bluuebunny/crossref_metadata_2025_split huggingface dataset:
Purification of the Chloroplast Pyruvate Dehydrogenase Complex from Spinach and Maize Mesophyll
Authors: Treede Hans-Jürgen , Heise Klaus-Peter 
Published: August 2018

Abstract
This paper deals with the partial purification of the pyruvate dehydrogenase complex (PDC) from chloroplasts of spinach and maize mesophyll which hitherto has been isolated only from pea chloroplasts. Starting with membrane free suspensions of lyophilized chloroplasts, and following a high-speed (140000 Xg) centrifugation of this “stromal extract”, the initial specific PDC-activities were concentrated by a factor 10 in the sediment. While most of the purification procedures described earlier resulted in almost complete loss of enzyme activities, a rate zonal sedimentation on linear glycerol gradients allowed for an additional up to 100-fold enrichment of the labile multienzyme complex, albeit with low yields. In contrast to chloroplast PDC from maize mesophyll, inactivation of the spinach complex during glycerol fractionation was due to the dissociation of its loosely bound dihydrolipoyl dehydrogenase component which collected in a lower density fraction of the gradient. Its recombination with PDC constituents of the bottom layer nearly restored initial activities.
The chloroplast complex has been identified as true PDC by its substrate specificity for pyru­vate, NAD+, and coenzyme A and the 1:1:1 stoichiometry of its reaction products NADH, CO2, and acetyl-CoA.
The chloroplast PDC of both plant species showed the well known higher pH-and Mg-requirements than the mitochondrial complex. The observed species-specific differences in the stability of this multienzyme system suggest a connection with the aggregation state of its components. Apparently, the individual subcomplexes are able to function either together in acetyl-CoA formation or independently from each other, e.g. in the synthesis of acetolactate via hydroxy-ethyl-thiamine pyrophosphate or dihydrolipoyl dehydrogenase activities.
Adsorbent Culture of Tobacco Cell Suspensions with Different Adsorbents
Authors: Maisch R. , Knoop B. , Beiderbeck R. 
Published: August 2018

Abstract
The release of secondary substances from plant cell suspensions can be enhanced by the addition of adsorbents to the culture medium. Tobacco cells react to a variety of different adsor­bents (Florisil. raw silk. Polyclar AT. and the adsorber resins XAD-4 and XAD-7) with important qualitative and quantitative changes of their secondary substance pattern, in some cases without changes of growth.
Evidence for the Intercalation of Thalidomide into DNA: Clue to the Molecular Mechanism of Thalidomide Teratogenicity?
Authors: Koch Heinrich P. , Czejka Martin J. 
Published: August 2018

Abstract
The intercalation of thalidomide (a-phthalimidoglutarimide) into nucleic acids was studied by spectrophotometric titrations, displacement of known intercalators, viscosity changes of DNA solutions, and by phase partition analysis. Specific binding of thalidomide was found to DNA of various specimens (human placenta, calf thymus, salmon sperm), but not to RNA (from bakers yeast, torula yeast).
Formation and Structure of Radicals from ᴅ-Ribose and 2-Deoxy- ᴅ-ribose by Reactions with SO4
·̅ Radicals in Aqueous Solution. An in-situ Electron Spin Resonance Study
Authors: Herak Janko N. , Behrens Günter 
Published: August 2018

Abstract
ESR spectroscopy has been used to analyse the conformation of the radicals produced by the reaction of SO4
·̅ with ᴅ-ribose (1), and 2-deoxy-ᴅ-ribose (6), at pH 1.3-5. From ribose three different types of radicals formed by H abstraction at C-1, C-2 and C-3 followed by a regio-selective α,β-water elimination have been identified: the 2-deoxy-ribonolacton-2-yl (3), the 1-deoxy-pentopyranos-2-ulos-1-yl (4). and the 4-deoxy-pentopyranos-3-ulos-4-yl (2). Using deoxyribose two radicals of similar type, formed by H abstraction at C-3 and C-4 followed by water elimination, have been observed: the 2,4-dideoxy-3-ulos-4-yl (7) and the 2,3-dideoxy-4-ulos-3-yl (8). In addition, from both sugars an a-hydroxyalkyl radical has been identified based in part on the timing of their conformational motions: the ribos-3-yl (5) (the precursor of 2) and the 2-deoxy-ribos-1-yl (9), respectively. For radical 5 the rate constant k(e) for the water elimination and hence transformation into radical 2 was estimated. From the analysis of selective line broadening the frequencies of conformational changes of radicals 2 and 7 have been estimated. For 7 the frequencies of exchange of the two methylene groups were found to differ by more than 3 orders of magnitude.
The Effect of Volatile Anesthetics on Giant Neurons in the Lobula Plate in the Fly
Authors: Kirschfeld K. 
Published: August 2018

Abstract
Movement sensitive giant neurons in the lobula plate of the fly (H1-neurons, V-neurons) are affected by low con­centrations of volatile anesthetics (halothane, N2O): the spike frequency generated by motion in the preferred di­rection decreases, that in the opposite direction increases. This means that the response to the motion stimulus de­fined as the spike frequency modulation decreases. Higher concentrations of the anesthetics lead to an increasing spike frequency which is unaffected by the motion stimulus, until eventually no spikes are generated any longer. The results are in agreement with the assumption that the anesthetics increase the membrane permeability of these neurons.
The Activation of the Cytochrome P-450 Dependent Monooxygenase System by Light
Authors: Müller-Enoch D. , Gruler H. 
Published: August 2018

The cytochrome P-450 dependent monooxygenase system of rat liver microsomes is investi- gated by light dosimetry (action spectroscopy). The scoparone-O-demethylation activity is en- hanced by light and depends on the wavelength of the irradiating light. The relative increase of the activity (about 15%) by the irradiating light (~ 0.5 mW/cm2) is maximal at a wavelength of 400 nm.
The light induced enhancement of the 7-ethoxycoumarin-O-deethylase activity was measured in reconstituted systems, consisting of one of the two P-450 enzymes (P-450βNF-B and P-450PB-B) with the NADPH-cytochrome P-450 reductase. The action spectrum of the reconstituted P-450βNF-B: NADPH-P-450 reductase complex shows a maximum between 420 and 440 nm. The relative increase of the activity induced by light of 420 nm was 7.3% and 9% for the reconstituted systems of P-450βNF-B and P-450PB-B. respectively. The results are discussed in analogy to the classic experiments of Warburg with its blocked CO- enzyme-complex.
The results can best be explained by the assumption that the light induced enhancement of the enzyme activity is due to an excitement of those intermediate states of the P-450 catalytic cycle (ferric and ferrous state of the heme iron) which are rate limiting.
Polymerization of Actin in the Absence and Presence of Cytochalasin B: Problems of Determining "Critical Concentration"
Authors: Fussmann Bernd , Dancker Peter 
Published: August 2018

Abstract
Various concentrations of actin (0.3 or 1 mᴍ MgCl2, 1 mᴍ ATP , 1 mᴍ EGTA) reached their final degree of polymerization (measured by a pyrene dye attached to actin) earlier in the presence of cytochalasin B than in its absence. The curves relating concentrations of polymeric F-actin to total actin concentration were under these conditions highly nonlinear making an unam biguous extrapolation to zero F-actin concentration (to deduce the “critical concentration” of actin poly­ merization) im possible. The concentration of actin, above which polymerization occurred, was unaltered by cytochalasin B (although for reasons not yet understood the specific fluorescence intensity of polymerized actin was lower in the presence of cytochalasin B than in its absence). The results show that a distinct “critical concentration” of actin polymerization must not always be well defined.
Triplet-Selective Chemistry : a Possible Cause of Biological Microwave Sensitivity
Authors: Keilmann Fritz 
Published: August 2018

Abstract
A hypothesis is proposed to explain resonant biological effects of microwaves. The interaction is thought to occur with low-frequency electronic transitions of transient triplet (or quartet etc.) molecules. As the transient molecules’ substate populations can be assumed to be far from thermal equilibrium the effect of resonant microwaves would be to equalize the population of two substates. Since the overall chemical reactivity of a molecule depends on its substate the result is an overall change of the molecules’ reaction rate which may cause further changes in the biochemical pathway.
The model can in principle account for fixed frequencies, narrow linewidths and low saturation thresholds as are reported to be characteristic of biological sensitivity to millimeter waves [1-4], The interaction at the molecular level predicts identical resonances in widely different living objects. These resonances may offer a useful tool in biology and they can furthermore influence the discussion of microwave environmental impact.
An Elicitor of the Hypersensitive Lignification Response in Wheat Leaves Isolated from the Rust Fungus Puccinia graminis f. sp. tritici I. Partial Purification and Characterization
Authors: Moerschbacher B. , Kogel K. H. , Noll U. , Reisener H. J. 
Published: August 2018

Several biotic and abiotic clicitors of the hypersensitive reaction in wheat leaves are described. The elicitors induce enhanced activity of phenylalanine ammonia-lyase with subsequent lignifica­tion, visible as a yellow autofluorescence. The deposited material stains positively with phloroglucinol. DEAE-dextran, epoxystearic acid and chitosan are strong elicitors, while the glucans tested have no activity.
A biotic elicitor (genuine Pgt-elicitor) was isolated from the germ tube walls of uredospores of Puccinia graminis f. sp. tritici. The high molecular weight, water soluble elicitor is heat stable and unaffected by mild acid and mild alkaline treatments. It seems to be a glycoprotein with the carbohydrate moiety bearing the active residues, as indicated by periodate sensitivity and pro­tease stability. The carbohydrate moiety consists mainly of glucose with some galactose and mannose.
Upon ultrafiltration and gel chromatography elicitor activity was associated with fractions of molecular weight of more than 100 kD.
When injected into the intercellular space of primary wheat leaves, the elicitor induces lignifica­tion, preceded by an increase in phenylalanine ammonia-lyase activity.
Photodestruction of Endogenous Porphyrins in Relation to Cellular Inactivation of Propionibacterium acnes
Authors: Melø Thor B. , Reisæter Gro 
Published: August 2018

Abstract
During growth of Propionibacterium acnes on Eagles medium protoporphyrin was accumulated inside the cells and coproporphyrin, both as a free base as metalcontaining, outside the cells. The photochemical processes in the endogenous porphyrins were studied by fluorescence spectroscopy during continuous irradiation of Propionibacterium acnes in suspension. The irradiation caused initially an increase in the content of protoporphyrin in the cells in comparison to that which had been accumulated during growth. Maximum light induced protoporphyrin production was achieved in 5 days old cultures. In old cultures where there was practically no initial protoporphy­rin release, the fluorescence intensities from all the porphyrins present in the culture vanished exponentially with the irradiation time. The metal containing form of fluorescent coproporphyrin, with a maximum emission at 580 nm, was photobleached about ten times faster than the free base forms of coproporphyrin and protoporphyrin. Among these three fluorescent substances in the cell culture only the free base forms of the porphyrins have longer lifetimes than the cells themselves irradiated at the same conditions.
Specific Binding of Calcium to Soluble Chromatin
Authors: Brust Rüdiger 
Published: August 2018

Abstract
Equilibrium dialysis studies and sedimentation experiments with soluble rat liver chromatin and radioactive 45Ca support the hypothesis that there is a specific binding of Ca2+ to chromatin molecules. At low ionic strength the binding constant is about 12 1/mᴍ indicating that more than half of the negative charges of the chromatin molecules are neutralized due to the binding of Ca2+ at appropriate concentrations. This effect possibly accounts for low concentration of Ca2+ and other divalent cations being effective in inducing compact higher order structures of chromatin. Monovalent cations are not specifically bound, but high concentrations cause unspecific shielding of the charges on the chromatin molecules and thus structural transformation. Even under these high salt conditions a specific binding of Ca2+ to chromatin occurs. The binding constant is, however, only 0.4 1/mᴍ due to the lower effective concentration of the charged chromatin molecules which is reduced by unspecific neutralizing.
(R)MandeIonitrile and Prunasin, the Sources of Hydrogen Cyanide in All Stages of Paropsis atomaria (Coleoptera: Chysomelidae)
Authors: Nahrstedt A. , Davis R. H. 
Published: August 2018

Abstract
(R)Mandelonitrile and the cyanogenic glucoside prunasin have been established as the source of HCN in all stages of the Australian beetle Paropsis atomaria. Quantitative data for both compounds and all life stages are presented. The larvae contain a β-glucosidase activity capable of hydrolysing prunasin and also β-cyanoalanine synthase activity enabling the disposal of free cyanide.
Further Characterization of Chickpea Isoflavone 7-O-Glucoside- 6"-O-malonate: malonylesterase: Evidence for a Highly Specific, Membrane-Bound Enzyme in Roots of Cicer arietinum L.
Authors: Hinderer Walter , Köster Johannes , Barz Wolfgang 
Published: August 2018

The specific malonylesterase from chickpea (Cicer arietinum L.), hydrolyzing biochanin A 7-O- glucoside-6″-O-malonate (BGM), has been purified to apparent homogeneity and characterized recently (Hinderer et al., Arch. Biochem. Biophys. 248, 570-578 [1986]). Its substrate specificity as well as the high molecular mass of the native enzyme were further investigated. The 5-deoxy- isoflavone conjugate corresponding to BGM, the formononetin 7-O-glucoside-6,,-O-malonate (FGM), was shown to be a substrate of the malonylesterase essentially as BGM. By contrast, methyl-BGM, a diester of malonic acid was a poor substrate. The purified enzyme completely lacked thioesterase activity with malonyl-CoA as substrate. The inability of the malonylesterase to hydrolyze synthetic acetyl or propionyl esters was further demonstrated with a highly sensitive fluorometric assay using esters of 4-methylumbelliferone. The enzyme-catalyzed hydrolysis of BGM was stimulated in the presence of dissociated carboxylic acids like citrate which was most effective at 30 mM and pH 7.5-8.0.
The purified malonylesterase as well as the enzyme activity in crude extracts were totally excluded in gelchromatography with Ultrogel AcA 22. The enrichment of the enzyme activity in microsomal fractions gave strong evidence that the malonylesterase is membrane-bound in vivo. Stimulation of the enzyme activity in vitro by detergents indicates the presence of lipid material in the enzyme and the activity profiles obtained after sedimentation analyses suggest that purifica­tion of a distinct membrane-protein complex had been achieved.
Phenylalanine and Tyrosine Biosynthesis in Sporeforming Members of the Order Actinomycetales
Authors: Hund Hilda-K. , Keller Brigitte , Lingens Franz 
Published: August 2018

Abstract
The enzymes of the terminal steps of phenylalanine and tyrosine biosynthesis, chorismate mutase, prephenate dehydratase, arogenate dehydratase, prephenate dehydrogenase and aroge­ nate dehydrogenase were studied in 13 sporeforming members of the order Actinomycetales. In these organisms tyrosine is synthesized exclusively via arogenate, phenylalanine, however, via phenylpyruvate. The regulation pattern of the corresponding enzymes was determined: No feed­ back inhibition of arogenate dehydrogenase by L-phenylalanine and ʟ-tyrosine was observed. Chorismate mutase was found to be inhibited in all organisms by ʟ-tyrosine and in most organisms by ʟ-tryptophan. ʟ-Phenylalanine was shown to inhibit prephenate dehydratase in the majority of bacteria tested and ʟ-tyrosine activated this enzyme in most cases.
The elution profiles for the phenylalanine and tyrosine biosynthetic enzymes were studied in three members of the order Actinomycetales by anion exchange chromatography on DEAE-cellulose.
Biopterin Synthesis in Mouse Spleen during Bone Marrow Transplantation Correlates with Unimpaired Hemopoietic Engraftment
Authors: Ziegler Irmgard , Thierfelder Stefan 
Published: August 2018

Abstract
Normal engraftment of bone marrow transplants depends on histocompatibility between donor and recipient. In this case reconstitution of hemopoiesis and lymphopoiesis in the mouse spleen is correlated with transient biopterin synthesis in these cells. Allogeneic bone marrow progeny cells undergo donor cell proliferation in the spleen prior to the incidence of graft-versus-host reaction. These cells are not committed to biopterin synthesis. Thy-1 monoclonal antibody fully repairs engraftment of allogeneic transplants together with biopterin synthesis.
Effect of pH on Glycolate and Ammonia Excretion in L-MSO Treated Chlorella Cells
Authors: Shiraiwa Yoshihiro , Schmid Georg H. 
Published: August 2018

Abstract
The effect of pH changes on the excretion of ammonia and glycolate from algal cells into the medium was investigated in L-MSO (final concentration, 0.5 mм) -treated High-and Low CO2-cells of Chlorella vulgaris 211-11 h. The excretion was analyzed in the condition in which the cells were continuously gassed with air at 25 °C. At the values tested, generally more ammonia was excreted in L-MSO-treated Low CO2-cells than in L-MSO treated High CO2-cells. In both kinds of algal cells more ammonia was excreted at low pH-values and absolutely no ammonia was excreted at pH 8. In the dark, no or only slight ammonia excretion was observed in both L-MSO-treated High and Low CO2-cells. Under all these conditions no or only very low glycolate excretion was observed in both L-MSO treated High and Low CO2-cells.
In High CO2-cells rates of photosynthesis were high at pH 6 and lower at higher pH values. On the other hand Low CO2-cells showed practically little dependence of photosynthetic rates on the pH. This result might indicate that the major part of the ammonia excretion observed, was not due to the inhibition of photosynthesis at acid pH values. It is known that ammonia excretion in L-MSO treated algal cells is due to the inhibition of the refixation of ammonia which originates from the glycine-serine aminotransferase reaction in the glycolate pathway. Our results demonstrate that glycolate production and glycolate metabolism are more intense at low pH values when compared to high pH values. This is valid for both High and Low CO2-cells. Low CO2-cells in Chlorella vulgaris 211-11 h exhibit a more active glycolate metabolism than High CO2-cells.
Enzymatic Acyloin Condensation of Acyclic Aldehydes
Authors: Abraham Wolf-Rainer , Stumpf Burghard 
Published: August 2018

Abstract
Corynespora cassiicola DSM 62474 and Diplodia gossypina ATCC 10936 were found to cleave some acyclic terminal terpendiols and prolongate them later by addition of a C2-unit to afford 1,2-dihydroxy-propyl-compounds. The enzymes involved in this reaction from both microorganisms displayed a strong stereoselectivity which is completely different in both strains. The stereochemi­cal requirements of the substrates for both strains and the mechanism were elucidated by using closely related substrates. The absolute configuration of the diols were solved by correlation with com pounds of known absolute configuration.
Spontaneous Release of Malondialdehyde from Ultraviolet Light Exposed Liposomal Membranes
Authors: Agarwal Sanjiv , Ghosh Anusua , Chatterjee S. N. 
Published: August 2018

Abstract
UV absorption spectroscopy revealed the presence of MDA with characteristic maximum at about 266 nm in the dialysate of the UV irradiated liposomal suspension. The amount of MDA released increased linearly with increasing UV dose. The fluorescence method for the assay of MDA was found nearly 1500-fold more sensitive than the TBA colour reaction method.
Pyrimidine Homoribonucleosides: Synthesis, Solution Conformation, and Some Biological Properties
Authors: Lassota Piotr , Kuśmierek Jarosław T. , Stolarski Ryszard , Shugar David 
Published: August 2018

Conversion of uridine and cytidine to their 5′-O-tosyl derivatives, followed by cyanation with tetraethylammonium cyanide, reduction and deamination, led to isolation of the hitherto un- known homouridine (1-(5′-deoxy-β-D-allofuranosyl)uracil) and homocytidine (1-(5′-deoxy-β-ᴅ-allofuranosyl)cytosine), analogues of uridine and cytidine in which the exocyclic 5′-CH2OH chain is extended by one carbon to CH2CH2OH. Homocytidine was also phosphorylated to its 6′-phosphate and 6′-pyrophosphate analogues. In addition, it was converted, via its 2,2′-anhydro derivative, to arahomocytidine, an analogue of the chemotherapeutically active araC.
The structures of all the foregoing were established by various criteria, including 1H and 13C NMR spectroscopy, both of which were also applied to analyses of the solution conformations of the various compounds, particularly as regards the conformations of the exocyclic chains.
The behaviour of the homo analogues was examined in several enzymatic systems. Homo- cytidine was a feeble substrate, without inhibitory properties, of E. coli cytidine deaminase. Homocytidine was an excellent substrate for wheat shoot nucleoside phosphotransferase; while homouridine was a good substrate for E. coli uridine phosphorylase. Although homoCMP was neither a substrate, nor an inhibitor, of snake venom 5′-nucleotidase, homoCDP was a potent inhibitor of this enzyme (Ki~6 μм). HomoCDP was not a substrate for M. luteus polynucleotide phosphorylase. None of the compounds exhibited significant activity vs herpes simplex virus type 1, or cytotoxic activity in several mammalian cell lines.
Effects of Plant Bioregulators on the Production of Iridoid Derived Terpenoids in Valeriana wallichii and Fedia cornucopiae Cell Suspension Cultures
Authors: Förster Wolfram , Becker Hans 
Published: August 2018

Abstract
Four plant bioregulators were tested for their effects on production of valepotriates in Valeriana
wallichii and Fedia cornucopiae cell suspension cultures. Concentrations of more than 10 ppm reduced valepotriate yield. At lower concentrations production was increased. For optimal activity, bioregulators had to be applied during early exponential growth, up to day 8 of the growth cycle. At equimolar concentrations dim ethylm orpholinium bromide (4 ppm) and dimethylpiperidinium chloride (3 ppm) significantly im proved total valepotriates in V. wallichii (up to 23%) and in F cornucupiae (up to 50% ) 2-(3,4-dichlorophenoxy ) - triethylamine (6 ppm ) and 2-(3,5-diisopropylphenoxy)-triethylam ine (6.4 ppm) increased valepotriate production in both cell cultures up to 40%. With dimethylpiperidinium chloride and dimethylmorpholinium bromide the ratio of m onoene to diene valepotriates in both cell systems was significantly shifted to the m onoene com pounds. A general use of these bioregulators to increase production of terpenoid secondary m etabolites in plant tissue cultures is indicated.
Enzymatic Synthesis of 1,6-Digalloylglucose from β-Glucogallin by β-Glucogallin: β-Glucogallin 6-O-Galloyltransferase from Oak Leaves
Authors: Schmidt Stephan W. , Denzel Klaus , Schilling Gerhard , Gross Georg G. 
Published: August 2018

Abstract
Cell-free extracts from oak (Quercus robur) leaves catalyze the transfer of the galloyl-moiety of β-glucogallin (1-O-galloyl-β-D-glucopyranose) specifically to the 6-position of the same compound, yielding 1,6-di-O-galloyl-β-D-glucopyranose, an intermediate of gallotannin biosynthesis, β- Glucogallin thus functions as both donor and acceptor molecule in this reaction. The partial purification and some general properties of this new acyltransferase are reported.