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The effect that sunlight has on the degradation rate of two model organic compounds, phenol and malic acid, by ozone is studied. The effect seems to be due to both direct light absorption (300-320 nm photons) by ozone, which produces the pollutant degradation, and light absorption by reaction intermediates. The presence of such a light notably improves the reactivity of ozone toward the organic species, leading to a faster and complete mineralization even at large initial total organic carbon values. The use of artificial sunlight (Xe lamp) is also explored. Finally, the simultaneous presence of sunlight and other ozone degradation catalyst like transition metal ions is studied, showing the beneficial effect of such a combination.
[reaction in text] Straightforward total syntheses of (-)-rosmarinecine have been achieved from L-malic acid derived pyrroline N-oxides by two novel useful cascade processes, which join the family of domino reactions. Both strategies, which furnished the target alkaloid in enantioenriched and enantiopure forms, respectively, allow complete control of configuration at all the three newly created contiguous stereogenic centers.
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Administration of dibenzylhydracide of D,L-malic acid (inhibitor of monoamine oxidase) into animals caused not only inhibition but also transformation of the mitochondrial monoamine oxidase activity, which acquired the property to deaminate histamine. Effect of the monoamine oxidase inhibitor on the antioxidative activity of lipids from mouse liver and brain tissues was studied. Effect of the dose administered and of the period of its action after administration were characterized. Influence of the inhibitor on oxidation of methyloleate was also studied in a model system. The data obtained suggest that the transformation-producing effect of the substance was not related to its immudiate action on the enzyme molecule but was apparently due to its influence on the intensity of lipid peroxidation in membranes.
The mutant IGC 40 x 1001 of the yeast Pichia anomala IGC 4380, which displays inverse diauxic growth in a medium with glucose and malic acid, was studied to elucidate the biochemical mechanisms underlying that behavior. Time course changes of enzyme activities during growth of the mutant in that mixture of substrates indicated that the gluconeogenic enzymes remained active during the first phase of diauxic growth, while glycolytic enzyme activities were significantly reduced. This reduction was essentially due to an alteration in the maximum velocity and not in substrate affinity. Malate, citrate, and adenosine triphosphate did not affect significantly the activities of the glucose phosphorylating enzymes in cell extracts of either the mutant or the wild strain. In P. anomala, unlike Saccharomyces cerevisiae, the fructose/glucose phosphorylating ratio was not associated with repression/derepression conditions.
An ion chromatographic separation with photometric detection using a chiral copper(II) complex as the eluent has been developed for the resolution of enantiomers of malic acid in commercially available apple juices. The results obtained by this method were in good agreement with those by an enzymatic method with separation by high-performance liquid chromatography.
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In order to investigate the effects of sample size, sample shape, and polymer composition on the hydrolytic degradation of water-insoluble benzylated poly(beta-malic acid) derivatives, three polymers were synthesized, namely PMLABe100, PMLABe90H10 and PMLABe80H20, containing 100, 90, and 80% of benzyl units respectively. For each polymer, 4-mm-thick compression molded pellets, 0.3-mm-thick casted films and 250-500 microns ground particles were made and allowed to age in 0.13 M, pH 7.4 sodium phosphate buffer at 37 degrees C. Degradation was monitored by measuring weight changes, variations of polymer composition, formation of benzyl alcohol, and molecular weight decreases. It was shown that degradation of particles and films depended initially on polymer composition due primarily to fast degradation of acid-rich segments present or formed by benzyl ester cleavages which led more or less rapidly to similar compositions for the three polymers. The higher the content in acid groups, the faster the degradation rate and the characteristic changes. It was also found that pellets made of PMLABe90H10 or PMLABe80H20 degraded heterogeneously and much faster than corresponding films and particles.
The major conclusion drawn was that malate generated in corn roots during a 15-minute period of CO(2) fixation and malate introduced into the tissue during a similar period from the bathing medium share a common extramitochondrial compartment, the cytoplasmic pool. The utilization of these 2 forms of malate is normally much slower than that of malate generated in the mitochondria by the tricarboxylic acid cycle. By lowering the pH of the medium or treating the tissue with malonate or 2,4-dinitrophenol, similar increases in the rates of utilization of both forms of cytoplasmic malate were brought about. Changes in (A) the demand for acetyl acceptors in the mitochondria and (B) mitochondrial permeability were invoked to account for the increased utilization of the cytoplasmic malate under the various experimental treatments.
The yeast Saccharomyces cerevisiae was entrapped within polyacrylamide gel beads by employing a procedure that uses sodium dodecylsulfate as a detergent to improve the spherical configuration of the beads. The resulting preparation showed a rate of fumarate bio-conversion to L-malic acid about 60 times higher than that found for the free cells. Almost all fumarate was converted in 30 min of incubation. The thermal stability of the immobilized cells did not significantly differ from the free cells. An optimal pH of 5.7 was found for the immobilized preparation and no succinic acid was detected as a byproduct in the incubation mixture.
Acidification of the starchy endosperm by the aleurone layer following germination has been established; however, the physiological and metabolic responses of this tissue to external pH have been incompletely investigated. In this investigation, isolated wheat (Triticum aestivum) aleurone layers were incubated in different solutions at initial pH values of 3, 4 and 6 in the absence of phytohormones. After 24 h of incubation, the initial pH of all malate and succinate buffers shifted towards a value close to 4.2. These results suggest the existence of a pH-stating mechanism, instead of the simple acidification process reported previously. The rise of initial pH 3 by aleurone layers was accompanied by a high net uptake of external malic- or succinic acid. In contrast, incubation in glycyl-glycine buffer (a supposedly non-permeating cation at pH 3) partially prevented that pH rise in a pH-3 solution. The 14C-malate taken up from media at pH 3 was mostly broken down to CO2, indicating that an effective metabolic control of the intracellular malate level was operating. At pH 6, an uptake of 14C-malate and 14CO2 production occurred as well, but at slower rates than at pH 3. When buffer concentration was increased, at initial pH values of 3 or 6, a higher uptake or secretion of malic acid, respectively, was carried out by the aleurone layers. The pH of these buffers varied less than that of dilute ones, but always showed a tendency toward a pH near 4. These results suggest that a balance between secretion and uptake of malic acid, accompanied by the corresponding biosynthesis or degradation, is the basis of this pH-stating mechanism.
In rats injected intramuscularly with sodium aurothio[1,4-14C]malate, 80% of the 14C was excreted in the urine, mostly in 24 h, 2% in the faeces and 10% as 14CO2 in the expired air during the first six hours with none thereafter. Urinary and faecal gold represented 5% and 2.5% of the dose, respectively. In rats given thio[1,4-14C]malic acid, 50% of the 14C was excreted in the urine, 10% in the expired air as 14CO2 and 2% in the faeces. Radioactivity was found in all tissues with distribution similar for the two compounds, the major sites of accumulation being bone, kidney and liver. Significantly higher amounts of 14C were found in the 14C-aurothiomalate-dosed animals, notably in bone and kidney. Gold was located principally in kidney, liver, lung and spleen with smaller amounts elsewhere. At least seven radioactive metabolites (including sodium aurothiomalate and thiomalic acid) were present in the urine of rats given 14C-aurothiomalate. Urine from 14C-thiomalic acid-treated rats contained at least five radiolabelled compounds, one of which was thiomalic acid. Results show that most of the gold was removed from the thiomalate moiety, however, the 14C distribution and the radioactive metabolites in urine demonstrated that some intact aurothiomalate remains.
Escherichia coli has been the appropriate focus for monitoring of potential enteric pathogens in water and foods. Although several methods have been used for the detection or enumeration of E. coli cells in water and foods, the time and accuracy limitations of these methods suggest the need of a rapid and specific method. By comparison of the gene sequences coding for malic acid dehydrogenase (mdh) of E. coli and non-E. coli strains, two oligonucleotides were designed and their possible use as E. coli-specific PCR primers was tested. All of the 110 E. coli strains tested, including non-pathogenic and various pathogenic strains, generated the expected PCR products with Mw equal to 392 bp. On the other hand, only 97 of these 110 E. coli strains were detectable using the BAM gas production method. With the exception of Shigella strains, non-E. coli strains, including strains of the family of Enterobacteriaceae, did not generate any false positive PCR results. When this PCR system was used for the monitoring of E. coli cells inoculated into water and milk samples, as low as 10(0) cfu per 100 ml of water or per ml of milk sample could be detected if an 8 h preculture step was performed prior to the PCR. Including the preculture step, the whole PCR detection process may be completed within 12 h.
Polymalic acid is receiving interest as a unique biopolymer of the plasmodia of mycetozoa and recently as a biogenic matrix for the synthesis of devices for drug delivery. The acellular slime mold Physarum polycephalum is characterized by two distinctive growth phases: uninucleated amoebae and multinucleated plasmodia. In adverse conditions, plasmodia reversibly transform into spherules. Only plasmodia synthesize poly(malic acid) (PMLA) and PMLA-hydrolase (polymalatase). We have performed suppression subtractive hybridization (SSH) of cDNA from amoebae and plasmodia to identify plasmodium-specific genes involved in PMLA metabolism. We found cDNA encoding a plasmodium-specific, spherulin 3a-like polypeptide, NKA48 (spherulin 3b), but no evidence for a PMLA-synthetase encoding transcript. Inhibitory RNA (RNAi)-induced knockdown of NKA48-cDNA generated a severe reduction in the level of PMLA suggesting that spherulin 3b functioned in regulating the level of PMLA. Unexpectedly, cDNA of polymalatase was not SSH-selected, suggesting its presence also in amoebae. Quantitative PCR then revealed low levels of mRNA in amoebae, high levels in plasmodia, and also low levels in spherules, in agreement with the expression under transcriptional regulation in these cells.
We have previously shown that laminin-8, a vascular basement membrane component, was overexpressed in human glioblastomas multiforme and their adjacent tissues compared to normal brain. Increased laminin-8 correlated with shorter glioblastoma recurrence time and poor patient survival making it a potential marker for glioblastoma diagnostics and prediction of disease outcome. However, laminin-8 therapeutic potential was unknown because the technology of blocking the expression of multi-chain complex proteins was not yet developed. To inhibit the expression of laminin-8 constituents in glioblastoma in vitro and in vivo, we used Polycefin, a bioconjugate drug delivery system based on slime-mold Physarum polycephalum-derived poly(malic acid). It carries an attached transferrin receptor antibody to target tumor cells and to deliver two conjugated morpholino antisense oligonucleotides against laminin-8 alpha4 and beta1 chains. Polycefin efficiently inhibited the expression of both laminin-8 chains by cultured glioblastoma cells. Intracranial Polycefin treatment of human U87MG glioblastoma-bearing nude rats reduced incorporation of both tumor-derived laminin-8 chains into vascular basement membranes. Polycefin was thus able to simultaneously inhibit the expression of two different chains of a complex protein. The treatment also significantly reduced tumor microvessel density (p < 0.001) and area (p < 0.001) and increased animal survival (p < 0.0004). These data suggest that laminin-8 may be important for glioblastoma angiogenesis. Polycefin, a versatile nanoscale drug delivery system, was suitable for in vivo delivery of two antisense oligonucleotides to brain tumor cells causing a reduction of glioblastoma angiogenesis and an increase of animal survival. This system may hold promise for future clinical applications.
An amperometric biosensor based on malate quinone oxidoreductase (MQO) was developed for monitoring of the malolactic fermentation of wines. Screen-printed electrodes coupled with appropriate mediators were used as transducers for this novel biosensor. MQO was immobilized by physical entrapment in a photo-cross-linkable poly(vinyl alcohol) polymer (PVA-SbQ) on the surface of the working electrode. Several electrochemical mediators were studied in order to lower the applied potential and minimise the matrix effects. Among them, 2,6-dichlorophenol indophenol (DPIP) and phenazine methosulfate (PMS) were chosen for further development. The working conditions (mediator concentration, applied potential and pH) were optimised for both DPIP and PMS. Detection limits for both types of biosensors were of 5 microM malic acid. Sensitivities obtained for the linear part of the calibration curve were 0.85 and 1.7 mA/M for the biosensors based on DPIP and PMS, respectively. Interferences due to non-specific oxidations were shown to be negligible when using PMS as mediator.