bluuebunny/crossref_metadata_2025_split huggingface dataset:
Asymmetrie Reduction of Synthetic Ketones by Marine Microorganisms
Authors: Yamazaki Yoshimitsu , Maruyama Akihiko , Hosono Kuniaki , Higashihara Takanori , Kobayash Harumi 
Published: August 2018

Abstract
Three strains of bacteria reducing (trifluoroacetyl)ferrocene (3) to optically pure (R)-2,2,2-trifluoro-l-hydroxyethylferrocene (4) and one bacterial strain reducing 3 to (S)-4 of moderate optical purity were isolated from sea-water collected at the coastal areas in Ibaraki prefecture of Japan. The former three strains were identified as Micrococcus lylae, Micrococcus luteus, and Deleya marina and the latter as Bacillus licheniformis. These strains also asymmetrically reduced some other synthetic ketones, e.g., 2,2,2-trifluoroacetophenone (7) and phenyl trimethylsilyl ketone (9). Further screening of microorganisms capable of reducing 3 was done with bacteria isolated from sea-water of the deep sea (Okinawa trough, Japan trench, and Mariana trough) and of the pelagic areas (Indian Ocean and South China Sea). Most of these marine strains preferentially reduced 3 to (R)-4 similar to the coastal strains, but the frequency of finding very highly enantioselective strains (i.e., those forming 4 of > 90% e.e.) was remark­ ably high in several sites of the deep sea and pelagic areas as compared with the coast and terrestrial environment.
Molecular Modelling of the Interactions between Optically Active Triazine Herbicides and Photosystem II
Authors: Mackay Simon P. , O' Malley Patrick J. 
Published: August 2018

Abstract
The QB binding site of photosystem II in green plants displays stereoselectivity for the (S′) stereoisomer of the α-methylbenzyl derivative of atrazine but not for derivatives with smaller substituents such as sec-butyl. We have shown that interactive models reflect the experimental data by determining the intermolecular energies between the D1 protein binding region (resi­dues Leu 210 to Val 280) and the triazine analogs. The intermolecular energy was calculated by van der Waals and electrostatic interactions after energy minimization of the combined structures to reduce inter and intramolecular strain. On the basis of these assumptions the role of stereoselectivity for optically active triazines was site responsible such stereoselectivity was identified.
Photoproduction of Hydrogen by Purple Bacteria: A Critical Evaluation of the Rate Limiting Enzymatic Steps
Authors: Klemme J.-H. 
Published: August 2018

Abstract
The enzymatic mechanisms and energetics of nitrogenase-catalyzed photoproduction of hydrogen from organic C-compounds by purple bacteria are discussed in respect to the question of which of the following three enzymes or enzyme systems are rate limiting for H2-production: (a) the nitrogenase-complex; (b) the enzymes and electron transport proteins involved in hydrogen transfer from the organic substrate(s) to nitrogenase; and (c) the system of photosynthetic ATP-regeneration. Calculations of maximum in vivo rates of photosynthetic ATPregeneration (gATP-values derived from growth rates), and of ATP-consumption by nitrogenase- catalyzed H2-production, and comparison of these rates with the specific activities of the enzymes of hydrogen or electron transfer from the C-substrate to the nitrogenase-complex, make it very likely that, in Rhodospirillum rubrum, nitrogenase-catalyzed H2-formation is limited by the availability of ATP and, possibly, of reducing power. In two other nonsulfur purple bacterial species (Rhodobacter capsulatus and Rhodobacter sphaeroides), H2-photoproduction is probably not energy-limited.
Spin Label Study of Apomembranes and Purple Membranes
Authors: Lazarova Tzvetana R. , Velitchkova Maya Y. 
Published: August 2018

Abstract
Three spin-labelled fatty acids were used to detect the dynamics of lipid bilayer of apomem branes and purple membranes. It was found that ESR spectra of spin labels bound to apo­ membranes showed a temperature-induced changes rather similar to those seen with purple membranes. At the same time, however, the values of hyperfine splitting parameter 2Tm were lower as compared to purple membranes. The results pointed out that the removal of the retinal from purple membranes affects the dynamics of lipid bilayer and apomembranes were more rigid structure than those of purple membranes.
Monte Carlo Simulation of Shot Noise Analysis for Reconstructing Elementary Events: Quantum Bumps in Photoreceptor Cells
Authors: Joeken Stephan , Schnakenberg Jürgen 
Published: August 2018

Abstract
Shot noise analysis is a frequently applied method for reconstructing elementary events from experimental data of noisy signals. The subject of this paper is the reconstruction of single photon responses in photoreceptors, the so-called quantum bumps, from experimental data which have been obtained at high light intensities where the quantum bumps can no longer be observed as individual events. The application of this method requires some basic prerequisites which are very likely not satisfied in photoreceptor cells. This situation makes the results of the method questionable. In order to estimate the reliability of shot noise reconstruc­tion in photoreceptors we directly compare the reconstruction results with well known input parameters by using a simulation model for the elementary mechanisms in the cell membrane which cause the response to light stimulation. The comparison shows that the reconstruction method starts to yield errors already at low intensities if only a few percent of the light con­ trolled ionic channels in the cell membrane are open on average. The errors of the method become about 100 percent in the light intensity regime between 10 percent open channels and the onset of bump speck contact on the membrane. The anticipation that the reconstruction method yields single channel events at high light intensities is disproved at least for physiologi­cally realistic intensities.
Das Biflavonoidmuster des Laubmooses Bartramia halleriana / The Biflavonoid Pattern from the Moss Bartramia halleriana
Authors: Salm Rudolf , Seeger Tassilo , Zinsmeister Hans Dietmar 
Published: August 2018

Abstract
From the moss Bartramia halleriana six biflavonoids have been isolated. Their structure was elucidated by chromatographic and spectroscopic methods. The compounds are bartramiaflavone, anhydrobartramiaflavone, philonotisflavone, 2,3-dihydrophilonotisflavone, 5′,3‴-dihydroxyamentoflavone and 5′,3‴dihydroxyrobustaflavone.
Exudate Flavonoids from Grindelia tarapacana of Chile
Authors: Wollenweber Eckhard , Dörr Marion , Timmermann Barbara N. , Strand Jennifer , Fuentes EduardoR. 
Published: August 2018

Abstract
Ten methylated flavonols have been identified in the lipophilic resinous exudate found on aerial parts of Grin­ delia tarapacana, a gum weed species of Chile.
Identification and Cytogenetic Analysis of an Abnormal Pig Chromosome for Flow Cytometry and Sorting
Authors: Hausmann Michael , Popescu C. Paul , Boscher Jeannine , Kerboœf Dominique , Dölle Jürgen , Cremer Christoph 
Published: August 2018

Abstract
For cytogenetics of pig (Sus scrofa domestica) and the influence of chromosome aberrations on pig production, high interest exists in flow sorted chromosomes for gene mapping, to estab­lish DNA-libraries, or to produce DNA-probes. Flow karyotyping and sorting as well as slit scan flow analysis of metaphase chromosomes of an abnormal cell type carrying a translocation marker chromosome 6/15 are described. Flow sorting of the largest chromosomes of these cells was performed. After sorting the chromosomes still had a well preserved morphology and were identified microscopically by G-banding. The quality of the band pattern of the sorted chromosomes was compatible to that of isolated chromosomes not subjected to flow cytometry. The sorted fraction showed an enrichment of chromosom e 6/15 and chromosome 1 which have quantitatively about the same integrated fluorescence intensity. Slit scan flow analysis was performed to discriminate these two chromosomes. Metacentric and submetacentric chromosom es were analyzed according to their bimodal slit scan profiles. Profiles of the largest chromosomes were distinguished by their different centromeric indices. Two groups were interpreted as the normal chromosome 1 and the translocation chromosom e 6/15.
Quinolizidine Alkaloid Profiles of South American Lupins: Lupinus linearis and the Lupinus gibertianus Complex
Authors: Planchuelo-Ravelo Ana , Witte Ludger , Wink Michael 
Published: August 2018

Abstract
The alkaloid composition of leaves of Lupinus linearis Desr. (3 ecotypes) and L. gibertia­ nus Smith (6 ecotypes) from Argentina and Brazil were studied by capillary gas-liquid chromatography and GLC-mass spectrometry (EI-MS). Both species are closely related according to morphological criteria. This view is supported by the alkaloid profiles which are very similar and share a series of new and uncommon alkaloids. Main alkaloids are lupanine, 13-hydroxylupanine, esters of 13-hydroxylupanine (e.g. 13-angeloyloxylupanine, 13-tigloyloxylupanine, 13-benzoyloxylupanine, 13-cis/trans-cinnamoyloxylupanine). Minor alkaloids are: sparteine, 11,12 -dehydrosparteine, ammodendrine, tetrahydrorhom bifoline, angustifoline, α-isolupanine, 5,6-dehydrolupanine, 11,12-dehydrolupanine, N-formylangustifoline, 13-cis-cinnamoyloxymultiflorine. New minor alkaloids which have been tentatively identified by GLC-MS are 13-hydroxy-17-oxolupanine and corresponding esters (13-an-geloyloxy-17-oxolupanine, 13-tigloyloxy-17-oxolupanine, 13-benzoyloxy-17-oxolupanine, 13-cis-cinnamoyloxy-17-oxolupanine, and 13-trans-cinnamoyloxy-17-oxolupanine).
The Unexpected Reduction of the Vinyl Group of Chlorophyll b by Sodium Borohydride in Methanolic Extracts of Maize Leaves and Its Inhibition by 8-Hydroxyquinoline
Authors: Porra R. J. , Schäfer W. , Cmiel E. , Katheder Ingrid , Scheer H. 
Published: August 2018

Abstract
During rapid extraction of chlorophylls from maize leaves under reducing conditions with methanol containing NaBH4, chlorophyll a remained unchanged but chlorophyll b yielded [7-hydroxymethyl]-chlorophyll b. The 3-vinyl group of chlorophyll b was also reduced forming significant am ounts, up to 60%, of [3-ethyl]-[7-hydroxymethyl]-chlorophyll b. This was unexpected since this reduction of the 3-vinyl group does not occur when isolated chlorophyll b is treated in an identical manner with methanolic borohydride. The vinyl-group of chlorophyll a is not reduced during the same extraction conditions suggesting that the presence of a formyl or hydroxyethyl group at C-7 is necessary. The presence of 8-hydroxyquinoline and NaBH4 in equimolar (16.5 m M) concentrations strongly inhibits the reduction of the 3-vinyl group of chlorophyll b in leaf extracts
Molecular Modelling of the Interaction of Cyanoacrylate Inhibitors with Photosystem II Part 2. The Effect of Stereochemistry of Inhibitor Binding
Authors: Mackay Simon P. , O’Malley Patrick J. 
Published: August 2018

Abstract
The 2-cyanoacrylate inhibitors are a potent class of herbicides which block electron transfer in photosystem II. The spatial arrangement of different functional groups are an important factor in determining activity and a number of derivatives have been used as stereospecific probes of the secondary quinone binding site. More than one region of stereoselectivity in the binding site has been identified which influences the interaction with specific groups of the inhibitor. We have studied the interaction of various stereoisomers of the cyanoacrylates with the binding site in the D1 protein (residues Leu 210 to Val 280) by determining the nonbonded intermolecular energies between the modelled structures calculated by van der Waals and electrostatic interactions after energy minimization of the combined structures to reduce inter and intramolecular strain and have found that the results reflect the experimentally determined data
Complete Sequence of One Copy of the psbA Gene from the Thermophilic Cyanobacterium Synechococcus elongatus
Authors: Kloos Ralf , Stevens Edward , Oettmeier Walter 
Published: August 2018

Abstract
One copy of the psbA. gene which codes for the photosystem II reaction center D-1 protein from the thermophilic cyanobacterium Synechococcus elongatus has been sequenced. It is feas­ible that a disulfide bridge between D-1 Cys212 and D-2 Cys2I2 is reponsible for the thermo­ stability of the photosystem II reaction center from Synechococcus elongatus.
Linear Free Energy Relationships for N(7)-Substituted Guanosines as Substrates of Calf Spleen Purine Nucleoside Phosphorylase. Possible Role of N(7)-Protonation as an Intermediary in Phosphorolysis
Authors: Bzowska Agnieszka , Kulikowska Ewa , Shugar David 
Published: August 2018

Abstract
Quantitative structure-activity relationships (QSAR) for a series of N(7)-substituted guanosines as substrates for calf spleen purine nucleoside phosphorylase (PNP) were developed, and compared with those for acid hydrolysis of these analogues. There is no correlation between the rates for enzymatic phosphorolysis and acid hydrolysis, indicating that for the enzymatic reaction labilization of the glycosidic bond is not the only, nor the predominant, effect of N(7)-substitution. Multiple regression analysis of the enzymatic process revealed that optimal substrate properties (minimal Michaelis constant) are associated with the Taft electronic constant equal zero and a substituent size, parametrized by the Taft steric constant, smaller than that for a methyl group. These results support the hypothesis of protonation of the N(7)-position of the base by the enzyme as a catalytic mechanism for calf spleen PNP.
Attention is drawn to the postulated similar mechanism of action of other purine N-glycosidases, including plant antiviral proteins which function as RNAN-glycosidases, and possibly some DNA N-glycosidases which function as repair enzymes
Isolation and Properties o f Trimethylamine N-Oxide/Dimethylsulfoxide Reductase from the Purple Bacterium Rhodospirillum rubrum
Authors: Sajitz Paul , Klemme Jobst-Heinrich , Koch Hans-Georg , Molitor Michael 
Published: August 2018

Abstract
Among 4 strains of the purple bacterium Rhodospirillum rubrum only one did not contain trimethylamine N-oxide/dimethylsulfoxide reductase and was unable to grow under anaerobic dark conditions in fructose media supplemented with trimethylamine N-oxide (TMAO) or dimethylsulfoxide (DMSO ). By growing the bacteria in media treated with charcoal or supplemented with tungstate (2 mM ), TM AO/DMSO reductase activity was lowered to about 10% of the value of the untreated control. The enzyme was purified from the periplasmic protein fraction of strain S1 and was shown to contain 2 subunits (mol. wt. of 40,000 and 36,000, respectively) in a 1:1 stoichiometry. Although the affinity of the reductase to DMSO (Km - 0.67 mM) was much higher than to TMAO (Km = 24 m M ) , the catalytic activity with the latter substrate was about 10 times as high (90-110 μmol/min X mg protein) as with DMSO
Phosphatidylglycerol and ß-Carotene Bound onto the D 1-Core Peptide of Photosystem II in the Filamentous Cyanobacterium
Authors: Kruse O. , Radunz A. , Schmid G. H. 
Published: August 2018

Photosystem II-particles from the cyanobacterium Oscillatoria chalybea were isolated by fractionating centrifugation. Purification of these particles was achieved by a 22 hours centrifugation over a linear sucrose density gradient at 217.500xg. The obtained particle fraction exhibited an oxygen evolution activity which corresponded to three times the rate of intact cells and to five times the rate of intact thylakoids. The chlorophyll protein ratio was 1:10 and the ratio manganese/chlorophyll 1:34.
SDS-polyacrylamide gel electrophoresis showed that the photosystem Il-fraction is composed of the core peptides D1 and D2, the chlorophyll-binding peptides CP 43 and CP 47, the extrinsic 33 kDa peptide (manganese stabilizing peptide, MSP) and phycobiliproteins with molecular masses between 16 to 20 kDa. Cyt b559 was not detected in our gel electrophoresis assay. Part of the peptides of the 30 kDa-region (D1, D2, MSP) occurred as aggregates with a molecular mass of 60 to 66 kDa.
The D 1-peptide was isolated from the PS Il-preparation by SDS-gel electrophoresis. The intrinisic peptide reacts in the Western blot procedure with the antiserum to phosphatidylglycerol and with the antiserum to β-carotene. Incubation of the peptide with the antisera to monogalactosyldiglyceride, sulfoquinovosyldiglyceride and zeaxanthine resulted negatively. The binding of phosphatidylglycerol onto the D 1-peptide was confirmed by lipid analysis in HPLC and fatty acid analysis by gas chromatography. Only this lipid, respectively the typical fatty acid mixture of this lipid was detected. The lipid is characterized by the fact that the hexadecenoic acid does not exhibit trans-configuration, as is true for phosphatidylglycerol of higher plants and algae, but occurs in cis-configuration.
With the antibody being directed towards the glycerol-phosphate residue and not towards the fatty acids, it can be concluded from the reaction of the antibodies with the bound lipid that the lipid is bound to the peptide via the fatty acid. The negatively charged phosphatidylglycerol increases the hydrophobicity of the peptide and leads to a negatively charged surface favouring binding of cations like calcium and magnesium. The fact that incubation of this PS Il-fraction with phospholipase inhibits photosynthetic activity by 25% which can be fully restored by addition of phosphatidylglycerol, shows that bound phosphatidylglycerol has a functional role.
Reconstitution of an Allophycocyanin Trimer Complex Containing the C-Terminal 21-23 kDa Domain of the Core-Membrane Linker Polypeptide Lcm
Authors: Gottschalk Lothar , Lottspeich Friedrich , Scheer Hugo 
Published: August 2018

Abstract
Allophycocyanin (AP) was isolated from extracts of the cyanobacterium Mastigocladus laminosus. A fraction enriched in AP-associated polypeptides with apparent molecular masses of 21 -23 kD a in SDS-PAGE, was isolated on a preparative scale and identified as a homolo­gous mixture of C-terminal fragments of the core-membrane linker polypeptide Lcm. The complex (αAPβAP)3 ·21 -23 kD a was reconstituted and characterized by sucrose density gradient ultracentrifugation, absorption, fluorescence emission and circular dichroism spectroscopy. The 21 -23 kD a polypeptides were found to induce spectral changes in AP similar to those induced by the small core linker polypeptide Lc
8.9. Possible functions of the complex in phycobilisomes are discussed.
Resonance Effect of Low-Intensity Millimeter Waves on the Chromatin Conformational State of Rat Thymocytes
Authors: Belyaev Igor Ya. , Kravchenko Vyacheslav G. 
Published: August 2018

Abstract
The method of anomalous viscosity time dependencies (AVTD) was modified for the study of the changes in the chromatin conformational state (CCS) of rat thymocytes of the Wistar line. The response of the thymocytes of male rats to low-intensity millimeter waves (MMW) was examined. It was shown that MMW at power densities (PD) of 1 μW/cm2 produced a resonance effect on the CCS in the frequency range of 41.56-41.67 GHz. The resonance fre­quency of the cell response did not vary significantly among five examined rats and was deter­ mined to be 41.61 ±0.01 GHz. A halfwidth of resonances was averaged to 40 MHz. The power dependence of the resonance effect was measured in the range of 10-11-10-4 W/cm2. Statistically significant changes in CCS were registered, starting with 10-9 /cm2. Right-and left-handed circularly polarized MMW were shown to differ in efficiency at the resonance fre­quency.
The established regularities in the thymocyte response to low-intensity MMW was very similar to those which have been previously found for E. coli cells.
The Effects of Externally Applied Lithium and Strontium on the Arsenazo-Monitored Cytosolic Calcium Signal of the Limulus Ventral Photoreceptor
Authors: Stieve Hennig , Rüsing Gabriele , Yuan Weijia , Hennig H. Thomas 
Published: August 2018

Abstract
The intracellular arsenazo signal indicating the transient light-evoked change in cytosolic Ca2+ (or Sr2+) concentration was measured in Limulus ventral photoreceptor simultaneously with the receptor potential at 15 °C. The decline of the arsenazo signal has two phases (D1 and D2) when the photoreceptor is bathed in physiological saline.
1. When calcium is replaced by strontium in the superfusate both receptor potential and arsenazo signal are markedly increased in amplitude and the membrane potential is hyper­ polarized. The decline of the arsenazo signal is prolonged and becomes monophasic; the fast phase D1 of the decline disappears.
2. In strontium saline under voltage clamp conditions the slope of the monophasic decline of the arsenazo signal is the steeper the more negative the membrane voltage.
3. After replacing sodium by lithium in the superfusate the rise of the receptor potential and of the arsenazo signal are not much altered. The decline of the arsenazo signal, however, is slowed down more than 3-fold; this is due to the complete suppression of the fast phase D1 and the retardation of the slow phase D2 of the calcium re-decline.
Interpretation:
1. The Na-C a exchanger can accept strontium as a calcium substitute. Strontium has a weaker desensitizing action than calcium. Strontium is not-or only very little -taken up by the endoplasmic cisternae.
2. In sodium-free lithium saline the Na-C a exchanger, the Na-K ATPase and the calcium uptake system of the endoplasmic cisternae do not function. Therefore the intracellular calcium level rises.
β-Carboline Alkaloids from Ribes nigrum L.
Authors: Blech St. , Budzikiewicz H. 
Published: August 2018

Abstract
From Ribes nigrum L. two β-carboline alkaloids (deshydroxymethyl flazin (1) and flazin methyl ether (2)) could be isolated in minute amounts. The structure elucidation is described. The two compounds are present in the freshly pressed juice, but they are also formed during storage of the juice by condensation of tryptophane with ascorbic acid or its degradation products. This could be shown by adding 14C-labelled ascorbic acid to the juice. After four weeks’ incubation radioactive 1 and 2 could be isolated.
On the Mechanism of Metabolic Reactions of Amino Acids Catalyzed by Vitamin B6 and Related Aldehydes
Authors: Sivý J. , Kettmann V. , Krätsmár-Šmogrovič J. 
Published: August 2018

Abstract
The crystal structure of [(N-salicylidene-ᴅ,ʟ-glutamato)(pyridine)]copper(II), a model for vitamin B6-amino acid-related metal complexes, has been determined by an X-ray analysis. A close examination of the structural data on this and other related complexes combined with quantum-chemical (INDO/2) calculations enabled us to make a clear distinction between two mechanisms proposed earlier for metabolic reactions of amino acids catalyzed by the vitamin B6 (or salicylaldehyde)-metal system. The results are consistent with a transient formation of a carbinolamine species resulting from the addition of a solvent water or alcohol molecule to the Schiff base double bond, thus supporting the mechanism of the catalysis as proposed by Gillard and Wootton.
Light-Harvesting Complexes of Aerobic Bacteriochlorophyll-Containing Bacteria Roseococcus thiosulfatophilus, RB3 and Erythromicrobium ramosum, E5 and the Transfer of Excitation Energy from Carotenoids to Bacteriochlorophyll
Authors: Yurkov Vladimir , Gad’on Nasser , Angerhofer Alexander , Drews Gerhart 
Published: August 2018

Abstract
The spectral analysis of membrane fractions and a fraction enriched in light-harvesting (LH) complex I + reaction center (RC) of Roseococcus thiosulfatophilus, RB3 and of the membrane fraction and of the isolated LH II and LH I + RC complexes of Erythromicrobium
ramosum, E5 is reported. Quantum yields of singlet energy transfer between carotenoids and bacteriochlorophyll (light-harvesting function) were calculated from comparison of absorption and fluorescence excitation spectra of the respective preparations. The results indicate that the excess of carotenoids in the membrane does not contribute to the lightharvesting function of the LH complexes.