food preferences and preparation procedures (i.e., using the grated form of the wild strains).

Antimutagenic Agents↗
PubMed2003

Analysis of isothiocyanate mercapturic acids in urine: a biomarker for cruciferous vegetable intake.

Cruciferous vegetables contain glucosinolates, which are degraded to isothiocyanates. These are easily absorbed, conjugated to glutathione, and excreted into the urine as their corresponding mercapturic acids. We have developed and validated a solid phase extraction-high-performance liquid chromatography-electrospray ionization mass spectrometry/mass spectrometry method for the specific analysis of individual isothiocyanate mercapturic acids in urine. The range of reliable analysis was 1.0-310 microM in urine. Urine samples fortified with three different levels of isothiocyanate mercapturic acids were measured on six different days by three independent technicians. The relative standard deviation (RSD) of repeatability was 12, 6, and 3%; the RSD of reproducibility was 19, 14, and 8%, and spike recoveries were 103, 104, and 103%, respectively, for 1.04, 10.5, and 313 microM levels. In 24 h urine collected from two volunteers after they consumed broccoli and cauliflower, clearly sulforaphane mercapturic acid (133 micromol) and allyl isothiocyanate mercapturic acid (4.7 micromol) were found. This procedure demonstrates a reliable and efficient method to study the intake and mode of action of isothiocyanates in animal studies and clinical trials.

Acetylcysteine↗
PubMed2006

Effect of isothiocyanates on nuclear accumulation of NF-kappaB, Nrf2, and thioredoxin in caco-2 cells.

Early effects (only 1 h of exposure) of three isothiocyanates (benzyl, phenylethyl, and sulforaphane) on nuclear accumulation of thioredoxin, APE/Ref-1, and transcription factors NF-kappaB and Nrf2, as well as production of reactive oxygen species (ROS) and reduced glutathione levels were examined in human adenocarcinoma Caco-2 cells. Nuclear increase of NF-kappaB, Nrf2, and thioredoxin contents was observed in all isothiocyanate-treated cells, whereas the nuclear Ref-1 and cytoplasmic Keap1 contents were not changed. Sulforaphane was the most potent inducer of Nrf2 nuclear accumulation (10 microM, 1.9-fold) and NF-kappaB nuclear accumulation at higher concentration (25 microM, 6.3-fold). In contrast, benzyl isothiocyanate induced more thioredoxin nuclear accumulation (10 microM, 2.9-fold), increased production of ROS, and gave the greatest induction of thioredoxin reductase 1 mRNA (10 microM, 10.2-fold), whereas phenylethyl isothiocyanate was more potent in the depletion of reduced glutathione levels. These results show that different individual isothiocyanates may possess some different activities in nuclear accumulation of thioredoxin, NF-kappaB, Nrf2, and production of ROS.

Caco-2 Cells↗
PubMed2003

A role for isothiocyanates in plant resistance against the specialist herbivore Pieris rapae.

We experimentally reanalyzed the classic interaction between Pieris rapae, a specialist lepidopteran herbivore, and isothiocyanates (mustard oils) that are characteristic phytochemicals of the Brassicaceae. Previous investigations have suggested that P. rapae is unaffected by isothiocyanates. Using whole plants, root extracts, and a microencapsulated formulation of allyl isothiocyanate, we now show that isothiocyanates reduce herbivore survival and growth, and increase development time, each in a dose-dependent manner. Neither the substrate allyl glucosinolate, nor myrosinase, the enzyme that results in the breakdown of glucosinolates, negatively affected P. rapae. Thus, we present strong evidence for a role for isothiocyanates in plant resistance against the specialist herbivore P. rapae.

Adaptation, Physiological↗
PubMed1987

Photoaffinity labelling of the cardiac calcium channel. (-)-[3H]azidopine labels a 165 kDa polypeptide, and evidence against a [3H]-1,4-dihydropyridine-isothiocyanate being a calcium-channel-specific affinity ligand.

The arylazide 1,4-dihydropyridine (-)-[3H]azidopine binds to a saturable population of sites in guinea-pig heart membranes with a dissociation constant (KD) of 30 +/- 7 pM and a density (Bmax.) of 670 +/- 97 fmol/mg of protein. This high-affinity binding site is assumed to reside on voltage-operated calcium channels because reversible binding is blocked stereoselectively by 1,4-dihydropyridine channel blockers and by the enantiomers of Bay K 8644. A low-affinity (KD 25 +/- 7 nM) high-capacity (Bmax. 21.6 +/- 9 pmol/mg of protein) site does not bind (-)- or (+)-Bay K 8644, but is blocked by high concentrations (greater than 500 nM) of dihydro-2,6-dimethyl-4-(2-isothiocyanatophenyl)-3,5-pyridinedicarboxy lic acid dimethyl ester (1,4-DHP-isothiocyanate) or, e.g., (+/-)-nicardipine. (-)-[3H]Azidopine was photoincorporated covalently into bands of 165 +/- 8, 39 +/- 2 and 35 +/- 3 kDa, as determined by SDS/polyacrylamide-gel electrophoresis. Labelling of the 165 kDa band is protected stereoselectively by 1,4-dihydropyridine enantiomers at low (nM) concentrations and by (-)- and (+)-Bay K 8644, whereas the lower-Mr bands are not. Thus, only the 165 kDa band is the calcium-channel-linked 1,4-dihydropyridine receptor. Photolabelling of the 39 or 35 kDa bands was only blocked by 10 microM-1,4-DHP-isothiocyanate or 50 microM-(+/-)-nicardipine but not by 10 microM-(-)-Bay K 8644. [3H]-1,4-DHP-isothiocyanate binds to guinea-pig heart membranes with a KD of 0.35 nM and dissociates with a k-1 of 0.2 min-1 at 30 degrees C. [3H]-1,4 DHP-isothiocyanate irreversibly labels bands of 39 and 35 kDa which are protected by greater than 10 microM-(+/-)-nicardipine or unlabelled ligand but not by 10 microM-(-)-Bay K 8644. Thus, [3H]-1,4-DHP-isothiocyanate is not an affinity probe for the calcium channel.

Affinity Labels↗
PubMed2004

Isothiocyanates in cancer prevention.

Isothiocyanates are sulfur-containing compounds which are largely responsible for the typical flavor of cruciferous vegetables. In animals and humans they are conjugated with glutathione; the first product of this reaction is a dithiocarbamate, which can be ultimately metabolized to the corresponding mercapturic acid, excreted in urine. Aliphatic and aromatic isothiocyanates, as well as dithiocarbamates, can react quantitatively with an excess of 1,2-benzenedithiol giving rise to a cyclic condensation product readily measured in biological fluids. The use of this assay as a biomarker of isothiocyanate or cruciferous vegetable intake can offer several advantages over food frequency questionnaires, mainly in the objectivity and accuracy of the measure and the lack of bias. Epidemiological studies on the relationship between cancer risk with isothiocyanate intake or excretion have shown inverse associations, mainly with lung cancer. The studies are also consistent in reporting a gene-environment interaction, with a stronger protective effect in persons null for the GSTM1 or GSTT1 genotype. However, further research is needed to better clarify the importance of these polymorphisms in modulating the effect of isothiocyanates in cancer development.

Animals↗
PubMed1993

Allyl isothiocyanate is selectively toxic to transformed cells of the human colorectal tumour line HT29.

Allyl isothiocyanate, a constituent of mustard and certain vegetables found in the human diet, was tested for cytotoxic and cytostatic effects in HT29 human colon carcinoma cells in vitro. For an exposure time of 24 h, allyl isothiocyanate exhibited a Dq of 0.32 microgram/ml and a D0 of 0.74 micrograms/ml. Following detransformation of the cells by treatment with sodium butyrate or dimethylformamide the cells became more resistant to the cytotoxic effects of allyl isothiocyanate, the Dq increasing to 0.74 microgram/ml and the D0 to 0.96 microgram/ml (with butyrate) or 0.84 microgram/ml (with dimethylformamide). At the Dq value for detransformed cells the survival of the control cells was reduced to 56%. Allyl isothiocyanate was also found to be less cytostatic to the mass growth of detransformed populations in that daily doses of 1.6 micrograms/ml over a week reduced the final number of detransformed cells relative to untreated cultures by < 25% whilst growth of the transformed cultures was reduced by > 60%. Given this increased sensitivity of the cells to allyl isothiocyanate when in the transformed state, it is hypothesized that, when consumed in the human diet, this compound may protect against the development of colorectal cancer by selectively inhibiting the growth of transformed cell clones within the gastrointestinal mucosa.

Butyrates↗
PubMed1982

The metabolism of benzyl isothiocyanate and its cysteine conjugate in guinea-pigs and rabbits.

1. Following oral administration of benzyl isothiocyanate or its cysteine conjugate the major metabolite isolated from urine of guinea-pigs and rabbits was a cyclic mercaptopyruvate conjugate, 4-hydroxy-4-carboxy-3-benzylthiazolidin-2-thione. 2. Renal excretion of the metabolite after oral administration of benzyl isothiocyanate or its cysteine conjugate to guinea-pigs amounted to 23% and 33% respectively. The corresponding N-acetylcysteine conjugate of benzyl isothiocyanate (a mercapturic acid) was present as a minor metabolite. 3. After oral or i.v. administration of the glutathione, cysteinylglycine, cysteine or N-acetylcysteine conjugates of benzyl isothiocyanate to guinea-pigs, the major metabolite in urine was 4-hydroxy-4-carboxy-3-benzylthiazolidin-2-thione, with the N-acetylcysteine conjugate of benzyl isothiocyanate present in traces only. 4. It is concluded that during formation of the cyclic mercaptopyruvate conjugate, the cysteine conjugate predominantly undergoes transamination, and only a small proportion undergoes N-acetylation.

Animals↗
PubMed2001

Dietary indoles and isothiocyanates that are generated from cruciferous vegetables can both stimulate apoptosis and confer protection against DNA damage in human colon cell lines.

The natural indoles 3,3'-diindolylmethane (DIM), ascorbigen (ASG), indole-3-carbinol (I3C), and indolo[3,2-b]carbazole (ICZ), as well as the natural isothiocyanates sulforaphane (SUL), benzyl isothiocyanate (BITC) and phenethyl isothiocyanate (PEITC), all possess cancer chemopreventive properties. It is now shown that DIM, ICZ, SUL, and BITC can each stimulate apoptosis in human colon adenocarcinoma LS-174 and Caco-2 cells. Treatment of LS-174 cells with nontoxic doses of DIM, ASG, I3C, or ICZ affected an increase of up to 21-fold in cytochrome P450 1A1 (CYP1A1). None of these indoles caused an elevation in either aldo-keto reductase 1C1 (AKR1C1) or the gamma-glutamylcysteine synthetase heavy subunit (GCS(h)), but DIM, I3C, and ICZ produced a very modest increase in NAD(P)H:quinone oxidoreductase 1 (NQO1). By contrast, nontoxic doses of SUL, BITC, or PEITC failed to induce expression of CYP1A1 in LS-174 cells, but caused an increase of between 11- and 17-fold in the protein levels of AKR1C1, NQO1, and GCS(h). Treatment of the colon cell line with ICZ or SUL caused increases in the levels of mRNA for CYP1A1, AKR1C1, and NQO1 that were consistent with the enzyme data. Exposure of Caco-2 cells to media containing indoles or isothiocyanates gave similar results to those obtained using LS-174 cells. Evidence is presented that the ability of indoles and isothiocyanates to stimulate either xenobiotic response element- or antioxidant response element-driven gene expression accounts for the two groups of phytochemicals inducing different gene batteries. Pretreatment of LS-174 cells for 24 h with ICZ and SUL before exposure for 24 h to benzo(a)pyrene (BaP) reduced to <20% the number of single-strand DNA breaks produced by the carcinogen. Neither ICZ alone nor SUL alone were able to confer the same degree of protection against DNA damage produced by BaP as they achieved in combination. Similar results were obtained with H(2)O(2) as the genotoxic agent. Together, these phytochemicals may prevent colon tumorigenesis by both stimulating apoptosis and enhancing intracellular defenses against genotoxic agents.

20-Hydroxysteroid Dehydrogenases↗
PubMedDate not supplied

Sulforaphane and 2-oxohexyl isothiocyanate induce cell growth arrest and apoptosis in L-1210 leukemia and ME-18 melanoma cells.

Flow cytometry and laser-scanning confocal microscopy were used to study the effect of sulforaphane (SFN) and 2-oxohexyl isothiocyanate on the growth and viability of mouse leukemia L-1210 and human melanoma ME-18 cells during their exponential growth. Sulforaphane belongs to a group of compounds known as isothiocyanates. Isothiocyanates mainly occur in Cruciferous family. In particular, they occur in many vegetables such as broccoli and their sprouts. SFN and 2-oxohexyl isothiocyanate are potent inducers of detoxication phase 2 enzymes in mouse tissues and murine hepatoma cells in culture. Sulforaphane was shown to induce cell growth arrest in a dose dependent manner, followed by cell death. Sulforaphane induced the cell death via an apoptotic process. Two markers of apoptosis were investigated: phosphatidylserine externalization, which occurs in the early stages of apoptosis, and DNA strand breaks. Our results strongly suggest of chemopreventive activity toward cancer by the induction of apoptosis by SFN and 2-oxohexyl isothiocyanate.

Animals↗
PubMed2004

[Determination of isothiocyanates in human urine by high performance liquid chromatography].

A reversed-phase high performance liquid chromatographic method (HPLC) was established for determination of isothiocyanates in human urine, which used the reaction of propyl isothiocyanate with 1,2-benzenedithiol as reference instead of the synthesis of 1,3-benzodithiole-2-thione. The linear regression of the standard curve was determined to be y = 0.418 2 x + 2.821 (r2 = 0.999 3), that was well matched with the regression of methyl isothiocyanate, y = 0.412 2x + 2.442 3(r2 = 0.996 6). The detection limit (at approximately S/N = 2.5) was 0.08 micromol/L. The mean relative standard deviation (RSD) (n = 21) for the intra-day reproducibility was (4.7 +/- 2.9)%. The mean RSD (n = 4) for inter-day reproducibility of three samples was (7.0 +/- 5.0)%. The recovery of four propyl isothiocyanate standards was (91.3 +/- 7.9)% (mean RSD 8.7%). The initial results obtained by this method may provide useful information regarding to the kinetics of isothiocyanates in dietary consumption and excretion of individuals.

Adult↗
PubMed1991

Metabolic activation of 4-(methylnitrosamino)-1-(3-pyridyl)-1-butanone as measured by DNA alkylation in vitro and its inhibition by isothiocyanates.

The bioactivation of the tobacco-specific nitrosamine, 4-(methylnitrosamino)-1-(3-pyridyl)-1-butanone (NNK), by microsomes from target organs was studied with an in vitro microsome-mediated DNA alkylation system. Mouse lung, rat lung, and rat nasal microsomes catalyzed a time- and protein-dependent DNA methylation by [methyl-3H]NNK with activities of 4.11, 0.95, and 137.4 pmol/mg DNA/mg protein/h, respectively. The DNA methylation of NNK catalyzed by all three microsomal systems was inhibited by cytochrome P-450 inhibitors, such as carbon monoxide and metyrapone, but not by the cyclooxygenase inhibitor, aspirin, or by prolonged preincubation in the absence of NADPH. The possible involvement of specific P450 isozymes was assessed by specific inhibitory antibodies. An anti-P450IIB1&2 antibody significantly inhibited the DNA methylation by 45 and 32% in mouse lung and rat lung, respectively, whereas anti-P450IA1 and anti-P450IIE1 antibodies failed to show significant inhibition. All antibodies showed no inhibition in rat nasal microsomes. Glutathione inhibited the DNA methylation in a concentration-dependent manner in all three microsomal systems. Phenethyl isothiocyanate (PEITC), at doses of 0.25 and 1.00 mmol/kg body weight, was given intragastrically 2 h before sacrifice to mice and 24 h before sacrifice to rats, respectively; both mouse and rat lung microsomal activities were inhibited by about 40 and 90% by the low- and high-dose PEITC treatments, respectively. The rat nasal microsomes were only inhibited by the high-dose PEITC treatment by about 40%. PEITC, 4-phenylbutyl isothiocyanate, and 6-phenylhexyl isothiocyanate all inhibited the microsome-mediated DNA methylation of NNK in vitro, with 4-phenylbutyl isothiocyanate and 6-phenylhexyl isothiocyanate being more potent than PEITC and the mouse lung microsomes more sensitive than the rat lung and nasal microsomes. All three microsomal systems were shown to catalyze the in vitro DNA pyridyloxobutylation by [5-3H]NNK. On an equal protein basis, the rat nasal microsomes were much more active in catalyzing the DNA pyridyloxobutylation.

Alkylation↗
PubMed1987

The ATP-binding site of the erythrocyte membrane Ca2+ pump. Amino acid sequence of the fluorescein isothiocyanate-reactive region.

The erythrocyte plasma membrane Ca2+-pumping ATPase is known to form an acyl-phosphate catalytic intermediate, but there is otherwise little structural information linking it to the other mammalian ion-pumping ATPases which also form phosphorylated intermediates (the Na+, K+-ATPase of plasma membranes, the Ca2+-ATPase of sarcoplasmic reticulum, and the H+, K+-ATPase of gastric mucosa). We show here that this enzyme possesses a fluorescein isothiocyanate-reactive region similar to that possessed by these other ATPases. Low concentrations (10 microM) of fluorescein isothiocyanate inhibit the ATPase activity of this pump, and this inhibition is prevented by 4 mM ATP. ATP also inhibits the reaction of fluorescein isothiocyanate with a single amino acid residue on the 138-kDa polypeptide chain. A tryptic fragment containing the fluorescein-conjugated residue was isolated by high pressure liquid chromatography. The sequence of this peptide was determined to be NH2-Met1-Tyr2-Ser3-Lys4-Gly5-Ala6-Ser7-Glu8++ +-Ile9-Ile10-Leu11-Arg12-COOH; fluorescein isothiocyanate reacts with the lysine residue. The identities of residues 4-8 are the same as those in a sequence common to the other ATPases mentioned above, except that serine-7 of this sequence is changed to a proline in those ATPases. This substitution, sometimes not considered a homologous one, is not expected to have a major effect on the secondary structure or polarity of this region. Outside of this 5-residue core region of the fluorescein isothiocyanate-reactive site, the homologies among the different ion-pumping ATPases are limited.

Adenosine Triphosphatases↗
PubMed1986

[Antineoplastic effects and mechanism of action of IFN-alpha on brain tumors with use of fluorescent isothiocyanate-labelled IFN].

The antineoplastic effects and mechanism of IFN-alpha with a newly designed fluorescent isothiocyanate-labelled IFN-alpha were studied on three established glioma-cell lines and cultured cells of clinical brain tumors. Viability, cell cycle and cells showing positive reaction with fluorescent isothiocyanate-labelled IFN were analyzed by flow cytometry. U373MG glioma cells in contact with 10(4) IU/ml of IFN for 24 hours had a dose dependency, decreased viability, S-phase block in the cell cycle and high rate of positive reaction with fluorescent isothiocyanate-labelled IFN. Two surgical cases, except for one case, showed similar results and other cell lines or meningiomas were not affected by IFN. As the antineoplastic effects of IFN-alpha correlated with the rate of occurrence of positive cells with fluorescent isothiocyanate-labelled IFN, sensitive tumor cells may have a respective specific receptor for IFN-alpha, and, therefore, fluorescent isothiocyanate-labelled IFN-alpha might be of clinical value with regard to the problem of the receptor as well as sensitivity test.

Adenoma↗
PubMed1990

Reversed-phase LC resolutions of chiral antiarrhythmic agents via derivatization with homochiral isothiocyanates.

The search for new antiarrhythmic agents has been intense, because the established drugs for the treatment of cardiac arrhythmias are neither uniformly effective nor well-tolerated. Among the recently introduced new antiarrhythmic agents are tocainide (TOC), mexiletine (MEX), flecainide (FLE), and propafenone (PRO). Each of these drugs is a chiral amine used clinically as the racemic mixture. We have examined the high-performance liquid chromatographic chiral resolution of the above four drugs via derivatization with homochiral derivatizing agents (HDAs). The amino functionality of the drugs was reacted with four homochiral isothiocyanates, 2,3,4,6-tetra-O-acetyl-beta-D-glucopyranosyl isothiocyanate (TAGIT), (R)-alpha-methylbenzyl isothiocyanate (RAMBI), (S)-1-(1-naphthyl)ethyl isothiocyanate (SNEIT), and (R)-1-(2-naphthyl)ethyl isothiocyanate (RBEIT). Complete separation of the two peaks (resolution factor R = 1.5) was achieved with all four HDAs for TOC, with TAGIT, RBEIT, and RAMBI for MEX, with TAGIT and SNEIT for PRO, and only with TAGIT for FLE. SNEIT was used to develop analytical procedures for the determination of the enantiomeric composition of TOC in human urine and blood serum. The four HDAs offer several advantages over many other HDAs and should be useful in studies of enantioselective drug action and disposition.

Anti-Arrhythmia Agents↗
PubMed1975

Isothiocyanates. A new class of uncouplers.

This paper describes the uncoupling effect of three isothiocyanates: p-bromophenylisothiocyanate, 4,4'-diisothiocyanatebiphenyl and beta-naphtylemthylisothiocyanate on the respiration of Ehrlich-Lettré cells and isolated mitochondria. The isothiocyanates are similar to other uncouplers (such as 2,4-dinitrophenol and carbonyl cyanide p-trifluoromethoxyphenylhydrazone) in that they: 1. stimulate respiration of state 4 mitochondria; 2. stimulate mitochondrial ATPase activity; 3. release the inhibition of mitochondrial respiration by oligomycin and 4. inhibit both mitochondrial respiration and mitochondrial ATPase activity at higher molar concentrations. The incoupling activity of these isothiocyanates correlates well with their biological activity. Maximal activation of a latent mitochondrial ATPase activity of rat liver mitochondria in the presence of p-bromophenylisothiocyanate was found at a concentration of 15 muM. The investigated isothiocyanates differ significantly in their solubility in organic solvents and their chemical reactivity. We assume that the greater the partition coefficient in a series of isothiocyanates grouped according to the increasing value of log P (partition coefficient for the system octanol/water, 25 degrees C), the greater will be their uncoupling activity, but only up to a certain degree. Any further increase of log P will be marked by a decrease of this activity.

Adenosine Triphosphatases↗
PubMed1969

The effect of pressure on the oxidation state of iron, iv. Thiocyanate and isothiocyanate ligands.

The effect of pressure on the Mössbauer resonance spectra of Fe(III) with thiocyanate (M-SCN) and isothiocyanate (M-NCS) ligands has been studied. Fe(NCS)(3).6H(2)O, which has the isothiocyanate structure, reduces with increasing pressure, reversibly, and with a pressure dependence for the conversion very similar to that shown by a wide variety of ionic ferric compounds. K(3)Fe(SCN)(6) has the thiocyanate structure. At low pressures, it exhibits a significantly larger reduction than the Fe(NCS)(3). With increasing pressure the thiocyanate complexes isomerize, each complex apparently exhibiting about the same degree of conversion at a given pressure. At 150 kb the isomerization is essentially complete. The reduction of the Fe(III) to Fe(II) is reversible but the isomerization is not, and the sample, when powdered and reloaded in the high-pressure cell, exhibits the isomer shift, quadrupole splitting, and Fe(III) to Fe(II) conversion characteristic of an isothiocyanate. Heating the thiocyanate to 110 degrees C at 5 kb yields a mixture of thiocyanate and isothiocyanate that converts with pressure completely to the isothiocyanate.

Journal Article↗