bluuebunny/crossref_metadata_2025_split huggingface dataset:
A Method for Estimating Glycine in the Presence of Excess Glutamate with o-Phthaldialdehyde
Authors: Lombardo Maria Elisa , Araujo Lidia Susana , Branca Andrea , Batlle Alcira M. del C. 
Published: August 2018

Abstract
We present a method to determine concentrations of glycine between 1 and 3 mM in the simultaneous presence of 25-100 mM glutamate, which is a modification of the procedure originally described by Klein and Linscr. Z. Physiol. Chem. 205,251 (1932). Glycine and glutamate react with 150 mM w-phthaldialdehyde, glycine is quantitatively con- verted into a colored o-phthaldialdehyde-glycine-glutamate complex. By recording the ab- sorbance of the complex at its maximum peak (around 540 nm). at 600 nm and 480 nm and applying a correction formula is possible to obtain a very good linear correlation when plot- ting the values of corrected absorbance versus the concentration of glycine. From these plots an extinction coefficient of 7.0 x 102 cm-1 m-1 was calculated for the complex. The method is highly reproducible and sensitive and solved the problem of glutamate interference when esti- mating low concentrations of glycine in mixture containing 10 to 50 times concentrations of the former aminoacid.
Solid State and Solution Structures of an Adenine Analogue of the Antiviral Acyclonucleoside 9-(1,3-Dihydroxy-2-propoxymethyl)guanine
Authors: Granzin Joachim , Saenger Wolfram 
Published: August 2018

Abstract
The title compound. 9-(1,3-dihydroxy-2-propoxymethyl)adenine (DHP-Ade). an analogue of the antiviral acyclonucleoside 9-(1,3-dihydroxy-2-propoxymethyl)guanine (DHPG), crystallizes in the monoclinic space group P21. with unit cell dimensions of a = 10.848(4), b = 8.765(3), c = 11.432(4) Å. β = 102.14(3)° . with two independent molecules in the asymmetric unit. The crystal structure of DHP-Ade was determined and compared with that for DHPG. The solution conformations of both acyclonucleosides were also determined with the aid of 1H and ,13C NMR spectroscopy. In the solid state the acyclic chain may adopt a “folded” form, i.e. gauche about the C(1′)-O(1′) bond (as in DHP-Ade), or an “extended” form (as in DHPG), results which corre- spond to the rotations about this bond in solution. A general discussion is presented of the conformations of the acyclic chains of various acyclonucleosides, from the antiviral 9-(2-hydroxyethoxymethyl)guanine (Acyclovir, ACV) through to 2′,3′-seco-nucleosides, both in the solid state and in solution, and the relevance of these to biological activities.
Photophysical and Photochemical Properties of 2,3-Dihydro-4(l H)-quinolinones. Part I. Fluorescence Properties
Authors: Bakalova Sn. , Biczók L. , Kavrakova I. , Bérces T. 
Published: August 2018

Abstract
Absorption spectra and fluorescence properties of 2,3-dihydro-4(1 H)-quinolinone derivatives were studied at room temperature in different solvents. It has been found that the fluorescence quantum yields and fluorescence decay times strongly depend on the molecular structure and solvent polarity. The character and the energy of excited states were determined by PPP and CNDO/S quantum-chemical calculations.
Asymmetrie Reconstitution of the Erythrocyte Anion Transport System in Vesicles of Different Curvature: Implications for the Shape of the Band 3 Protein
Authors: Lindenthal Sabine , Scheuring Uwe , Ruf Horst , Kojro Zbigniew , Petrasch Peter , Schubert Dieter 
Published: August 2018

Abstract
The anion transport protein of the human erythrocyte membrane, band 3, was solubilized and purified in solutions of the non-ionic detergent nonaethylene glycol lauryl ether and then reconstituted in spherical egg phosphatidylcholine bilayers as described earlier (U. Scheuring, K. Kollewe, W. Haase, and D. Schubert, J. Membrane Biol. 90, 123-135 (1986)). The resulting paucilamellar proteoliposom es of average diameter 70 nm were transformed into smaller vesicles by French press treatment and fractionated according to size by gel filtration. The smallest protein-containing liposomes obtained had diameters around 32 nm; still smaller vesicles were free of protein. All proteoliposome samples studied showed a rapid sulfate efflux which was sensitive to specific inhibitors of band 3-mediated anion exchange. In addition, the orientation of the transport protein in the vesicle membranes was found to be “right-side-out” in all samples. This suggests that the orientation of the protein in the vesicle membranes is dictated by the shape of the protein’s intramembrane domain and that this domain has the form of a truncated cone or pyramid
Elicitor Induction of Cytochrome P-450 Monooxygenases in Cell Suspension Cultures of Chickpea (Cicer arietinum L.) and Their Involvement in Pterocarpan Phytoalexin Biosynthesis
Authors: Gunia Werner , Hinderer Walter , Wittkampf Uta , Barz Wolfgang 
Published: August 2018

Abstract
A yeast glucan elicitor causes the accumulation of the pterocarpan phytoalexins medicarpin and maackiain in chickpea (Cicer arietinum) cell suspension cultures established from seeds. A cell culture line from a chickpea cultivar resistant against its main fungal pathogen Ascochyta rabiei accumulates large amounts (944 nm ol/g fr. wt.) whereas a cell culture line from a susceptible cultivar accumulates only low amounts (38 nm ol/g fr. wt.) of the phytoalexins. This is consistent with differential accumulation of pterocarpan phytoalexins in intact plants [1], The first reactions in the pterocarpan-specific branch of biosynthesis are hydroxylation of the isoflavone intermediate form ononetin in position 2′ or 3′, catalyzed by microsomal cytochrome P-450 monooxygenases. Upon elicitation form ononetin 2′-hydroxylase undergoes a strong transient induction in the cell suspension culture of the resistant cultivar, whereas in the cell culture from the susceptible cultivar it is only slightly induced. In both cell suspension cul­tures the induction of cinnamic acid 4-hydroxylase and of form ononetin 3′-hydroxylase does not show a clear correlation with phytoalexin accumulation. Experiments with different elici­tor concentrations confirm that formononetin 2′-hydroxylase is much more induced in cell cul­tures from the resistant cultivar than from the susceptible one. It is concluded that the massive difference in phytoalexin accumulation between cell suspension cultures from the resistant and susceptible cultivar is determined mainly by the differential induction of form ononetin 2′-hydroxylase activity.
On the Accessibility of Essential Tyrosines in Isolated and Activated Chloroplast H+
-ATPase
Authors: Bickel-Sandkötter Susanne , Esser Kordula , Horbach Martina 
Published: August 2018

Abstract
The addition of 7-chloro-4-nitrobenzofurazan to isolated and activated CF1, creates a completely changed binding stoichiometry and subunit-distribution of bound modifier in contrast to the binding pattern in not-activated CF1. The activation of CF1, by dithiothreitol and heat results in the accessibility of three additional tyrosines in β-subunits and one additional tyro­ sine in α-subunits. Binding of pyridoxalphosphate to lysine in the active state suppresses the accessibility of the additional tyrosines, suggesting that PLP inactivates the ATPase by induc­ing a conformational change. Furthermore, two NBD -molecules are bound to γ-subunits when CF1, is activated. These two molecules may be bound to sulfhydryl groups of cysteines which become accessible to NBD after activation.
Characterization of Reaction Center-B875 Complex of Rhodocyclus gelatinosus: QB Site Properties Derived from Reconstitution Experiments
Authors: Agalidis I. , Rivas E. , Reiss-Husson F. 
Published: August 2018

Abstract
Purified reaction center-B875 pigment-protein complex isolated from Rc. gelatinosus (I. Agalidis, E. Rivas, and F. Reiss-Husson, Photosynth. Res. 23, 249 - 255 (1990)) was further characterized. In the chromatophores, the quinone content was shown to be 6 menaquinones 8 and 16 ubiquinones 8 per reaction center, indicating that the pool contained both quinone types. Besides the primary (MK8) and secondary (UQ8 ) electron acceptors of the reaction cen­ter, the complex contains residual quinones from the membrane pool (about 3 MK8 and 5 UQ8) probably associated with the phospholipids. Apparent particle weight of the complex including bound detergent was 520 ± 46 kDa.
The secondary quinone QB was partially removed from the RC by treatment with 2 -3 % octaethyleneglycol dodecyl ether and 3 -4 mᴍ orthophenanthroline. Reconstitution experi­ments showed that UQ6, UQ9 and UQ10 could replace QB but that MK8 and MK9 could not. It was concluded that QB site has a clear specificity towards ubiquinone binding.
Product Release is Not the Rate-Limiting Step during Cytochalasin B-Induced ATPase Activity of Monomeric Actin
Authors: Dancker Peter , Hess Lore , Ritter Karl 
Published: August 2018

Abstract
Under conditions where cytochalasin B induces ATPase activity of monomeric actin (0.3 mᴍ MgCl2, 1 mᴍ EGTA , 30 (μᴍ cytochalasin B, 1 mᴍ ATP) the rate constant of the ex­change of actin-bound ε-ATP for free ATP is about 4 -6 times faster than steady state ATPase activity. When a stoichiometric ATP -actin complex is extracted with PCA (single turnover ex­periment) the apparent rate constant of Pi generation is not faster than steady state ATPase activity. -The experiments suggest that the hydrolysis of actin-bound ATP and not the subse­quent release of hydrolysis products is rate-limiting during cytochalasin-induced ATPase activi­ty of actin.
Isolierung und spektroskopische Charakterisierung des Pyoverdin-Chromophors sowie seines 5-Hydroxy-Analogen [1] / Isolation and Spectroscopic Characterization of the Pyoverdin Chromophore and of Its 5-Hydroxy Analogue [1]
Authors: Michels J. , Benoni H. , Briskot G. , Lex J. , Schmickler H. , Taraz K. , Budzikiewicz H. , Korth H. , Pulverer G. 
Published: August 2018

Abstract
The isolation of the common chromophore of the pyoverdins isolated from iron-deficient cultures of fluorescent Pseudomonas strains and of its 5-hydroxy analogue as well as the spectroscopic characterization of the two compounds is described.
Inactivation of Photosynthetic O2 Evolution in the Cyanobacterium Anacystis nidulans PCC 6301: Influence of Nitrogen Metabolites and Divalent Cation Concentration
Authors: Wälzlein Gudrun , Pistorius Elfriede K. 
Published: August 2018

Abstract
An investigation about the in vivo inactivation of photosynthetic water oxidation has been carried out in the cyanobacterium Anacystis nidulans (Synechococcus PCC 6301). Photosystem II and photosystem I activity as well as the relative amount of the D1 and manganese stabilizing peptide of photosystem II were determined after growing the cells in nutrient media with variations in the nitrogen source and the concentration of the major divalent cations (Mg2+ and Ca2+). The results show a rapid inactivation of water oxidation in A. nidulans in response to nitrogen deficiency and in response to reduced Mg2+ and Ca2+ concentrations. The inactivation of water oxidation observed under divalent cation deficiency could be greatly accelerated when L-amino acids instead of ammonia or nitrate were used as nitrogen source. Under these conditions inactivation of water oxidation correlated with a rapid loss of D1 and with a slower loss of the manganese stabilizing peptide from photosystem II. A possible regulation of the photosystem II activity in A. nidulans by nitrogen metabolites is suggested.
Notes: Partial Characterization of anti-H L A Class II Antibodies Isolated by Aid of Sepharose-Peptide Immunoadsorbents
Authors: Chersi Alberto , Morganti-Kossmann Maria Cristina 
Published: August 2018

Synthetic peptides selected from HLA-DQ and HLADP glycoproteins were coupled to Sepharose, and used for the isolation of anti-HLA Class II antibodies from the immune sera of rabbits immunized with human lymphoblastoid cells expressing Class II antigens.
Antibodies from early and late bleedings displayed remarkable differences in affinity for peptides and for soluble membrane proteins: these differences might be due to an early immune response directed preferentially against surface linear determinants, and to a late response to assembled (discontinuous) sites.
The possibility that such antibodies might be used for the identification of amino acid stretches involved in the formation of the same assembled determinant is considered.
Zwei Pyoverdine aus Pseudomonas aeruginosa R. / Two Pyoverdins from Pseudomonas aeruginosa R
Authors: Gipp S. , Hahn J. , Taraz K. , Budzikiewicz H. 
Published: August 2018

Abstract
The structure elucidation of two pyoverdins from the strain R. of Pseudomonas aeruginosa is described.
Activity of Photosystem II Herbicides Is Related with Their Residence Times at the D 1 Protein
Authors: Naber J. Dirk , van Rensen Jack J. S. 
Published: August 2018

Abstract
The reversible binding kinetics of atrazine, diuron and ioxynil were measured via their binding and release parameters during steady state inhibition of electron transport. The parameters were determined in isolated chloroplasts of peas and of triazine-resistant and -susceptible bio­ types of Chenopodium album using a kinetic model. This model is based on the flash-induced oxygen evolution patterns of isolated broken chloroplasts.
It was found that the binding parameters were always significantly higher in the case of an oxidized acceptor quinone complex as compared with a semi-reduced complex. Triazine resistance seems to originate from a significant increase of the release kinetics. The release parameters could be used to calculate the residence times of the herbicides at the D 1 protein. The values of these residence times were always much higher for the herbicides than for Q B; this explains the inhibition of electron transport. The only exception was the residence time of atrazine in the resistant biotype, where the value was close to that of Q B.
It is concluded that the “on” kinetics of a compound to its binding environment at the D 1 protein are determined principally by the accessibility of the niche to the compound. The differences in activity between herbicides are mainly due to variations in the release kinetics.
Activities and Regulation of Enzymes of Carbohydrate Metabolism in Spruce ( Picea abies)
Authors: Boll Meinrad 
Published: August 2018

Abstract
Activities of the glycolytic enzymes were determined in seedlings, callus cultures and cell sus­ pension cultures of spruce (Picea abies) (L.) (Karst). The rate-limiting enzymes of the pathway were the hexokinases, ATP: phosphofructo-kinase, fructose-1,6-bisphosphatase and pyruvate kinase. Two phosphofructokinases were found: ATP : fructose-6-phosphate 1-phosphotransferase (PFK) and pyrophosphate :fructose-6-phosphate 1-phosphotransferase (PFP). In the presence of its activator fructose-2,6-bisphos-phate, PFP had a 4 -5-fold higher specific activity than PFK. PFP could be activated about 20-fold by fructose-2,6-bisphosphate at saturating concentrations of the substrates (fructose-6-phosphate and pyrophosphate). The increase of Vmax was accompanied by a strong increase in the apparent affinity of the enzyme for the substrates. Km for fructose-6-phosphate and pyrophosphate was 0.44 mM and 24 μM, respectively. Ka for fructose-2,6-bisphosphate was 24 nM.
In seedlings, specific activity of the glycolytic enzymes was 30-300 percent higher in the hypocotyls, except for fructose-1,6-bisphosphate aldolase, glyceraldehyde-3-phosphate dehydrogenase and phosphoglycerate kinase, their activity being 100-150percent higher in the cotyledons, This distribution remained unchanged during periods of 2 -16 weeks of cultivation of the seedlings.
In callus cultures and in cell suspension cultures, grown mixotrophically with different car­ bohydrates, all enzymes were between 1-and 7-fold higher than in autotrophically grown seed­ lings. Incubation of seedlings in mineral salt mixture containing a carbohydrate resulted in a rapid coordinate increase of the activities to the levels of callus-or cell suspension cultures. This induction required a carbohydrate and oxygen. During prolonged cultivation of cell suspension cultures, when carbohydrate became limiting, activity of the enzymes slowly declined.
Contrasting pH-Optima of Light-Driven O2-and H2O2-Reduction in Spinach Chloroplasts as Measured via Chlorophyll Fluorescence Quenching
Authors: Schreiber Ulrich , Reising Heinz , Neubauer Christian 
Published: August 2018

Abstract
Quenching analysis of chlorophyll fluorescence by the saturation pulse method is used to investigate the pH-dependency of O2-dependent electron flow in intact spinach chloroplasts with high ascorbate peroxidase activity. When carboxylase/oxygenase activity is blocked, pho­tochemical and non-photochemical quenching are initially low and increase with illumination time. Quenching shows a pH-optimum around pH 6.5, but only when ΔpH-formation is al­ lowed. It is suggested that overall O2-dependent electron flow involves two major components, namely O2-reduction (Mehlerreaction) and reduction of the H2O2 formed in the Mehlerreaction, involving enzymic activity of ascorbate peroxidase and monodehydroascorbate reductase. The separated pH-dependencies of light driven O2-reduction (presence of KCN) and of H2O2-reduction (anaerobic conditions) reveal contrasting pH-optima around pH 5 and 8.5, respectively. Energy-dependent, dark relaxable non-photochemical quenching is not observed with O2-reduction but with H2O2-reduction, and only at pH-values above 6.5. The relevance of these findings with respect to regulation of photosynthetic electron flow is discussed. It is suggested that upon limitation of assimilatory electron flow O2-dependent non-assimilatory flow is responsible for ΔpH-formation, by which it is autocatalytically stimulated. It is proposed that this autocatalytical reaction sequence is the basis of the so-called “Kautsky effect” of chlorophyll fluorescence induction.
Propagation of Voltage Transients in Arborized Neurites of Retzius Cells of the Leech in Culture
Authors: Fromherz Peter , Vetter Thomas 
Published: August 2018

Abstract
Propagation of electrical signals is studied in Retzius cells of the leech in culture using voltage-sensitive fluorescent dyes at a spatial resolution of 8 × 8 μm2 and 14×14 μm2 and at a sam pling interval of 0.12 ms. The neurons are stimulated by a microelectrode impaled in the soma. Action potentials of a halfwidth of 2 -3 ms are triggered close to the end of the primary neurite dissociated from the leech. They propagate back to the soma at invariant halfwidth at a veloci­ ty of 50-230 μm/ms. They pervade extended arborized secondary neurites which are grown on extracellular matrix protein. Their width is enhanced up to a factor two. The velocity is around 100-150 μm/ms such that delays up to 3.5 ms are observed. Accordingly the neuritic trees are not isopotential. The features of propagation are found to be incompatible with passive spread.
Surface Structure and Chemical Composition of Epicuticular Waxes during Leaf Development of Tilia tomentosa Moench
Authors: Gülz Paul-Gerhard , Prasad R. B. N. , Müller Edith 
Published: August 2018

Abstract
The very young leaflets of silver lime trees (Tilia tomtentosa), just unfolding from buds, con ­ tained a continuous wax layer without any wax sculptures. The wax on young leaves is quite different in yield and composition than that of mature leaves. After unfolding of leaves a very dynamic biosynthesis of most wax lipids was started. Fifteen days after leaf unfolding the de novo biosynthesis of β-amyrenyl acetate and later on of aldehydes could be detected for the first time. The biosynthesis of wax components in silver lime leaves was finished at the end of June and the wax remained nearly constant in amount and composition during the remaining season. At the same time, when β-amyrenyl acetate was found for the first time, wax sculptures were observed in silver lime leaf waxes coming out of the continuous wax layer, exclusively on the upper leaf side. These wax sculptures increased in quantity in the next weeks and resulted in a crystalloid shape of most solitaire quadrangular rodlets. These crystals were remained all over the season and were formed from β-amyrenyl acetate, the dominating main wax compo­nent {ca. 49% wax).
Sequence Analysis of the D1 and D2 Reaction Center Proteins of Photosystem II
Authors: Svensson Bengt , Vass Imre , Styring Stenbjörn 
Published: August 2018

Abstract
A compilation of 38 sequences for the D1 and 15 sequences for the D 2 reaction center pro­teins of photosystem II is presented. The sequences have been compared and a similarity index that takes into account the degree of conservation and the quality of the changes in each posi­tion has been calculated. The similarity index is used to identify and describe functionally im­portant domains in the D1 / D2 heterodimer. Comparative hydropathy plot are presented for the aminoacid sidechains that constitute the binding domain of the tyrosine radicals, TyrZ and TyrD, in photosystem II. The structure around TyrZ is more hydrophilic than the structure around TyrD. The hydrophilic residues are clustered in the part of the binding pocket for TyrZ that is turned towards the lumenal side of the thylakoid membrane. Most prominent is the presence of two conserved carboxylic am inoacids, D1-Asp 170 and D1-Glu 189. Their respec­tive carboxyl-groups come close in space and are proposed to constitute a metal binding site together with D1-Gln 165. The distance between the proposed metal binding site and the cen­ter of the ring of TyrZ is approximately 7Å . The cavity that constitutes the binding site for TyrD is composed of residues from the D 2 protein. Its character is more hydrophobic than the TyrZ site and the environment around TyrD lacks the cluster of putative metal binding side­-chains.
Glutathione S-Transferase Activity in Nontreated and CGA-154281- Treated Maize Shoots
Authors: Dean John V. , Gronwald John W. , Anderson Michael P. 
Published: August 2018

Abstract
Fast protein liquid chromatography (anion exchange) was used to separate glutathione S-transferase isozymes in nontreated etiolated maize shoots and those treated with the herbi­cide safener CGA -1542814-(dichloroacetyl)-3,4-dihydro-3-methyl-2 H-1 ,4-benzoxazine. Non­treated shoots contained isozymes active with the following substrates: trans-cinnamic acid (1 isozyme), atrazine (3 isozymes), 1-chloro-2,4-dinitrobenzene (1 isozyme), metolachlor (2 isozymes) and the sulfoxide derivative of S-ethyl dipropylcarbamothioate (2 isozymes). Pre­treatment of shoots with the safener CGA -154281 (1 μM) had no effect on the activity of the isozymes selective for trans-cinnamic acid and atrazine but increased the activity of the constitutively-expressed isozymes that exhibit activity with 1-chloro-2,4-dinitrobenzene, metola­chlor and the sulfoxide derivative of S-ethyl dipropylcarbamothioate. The safener pretreat­ment also caused the appearance of one new isozyme active with 1-chloro-2,4-dinitrobenzene and one new isozyme active with metolachlor. The results illustrate the complexity of gluta­thione S-transferase activity in etiolated maize shoots, and the selective enhancement of gluta­thione S-transferase isozymes by the safener CGA -154281.