Effects of triphenylsulphonium ions on mitochondria. Inhibition of adenosine triphosphatase activity

Bioconcentration potential and microbial toxicity of onium cations in photoacid generators

Despite the widespread utilization of onium salts as photoacid generators (PAGs) in semiconductor photolithography, their environmental, health, and safety (EHS) properties remain poorly understood. The present work reports the bioconcentration potential of five representative onium species (four sulfonium and one iodonium compound) by determining the octanol-water partition coefficient (P_OW) and lipid membrane affinity coefficient (K_MA); microbial toxicity was evaluated using the bioluminescent bacterium Aliivibrio fischeri (Microtox bioassay). Four of the oniums exhibited varying degrees of hydrophobic (lipophilic) partitioning (log P_OW: 0.08-4.12; K_MA: 1.70-5.62). A strong positive linear correlation was observed between log P_OW and K_MA (K_MA = log P_OW + 1.76, R² = 0.99). The bioconcentration factors (log BCF) estimated from P_OW and K_MA for the four oniums ranged from 0.13 to 3.67 L kg^-1. Bis-(4-tert-butyl phenyl)-iodonium and triphenylsulfonium had 50% inhibitory concentrations (IC₅₀) of 4.8 and 84.6 μM, whereas the IC₅₀ values of the other three oniums were not determined because these values were higher than their aqueous solubility. Given the increased regulatory scrutiny regarding the use and potential health impacts from onium PAGs, this study fulfills critical knowledge gaps concerning the EHS properties of PAG oniums, enabling more comprehensive evaluation of their environmental impacts and potential risk management strategies.

Biodegradability, cytotoxicity, and physicochemical treatability of two novel perfluorooctane sulfonate-free photoacid generators

There is a need for effective, environmentally compatible photoacid generators (PAGs) for application in photolithography for microelectronic device fabrication. Perfluoroalkyl sulfonates (PFAS) used in conventional PAG formulations, such as perfluorooctane sulfonate (PFOS), are under increasing scrutiny due to their widespread environmental distribution and toxicity. Recently, two new PFAS-free, PAG anions with semifluorinated sulfonate anions containing biomolecules (γ-butyrolactone or D-glucose groups) were successfully applied as PAGs. In this study, the biodegradation potential, cytotoxicity, and physicochemical treatability of the new PAG anions was evaluated. PFOS and perfluorobutane sulfonate (PFBS) were used as reference materials in all of the assays. The new PAGs were susceptible to partial degradation by microorganisms in aerobic activated sludge, and these were also readily removed by chemical oxidative treatment with Fenton's reagent [H(2)O(2)/Fe(II)]. In contrast, the compounds were resistant to microbial and chemical attack under reductive conditions as indicated by the low removal efficiencies observed with anaerobic biodegradation assays and chemical assays with zero-valent iron, respectively. The enhanced biodegradation potential and treatability make of the new PAGs attractive materials to resolve current issues related to the lithographic performance and environmental concerns.

Proton ATPase of rat liver mitochondria: a rapid procedure for purification of a stable, reconstitutively active F1 preparation using a modified chloroform method

A method is described for the purification of rat liver F1-ATPase by a modification of the chloroform extraction procedure originally described by Beechey et al. (Biochem. J. (1975) 148, 533). Purified liver membrane vesicles are extracted with chloroform in the presence of ATP and EDTA. The procedure yields pure F1 in only 2-3 h without the necessity of ion-exchange chromatography. The enzyme exhibits the alpha, beta, gamma, delta, and epsilon bands characteristic of F1-ATPase. It has a high ATPase specific activity, and is reconstitutively active, catalyzing high rates of ATP synthesis. Significantly, it can be readily crystallized. If desired, the enzyme can be passed over a gel filtration column to place it in a stabilizing phosphate-EDTA buffer, lyophilized and stored indefinitely at -20 degrees C.

Further Characterization on the Transport Property of Plasmalemma NADH Oxidation System in Isolated Corn Root Protoplasts

Recent experiments show that exogenous NADH increases the O(2) consumption and uptake of inorganic ions into isolated corn (Zea mays L. Pioneer Hybrid 3320) root protoplasts (Lin 1982, Proc Natl Acad Sci USA 79: 3773-3776). A mild treatment of protoplasts with trypsin released most of the NADH oxidation system from the plasmalemma (Lin 1982 Plant Physiol 70: 326-328). Further studies on this system showed that exogenous NADH (1.5 millimolar) tripled the proton efflux from the protoplasts thus generating a greater electrochemical proton gradient across the plasmalemma. Trypsin also released ubiquinone (11.95 nanomoles per milligrams protein) but not flavin or cytochrome from the system. Kinetic analyses showed that 1.5 millimolar NADH quadrupled V(max) of the mechanism I (saturable) component of K(+) uptake, while K(m) was not affected. Diethylstibestrol and vanadate inhibited basal (ATPase-mediated) K(+) influx and H(+) efflux, while NADH-stimulated K(+) uptake was not or only slightly inhibited. p-Chloromercuribenzene-sulfonic acid, N,N'-dicyclohexylcarbodiimide, ethidium bromide, and oligomycin inhibited both ATPase- and NADH-mediated H(+) and K(+) fluxes. A combination of 10 millimolar fusicoccin and 1.5 millimolar NADH gave an 11-fold increase of K(+) influx and a more than 3-fold increase of H(+) efflux. It is concluded that a plasmalemma ATPase is not involved in the NADH-mediated ion transport mechanism. NADH oxidase is a -SH containing enzyme (protein) and the proton channel is an important element in this transport system. Fusicoccin synergistically stimulates the effect of NADH on K(+) uptake.

Phenothiazines and related compounds disrupt mitochondrial energy production by a calmodulin-independent reaction

Phenothiazines and related compounds bind to mitochondrial membranes in approximate proportion to their affinities for calmodulin. Penfluridol (16 microM), pimozide (20 microM), or trifluoperazine (66 microM) completely inhibit ADP-stimulated respiration in isolated rat liver mitochondria, but exert no effect on either uncoupler- or Ca2+-stimulated respiration. The inhibition of ADP-stimulated respiration results from inhibition of the oligomycin-sensitive ATPase. Inhibition of the ATPase does not involve interaction of phenothiazine with calmodulin. The addition of calmodulin with or without calcium to mitochondrial inner membrane preparations has no effect on ATPase activity. The addition of EGTA and the ionophore A23187 prior to the addition of phenothiazine does not prevent the phenothiazine-induced inhibiton of the ATPase. Measurements of inner membrane calmodulin content by gel electrophoresis or cyclic nucleotide phosphodiesterase activation are negative. Despite the absence of calmodulin in the inner membrane preparations, 12.5 nmol trifluoperazine bind per 100 microgram of membrane protein with an association constant, K, of 6.5 . 10(4) M-1. We conclude that calmodulin-binding neuroleptic agents, when added to whole cells, have the potential to disrupt mitochondrial energy production by a reaction which apparently does not involve a phenothiazine-calmodulin interaction.

Optimization of the purification of mitochondrial F1-adenosine triphosphatase

A simple technique of purification of the soluble pig heart mitochondrial F1-ATPase is described. It consists of removal of extrinsic proteins from mitochondrial membranes before extraction with chloroform and ammonium sulfate fractionation. A high degree of purity, an excellent stability and a good yield are attained after gel filtration through an Ultrogel ACA 34 column equilibrated in the presence of 50% glycerol. The tested properties of the F1-ATPase prepared by this method are similar to those of the same enzyme extracted by sonication. The enzyme is virtually devoid of tightly bound nucleotides. In addition, some characteristics of the behaviour of the beta subunit are shown.

Stabilization of rat liver mitochondrial F1-adenosine triphosphatase during chloroform-induced solubilization

1. Isolation of ATPase from rat liver submitochondrial particles by chloroform treatment requires the presence of ATP or ADP during enzyme solubilization. In the absence of adenine nucleotides the enzyme activity is very low although all protein components of F1-ATPase are released. The low concentrations of ATP or ADP required (5 microM) indicate that the high affinity nucleotide-binding sites are involved in enzyme stabilization. Other nucleotides tested (ITP, GTP, UTP, CTP) were found to be less effective. 2. Polyacrylamide gel electrophoresis and immunodiffusion in agar plates revealed that in the absence of adenine nucleotides a fraction of F1-ATPase released by chloroform treatment is split into fragments. The part of the dissociated enzyme molecule has a molecular weight identical with that of a beta-subunit of F1-ATPase. 3. Dissociation of the F1-ATPase molecule could also be prevented by aurovertin. 4. Crude F1-ATPase solubilized by chloroform treatment can be further purified by Sepharose 6B gel filtration. Specific ATPase activity of the purified enzyme was 90 mumol Pi/min per mg protein and the enzyme was composed of five protein subunits (alpha, beta, gamma, delta, epsilon) with molecular weights 58 000, 55 000, 28 000, 13 000 and 8000, respectively. 5. Chloroform-released F1-ATPase from rat liver mitochondria displayed immunochemical cross-reactivity with that isolated from beef heart mitochondria.

Effects of inhibitors on the plasma membrane and mitochondrial adenosine triphosphatases of Neurospora crassa

A comparative study has been made of the effects of a variety of inhibitors on the plasma membrane ATPase and mitochondrial ATPase of Neurospora crassa. The most specific inhibitors proved to be vanadate and diethylstilbestrol for the plasma membrane ATPase and azide, oligomycin, venturicidin, and leucinostatin for mitochondrial ATPase. N,N'-Dicyclohexylcarbodiimide, octylguanidine, triphenylsulfonium chloride, and quercetin and related bioflavonoids inhibited both enzymes, although with different concentration dependences. Other compounds that were tested (phaseolin, fusicoccin, deoxycorticosterone, alachlor, salicyclic acid, N-1-napthylphthalamate, triiodobenzoic acid, cyclic AMP, cyclic GMP, theobromine, theophylline, and histamine) had no significant effect on either enzyme. Overall, the results indicate that the plasma membrane and mitochondrial ATPases are distinct enzymes, in spite of the fact that they may play related roles in H+ transport across their respective membranes.

Purification and properties of adenosine triphosphatase solubilized from beef heart mitochondria by chloroform

Soluble, oligomycin-insensitive ATPase released from beef heart mitchondria by chloroform extraction can be further purified by Sepharose 6B gel filtration. This purification increases enzyme activity 4--5 times (100-130U/mg). According to specific activity, high purity and ability to reconstitute oligomycin-sensitive complex, isolated ATPase is quite comparable with enzyme preparations isolated by other methods.

Evidence supporting the identity of beef heart mitochondrial chloroform-released adenosine triphosphatase (ATPase) with coupling factor I

Highly purified mitochondrial chloroform-released beef heart ATPase had molecular weight 330 000, five bands (alpha, beta, gamma, delta, epsilon) in sodium dodecyl sulfate gel electrophoresis and could restore the oxidative-phosphorylation function of A particles. Maximal inhibition (90%) of the enzyme by N,N'-dicyclohexylcarbodiimide was achieved at a molar ratio of inhibitor to protein of 30 : 1. Chloroform introduced into an aqueous solution of beef heart coupling factor I protected it from cold inactivation.