bluuebunny/crossref_metadata_2025_split huggingface dataset:
Preparation and Properties of Chromopeptides from the Pfr Form of Phytochrome
Authors: Thümmler Fritz , Brandlmeier Thomas , Rüdiger Wolfhart 
Published: August 2018

Abstract
Chromopeptides were prepared from the Pfr form of phytochrome by pepsin digestion. After separation from colorless peptides and Pr peptides by column chromatography, spectral characteristics of this Pfr peptide were determined (λ1
max = 610nm, λ2
max = 380nm in acid methanol). Irradiation of Pfr peptide produces Pr peptide without liberation of a detectable compound. The Pfr peptide is more sensitive to oxidation and reduction than the Pr peptide. Oxidation with iodine and reduction with dithionite leads to partial chemoconversion of the Pfr peptide to the Pr peptide. The results favor the model of cis-trans isomerization for the Pr ⇌ Pfr transformation.
Sukkulenz — Induktion bei Kalanchoe bloßfeldiana im Langtag durch eine lipophyle Fraktion aus blühenden Kalanchoe und MS-Identifikation von Pterosteron / Succulence — Induction in Kalanchoe bloßfeldiana under Long-Day Conditiones by a Lipophilic Fraction out of Flowering K alanchoe and MS-Identification of Pterosterone
Authors: Janistyn Boris 
Published: August 2018

Abstract
Succulence-induction in Kalanchoe bloßfeldiana is demonstrated under long-day condition by application of a lipophilic fraction from flowering Kalanchoe. Different preparative TC separation steps yielded a partial purification of this fraction and the MS-identification of pterosterone (10-6 m), which is not necessary correlated with the above described physiological activity.
The Isolation of Antibodies Specific for 5-Methyl-Cytidine-Bovine Serum Albumin
Authors: Mastronicolis Sofia K. , Kapoulas Vassilios M. , Kröger Hans 
Published: August 2018

Abstract
By coupling 5-Methyl-cytidine to bovine serum albumin, a conjugate containing 18 mol of 5-Methyl-cytidine per mol of BSA was prepared. Antibodies to this conjugate were produced by immunization of rabbits. Specificity of the antibody was assesed by gel diffusion in agar containing excessive amounts of the carrier BSA. A slight cross-reactivity with cytidine was eliminated by adsorption on the cross-reacting antigen.
The isolation of 7 S immunoglobulin from the total globulin fraction was accomplished by chromatography on DEAE Sephadex-A-50, and a method for the rapid quantitation of the antibodies showed that 12.7% of the IgG protein are monospecific against 5-Methyl-cytidine bovine serum albumine.
Vascular Specialization in Fish, but No Evidence for Lymphatics
Authors: Vogel Walter O. P. , Claviez Michael 
Published: August 2018

Abstract
Blood distribution in the systemic circulation of bony fishes is effected by a dualistic construction of the vasculature: A secondary arterial system originates from the well known (primary) arteries by multiple root-like shunt vessels. These secondary arteries and the vessels they supply should no longer be regarded as lymphatics. After an intensive search for unequivocally lymphatic vessels in fish, it appears doubtful whether there are any at all in this class of vertebrates.
Effect of Hydrogen Ion Concentration on the Absorption Spectrum and Fluorescence Life Time of Chloroplasts
Authors: Brody Seymour Steven , Gregory Richard P. F. 
Published: August 2018

Abstract
Subjecting pea chloroplasts to hydrogen ion gradients results in small but significant changes in the absorption and circular dichroic spectra. The relative intensities of the fast and slow fluorescence decays are modified by the hydrogen ion concentration. The life time of the slow components is only slightly altered. At pH 11 the circular dichroic peak at 690 nm, assigned to Photosystem I chlorophyll-protein complex, is clearly resolved. Also, there is a splitting of the peak at 650-640 nm, attributed to Photosystem II chlorophyll-protein. At pH 3.9 splitting of the 650-640 nm peak is observed. There is also a positive component at 705 nm which may be associated with an aggregated form of chlorophyll or pheophytin. The changes in absorption spectra are determined by measuring the difference in spectra between identical chloroplasts suspensions one at pH 7.6 and the other at alkaline or acidic pH. At pH 2 and pH 3.7 there are time dependent increases in absorbance at 430, 445, 520, 538, 670 nm, and a decrease in absorbance at 606 nm. After a delay of 11 min at pH 2, there is also an increase in absorbance at 700 nm. The latter is interpreted as possible formation of aggregated pheophytin. At pH 11.0 there are time dependent increases in absorbance at 638, 454 and 440 nm, and decreases in absorbance at 675, 660, 508 and 472 nm. The changes in absorbance of the pigment around 520 nm (associated with an electrochromic effect) is interpreted as resulting from a leakage of hydrogen ion across the thylakoid membrane. The spectral changes that occur during the first 9 min are reversible. After the chloroplasts have incubated for more than 15 min most of the spectral changes are not reversible.
Oxidation of Flavanones to Flavones with Flower Extracts of Antirrhinum majus (Snapdragon)
Authors: Stotz G. , Forkmann G. 
Published: August 2018

Abstract
Enzyme preparations from flowers of Antirrhinum majus catalysed the oxidation of naringenin to apigenin and of eriodictyol to luteolin. Enzyme activity was found to be localized in the microsomal fraction. The reaction required NADPH as cofactor and had a pH optimum of about 7.0. The NADPH-dependent microsomal enzyme activity was also present in flower extracts of other flavone-producing plants, whereas flower extracts of plants which lack flavones were found to lack also this enzyme activity.
Carotenoids in the Stick Insect, Ectatosoma tiaratum Isolation of β,Ɛ-Caroten-2-ol and β,Ɛ-Caroten-2-one
Authors: Kayser Hartmut 
Published: August 2018

Abstract
2-Oxo-carotenoids, 2-Hydroxy-carotenoids, [uC]/β-Carotene, Metabolism, Stick Insects The carotenoids of the stick insect, Ectatosoma tiaratum, were studied by spectroscopic and chemical methods. The β,β-type pigments are β,β-carotene, β,β-caroten-2-one, β,β-caroten-2-ol, β,β-carotene-2,2'-dione, 2'-hydroxy-β,β-caroten-2-one, β,ε-carotene-2,2'-diol, 3,4-didehydro-β,β-carotene-2,2'-dione, 2'-hydroxy-3,4-didehydro-β,β-caroten-2-one, and 3,4,3',4'-tetradehydro-β,β-carotene-2,2'-dione. In addition, the following β,ε-type pigments were identified: β,ε-carotene, β,e-caroten-2-ol, and β,e-caroten-2-one. This is the first report on the occurrence of β,e-caroten-2-ol in an animal and of β,ε-caroten-2-one in nature at all. On treatment with BF3 in chloroform β,ε-caroten-2-ol is dehydrated to a specific product with the proposed structure of 2,3-didehydro-4,7'-retro-β, e-carotene.
The biogenesis of the β,β-type carotenoids from β,ε-carotene is demonstrated by feeding [14C]β-carotene to the insects. Radiolabel was incorporated into all major metabolites of this type. The metabolism of carotenoids in stick insects is discussed applying the "half-molecule sub­ strate" hypothesis to the enzymic transformations of the pigments.
Reassociation of Lactic Dehydrogenase from Pig Heart Studied by Cross-Linking with Glutaraldehyde
Authors: Bernhardt Günther , Rudolph Rainer , Jaenicke Rainer 
Published: August 2018

Abstract
Cross-linking with glutaraldehyde has been successfully applied in order to analyze the kinetics of reassociation of oligomeric enzymes (R. Hermann, R. Rudolph, and R. Jaenicke Nature 277, 243-245 (1979)). In the present study the assembly of lactic dehydrogenase from pig heart is investigated using this approach.
In order to eliminate perturbations caused by excessive folding reactions, acid dissociation was performed in the presence of 0.8 M Na2SO4 at 0°C . Under optimum conditions complete cross-linking of the tetrameric enzyme was achieved in less than 2 minutes.
Cross-linking during reconstitution proves the dimer to be the only intermediate of reasso­ ciation. The dimer → tetramer transition is found to be rate-limiting for both reassociation and reactivation, suggesting the tetramer to be the enzymatically active species.
The presence of monomers during reconstitution indicates that tetramer formation is preceded by a fast monomer-dimer equilibrium.
The kinetic model describing the experimental data

is characterized by an equilibrium constant K = 3 ± 1 · 107 liter · m ol-1, and a second-order rate constant k = 1.4 ± 0.2 · 104 liter · mol-1 · s-1.
Immunoadsorption as a Means for the Purification of Low Molecular Weight Compounds: Isolation of Ecdysteroids from Insects
Authors: Reum Lutz , Haustein Dieter , Koolman Jan 
Published: August 2018

Abstract
Ecdysteroid, Immunoadsorption of Steroids, Antiserum Specificity Two ecdysteroid-specific antisera, anti-ecdysone-albumin and anti-20-hydroxyecdysone-al-bumin, were induced in rabbits. The properties of both antisera were tested with a large number of ecdysteroids. The former antiserum was unique in its ability to discriminate between the moulting hormones, ecdysone and 20-hydroxyecdysone, whereas the latter had a broad specificity for ecdysone and several of its metabolites.
y-globulin fractions of both antisera were covalently linked to Sepharose 4B and used as immunoadsorbents. These were able to bind ecdysteroids from crude extracts of insects. Bound ecdysteroids could be eluted quantitatively from the adsorbents using 3 M sodium trichloroacetate. When a mixture of ecdysteroids which contained ecdysone and at least six different ecdysone me­ tabolites were run over a column with anti ecdysone immunoadsorbent only ecdysone and its hy-droxyderivatives 20-and 26-hydroxy ecdysone were bound to and subsequently eluted from the adsorbent. In contrast a column with anti-20-hydroxyecdysone immunoadsorbent retained most of the different ecdysteroids due to the broader specificity of the antibodies.
These immunoadsorbents provide the potential not only to purify ecdysteroids but also proteins crosslinked to ecdysteroids via photoaffinity labelling. It is well known that immuno-adsoiption is a powerful tool for the isolation of proteins. The results described here demonstrate that immunoadsorption may also be useful in the isolation of low molecular weight compounds of biological and medical interest.
Neutral Red Fluorescence of Chromatin: Specificity and Binding Mechanism
Authors: Espelosin Roberto H. , Stockert Juan C. 
Published: August 2018

Abstract
Neutral Red, Chromatin Fluorescence, Nucleic Acid Cytochemistry, Intercalative Binding to DNA After treatment with neutral red at low concentrations (10-6, 10-5 m), the chromatin o f chicken erythrocytes shows an intensive red fluorescence, which is reduced or prac­ tically abolished when nuclei become stained by using the dye at concentrations higher than 10~* M. Both the fluores­ cence and staining reactions are dependent on the DNA content of chromatin. Neutral red fluorescence o f nuclei increases considerably after treatment with inorganic cations (Al3+, Ba2+), while previous treatments with meth­ ylene blue reduce the fluorescence intensity. The possi­ bility that chromatin fluorescence depends on the inter­ calative binding of neutral red is suggested.
Changes of C-Phycocyanin in Synechococcus 6301 in Relation to Growth on various Sulfur Compounds Materials and Methods
Authors: Schmidt Ahlert , Erdle Ingrid , Köst Hans-Peter 
Published: August 2018

The cyanobacterium Synechococcus 6301 is able to use a limited number of sulfur compounds as the only source of sulfur supply such as sulfate, thiosulfate, thioacetic acid, mercaptoacetic acid, thioacetamide, ʟ-cysteine and glutathione. Compounds containg thioether linkages such as methionin or S-methylcysteine and all compounds investigated so far containing sulfonic acid structures do not support growth. Growth inhibiton was observed by addition of aminomethane- sulfonic acid or cysteamine.
When non-growth sustaining sulfur compounds are added as sulfur source, the C-phycocyanin content of the Synechococcus cultures decreased drastically, causing a shift in color from blue- green to yellow-green. An analysis reveals the degradation of C-phycocyanin whereas chlorophyll formation still proceeds to a certain degree in growing sulfur-starved cells. Supplementation of a suitable sulfur source induces a period of intense and preferential C-phycocyanin synthesis prior to resumption of normal growth.
The Tautomerism of Cytosine and Hydroxycytosine. A Quantum-Mechanical Study
Authors: Kwiatkowski Józef S. , Lesyng Bogdan , Palmer Michael H. , Saenger Wolfram 
Published: August 2018

Abstract
Semi-empirical studies by the MNDO and MINDO-3 methods together with ab initio studies by the Hartree Fock method, have been performed on the tautomers of cytosine (C) and hydroxycytosine (HC), in each case with full optimisation of the molecular skeleton. The results are in agreement with recent solution studies of these systems, and show that the amino form of C and the oxime form of HC are the lowest energy tautomers. Thus the property is one of the ring system rather than environment.
Various conformers of the imino tautomer of 5-methyl-N(4)-hydroxycytosine were studied by MINDO/3 and PCILO calculations; although only partial geometry optimisation was performed, it seems unlikely that the molecule can be a complementary base to adenine in the Watson-Crick sense.`
The Reversibility of the Vitamin C Redox System: Electrochemical Reasons and Biological Aspects
Authors: Sapper Helmut , Institut für Biophysik der Justus-Liebig-Universität Gießen, Sa-Ouk , Paul Hans-Helmut , Lohmann Wolfgang 
Published: August 2018

Abstract
The biological efficacy of vitamin C depends on its redox abilities as given by the relations between ascorbic acid, semidehydroascorbic acid, and dehydroascorbic acid. It is shown by means of proton magnetic resonance spectroscopy that the enzymatic (by ascorbate oxidase) as well as non-enzymatic (by iodine) oxidation of ascorbic acid is, in principle, reversible despite the hydration and structural changes during the formation of dehydroascorbic acid. The strong redox activity of semidehydroascorbic acid which results in a fast disproportionation to ascorbic acid and dehydroascorbic acid is inferred from an inversion of the electrochemical potentials of the vitamin C redox system. The capacity of this is maintained by a fast reduction of dehydro­ ascorbic acid e.g. by reduced glutathione, preventing its delactonization and further degradation.
Differentiation in Volvox carteri: Study of Pattern Variation of Reproductive Cells
Authors: Gilles Rainer , Jaenicke Lothar 
Published: August 2018

Abstract
Asexual spheroids of the multicellular green alga Volvox are composed of two types o f cells: non-flagellated reproductive gonidia and Chlamydomonas-like flagellated somatic cells. They are committed by a differentiating cleavage during embryogenesis. The gonidia of the adult spheroids form a symmetrical pattern consisting of four layers of four gonidia each; their position is established already in the embryos by the gonidial initials. Whereas, generally, the 16-gonidia pattern is assumed to be the basic one, most o f the spheroids have fewer gonidia (down to 8). The nine possible gonidial patterns (8 to 16 gonidia) are described and correlated to the gonidial stem cells which have been differentiated. Defects in gonidial pattern are of particular interest, since any model of differentiation has to explain not only the basic pattern formed, but also its systematic variations. Our study shows that the pattern reduction is by no means random, but governed by an intrinsic mechanism which shifts the first unequal cleavage from the 32-celled stage to the 16-celled stage. All the patterns formed can be deduced from cleavage pathways involving non-synchronous differentiation of the stem cells. Thus, pattern formation can be correlated to timing and spacing signals regulating events during embryogenesis.
Biological Activities of Sesquiterpene Lactones from Helianthus annuus: Antimicrobial and Cytotoxic Properties; Influence on DNA, RNA, and Protein Synthesis
Authors: Spring O. , Kupka J. , Maier B. , Hager A. 
Published: August 2018

Abstract
Sesquiterpene lactones, produced in light and capable of inhibiting auxin-induced elongation growth of coleoptile and hypocotyl segments, were isolated from young leaves of Helianthus annuus (Spring and Hager, Planta in press, 1982).
These compounds have an antibiotic effect on gram-negative and gram-positive bacteria as well as on some fungi. The minimal inhibiting concentration (MIC) of compound II (15-hydroxy-3- dehydrodesoxyfruticin. Fig. 1), for example, is 15μg/ml for Bacillus brevis, and 95 μg/ml for the fungus Eremothecium ashbyi.
In addition, cytotoxic effects on mouse myeloma cells (NS-1) were also shown. Compound II causes a 50% inhibition of cell proliferation (ED50) at a concentration of 170nᴍ, compound I (niveusin C, Fig. 1) at 220 nᴍ. The LD50-values were 0.15 μg ll/ml and 1.24 μg I/ml, respectively.
By measuring 14C-labelled thymidine, uridine and leucine incorporation into murine cells of the ascitic form of Ehrlich carcinoma (EAC) it could be shown that compounds I and II inhibit DNA and RNA synthesis, but do not affect the translation processes involved in protein synthesis.
Furthermore, it could be shown that the exocyclic methylene group in the molecules of I and II plays an important role in triggering the described inhibitory effects.
Some Observations on the Saponin Accumulation in Oat Seedlings and on the Transformation of the Avenacosides to the Antibiotic 26-Desgluco-avenacosides
Authors: Laudenbach Ute , Kesselmeier Jürgen 
Published: August 2018

Abstract
The accumulation of the steroidal saponins avenacoside A and B in oat was investigated in green and etiolated seedlings and was found to be strictly bound to the growth of the seedlings. No significant differences were detected between green and etiolated seedlings, showing that there is no relation between saponin accumulation and plastid development. As the role of the oat saponins has to be seen as a protective device against fungi and bacteria, the transformation of the inactive avenacosides to their corresponding antibiotic 26-desgluco-avenacosides was tested in dependence of pH and temperature. During disruption of leaves, transformation occurs almost completely over a wide pH-range (pH 4 -pH 10); the degree of transformation exhibits no distinct temperature optimum but a drastic decrease at 70 °C.
Statistical Description of Isotope Exchange Processes: A Multisite Model for the 18O Exchange
Authors: Rösch Paul 
Published: August 2018

Abstract
An analytical procedure has been developed for the determination of isotope exchange processes as exemplified by the 18O exchange catalysed by enzyme-nucleotide complexes. The model is able to handle more than one type of active site per reaction solution and is also able to distinguish between different types of inequivalence of the oxygens of enzyme bound Pi. Use of transition matrix formalism and basic statistical considerations lead directly to the simple model. A data refinement procedure is introduced and model calculations are shown.
Fluorescence Studies on N-(3-Pyrene)Maleinimide-Labeled Sarcoplasmic Reticulum ATPase in Native and Solubilized Membranes
Authors: Lüdi Hans , Hasselbach Wilhelm 
Published: August 2018

Abstract
Fluorescence polarization and formation of excimers were studied in N-(3-pyrene)maleinimide-labeled sarcoplasmic reticulum vesicles.
1. The polarization of pyrenemaleinimide labeled vesicles does not change with temperature and shows a pronounced decrease at labeling concentrations larger than 1 mol pyrenemaleinimide per 10 mol ATPase.
2. Solubilization of the membrane with myristoylglycerophosphocholine renders the polarization temperature dependent, but does not affect the concentration dependent depolarization observed in native vesicles.
3. The polarization of labeled vesicles is much smaller than to be expected from the temperature independent polarization indicating that the pyrenemaleinimide polarization did not monitor the rotation of the entire ATPase. Thus segmental motion occurs.
4. Pyrene excimers are observed at label concentrations larger than 1 mol label per 2.5 mol ATPase.
5. The amount of excimers was critically dependent on added detergents. From the fact that non-solubilizing amounts of myristoylglycerophosphocholine strongly reduced the amount of pyrene excimers it is concluded that in the native sarcoplasmic reticulum vesicles at least two ATPase molecules must be in close contact.
Diterpenes of Cheilanthes argentea, a Fern from Asia
Authors: Wollenweber Eckhard , Rüedi Peter , Seigler David S. 
Published: August 2018

Abstract
The major components o f the white exudate or farina from the abaxial side of fronds of the fern Cheilanthes argentea are the diterpenoid acids ent-8(17),E-13-labdadien-15-oic acid and its 3 R-hydroxy derivative. This is the first report of the first o f these compounds as a natural product. Both are highly crystalline. Plants from the Asian mainland and Japan contain mostly the first compound whereas plants from Taiwan contain mostly the 3 R-hydroxy derivative. Thus, there are at least two distinct chemical races of the species Cheilanthes argentea.
Isolation and Synthesis of a Hemoregulatory Peptide
Authors: Paukovits Walter R. , Laerum Ole D. 
Published: August 2018

Abstract
A peptide was isolated in pure form from human leukocytes which strongly inhibits the proliferation of immature meyloid cells in vitro (committed stem cells). Structural investigations yielded pGlu-Asp or Glu-Asp or Glu-Cys-Lys-OH as the probable sequence of this peptide. The Glu2,Asp3-analog, prepared synthetically, displayed similar activities and when applied in vivo showed effects on the hemopoietic system ranging from an inhibition of pluripotent and committed stem cells to variations in the bone marrow proliferation and alterations in peripheral blood counts.
Isolierung von PS II-Partikeln mit in vivo Eigenschaften aus Euglena gracilis, Stamm Z / Isolation of PS II-Particels with in vivo Characteristics from Euglena gracilis, Stamm Z
Authors: Schuler F. , Brandt P. , Wießner W. 
Published: August 2018

Abstract
An improved method for isolation of (photosystem II)-particles from Euglena gracilis, strain Z was established. PS II-particles isolated by ultrasonic treatment and following differential centrifugation show fluorescence emission and absorption spectra identical with in vivo properties of Euglena gracilis. These PS II-particles have only PS II-activity and contain CP a, the typical chlorophyll-protein-complex of PS II. No contamination of PS I-components are detectable.
Volatile Compounds from Cephalic Secretions of Females in two Cleptoparasite Bee Genera, Epeolus (Hym., Anthophoridae) and Coelioxys (Hym., Megachilidae)
Authors: Tengö J. , Bergström G. , Borg-Karlson A.-K. , Groth I. , Francke W. 
Published: August 2018

Abstract
Volatile cephalic secretions from females of four cleptoparasitic bee species, Epeolus cruciger (Pz.), E. variegatus, (L.) (Anthophoridae) and Coelioxys (Coelioxys) quadridentata (L.), C. (Schizocoelioxys) mandibularis Nyl. (Megachilidae) were analysed by combined gas chromatography/mass spectroscopy. There are considerable similarities between the two species within each genus, and also some qualitative correspondences between the two genera. The Epeolus species contain spiroacetals, 2-alkanols and pyrazines while the Coelioxys species contain spiroacetals, 3-alkanols and 3-ketones along with unsaturated alcohols. Two of the spiroacetals are first found in nature.