bluuebunny/crossref_metadata_2025_split huggingface dataset:
Characterization of Pectic Enzymes from the Chickpea Pathogen Ascochyta rabiei
Authors: Tenhaken Raimund , Barz Wolfgang 
Published: August 2018

Abstract
The chickpea pathogenic fungus Ascochyta rabiei when growing in a pectin containing min­eral medium secretes an exo-polygalacturonase (PG) and a pectin methyl esterase into the cul­ture medium. The induction of the PG is controlled by catabolite repression. The PG was puri­fied to apparent homogeneity from the culture fluid by acetone precipitation and chromato­graphy on a Mono S and a Mono Q column. The molecular weight of the purified glycoprotein enzyme in SD S-PAGE was about 70 kDa, whereas the Mr by gelfiltration it was estimated to be 53 kDa. Polygalacturonic acid is the only substrate of the PG whereas pectin is not degraded. The PG releases only galacturonic acid from polygalacturonic acid and no oligogalacturonides which might elicitate chickpea plants and trigger plant defense response. The enzyme is not inhibited by pectin, the released proteins or phenolics.
Omphalone, an Antibiotically Active Benzoquinone Derivative from Fermentations of Lentinellus omphalodes [1]
Authors: Stärk Andreas , Anke Timm 
Published: August 2018

Abstract
Omphalone, a new antibiotic, cytotoxic, and phytotoxic pigment has been isolated from fermentations of a Canadian strain of Lentinellus omphalodes. Its structure has been established as 2-(4-methylfuran-2-yl)-l,4-benzoquinone (1) by spectroscopic investigations and conversion into leuco-acetate 2.
Studies on Porphobilinogen-Deaminase from Saccharomyces cerevisiae
Authors: García Susana Raquel Correa , Rossetti Maria Victoria , del Carmen Batlle Alcira María 
Published: August 2018

Abstract
Porphobilinogen-deaminase from Saccharomyces cerevisiae has been isolated and partially purified 80-and 230-fold in the absence or presence of phenylmethylsulphonyl fluoride, respectively.
Some properties of the isolated enzyme were studied. Porphyrin formation was linear with time and protein concentration. Optimum pH was about 7.5-7.8. Molecular mass of the protein was 30,000 ± 3000 Dalton when the enzyme was purified in the presence of phenylmethyl­ sulphonyl fluoride. A less active and unstable 20,000 Da molecular mass species was obtained when purification was performed in the absence of the protease inhibitor.
Porphobilinogen-deaminase exhibited classical Michaelis-Menten kinetics. The apparent Km for uroporphyrinogen formation was 19 μм; Vmax was 3.6 nmol uroporphyrin/h and the Hill coefficient was n = 1.
Also the action of several reagents on the activity was studied. Protective thiol agents had no effect. Heavy metals inhibited both porphyrin formation and porphobilinogen consumption, but known sulphydryl inactivating chemicals inhibit the former without modifying the latter. Ammonium ions had no effect on the activity while hydroxylamine completely inhibited both porphyrin formation and porphobilinogen consumption.
The Flash Pattern of Photosynthetic Oxygen Evolution after Treatment with Low Concentrations of Hydroxylamine as a Function of the Previous S1/S0-Ratio Further Evidence that NH2OH Reduces the Water Oxidizing Complex in the Dark
Authors: Messinger J. , Pauly S. , Witt H. T. 
Published: August 2018

Abstract
Flash induced oxygen evolution patterns of isolated PS II complexes from the cyanobacterium Synechococcus were measured with a Joliot-type electrode. By suitable preflash and dark adaptation procedures, samples were prepared in the state S1 (100%), as well as enriched in S0 (60% S0, 40% S,). After treatment with low concentrations of NH2OH (≤ 100 μм), the two flash patterns were identical. This is further evidence for a reduction of the water oxidizing complex by hydroxylamine in the dark. Two reduced states (S-1 and S-2) below S0 are formed by this reduction.
Uresiphita reversalis (Lepidoptera: Pyralidae): Carrier-Mediated Uptake and Sequestration of Quinolizidine Alkaloids Obtained from the Host Plant Teline monspessulana
Authors: Wink Michael , Montllor Clytia B. , Bernays Elizabeth A. , Witte Ludger 
Published: August 2018

Larvae of Uresiphita reversalis feed almost exclusively on legumes of the tribe Genisteae, whose characteristic secondary metabolites are quinolizidine alkaloids (QA). Aposematic larvae store host plant-derived QA in their integument, while the pupae are almost alkaloid-free. In the last instar larvae, alkaloids were concentrated in the larval head, possibly in the silk glands. About 80% of the alkaloids were transferred to the cocoon silk and 19% were lost with larval exuviae.
The larval alkaloid pattern was characterized by capillary GLC and GLC-MS and compared to that of the host plant, Teline monspessulana. Whereas the host plant contained mainly epiaphylline, dehydroaphylline and aphylline, larvae selectively accumulated N-methylcytisine, a relatively minor component of the plant QA; the faeces contained mainly epiaphylline and dehydroaphylline. Thus uptake and sequestration must be selective processes. Uptake by isolated larval midguts was time-, pH- and temperature-dependent and displayed an activation energy between 50 and 80 kJ/mol. Furthermore the in vitro uptake of 13-hydroxylupanine was competitively inhibited by cytisine. All these data provide evidence that QA uptake does not proceed by simple diffusion but instead with the aid of a carrier mechanism; this could explain the differential alkaloid uptake observed in living larvae.
Analysis of Light-Induced Absorbance Changes in the Near-Infrared Spectral Region I. Characterization of Various Components in Isolated Chloroplasts
Authors: Klughammer Christof , Schreiber Ulrich 
Published: August 2018

Light-induced absorbance changes in the near-infrared (NIR ) spectral region (700-950 nm) are analyzed in isolated spinach chloroplasts using pulsed light-emitting diodes as modulated measuring light sources. With chloroplasts under coupled conditions the light-induced signal is dominated by a relatively slow scattering change displaying a flat difference spectrum. More specific changes can be distinguished by faster induction and relaxation kinetics and in the presence of valinomycin/nigericin which prevents scattering changes. Besides the dominant P700 change, with a narrow bleaching band around 703 nm and a broad absorbance increase between 750 and 850 nm (peak at 815 nm) the following absorbance changes were identified in the NIR:
1) An absorbance increase caused by plastocyanin (PC) oxidation, with a relatively flat spectrum.
2) An absorbance decrease gaining amplitude towards longer wavelengths, which reflects reduction of a low potential acceptor of PSI different from ferredoxin.
3) A field indicating absorbance decrease peaking around 730 nm, the properties of which correspond to those of P515. 4) An uncoupler insensitive absorbance decrease stimulated by dark adaptation and anaerobic conditions, the difference spectrum of which resembles that of ferredoxin reduction.
The relative contributions of P700 and PC to the overall oxidized-reduced difference spectrum are determined by redox titration. At 706 nm, 815 nm and 950 nm the P 700/PC is - 119/ 19, 67/37 and 31/69, respectively. From these ratios and the molar extinction coefficients a molar P 700/PC stoichiometry of 1 /3 is determined.
Single Photon-Evoked Events Of The Ventral Nerve Photoreceptor Cell Of Limulus Facilitation, Adaptation And Dependence Of Lowered External Calcium
Authors: Stieve H. , Reuß H. , Hennig H. T. , Klomfaß J. 
Published: August 2018

Bumps, the elementary excitatory events of the Limulus ventral nerve photo receptor following a weak flash of light were recorded under voltage clamp conditions. The statistical distribution of various bump parameters and their changes caused by weak conditioning pre-illumination are described, and the influence of lowered external Ca2+-concentration together with normal or raised Mg2+-concentration (15 °C).
1) Weak conditioning pre-illumination causes desensitization: the bump current amplitude, bump duration , bump area (current-integral), and the bump latency are diminished, the more, the stronger the conditioning flash, i.e. the light adaptation. Very weak conditioning pre-illumination causes facilitation, expressed by an increase in number and size of the observed bumps. The average bump latency, however, is already shortened under these conditions.
2) Lowering the external Ca2+-concentration from 10 mmol/l to 250 (µmol/1 has its primary effect on the dark -adapted photoreceptor (without substantially reducing the ability for light adaptation ). It causes the following average changes: the amplitudes, durations, current-integrals, and the latencies of current bumps are greatly enlarged and the number of bumps is raised.
3) Raised magnesium concentration from 50 to 100 mmol/l can partially compensate for the lack of calcium ; however, it enhances the effect of calcium deficiency on the latency, i.e. it further enlarges the average latencies. The results can be explained on the basis of our model of bump generation by two assumptions.
1) Lowering the external calcium concentration causes a decrease in the cytosolic Ca2+-level without substantially reducing the intracellular calcium stores from which the light-adapting calcium release is fed. The lowered cytosolic Ca2+-concentration induces an “extra” dark adaptation resulting in greater bumps and more bumps exceeding the threshold of recognition. The bump latency, however, which behaves differently from all other bump parameters, is determined by a separate calcium -dependent reaction where magnesium competes with calcium antagonistically.
2) Facilitation is due to cooperativity of transmitter binding in order to open the ion channels
Pseudobactin-und Pseudobactin A-Varianten: Neue Peptidsiderophore vom Pyoverdin-Typ aus Pseudomonas fluovescens "E2" / Variants of Pseudobactin and Pseudobactin A: New Pyoverdin Type Peptide Siderophores from Pseudomonas fluorescens "E2"
Authors: Taraz K. , Seinsche D. , Budzikiewicz H. 
Published: August 2018

Abstract
From a strain of Pseudomonas fluorescens pseudobactin and several related compounds were isolated and their structures were elucidated. In this way a reference compound (5) could be obtained for the unambiguous determination of the absolute configuration of C-1 of the pyoverdin chromophore in newly isolated representatives of this class.
A Contact Site between the Two Reaction Center Polypeptides of Photosystem II Is Involved in Photoinhibition
Authors: Trebst A. 
Published: August 2018

Abstract
A new contact site between the two reaction center polypeptides D 1 and D 2 of photosystem II close to arg 238 and arg 234 respectively is proposed. The amino acid sequences involved are between the 4 th transmembrane and a connecting parallel helix. The sequence includes a tryp­ sin sensitive site in both polypeptides, the likely cleavage site in the rapid turnover of the D 1 polypeptide and part of the herbicide binding site. The contact site is oriented towards both quinone binding sites Q A and Q B. A folding of the backbone of the amino acid sequences involved is proposed.
Basis for Differential Chemical Selectivity of MG-191 Safener against Acetochlor and EPTC Injury to Maize
Authors: Jablonkai Istvan 
Published: August 2018

Abstract
The influence of MG-191 safener on the uptake, translocation and metabolism of [14C]acetochlor and [14C]EPTC was studied. The amounts of absorbed radioactivity by maize seedlings at 3, 6, 24, and 72 h after applications of [14C]labeled herbicides and [14C]MG-191 were different. Plants treated with [14C]acetochlor took up 30-to 50-fold more radiolabel with­in 72 h than [14C]EPTC-or [14C]MG-191-treated plants. Addition of MG-191 caused only mi­nor changes in the rate of herbicide absorption. EPTC and MG-191 and/or their metabolites moved quickly acropetally and partitioned equally between root and shoot tissues up to 72 h. The amount of acetochlor and/or its labeled metabolites translocated to shoot tissues was less than 10%. MG-191 practically had no influence on herbicide translocation rates. With all chemicals the amounts of water-soluble and unextractable fractions increased while the ratio of hexane-extractable metabolites decreased with time. TLC analyses of both water-and hex­ane-soluble metabolites confirmed the fast metabolism of acetochlor. The acetochlor metabo­lism took place via GSH conjugation and more polar, non-conjugated metabolites compared to parent molecule were detected in hexane-soluble fraction. MG-191 enhanced acetochlor metabolism by decreasing the portion of non-metabolized acetochlor. EPTC metabolism re­sulted in water-soluble metabolites having similar chromatographic properties to those of ace­tochlor. However, there was no safener effect on non-metabolized EPTC content of plants. It appears that MG-191 protects maize against EPTC by enhancing the early rate of conjugation with GSH after initial oxidative metabolism.
Metabolism of the Aryloxyphenoxypropanoate Herbicide, CGA 184927, in Wheat, Barley and Maize: Differential Effects of the Safener, CGA 185072
Authors: Kreuz Klaus , Gaudin John , Stingelin Jürg , Ebert Edith 
Published: August 2018

Abstract
The influence of the safener, CGA 185072 (5-chloro-8-quinolinoxy-acetic acid-1-methylhexyl-ester), on the metabolism of the aryloxyphenoxypropanoate herbicide, CGA 184927 (2-propynyl-R-2-[4-(5-chloro-3-fluoro-2-pyridinyloxy)-phenoxy]-propionate), was studied in excised leaves of wheat, barley, and maize. In wheat and barley, CGA 184927 readily under­went ester hydrolysis followed by hydroxylation at the pyridinyl moiety as well as ether cleav­age between the pyridinyl and the phenyl ring. Ether cleavage constituted the minor pathway in both species. All metabolites were subject to glycosyl conjugation. Tetcyclacis strongly in­hibited pyridinyl-ring hydroxylation in wheat. Metabolism by hydroxylation and ether cleav­age was more rapid in wheat than in barley, and was found to be accelerated in the presence of the safener CGA 185072 in both wheat and, to a lesser degree, in barley. Moreover, the safener increased the capacity for O-glycoside formation in wheat as suggested from studies using the ,4C-labelled pyridinyl-ring hydroxylated metabolite as a precursor. In maize, which is highly susceptible to CGA 184927, rapid ester hydrolysis of CGA 184927 and partial conversion of the corresponding carboxylic acid to glycosyl ester conjugate(s) occurred. However, no further transformation of the herbicide was found in maize, both in the absence or presence of CGA 185072. It is concluded that the ability of CGA 185072 to protect wheat from injury by the herbicide, CGA 184927, and to confer partial protection to barley, is related to the ability of the safener to stimulate herbicide metabolism in these crop species.
Effect of the Safener Dichlormid on Maize Peroxygenase and Lipoxygenase
Authors: Blée Elizabeth 
Published: August 2018

Abstract
S-Ethyl-N,N-dipropylthiocarbamate (EPTC) was oxidized into its corresponding sulfoxide by microsomal fractions from etiolated maize seedlings. This reaction is catalyzed by a hydroperoxide-dependent enzyme, identified as a peroxygenase. The hydroperoxides formed from fatty acids by a lipoxygenase are efficient co-substrates of the EPTC sulfoxidation. The effects of the safener dichlormid on the peroxygenase and lipoxygenase activities were studied in vitro and in vivo. In vitro, the safener is not an inhibitor of these enzymes. Dichlormid seems to act, in vivo, by modulating the amounts of peroxygenase and lipoxygenase in treated plants.
Studies on the Chemistry of the Lichen Genus Umbilicaria Hoffm.
Authors: Posner B. , Feige G. B. , Huneck S. 
Published: August 2018

Abstract
The aromatic compounds of more than 400 specimens of 33 species of the lichen genus Umbilicaria have been investigated by HPLC. Additionally to gyrophoric, hiascic, lecanoric, ovoic and umbilicaric acids, atranorin, norstictic and stictic acids, the new depside crustinic acid has been found. Structure elucidation of crustinic acid was made by means of HPLC cochromatography, NMR , UV and mass spectrometry. Now the secondary product patterns of Umbilicaria species are discussed and their significance for systematic purposes is shown.
Modulation of the Activities of Membrane Enzymes by Cereal Grain Resorcinolic Lipids
Authors: Kozubek Arkadiusz , Nietubyc Malgorzata , Sikorski Aleksander F. 
Published: August 2018

Abstract
Resorcinolic lipids, amphiphilic compounds from cereal grains show strong effects upon the activity of membrane enzymes. The concentrations for 50% inhibition of erythrocyte membrane acetylcholinesterase were in the range of 18 -90 μᴍ and were dependent on the length of the aliphatic side chain of the homologue and on the modification of hydroxyl groups in the benzene ring. Sulfonation of OH groups resulted in a drastic decrease of the inhibitory potency. The effect of resorcinolic lipids on the activity of Ca2+(calmodulin)-ATPase was the opposite. Up to concentrations of 50 μᴍ alk(en)ylresorcinols stimulated the activity of this enzyme and only slight inhibition (approx. 30%) was observed above 100 μᴍ. The results suggest that the effect of resorcinolic lipids might depend on their ability to alter the bilayer properties. Most probably these compounds decrease the mobility of membrane phospholipid molecules.
Metabolism of the Herbicide Bromoxynil in Hordeum vulgare and Stellaria media
Authors: Schaller Barbara , Schneider Bernd , Schütte Horst Robert 
Published: August 2018

Abstract
The metabolism of [3,5-14C]3,5-dibromo-4-hydroxybenzonitrile (bromoxynil) was studied in Hordeum vulgare and Stellaria media.
In excised barley seedlings the time course of metabolism was followed over 48 h and the distribution of radioactivity to various metabolic fractions measured. The metabolites, separated by TLC and HPLC, were identified by chemical and spectrometric methods. Bromohydroquinone and 2,6-dibromohydroquinone were found, indicating partly debromination and replacement of the nitrile group by hydroxyl. The major parts of bromoxynil and of the metabolites were recovered in glucosidic conjugates.
In Stellaria media the same metabolites as in Hordeum vulgare were determined. Additionally, metabolites of unknown structures without bromine were detected.
How Many Ryanodine Binding Sites Are Involved in Caffeine Induced Calcium Release from Sarcoplasmic Reticulum Terminal Cysternae Vesicles?
Authors: Hasselbach Wilhelm , Migala Andrea 
Published: August 2018

Abstract
The inhibition by ryanodine of caffeine induced calcium release from actively loaded heavy sarcoplasmic vesicles has been studied in order to analyse the relation between the occupancy of the vesicular calcium release channels by ryanodine and channel function. Ryanodine binding was monitored with [3H]ryanodine under ionic conditions favouring the establishment of binding equilibrium. Binding follows 1 : 1 stoichiometry yielding dissociations constants between 7 - 12 nᴍ and 12-15 pmol ryanodine/mg vesicular protein as maximum number of ryanodine binding sites. When ryanodine labeling was monitored by measuring the decline of the amplitude of caffeine induced calcium release 50% inhibition occurred at a free ryanodine concentration of 1 nM. At this concentration less than 10% of the available ryanodine binding sites are occupied. Caffeine induced calcium release is completely abolished when 3 pmol ryanodine/mg have reacted. A corresponding divergence between ryanodine binding and its effect on caffeine induced calcium release was observed when the initial rate of ryanodine binding was measured either by labeling the vesicles with [3H]ryanodine or by following the decline with time of caffeine induced calcium release. Caffein induced calcium release declines four times faster than the fraction of unoccupied ryanodine binding sites, k = 4.3 x 104 ᴍ-1 s-1 versus 1.2 x 104 ᴍ-1 s-1. The observed interrelation between the occupation of ryanodine binding sites and its effect on caffeine induced calcium release indicates that the caffeine sensitive calcium channel functions as an assembly of at least 4 ryanodine binding sites whereby the occupation of one site suffices to abolish calcium release. The stoichiometric composition appears to be not fixed but might change according to the size of the fraction of ryanodine receptors exhibiting caffeine sensitivity. The reported data were evaluated according to the algorithm derived by H. Asai and M. F. Morales, J. Biol. Chem. 4, 830-838 (1965) for the activity of a macromolecule and the extent of an inhibiting reaction.
Umwandlung von [5' -3H]Riboflavin in 5,6-Dimethylbenzimidazol / Transformation of [5'-3H]Riboflavin into 5,6-Dimethylbenzimidazole
Authors: Kolonko Bernhard , Hörig Joachim A. , Renz Paul 
Published: August 2018

Abstract
The 5,6-dimethylbenzimidazole unit of vitamin B12 is formed from riboflavin via FMN in aerobic and some aerotolerant bacteria. Thereby C-1′ of the ribityl side chain gets C-2 of 5,6-dimethylbenzimidazole. Experiments with homogenates of Propionibacterium shermanii on the fate of C-atoms 2′ to 5′ of the ribityl side chain of riboflavin in this transformation are reported. It was found that [5′-3H]riboflavin leads to radioactive sugar phosphates. These were isolated, dephosphorylated, and separated. Thus 3H-D-fructose and 3H-D-glucose were detected. The degradation of 3H-D-glucose revealed that 14 per cent of the of the total radioactivity was located in C-1, and 86 per cent in C-6. This indicates that during 5,6-dimethylbenzimidazole biosynthesis a three carbon unit is formed from the ribityl side chain of riboflavin.
Hairy Root Cultures of Peganum harmala II. Characterization of Cell Lines and Effect of Culture Conditions on the Accumulation of ß-Carboline Alkaloids and Serotonin
Authors: Berlin J. , Kuzovkina I. N. , Rügenhagen C. , Fecker L. , Commandeur U. , Wray V. 
Published: August 2018

Abstract
Hairy root cultures of Peganum harmala established by genetic transformation with Agrobacterium
rhizogenes wild type strains A4, 15834 or carrying the binary vector pLTCgus 1, respectively, were analyzed with respect to their tryptophan-derived metabolites. Beside the previously detected β-carboline alkaloids harmine, harmol, harmaline and harmalol all hairy root cultures were found to contain the β-carboline glucoside ruine and serotonin. The appearance of the root cultures and the levels of β-carboline alkaloids were greatly affected by the nitrogen source of the medium. In the presence of higher levels of ammonium ions (as in MS medium) the roots were short and thick, while in B50 medium (low ammonium) they were thin and long. Ammonium ions had a negative effect on the levels of β-carbolines. The best root cultures accumulated on B50 1.5-2% β-carbolines on a dry mass basis and in the presence of 6% sucrose ca. 10 mg β-carbolines/L x d were formed. In the presence of phytohorm ones root cultures were converted into low producing suspension cultures, from which the highly productive roots were reinduced on phytohormone-free medium.
Pyoverdine aus Pseudomonas putida / Pyoverdins from Pseudomonas putida
Authors: Gwose I. , Taraz K. 
Published: August 2018

The structures of two pyoverdins (Pp 1 and Pp 2) and one dihydropyoverdin (dihydro-Pp 2) from a strain of Pseudomonas putida have been elucidated by spectroscopic methods and degradation studies. The pyoverdins Pp 1 and Pp2 consist of a chromophore which was identified as (1 S)-5-amino-2,3-dihydro-8,9-dihydroxy-1 H-pyrimido[1,2-a]quinoline-1-carboxylic acid substituted at the amino group with a 3-carboxypropanoyl or a succinamoyl residue and at the carboxy group with the N-terminus of L-Ser-L-Thr-D-Ser-L-Orn-L-threo-(OH)Asp-[D-Gln + L-Dab]*-L-Ser-D-allo-Thr-L-c(OH)Orn.
Dihydro-Pp 2 differs from Pp 2 only in the chromophore, which is saturated at carbons 5 and 6. All compounds contain a tetrahydropyrimidine moiety ([D-Gln + L-Dab]*) resulting from the condensation of 2,4-diaminobutyric acid and glutamine.