bluuebunny/crossref_metadata_2025_split huggingface dataset:
Photochemically Reversible Dimer Electroreduction Product of 2-Oxopurine
Authors: Czochralska Barbara , Fritsche H. , Shugar D. 
Published: August 2018

Abstract
The electrochemical reduction of 2-oxopurine in buffered aqueous medium was found to proceed via two successive one-electron additions. The initial one-electron step involves the addition of a proton, leading to formation of a free radical which rapidly dimerizes. At more negative potentials, reduction leads to formation of 1,6-dihydro-2-oxopurine. The product of reduction on wave I was isolated and identified by various spectroscopic techniques as the dimer 6,6′-bis-(1,6-dihydro-2-oxo-purine). In neutral aqueous medium this dimer reduction product (but not the product of reduction on wave II, 1,6-dihydro-2-oxopurine) underwent quantitative photochemical dissociation to the parent 2-oxopurine, with a quantum yield at 254 nm of 0.03. The dimer reduction product also quantitatively regenerated the parent monomer in an alkali-catalyzed reaction at room temperature. The proposed mechanism of the reduction reaction, and susceptibility of the reduction product to photodissociation, is compared with the corresponding behaviour of other purine, and pyrimidine, derivatives.
Conformational Studies on C-Phycocyanin from Spirulina platensis
Authors: Scheer Hugo , Kufer Werner 
Published: August 2018

Abstract
The chromophore-protein interactions of C-phycocyanin (C-PC) from Spirulina platensis have been studied by following the partial and complete denaturation with UV-Vis spectroscopy. From comparison with published MO calculations, an elongated conformation of the chromophore is suggested for native C-PC, a cyclic one for denatured C-PC. By means of partial denaturation, a step­ wise unfolding of the protein has been demonstrated. The presence of at least two sets of spectro­ scopically different diromophores is suggested from the partial denaturation and low temperature experiments.
Pilzpigmente, XXXII 3-Methylriboflavin aus Panellus serotinus (Agaricales) / Pigments of Fungi, XXXII. 3-Methylriboflavine from Panellus serotinus (Agaricales)
Authors: Steglidi Wolfgang , Zechlin Lothar 
Published: August 2018

Abstract
The isolation and identification of 3-methylriboflavine from the toadstool Panellus serotinus is described.
Immunological Reaction of UV-Induced Radiation Damage in Coliphage DNA
Authors: Fink Angelika , Hotz Gerhart 
Published: August 2018

Abstract
Denatured DNA of coliphage Tl, poly-dT and dTpT were UV-irradiated (2537 Å) and con­jugated to methylated bovine serum albumin. These molecules act as haptens after injection into rabbits. Antibodies are predominantly formed against UV-induced cyclobutane-type of cis-syn thymine dimers. They belong to the IgG-type of antibody molecules. Antigen-antibody complexes were detected by means of the CsCl-density gradient method. Denaturation of the DNA strongly influences the amount of specific antibodies bound to the antigen. In native DNA thymine dimers are masked concerning their reaction with antibodies. Photoproducts of UV-irradiated dTpT induce a specific production of antibody. Our results indicate that the cyclobutane type of thymine dimers is the relevant antigenic determinant group in UV -irradiated DNA.
Eigenschaften der [ω-(3-Acetylpyridinium)-n-alkyl]-adenosin-pyrophosphate als Strukturanaloge des Coenzyms NAD / The Properties of [ω-(3-Acetylpyridinio)-n-alkyl] Adenosine Pyrophosphates, Structural Analogs of the Coenzyme NAD
Authors: Jeck Reinhard 
Published: August 2018

[ω- (3-Acetylpyridinio) -n-alkyl] adenosine pyrophosphates are coenzyme analogs of NAD⊕. The adenosine pyrophosphate moiety and the 3-acetylpyridine ring of the analogs are connected by n-alkyl chains of different lengths (ethyl -hexyl). The analogs form strong dissociating complexes with lactate dehydrogenase. The complex formation is predominantly achieved by interaction of the ADP moiety with its respective binding domain at the active site.
The redox potentials of the analogs and NAD are of similar magnitude. The coenzyme function of the analogs depends upon the length of the hydrocarbon chain. Lactate dehydrogenase and alcohol dehydrogenases from yeast and horse liver do not catalize hydrogen transfer from their substrates to any other alkyl analog but [4- (3-acetylpyridinio)-n-butyl] adenosine pyrophosphate, aldehyde dehydrogenase from horse liver catalizes hydrogen transfer from acetaldehyde to the pentyl derivative and glyceraldehyde-3-phosphate dehydrogenase catalizes hydrogen transfer to both analogs. In no case, hydrogen transfer from or to one of the 3-acetylpyridine-n-alkyl analogs proceeded with a velocity comparable to NAD or its 3-acetylpyridine analog. The results show that the nicotinamide bound ribose in NAD is involved in the binding and the activation of the coenzyme.
Binding of Antibodies onto the Thylakoid Membrane II. Distribution of Lipids and Proteins at the Outer Surface of the Thylakoid Membrane
Authors: Radunz Alfons 
Published: August 2018

Abstract
The number of antibody molecules which stroma-freed chloroplasts can bind out of the mono-specific antisera to monogalactosyl diglyceride, tri-and digalactosyl diglyceride, sulfoquinovosyl diglyceride, phosphatidyl glycerol, sitosterol, plastoquinone, lutein and neoxanthin was determined. This number was compared to the number of antibody molecules which stroma-freed chloroplasts can maximally bind. The result is that the antibodies to the individual lipids cover at most 17 per cent of the accessible thylakoid membrane surface.
From a serum which contains both antibodies to the proteins and lipids of the thylakoid membrane, not more antibody molecules are bound than from a serum to the proteins. This means that antibodies to proteins are able to cover up the entire accessible surface of the thylakoids whereas a mixture of antibodies to the lipids, listed above, cover only one forth of the surface. Consequently, antibodies which are bound to proteins can cover up the lipid areas entirely and in turn antibodies which are bound to lipids cover up parts of the protein areas. From this it follows that the portion of the surface, which is made up by lipids must be considerably smaller than 24 per cent. Furthermore, it follows from these experiments that the lipid areas are small and that lipids probably only fill up the gaps between the protein molecules.
The Degree of CF1 Release and the Reconstituting Capacity of the Depleted Membranes
Authors: Schopf Reinhard 
Published: August 2018

Abstract
Uncoupling of photophosphorylation was shown in chloroplasts from spinach which were iso­ lated in media containing pyrophosphate and thereafter suspended in salt-free solutions. The effective concentration of pyrophosphate to uncouple was determined by the addition of pyrophos­ phate to free thylakoid systems and shown to be dependent on the presence of the completely dissociated species which favoured complex formation with bivalent cations. Higher concentrations of pyrophosphate led to a stabilization of photophosphorylation. The uncoupling is due to the release of the coupling factor. The degree of liberation was shown to be dependent on the chlorophyll concentration. The capacity of extracted membranes to reconstitute photophosphoryla­tion with their corresponding supernatant or with purified CF1 was directly correlated to the amount of the liberated coupling factor.
Dissociation and Reassociation of Poliovirus II. Protein Components Obtained by Urea Treatment of the Virus Particle
Authors: Yamaguchi-Koll Ursula , Wiegers K. J. , Drzeniek R. 
Published: August 2018

Abstract
Dissociation of poliovirus by 9 ᴍ urea in 0.015 ᴍ NaCl at 25 °C resulted in the liberation of 35S RNA and of polypeptides sedimenting at 2S in sucrose gradients containing 9 ᴍ urea. However. a ribonucleopolypeptide (RNPP) complex sedimenting at 45S and oligomers of the viral polypeptides sedimenting at 7 -8S were found in addition to the monomers sedimenting at 2S when the urea concentration was lowered to 5 M after the dissociation procedure. Ribonuclease treatment prevents the appearance of the RNPP-complex. The amount of the RNPP-complex de­ creased, when the dissociation was performed at higher ionic strength. Under these conditions small amounts of empty capsids were detected.
Polyacrylamide gel electrophoresis showed that the RNPP-complex contained the polypeptide VP1. The oligomers (7 -8S) contained the polypeptide VP3 and small amounts of VP2. The bulk of VP2 and some VP3 were found in the 2S position together with VP4.
The molecular weight of the dissociation products in urea and phosphate buffer was determined by gel filtration to be about 30,000 for the monomeric polypeptides containing predominantly VP2 and about 70,000 for the oligomeric polypeptides containing predominantly VP3.
Our results demonstrate that the oligomers and the RNPP-complex are not primary products obtained by dissociation of the virus particle by urea but are due to a reassociation of the poly­ peptides or of VP1 and RNA.
Aerobic Oxidation of p-Hydroquinone by Horse Radish Peroxidase in the Presence of a Thiol and MnCl2
Authors: Esterbauer Hermann , Schwarzl Elisabeth 
Published: August 2018

Abstract
In the presence of MnCl2 and a thiol (glutathione, cysteine, 2-nitro-5-thiobenzoic acid) horse radish peroxidase oxidizes ρ-hydroquinone to ρ-benzoquinone which in turn immediately adds the thiol present yielding 2-S-substituted ρ-hydroquinone.
Biologically Active Constituents of Leaves and Roots of Aloe arborescens var. natalensis
Authors: Hirata Toshifumi , Suga Takayuki 
Published: August 2018

Abstract
Several biologically active substances, such as aloenin (1), magnesium lactate, aloe-emodin (4), barbaloin (5), and succinic acid, were found to be contained in the leaf juice of Aloe arborescens Mill. var. natalensis Berger, which has widely been used in domestic medicines. Aloenin (1) and magnesium lactate were elucidated to exhibit an inhibitory action on the gastric juice secretion of rats. Various constituents other than the above bioactive substances were found in the leaves and the roots of the plant.
Assimilatory Sulfate Reduction by Chloroplasts: The Regulatory Influence of Adenosine-mono-and Adenosine-diphosphate
Authors: Schwerin Jens-Dirk , Depka Brigitte 
Published: August 2018

Abstract
The first three enzymatic steps of assimilatory sulfate reduction in chloroplasts of higher plants have been investigated with emphasis on the influence of adenosine-mono-and -diphosphate upon the formation of APS, PAPS and bound sulfite.
The data show that the activation process is governed by the energy charge of the chloroplast. The regulatory step is localized at the ATP-sulfurylase reaction. It was found that this enzyme is inhibited by low concentrations of AMP and ADP, with apparent KiAMP = L8mм and KiADP=0.5 mм for the chloroplast preparations. The isolated purified ATP-sulfurylase is inhibited by the nucleotides accordingly, with KiAMP=0.2mм and KiADP=0.4mм. The results are interpreted as a regulatory mechanism for the complete process of assimilatory sulfate reduction in the chloro­ plast.
Hill-Activity and P700 Concentration of Chloroplasts Isolated from Radish Seedlings Treated with -Indoleacetic Acid, Kinetin or Gibberellic Acid
Authors: Buschmann Claus , Lichtenthaler Hartmut K. 
Published: August 2018

Abstract
The Hill-activity (reduction of DCPIP or methylviologen) and the concentration of P700 were studied in chloroplasts isolated from cotyledons of radish seedlings (R aphanus sativu s L. Saxa Treib), which had been grown with the addition of β-indoleacetic acid (IAA), kinetin, or gibberellic acid.
1) The photosynthetic activity of young chloroplasts from 3 day old Raphanus seedlings is very high (c. 180 μmol O2/mol chlorophyll × h) and decreases continuously thereafter with increasing age. The steady state Hill-activity is readied after 8 to 10 days (values of 55 to 50 μmol 02/mg chlorophyll × h).
2) Chloroplasts from plants treated with IAA or kinetin not only exhibit higher plastoquinone levels 1,2, but also a higher P700-content and a higher Hill-activity. The promotion effect is more pronounced with kinetin (+ 36 to 40%) than with IAA (+ 12 to 17%).
3) Gibberellic acid has a different effect on composition and activity of chloroplasts. In younger seedlings the Hill-activity appears to be somewhat stimulated, without promotion effect on plasto­ quinone 2 or P700 concentration. After 10 days GA3-treated plants show signs of chlorosis combined with a strong decrease in photosynthetic activity.
4) The data clearly demonstrate that the composition and activity of the photosynthetic ap­ paratus are under phytohormone control. IAA and even better kinetin promote the light induced formation of pigment systems and electrontransport chains. GA3 seems to block the rebuilding of the photosynthetic apparatus under steady state conditions.
Localization and Functional Characterization of Three Thylakoid Membrane Polypeptides of the Molecular Weight 66000
Authors: Koenig Friederike , Menke Wilhelm , Radunz Alfons , Schmid Georg H. 
Published: August 2018

Abstract
Three polypeptide fractions with the apparent molecular weight 66 000 were isolated from stroma-freed Antirrhinum chloroplasts which were solubilized with dodecyl sulfate. Antisera to these fractions affect electron transport in distinctly different ways. For the characterization of the three antisera photochemical reactions of chloroplast preparations with artificial electron donors and acceptors as well the analysis of fluorescence rise curves were used. Antiserum 66 000 PSI-96 inhibits electron transport apparently on the acceptor side of photosystem I, provided the antibodies are adsorbed onto the outer surface of the thylakoid membrane. Antiserum 66 000 PSI-88 probably acts directly on the reaction centre I or on its immediate vicinity, if the antibodies are adsorbed at the inner surface of the thylakoid membrane. Antiserum 66 000 PSII-42 inhibits electron trans­ port in the region of photosystem II. The antigen towards which the antiserum is directed appears to belong to the reaction centre II, as also in the condition of high inhibition degrees, the fluorescence intensity remains unchanged. The antigenic determinants are located at the outer surface of the thylakoid membrane.
Genetic Information Analysis of Bacteriophage Φx 174
Authors: Figueroa R. , Sepúlveda A. , Soto M. A. , Tohá J. 
Published: August 2018

Abstract
The genetic information of Φx 174 genome (genes and intermediate segments) is analyzed in terms of its independent (D1 index) and dependent information (D2 and D3 Markovian indexes), as well as of its ability to generate secondary structure.
Genes B and E, enclosed in A and D respectively, have: 1) values of D1 and D3 indexes closer to the theoretical random distribution curves than those of (A -B) and (D -E) gene fractions, and 2) in the ability for secondary structure generation minor differences with genes A and D.
F → G and mRNA start → A intermediate segments differ from randomness in their D1 and D2 indexes, but not so much in the D3 values.
All these data point out the use of code degeneracy for increasing the genetic information density of the virus.
Polarization, Isopotential Maps and Tunneling in Guanine, Cytosine, and Tautomeric Forms
Authors: Marañon Julio , Sorarrain Oscar M. 
Published: August 2018

Abstract
We have used the CNDO/2-CI method to calculate the isopotential maps for the fundamental state and the direction of the polarizations corresponding to several singlet transitions in the mole­ cules of guanine, cytosine and tautomeric forms. We have also calculated the times for proton tunneling and equilibrium constants between both conformers corresponding to the fundamental and some excited states. The results have been compared with the available experimental data.
Isolierung und Charakterisierung Antipyrin-abbauender Bakterien / Isolation and Characterization of Antipyrine-degrading Bacteria
Authors: Blecher Hartmut , Blecher Renate , Müller Rudolf , Lingens Franz 
Published: August 2018

Abstract
Five different strains of bacteria ultilizing antipyrine as sole source of carbon were isolated from soil. It was shown by morphological and physiological examinations, that the new isolates are closely related to strains selected with the herbicide chloridazon. A ll of these bacteria are charac­ terized by special features and cannot be classified according to Bergey’s Manual of Determinative Bacteriology.
Part of the strains which were selected with antipyrine not only grow with antipyrine but also with chloridazon. The others cannot be grown on chloridazon. However, resting cells of the latter group convert chloridazon to its catechol derivative (5-amino-4-chloro-2 (2,3-dihydroxyphenyl) -3 (2H)-pyridazinone). In these bacteria a catechol-2,3-dioxygenase (catechol: oxygen 2,3-oxido-reductase, EC 1.13.11.2) was found which readily catalyzes the cleavage of the catechol derivative of antipyrine (2,3-dimethyl-l-(2,3-dihydroxyphenyl)-pyrazolone (5)). The enzyme shows only slight activity with the corresponding derivative of chloridazon.
Antibiotika aus Basidiomyceten, VI [1 ] Merulinsäuren A , B und C, neue Antibiotika aus Merulius tremellosus Fr. und Phlebia radiata Fr./ Antibiotics from Basidiomycetes, VI Merulinic Acids A, B, and C, New Antibiotics from Merulius tremellosus and Phlebia radiata
Authors: Giannetti Bruno Max , Steglieh Wolfgang 
Published: August 2018

Abstract
Three new antibiotics, merulinic acids A, B, and C, have been isolated from fruiting bodies of Merulis tremellosus and Phlebia radiata. They are closely related derivatives of β-resorcylic and salicylic acid, carrying monounsaturated C17-alkyl side chains in 6-position. The merulinic acids are mixtures of the Δ8′-compounds with minor amounts of the corresponding Δ10′-, dehydro, and dihydro derivatives, separable only by means of HPLC. Δ8′-Merulinic acid A (1) was synthesized via a biomimetic cyclization of a linear precursor. The merulinic acids inhibit a variety of bacteria and are not active against fungi. RNA, DNA, and protein synthesis in Bacillus brevis and Ehrlich carcinoma ascites cells are inhibited shortly after the addition of the antibiotics. Almost complete hemolysis of human erythrocytes is caused by 25 μg/ml of merulinic acid B and C or by 73 μg/ml of merulinic acid A.
Purine Nucleosides and Nucleotides Unequivocally in the Syn Conformation: Guanosine and 5′-GM P with 8-tert-Butyl and 8-( α-Hydroxyisopropyl) Substituents
Authors: Pless Reynaldo , Dudycz Lech , Stolarski Ryszard , Shugar David 
Published: August 2018

Direct alkylation via a free radical reaction was utilized to prepare 8-tert-butylguanosine-5′- phosphate; this was dephosphorylated with alkaline phosphatase to give the parent nucleoside. The 8- (α-hydroxyisopropyl) derivatives of 5′-GMP and guanosine were prepared in an analogous manner.
The foregoing products, which are necessarily in the syn conformation about the glycosidic bond because of the bulky 8-substituents (van der Waals’ radii 3.5-4 Å), were characterized by elementary analysis, UV spectra and 1HNMR spectroscopy. The changes in chemical shifts of H (1′), H (2′) and H (3′) of each of the foregoing derivatives, relative to those for guanosine and 5′-GMP, were consistent with their being in the syn conformation and, furthermore, pointed to guanosine and 5′-GMP being predominantly anti, in aqueous medium or DMSO. They also demonstrated that, contrary to the prevailing opinion, 8-bromo-5′-GMP and 8-bromoguanosine are not necessarily ex­clusively in the syn conformation in solution.
While 8-bromoadenosine-5′-phosphate was slowly dephosphorylated by snake venom 5′-nucleoti- dase, the 8-tert-butyl and 8-(α-hydroxyisopropyl) derivatives of 5′-GMP were fully resistant to this enzyme.
Calculation of the Circular Dichroism of Chironomus Hemoglobin in the Light of the Quality of Its X-Ray Structure
Authors: Straßburger Wolfgang , Wollmer Axel , Thiele Herbert , Fleischhauer Jörg , Steigemann Wolfgang , Weber Erns 
Published: August 2018

For the larval hemoglobin III of the insect Chironomus thummi thummi, the rotational strength of the B (Soret) and Q band is calculated with a monopole/monopole and a dipole/dipole approximation applied to the atomic coordinates of the X-ray structures at 2.5 and 1.4 Å resolution.
In previous calculations using the 2.5 Å coordinates and with perturbing groups being restricted to aromatic side-chains, the dipole/dipole approximation clearly confirmed the negative sign ob­served by experiment. The predominant interactions were those of phenylalanine residues.
Recalculation with X-ray data refined to the present limits of performance corroborates the negativity of the rotational strength, but now the most important contributions are due to the peptide bonds formerly neglected. Also for the 2.5 Å coordinates it is learned that in contrast to earlier expectation the influence of the backbone in this hemoglobin is rather strong. A substantial contribution is further obtained for the perturbation by one of the propionic acid carboxylate groups of the heme.
Perspectives and problems of the approach are outlined.
Binding of Antibodies onto the Thylakoid Membrane IV. Phosphatides and Xanthophylls in the Outer Surface of the Thylakoid Membrane
Authors: Radunz Alfons 
Published: August 2018

Antisera to the phosphatides phosphatidyl inositol and phosphatidyl choline as well as to the xanthophylls violaxanthin and zeaxanthin were obtained by immunization of rabbits.
The phosphatidyl choline antiserum did not give cross reactions with thylakoid membrane glycolipids, nor with phosphatidyl glycerol and phosphatidyl inositol. The antiserum to phosphatidyl inositol also did not react with the glycolipids and phosphatidyl choline. However, a cross reaction with phosphatidyl glycerol was observed. Exhaustion tests revealed, that the phosphatidyl inositol antiserum was fully neutralized with the homologous phosphatide, but not with phosphatidyl glycerol.
Antibodies to the phosphatides phosphatidyl inositol and phosphatidyl choline react with stroma- freed, not swellable chloroplasts of Antirrhinum majus only in a monovalent manner as demon­strated by means of the anti-y-globuline consumption test. Sonicated and spun down chloroplasts, however, are agglutinated. Also an antiserum to phosphatidyl inositol treated with exhausting quantities of phosphatidyl glycerol agglutinates this ultrasonic sediment. This type of chloroplast preparation binds approximately double the amount of antibodies to phosphatides. Small membrane fragments of the ultrasonic supernatant in which the outer as well as the inner surface of the thylakoid membrane is accessible to antibodies, are not precipitated. They react with phosphatide antisera just like untreated chloroplasts. Chloroplasts of Antirrhinum majus and of Nicotiana tabacum, which were isolated in Tris buffer and whose thylakoids are swellable and exhibit high Hill reaction rates, were agglutinated by the phosphatide antisera.
The antisera to violaxanthin and zeaxanthin gave with the described chloroplast preparations the same reactions as the phosphatide antisera. From this it is concluded that antigenic determinants of the phosphatides and xanthophylls are located in the surface of the thylakoid membrane directed towards the outside.
Quantitative investigations on the maximal binding of antibodies showed that 1g stromafreed not swellable chloroplasts of Antirrhinum majus bind maximally 0.06 g antibodies to phosphatidyl choline and approximately four times the amount of antibodies to phosphatidyl inositol. Antibodies to the xanthophylls were bound in an amount of 0.04 to 0.09 g. The order of magnitude of these values fits the values of the maximal binding of antibodies to the glycolipids and also to proteins, which participate in photosynthetic electron transport. Onto the outer surface of the thylakoid membrane, accessible to antibodies, 1 g of antibodies can be maximally bound by 1 g chloroplasts.