bluuebunny/crossref_metadata_2025_split huggingface dataset:
Various Metallopheophorbides as Substrates for Chlorophyll Synthetase
Authors: Helfrich Michael , Rüdiger Wolfhart 
Published: August 2018

Abstract
Pheophorbide a was prepared from a mixture of chlorophylls a and b by differential extraction with HCl and saponification. The insertion of the following metal ions was investigated: Mg, Zn, Co, Cu, Ni. In the enzyme test with chlorophyll synthetase, the metallopheophorbides fall into two categories: the Mg- and Zn-complexes are good substrates, the Co-, Cu- and Ni-complexes are neither substrates nor competitive inhibitors for the enzyme reaction. This corresponds to two categories of complex structures: Mg- and Zn-porphyrins prefer pentacoordinate square-pyramidal structures, Co-, Cu- and Ni-porphyrins prefer tetracoordinate square-planar structures. A model for substrate binding to chlorophyll synthetase is proposed.
Effect of Tentoxin on the Activation and on the Catalytic Reaction of Reconstituted H+-ATPase from Chloroplasts
Authors: Max-Volmer Petra Fromme , Friedrich-Schiller Ingo Dahse , Gräber Peter 
Published: August 2018

Abstract
The proton-translocating ATPase from chloroplasts, CF0F1, was isolated, purified and reconstituted into asolectin liposomes. The effect of the energy transfer inhibitor, tentoxin, on different functions of the enzyme was investigated. Tentoxin does not inhibit the nucleotide release during energization by a pH /ΔΨ jump, i.e. the activation of the enzyme is not influenced. ATP synthesis driven by a pH /ΔΨ jump and multi-site ATP hydrolysis are completely inhibited by tentoxin, whereas uni-site ATP hydrolysis is not influenced.
RNA Metabolism, DNA Damage and Cellular Resistance to X-Rays: Investigations in Chick Embryo and Rat Cells
Authors: Link A. , Tempel K. , Hund M. 
Published: August 2018

Abstract
Three hours after X-irradiation in vivo with 8 Gy the in vitro incorporation of [3H]uridine into total RNA of liver(L)- and brain(B)-cells of the chick embryo was reduced to 77% and 90%, respectively; the m RNA fraction was strongest inhibited. Under the same conditions, protein synthesis of L-cells declined to 62%, while protein synthesis of B-cells was not influenced. RNA and protein metabolism was not altered following X-irradiation in vitro (1.75 -56 Gy). - Compared to thymic - and splenic cells of the rat, chicken embryo cells exhibited higher constitutive poly(adenosine diphosphate-ribose)polymerase activity and lower X-irradiation-induced DNA damage. - Whereas the slight inhibition of RNA and protein synthesis by X-irradiation in ovo may be an abscopal and/or secondary phenomenon reflecting DNA and/or cellular damage, the present investigations comprising various cell types argue for an efficient DNA repair in chicken embryo cells caused, at least partly, by a high constitutive activity of DNA repair proteins.
Formation of ssb, dsb, and Uracil in Monofilarly and Bifilarly Bromouracil-Substituted DNA Molecules
Authors: Menke Henning , Köhnlein Wolfgang 
Published: August 2018

Abstract
Bifilarly BU-substituted ColE 1 plasmid and monofilarly BU-substituted M 13 phage DNA were irradiated with UV light of 313 nm. Using agarose gel electrophoresis and “reversed phase” HPLC technique ssb, dsb induction and uracil formation, respectively, could be detected in the irradiated DNA in dependence on the UV fluence. The analysis of the strandbreaks in bifilar Col E1 DNA shows a significant part of directly induced dsb.
Cross sections of ssb induction from 4.1 m2/J x 107 in 28%, 3.9 m2/J x 107 in 55% and 3.1 m2/J x 107 in 8 5 -9 0% BU-substituted DNA were calculated. The cross section for dsb induction was found to be 0.04 m2/J x 107, estimated from the linear part of the fluence effect curve. In monofilar M13 DNA a linear fluence effect curve for dsb induction was obtained. Excluding other than the direct production of dsb by using an in vitro approach for M13 DNA , the results strongly support the hypothesis that dsb can be induced by one photochem ical absorption event. The cross section for ssb was 3.8 m2/J x 107 and for dsb 0.05 m2/J x 107 in 41.5% monofilarly BU-substituted M13 DNA .
The comparison of ssb, dsb, and uracil production in bifilar and monofilar DNA with similar BU substitution showed no significant difference between the two DNA systems (ColE 1, M 13), indicating that the location of BU molecules in one or in both DNA strands will not lead to a different number of lesions after UV313 exposure.
Interaction of 2 ,3 -O-(2,4,6-Trinitriphenyl)adenosine Diphosphate and 2,4,6-Trinitrophenol with Thylakoid Membrane Proteins
Authors: Ponse Gudrun , Thelen Renate , Strotmann Heinrich 
Published: August 2018

Abstract
2′,3′-O-(2,4,6-trinitrophenyl)ADP (= TNP-ADP) is a competitive inhibitor of photophosphorylation of A DP. Here, the interaction of TNP-ADP with the H+-translocating chloroplast ATPase and other thylakoid membrane proteins was studied more in detail and compared with the interactions of the parental compounds ADP and 2,4,6-trinitrophenol (= picric acid). The following results were obtained:
(1) Preilluminated thylakoids incorporate about 1 nmol [14C]ADP per mg chlorophyll or the same amount of T N P-[14C]ADP in the following dark. If T NP-[I4C]ADP is present in the light, however, up to 4 nmol label is bound per mg chlorophyll whereas the amount of incorporated [14C]ADP is unchanged. [14C]ADP is exclusively bound to CF1, yielding a molar ratio of 1 nucleotide per enzyme. Likewise 1 mol of 14C label per mol enzyme is found in CF, when thylakoids are illuminated in the presence of TNP-[14C]ADP; the residual bound radioactivity is related with other components of the thylakoid membrane.
(2) TNP-ADP as well as picrate are electron acceptors of the photosynthetic electron transport chain. Picramate is one main product of photosynthetic reduction of picrate. Hence at least one of the three nitro groups of the trinitrophenyl moiety is reduced to an amino group. However, additional non-identified, reactive intermediates are formed, which can bind to membrane components. About 20% of the bound label is covalently linked to membrane proteins.
(3) The patterns of covalently labeled polypeptides are identical whether [14C]picrate or TNP- [14C]ADP is employed, except for α and β subunits of CF1 which are specifically labeled in the presence of TNP-[14C]ADP. This reaction is protected by (A DP + Pi) > ATP > ADP > Pi.
Most likely radicalic intermediates of picrate or TNP-ADP photoreduction are responsible for covalent binding. In case of CF, the radicalic intermediate of TNP-ADP reduction may be accomodated by its ADP moiety into a nucleotide binding site. Subsequent covalent linkage via the reactive phenyl ring substituent seems to occur in both, the nucleotide and the Pi binding domain.
Protective Effects of Phenolic Compounds on CCl4-Induced Toxicity in Isolated Rat Hepatocytes
Authors: Añón M.T. , Ubeda A. , Alcaraz M.J. 
Published: August 2018

Abstract
The protective effects of a series of phenolic compounds, phenolic acids and flavonoids on the cytotoxicity of CCl4 in rat hepatocytes were studied. A number of flavones, 7,8-dihydroxyflavone, luteolin and hypolaetin-8-glucoside, flavonols, morin, quercetin, robinetin and gossypin, phenolic acids, gallic, caffeic and chlorogenic acids, as well as the flavane ( + )-catechin significantly inhibited alanine amine transferase (ALT) release. Catechol groups are determinant for the protective activity of flavonoids and cinnamic acid derivatives, as well as the resorcinol or pyrogallol moieties in the B ring of flavonoids. In benzoic acid derivatives a pyrogallol group is required. This feature is associated with the inhibition of ALT spontaneous release.
Dufour’s Gland Composition in the Desert Ant Cataglyphis: Species Specificity and Population Differences
Authors: Hefetz Abraham , Lenoir Alain 
Published: August 2018

Abstract
Dufour’s gland secretion of several species of the desert ant Cataglyphis from different geographical localities was analyzed. The secretions constituted mostly of alkanes ranging from undecane to nonadecane. Species specificity is expressed as variations in the major component as well as the relative intensities of the additional constituents. Phylogenetically related species that are allopatric exhibited similar secretory composition whereas their sympatric counterparts had disparate composition, suggesting that character displacement occurred. Analyses of colonies of C. cursor from different localities also showed divergence in their glandular composition.
Relative Affinities of Nucleotide Substrates for the Yeast tRNA Gene Transcription Complex
Authors: Szafranski Przemyslaw , Smagowicz W. Jerzy 
Published: August 2018

Abstract
Apparent Michaelis constants for nucleotides in transcription of yeast tRN Agene by hom ologous RNA polymerase III with auxiliary protein factors, were found to be remarkably higher in initiation than in elongation of RNA chain. This supports presumptions regarding topological similarities between catalytic centers of bacterial and eukaryotic RNA polymerases.
Glycogen Synthesis in Rat Liver from a Pool of Free Glucose
Authors: Schimassek H. , Meißner Ingrid 
Published: August 2018

Glycogen synthesis in isolated perfused livers or livers of anesthetized rats (in situ), was studied using radioactively labelled fructose, lactate, and inositol as substrates. The specific radioactivity of glucose and glycogen was measured at various times and compared with that of some intermediates.
The results suggest that liver glycogen is formed from the pool of free glucose which in turn is fed by the so-called “direct and indirect pathway” of glycogen synthesis. This points to an important role of glucose-6-phosphatase, an enzyme complex subject to regulation by glucocorticoids, well known promoters of hepatic glycogen synthesis.
Segregation of Activity Profile in Benzimidazoles: Effect of Spacers at 5(6)-Position of Methyl Benzimidazole-2-carbamates [1]
Authors: Agarwal Shiv K. , Sharma Satyavan , Bhaduri A. P. , Katiyar J. C. , Chatterjee R. K. 
Published: August 2018

Abstract
The design and synthesis of a series of methyl 5(6)-substituted benzimidazole-2-carbamates as possible anthelmintics have been described. A rational analysis of the structural parameters which segregate the activity of resulting benzimidazole-2-carbamates against enteric and tissue dwelling helminths is presented. The influence of single and multiple spacers, which link the pharmacophores at 5(6)-position of benzimidazole-2-carbamate, on the activity against Ancylostoma ceylanicum (hookworm), Syphacia obvelata (pinworm), Hymenolepis nana (tapeworm), Litomosoides carinii and Acanthocheilonema viteae (filarial worm) has been presented. This analysis indicates that for activity against intestinal helminth the presence of one spacer holding the pharmacophore approximately 3 Å apart from the parent nucleus is usually preferred. While for activity against tissue dwelling parasite, the repetition of the benzimidazole-2-carbamate nucleus joined together through the 5,5′-position with one spacer kept apart by distance of 3 Å unit is usually desired.
Bisbibenzyl Formation in Aseptic Cultures of Marchantia polymorpha L
Authors: Adam Klaus-Peter , Becker Hans 
Published: August 2018

Abstract
Three new aseptic cultures of Marchantia polymorpha from different collecting sites have been induced from the gametophytes. The formation of bisbibenzyls in differentiated cultures and cell suspension cultures was investigated. We observed that the production of the main bisbibenzyl, Marchantin A was induced by lack of nitrate and the addition of cupric sulfate to the medium. The comparison of bisbibenzyl patterns in three different cultures suggest the existence of chemical races of M. polymorpha. Bisbibenzyl patterns in differentiated cultures and cell suspension cultures appeared to be similar.
Transport of Oxidized Glutathione into Barley Vacuoles: Evidence for the Involvement of the Glutathione-S-Conjugate ATPase
Authors: Tommasini Roberto , Martinoia Enrico , Grill Erwin , Dietz Karl-Josef , Amrhein Nikolaus 
Published: August 2018

Abstract
Glutathione in its oxidized form (GSSG) is rapidly taken up into isolated barley vacuoles, while uptake of reduced glutathione (GSH) is only marginal. GSSG transport is strictly ATP-dependent and is a saturable process (Km 0.4 to 0.6 mм). Uptake is inhibited by vanadate, but not by bafilomycin, a specific inhibitor of the vacuolar H +-ATPase. The observation that i) the non-hydrolysable ATP analogue adenylylim idodiphosphate does not stimulate, but rather inhibits the ATP-dependent uptake of GSSG and ii) that a four-fold accumulation of GSSG is observed in the presence of bafilomycin, suggests that GSSG is transported into the vacuole by a primary active process similar to that of glutathione S-conjugates (E. Martinoia, E. Grill, R. Tommasini, K. Kreuz, N. Amrhein, Nature 364, 247-249 (1993)). U ptake of GSSG is competitively inhibited by the glutathione S-conjugate of the herbicide m etolachlor (Ki 80 μм), indicating that transport of GSSG is mediated by the glutathione S-conjugate ATPase.
Antibiotic and Cytotoxic Activity of Brominated Compounds from the Marine Sponge Verongia aerophoba
Authors: Teeyapant R. , Woerdenbag H. J. , Kreis P. , Hacker J. , Wray V. , Witte L. , Proksch P. 
Published: August 2018

Abstract
Analysis of the marine sponge Verongia aerophoba from the Canary Islands afforded eight brominated secondary metabolites including the small molecular weight compounds aeroplysinin-1 (5) and the dienone (7) which were previously shown to arise by enzymatically catalyzed degradation of aerophobin-2 (4) and isofistularin-3 (1) following breakdown of the cellular compartmentation of the sponge. All compounds were identified from their NMR and mass spectra. Aeroplysinin-1 as well as dienone which arise from isofistularin-3 or aeropho­ bin-2 by biotransformation within the sponge showed a significantly higher antibiotic as well as cytotoxic activity than their biogenetic precursors. Antibiotic activity was studied with re­spect to several gram-positive and gram-negative bacteria including B. subtilis, S. aureus and E. coli. The MICs (MBCs) of aeroplysinin-1 (5) and the dienone (7) varied between 12.5-25 (50-100) μg/ml respectively. Cytotoxicity was tested in vitro towards HeLa cells, a human cervix uteri tumour cell line. Aeroplysinin-1 (5) and the dienone (7) displayed pronounced cytotoxic activity with IC50s of 3.0 and 3.2 μм respectively. A five-fold increase in cytotoxicity was observed after O-acetylation of the dienone (7). The IC50 of the dienone O-acetate (0.6 μм) was comparable to that of the clinically used anticancer drug cisplatin (0.7 μм).
Research on Biochemistry of Herbicides: An Historical Overview
Authors: Moreland Donald E. 
Published: August 2018

Abstract
Otto Warburg, the father of cellular bioenergetics, seems to have been the first investigator to report on inhibition of a plant biochemical reaction by a progenitor of a selective herbicide. The year was 1920 and the compound was phenylurethane (ethyl N-phenylcarbam ate or EPC). Warburg found that it strongly inhibited photosynthesis in Chlorella. EPC did not develop into a commercial herbicide, but the isopropyl derivatives (propham and chlorpropham) which were introduced in the late 1940s became selective herbicides. The phenylureas (monuron and diuron) were introduced in the early 1950s and shortly thereafter, interference with the Hill reaction by both phenylureas and phenylcarbamates was reported. During the latter part of the 1950s, into the 1960s, and even now, additional herbicidal chemistry was and is being announced that interferes with the Hill reaction. Duysens, in 1963, identified the site of action of diuron, i.e., on the acceptor side of PS II. Corwin Hansch, in 1966 introduced the SAR or QSAR concept in which inhibitory action of Hill inhibitors was related to various chemical and physical parameters.
Because of differential responses to partial, thylakoid-associated reactions, the Hill inhibitors were subsequently divided into two groups: pure electron transport inhibitors (phenylureas, s-triazines, triazinones, and uracils) and inhibitory uncouplers (acylanilides, dinitrophenols, benzimidazoles, dinitroanilines, and benzonitriles). The inhibitory uncouplers (dinoseb-types), unlike the diuron-types, uncoupled photophosphorylation by interacting with the coupling factor complexes in both chloroplasts and intact mitochondria. Additionally, the bi-pyridyliums were shown to be reduced by PS I, hence, diverted electrons from the native acceptor.
Field observations of triazine resistance were reported in 1970 and resistance was subse­ quently demonstrated at the thylakoid level. Application of the techniques of genetic engineering and biotechnology resulted in identification of the 32 kD a herbicide-binding protein and determination of its amino acid sequence. Crystallization and X-ray examination of the photosynthetic reaction center from Rhodopseudomonas by Michel et al. in the mid-1980s provided new models to account for interactions of herbicides with the D -1 protein.
During the 1980s, herbicides were identified that interfered with biochemical machinery in chloroplasts that is not involved in electron transport and light harvesting: inhibition of lipid biosynthesis by aryloxyphenoxypropionates and cyclohexanediones, aromatic amino acid bio­ synthesis by glyphosate, branched chain amino acid biosynthesis by sulfonylureas and imidazolinones, carotenoid biosynthesis by pyridazinones, and porphyrin biosynthesis by diphenylethers and oxadiazoles. The current status of research in most, if not all, of the above areas was reported through oral and poster presentations at this Omiya Symposium.
N-Methylanilinocyanoacrylate Photosystem II Inhibitors. Structure-Activity Relationships
Authors: Banham Wendy K. , Huppatz John L. , Phillips John N . 
Published: August 2018

Abstract
Many 3-N-methylanilino cyanoacrylate derivatives are potent inhibitors of photosynthetic electron transport at the PS II level in a thylakoid system isolated from Pisum sativum. These inhibitors are somewhat unusual in that they take more than 15 min to equilibrate with the binding site in contrast to most classical PS II inhibitors which tend to equilibrate rapidly i.e. within the mixing time of seconds. The effects of mono-and disubstituents in the aryl nucleus on inhibitory activity were studied. The nature and position of the substituent had no detectable influence on equilibration rate but a pronounced influence on inhibitory activity as measured by equilibrium pI50 values. Substituent position enhanced inhibitory activity in the order 3′ > 2′ ⋙ 4′ . As regards the nature of the substituent, size appeared to be the most important parameter -the smaller the substituent the greater the activity. Such influences were in contrast to those in analogous 3-anilino-and 3-benzylamino-2-cyano-acrylate series where the comparable order of substituent position effect was 3′ and 4′ ⋙ 2′ and where substituent hydro-phobicity rather than size was the most important factor. Disubstituted fluoro derivatives have given interesting insights into the preferred orientation of these inhibitors at the binding site with the 2′-and 5′-positions interacting positively, the 4′-position, negatively, and the 3′-position neutrally.
On the Orientation of Photosystem II Inhibitors in the QB-Binding Niche: Acridones, Xanthones and Quinones
Authors: Oettmeier Walter , Masson Klaus , Kloos Ralf , Reil Ellen 
Published: August 2018

Abstract
The orientation of acridones, xanthones, 1,4-benzo-and naphthoquinones within the photosystem II QB herbicide-binding niche was studied by means of mild trypsination and by estimation of pI50-values in Chlamydomonas reinhardtii D 1 mutants (Val219 > lie, Ala251 > Val, Phe255 > Tyr, Ser264 > Ala, Asn266 > Thr, and Leu275 > Phe). As judged from the R/S-values (ratios of I50 -values resistant versus susceptible type) close to 1 in all mutants, the acridones and xanthones do not have strong interactions with the parent amino acids. Contrary, the quinones exhibit extreme low R/S-values down to 0.003 (for 2,5-dibromo-3-methyl-6-isopropyl-1,4-benzoquinone; DBMIB) in the Ser264 mutant. This extreme negative cross resistance or supersensitivity indicates that the quinones do not form a hydrogen bond to the serine hydroxyl group.
Photosystem II Inhibition by Phloroglucinol Derivatives Having Both Phenol and Urea Functionalities
Authors: Honda Ichiro , Sibagaki Makoto , Yoneyama Koichi , Nakajima Yoshihiro , Konnai Makoto , Takahashi Nobutaka , Yoshida Shigeo 
Published: August 2018

Abstract
Esters of 3-nitrophloroglucinecarboxylic acid were found to be active photosystem II (PS II) inhibitors, as were the amides, indicating that, in their structures, the substituted phloroglucinol nuclei themselves plays a major roles in PS II inhibition. Among the phenylureidoalkyl esters tested, 3,4-dichlorophenylurea compound having two amino hydrogen atoms showed high activities. Optimal activity was associated with compounds in which the oxygen atom and the urea structure in the ester side chain were connected via an ethylene group.
Comparison of Experimental and Calculated Hydrogen Bonding Properties of Some Urea and Triazine Inhibitors of Photosystem II
Authors: Creuzet Sophie , Miranda Teresa 
Published: August 2018

Abstract
Previous studies of structure/activity relationships of photosystem II inhibitors, including comparisons of their inhibitory power in herbicide-resistant and susceptible chloroplasts, have led to predict the role of hydrogen bonding, associated to hydrophobicity, in the binding onto the QB site. The crystallographic structures of bacterial reaction centers now allow these bonds to be identified. In order to be able to understand the binding of various herbicides and the effects of resistance mutations within the QB site, a reliable estimation of hydrogen bonding strengths is needed. We show here, by calculating interactions with model compounds, controlled by physicochemical measurements, that the hydrogen bonding properties of the C = X nucleophilic moiety present in most PS II inhibitors are different for triazines as compared to urea or amide derivatives. Semiempirical methods (AM 1) fail to reproduce the energies of hy­drogen bonds between a triazine ring nitrogen and a phenolic proton. An empirical method (SIBFA), designed to reproduce interaction energies, has been adapted with the aim of calculating the binding energies of various herbicides with models of the QB site.
Structural Analysis of the QB Pocket of the D 1 Subunit of Photosystem II in Synechocystis PCC 6714 and 6803
Authors: Astier Chantal , Perewoska Irene , Picaud Martine , Kirilovsky Diana , Vernotte  
Published: August 2018

Abstract
Various herbicides inhibit photosynthesis by displacing the second electron acceptor QB from its binding site at the D 1 protein. Different amino acid substitutions within this binding site have been found to reduce herbicide affinities, thereby conferring herbicide resistance. In Synechocystis PCC 6714 we have selected 7 single mutants and 6 double mutants resistant to various herbicides due to amino acid substitutions at different positions in the QB pocket. Characterization of these mutants consists in molecular determination of the mutations in the psbAl genes and in transformation of Synechocystis PCC 6803 by the cloned mutated genes to analyze the role of the mutations in the mutant phenotypes. Comparison with equivalent Chlamydomonas mutants is presented. These studies allow us to specify the interactions of several amino acid residues with herbicides and QB and with each other. Furthermore some Synechocystis mutants present additional characteristics such as an increased sensitivity to photoinhibition, or resistance to formate or modification of the oscillatory pattern of oxygen evolution. Among the 6 point-mutations giving herbicide resistance, only those located at the limit of the loop and the parallel helix produced additional effects on photosystem II function.