bluuebunny/crossref_metadata_2025_split huggingface dataset:
A Labile CO2-Fixing Enzyme Complex in Spinach Chloroplasts
Authors: Müller Bruno 
Published: February 2015

Activity and activation of ribulose 5-phosphate kinase, ribulose diphosphate carboxylase, phosphoglycerate kinase, and the NADP- and NAD-dependent glyceraldehyde phosphate dehydrogenases from isolated diloroplasts were traced in the course of differential ultracentrifugation. Activation of some of these enzymes was carried out by incubation with NADPH2 or ATP. Activity of ribulose diphosphate carboxylase could be increased 2,4-fold by incubation with NADPH2 while phosphoglycerate kinase could not be activated.
The degree of activation of the NADP-specific glyceraldehyde phosphate dehydrogenase and ribulose phosphate kinase was correlated with the velocity of sedimentation. Enzymes, which could be activated manifold, sedimented more quickly. Two fractions could be obtained after ultracentri fugation: the sedimented fraction could be highly activated while the fraction in the supernatant could not.
It was shown by gel chromatography with Sephadex for the NADP-specific glyceraldehyde phosphate dehydrogenase and ribulose phosphate kinase that the enzyme fractions which could be greatly activated had molecular weights of at least 400 000. In contrast, the enzyme fraction which could not be activated had a molecular weight of 50 000 for the ribulose phosphate kinase and of 240 000 for the glyceraldehyde phosphate dehydrogenases.
Results are discussed in the way that a reversible dissociation of a labile enzyme complex takes place between ribulose phosphate kinase, glyceraldehyde phosphate dehydrogenases, and ribulose diphosphate carboxylase. Enzyme activity changes with the state of aggregation. The dissociated enzymes have higher activity than the complexed ones. Dissociation can be performed by ATP and NADPH2, which are assumed to be the physiological regulators, and by unphysiological means as dilution and high salt concentrations.
The Distribution of Photosynthetic Reactions in the Chloroplast Lamellar System
Authors: Sane P. V. , Hauska G. A. 
Published: February 2015

Plastocyanin is released from chloroplasts by sonication, by passing through the French-press, by extraction with detergents, by treatment with organic solvents and by freezing and thawing. No plastocyanin is liberated during osmotic shock of either class I or class II chloroplasts, or by extraction of class II chloroplasts with dilute solutions of EDTA.
Under special conditions it is possible to separate grana and stroma lamellae, which retain plastocyanin. The distribution of plastocyanin between these membrane fractions parallels the distribution of photosystem I.
The different reactivity of plastocyanin with various chloroplast membrane preparations is not always correlated to plastocyanin content. Other parameters, like pH, seem to influence the interaction of plastocyanin with the surface of the chloroplast membrane.
The Distribution of Photosynthetic Reactions in the Chloroplast Lamellar System
Authors: Hauska G. A. , Sane P. V. 
Published: February 2015

Chloroplast fragmentation, ATPase, Proton pump, Cyclic Phosphorylation, NH4Cl-uncoupling
Cyclic phosphorylation and latent ATPase follow the distribution of photosystem I in the chloroplast membrane. Both activities are found higher in stroma lamellae than in grana. The extent of proton uptake is found to be higher in the grana. Since this uptake depends on internal volume and buffer capacity besides proton pump activity, the distribution of the proton pump proper remains to be elucidated.
Any fragmentation of the large inner compartment of the chlorolast lamellar system into smaller vesicles results in decreased sensitivity of cyclic phosphorylation to uncoupling by ammonium chloride. Consequently both, isolated grana and stroma lamellae, show decreased uncoupling by ammonium chloride. The effect can be explained by the action of a membrane potential in photophosphorylation which builds up during illumination and might be more stable in a system with the larger number of individual compartments just for statistical reasons. No assumption on changes in specific ion permeabilities during fragmentation of chloroplasts are needed.
Acid and Alkaline Phosphatase Levels in Various Tissues of a Lizard during Activity and Hibernation
Authors: Aziz Shakila , Hasnain S. N. , Zain-Ul-Abedin M. 
Published: February 2015

1. Acid phosphatase (AcPase) and alkaline phosphatase (AlPase) activities and specific activities were determined in six different tissues of Uromastix during active and hibernating periods.
2. The protein concentration was significantly reduced in all the tissues during hibernation.
3. pH optima of acid and alkaline Pases were found to be 4.2 and 9.2 respectively.
4. AcPase activity was increased in all the tissues except liver and small intestine during hibernation.
5. AlPase activity was increased in all the tissues except small intestine during hibernation.
6. Specific activities of both the enzymes were increased during hibernation.
Anreicherung und Charakterisierung einer „Transhydrogenase-Aktivität“ und der 17 β-Hydroxysteroid-Oxidoreduktase aus der Cytoplasma-Fraktion der Leber von weiblichen Ratten / The Enrichment and Characterisation of Cytoplasmatic “Transhydrogenase-activity” and 17 β-hydroxysteroid-oxidoreductase from Rat Liver
Authors: Pollow Kunhard , Pollow Barbara 
Published: February 2015

The cytoplasmatic fraction of rat liver contains both 17 β-hydroxysteroid-oxidoreductase and a “transhydrogenase-activity”, which catalyses the transfer of hydrogen from the 17 β-position of estradiol-17 β to the 17-position of 4-androstene-3,17-dione. The 17 β-hydroxysteroid-oxidoreductase was purified 718-fold and the “transhydrogenase-activity” 264-fold by ammonium sulphate precipitation, gel chromatography with Sephadex G-200, column chromatography on DEAE-Sephadex and isoelectric focusing. The two enzymic activities could not be separated. The characteristics of the two enzymatic activities give some evidence that the “transhydrogenase-activity” is identical with the already known 17 β-hydroxysteroid-oxidoreductase.
Isoelectric focusing of the chromatographycally enriched 17 β-enzyme gave an isoelectric point at 5,2. The 17 β-enzyme has a molecular weight of 62 — 65 000 as determined by mobility on Sephadex G-200 superfine.
The kinetic constants for both the 17 β-enzyme and the “transhydrogenase-activity” were determined.
4a,5-Cycloaddition Reactions of Acetylenic Compounds at the Flavoquinone Nucleus as Mechanisms of Flavoprotein Inhibitions
Authors: Zeller E. A. , Gärtner B. , Hemmerich P. 
Published: February 2015

4a,5-Cycloaddition at the flavoquinone, Mechanism of flavoprotein inhibitions
Photochemically, covalent cycloaddition products of flavoquinone and acetylenic enzyme inhibitors have been prepared and elucidated, which appear analogous to flavoprotein-inhibitor complexes (monoamine and lactate oxidase). The additions occur with inhibitors of general type HC≡C-CH< at the C (4a) = N (5) azomethine grouping of oxidized flavin. The spectral properties of adducts and their chemical reactivity is described.
Comparative Kinetics between Matrix-bound Lipoamide Dehydrogenase and the Free Enzyme
Authors: Visser Jaap , Havekes Louis , Veeger C. 
Published: February 2015

Lipoamide dehydrogenase (EC 1.6.4.3) has been succesfully linked to a CNBr-activated polysaccharide matrix, Sepharose-4B, under different reaction conditions. The enzyme is probably bound more homogeneously at lower pH values (pH 7.5) than at pH 8.5. Such immobilized preparations yield V values 8-30% of the value of the V of the free enzyme (18,600 mole/min/mole of flavin). A low level of CNBr-activation in combination with substrate protection and a pH of 7.5 during the coupling reaction leads to the most active preparations. The Km values for both substrates increase considerably.
The overall kinetic pattern of the matrix-bound enzyme preparations is not different from that of the free enzyme. Both activation by high concentration of lip (SH)2NH2 at low NAD+ levels and a stimulation of the V by increased phosphate concentration in the assay buffer is observed with free and some immobilized enzymes.
Untersuchungen an biochemisch wirksamen Ligandensystemen, V
Authors: Barz P. , Fritz H. P. 
Published: February 2015

1,2-Dimethylhydrazine co-ordinates to numerous metal cations. The structures of the complexes of Cr, Mn, Co, Ni, Cu, Zn, Cd, Hg and Pt are discussed and the complexing abilities of the 1,2-dimethylhydrazine molecule are determined on the basis of the ligand field spectra of the nickel and the chromium derivative.
The results of polarography, cyclic voltammetry and photoelectron spectroscopy yield evidence on the redox properties of the neutral molecule. By means of EPR spectroscopy the nature of the radical products obtained by irradiation of 1,2-dimethylhydrazine, especially of the radical cation, is determined.
Salzbildung der Diazoaminobenzole (Triazene) im Zuge der Elektrolyse in aprotischem Lösungsmittel / Salt Formation during Electrolysis of Diazoaminobenzenes (Triazenes) in Aprotic Solvent
Authors: Holleck Ludwig , Kazemifard Gholamali 
Published: February 2015

In contrast to aqueous and methanolic solutions the polarographic reduction of diazoaminobenzenes (DAAB) in the aprotic solvent dimethylformamid occurs in two waves with the combined hight corresponding to a four electron reduction.
The first wave results from the four electron reduction of the fraction (1/5) of the DAAB molecules which obtain the necessary protons from the remaining (4/5) DAAB molecules. The resulting DAAB anions are only reduced at the considerably more negative potentials of the second wave. Then the reduction occurs also in a four electron step and leads to the cleavage of the molecule. Potentiostatic electrolysis at the limiting current region of the first polarographic wave results in coloured solutions. The colour depends on the nature of the substituent. Salt formation was monitored spectrophotometrically and inferences pertaining to structure are drawn. The experimental results show that mercury compounds which might possibly be formed as intermediary species react immediately with the cations of the supporting electrolyte to form the corresponding DAAB salts.
Über die stufenweise Oxidation von Graphit in nichtwäßrigen, neutralen Elektrolyten / On the Stage-Wise Oxidation of Graphite in Nonaqueous, Neutral Electrolytes
Authors: Besenhard Jürgen , Fritz Heinz P. 
Published: February 2015

Electrolytic lamellar compounds of graphite with well-defined oxidation stages were indicated by characteristic changes in the potential of a graphite anode during galvanostatic oxidation in nonaqueous, aprotic electrolytes.
In analogy to the well-known graphite salts in acid media e. g. C24HSO4·2 H2SO4
1,2 a Cn-stage with n = 24 besides others with n&gt;24 was obtained in solutions of LiClO4, NaBF4 or KPF6 in propylene carbonate; further oxidation of graphite does not cause significat changes in the potential of the electrode. Such defined stages of oxidation were observed at graphite anodes in various nonaqueous electrolytes.
According to the present results simple salt-like lamellar compounds of the general type CnX are proposed; contrary to graphite salts prepared in concentrated acids, intercalation of free electrolyte is not a matter of priciple.
Untersuchungen zur Konfiguration von 4-Nitroimidazolnucleosiden / Investigations on the Configuration of 4-Nitro Imidazole Nucleosides
Authors: Vergin Hartmut , Bauer Hermann , Kuhfittig Gisela , Voelter Wolfgang 
Published: February 2015

It is demonstrated that the 220—225 nm Cotton effect of 4-nitro imidazole nucleosides can be used for the determination of the configuration of this class of compounds. A more detailed picture about conformation and configuration of the sugar residue is received from the copperammonia complexes of these nucleosides.
The pH-dependency of the stability and the complex ratio are discussed for a furanose moiety. Correlation between signs and intensities of the Cotton effects and configurations and conformations of the diol structures are discussed.
5. Mitt.: Über den Einfluß von Ethambutol auf den endogenen Stoffwechsel von M. smegmatis / The Endogenous Metabolism of Mycobacteria V: The Influence of Ethambutol on the Endogenous Metabolism of M. smegmatis
Authors: Reutgen H. , Iwainsky H. 
Published: February 2015

1. Under conditions of the endogenous respiration the mode of action of ethambutol on mycobacteria was studied. Oxygen uptake, 32P-incorporation and changes in the phosphate-content were measured as parameters for the behaviour of the metabolism.
2. In order to localize the first step of inhibition the radioactive isotope was applicated in a fixed chronological order and a fractionation in acid-soluble fraction, polyphosphate-, RNA- and DNA-fraction was carried out.
3. Proportional to the incubation periode the 32P was incorporated into the acid-soluble fraction, into the polyphosphate- and into the RNA-fraction in about the same proportions. The content in the DNA-fraction is nearly 200-times lower than in the RNA-fraction.
4. The main part of the phosphate is localized in the RNA (∼60%). Only in the begin of the incubation periode the part of the acid-soluble fraction is higher than that of the polyphosphate fraction.
5. The main part of the phosphate, transferred from the culture medium into the bacteries, was found in the polyphosphate fraction. During the incubation periode the phosphate-content in the RNA-fraction remains nearly unchanged. After decreasing to the begin the same was found for the acid-soluble fraction.
6. The specific activity of the polyphosphate fraction rises not continuously, according to the changes of the polyphosphate-content. Depending on the incubation periode the occured changes in the relations of the single fractions are similar in both the control- and the Ethambutol-trial.
7. In contrary to the results of other authors these investigations showed the same degree of inhibition of the phosphate metabolism in the acidsoluble fraction, the polyphosphate and the RNA-fraction.
8. Under conditions of the endogenous respiration ethambutol is inhibiting the phosphorylation of specific compounds of the intermediar-metabolism in the acid-soluble fraction or their further reactions. On the other side the changed incorporation of the 32P can be explained with a alterated permeability of the cell wall of the bacteria.
Kinetische und proteinchemische Untersuchungen am Succinyl-Papain / Kinetic and Chemical Investigations of Succinyl-Papain
Authors: Löffler H. G. , Schneider Fr. 
Published: February 2015

Kinetic studies of the reaction of papain with succinic anhydride demonstrate the reactivity of 10 amino groups, two of which are easily deacylated giving a stable succinylpapain with 3 free amino groups one of which is the free amino group of the terminal isoleucin. This modified enzyme has the tenfold solubility of papain between pH 5,9 - 9 and is a little more sensible to temperature than papain. Kinetic parameters of succinylpapain with N-Benzoyl-ʟ-arginine ethylester are: Km app =1,2 x 10-2 ᴍ( papain: 1,8 x 10-2 M) κcat=505 min-1 (papain: 475 min-1) at pH 6,2 and 37°C. The activity with the anionic substrate casein was 120 ± 10%, with the cationic protamine was 200 ± 20% of the activity of papain.
Nitration of 17 ± 1 tyrosines of succinylpapain with tetranitromethane has only a limited effect on the activity of the enzyme. The kinetics of this reaction suggests the existence of three groups of tyrosines with different reactivity. The reaction of papain with tetranitromethane gives only insoluble, cross-linked products.
Three of five present tryptophanes of papain and succinylpapain are oxidized by N-bromosuccinimide in the native state; in 8 ᴍ urea all residues are accessible. The esterase- and proteolytic activity of the oxidized enzyme decrease to less than 50% of controls while with benzoyl-ᴅ, ʟ-arginine-p-nitro-anilide there was observed an increased activity of about 250%. The stability of the enzyme drops considerably after oxidation of five tryptophane residues. Function and reactivity of the modified amino acids are discussed with regard to the results of the x-ray analysis of the enzyme
The Effect of some Sodium Substitutes on the Receptor Potential of the Crayfish Photoreceptor Cell
Authors: Stieve H. , Gaube H. , Malinowska T. 
Published: February 2015

Isolated crayfish retinas were perfused with four solutions in which Li+, ΝΗ4
+, Tris H+ and glucose were substituted for the sodium ions in the physiological salt solution.
The changes of the extracellularly recorded receptor potential (ReP) evoked by short or long stimuli were measured. The changes in the shape of ReP by test solutions were different for each Na-substitute.
For lithium ions as a Na-substitute (Tab. I and Fig. 3) the plateau value he was considerably decreased (to ∼20%) contrary to the peak-amplitude hmax which even slightly increased.
Ammonium ions show quite a different effect than all the other substitutes. The ReP is decreased strongly and irreversibly (Tab. II and Fig. 4).
When Tris (hydroxymethyl-ammoniummethane-hydrochloride) is substituted for Na, hmax decreased to about 60 per cent and the plateau is even more reduced (to 20 per cent; Tab. III). Only the recovery-value for he (50% smaller) is markedly different contrary to our former experiments where choline was used as Na-substitute (decrease 20%).
Glucose as a substitute for sodium chloride caused strongly decreased peak-amplitude hmax 26%
(Tab. IV and Fig. 9). Increased osmotic pressure due to excess glucose causes irreversible damage of the ReP (Tab. V). All the changes except those produced by NH4
+ were reasonably reversible.
The results can be explained by the following assumptions:
a) the maximum of the ReP is caused mainly by an increase in the permeability of the cell membrane for sodium. Ca- and Mg-ions also contribute to it to a certain degree.
b) The plateau value of the ReP to long light stimuli is determined:
1. by the sodium concentration gradient,
2. by active transport processes,
3. by the Ca++ - and Mg++-gradients,
4. the chloride gradient may perhaps contribute to this value
Die γ-Radiolyse und Pulsradiolyse des Schwefelkohlenstoffs in wäßriger Lösung / The γ-Radiolysis and Pulse Radiolysis of Carbon Disulfide in Aqueous Solution
Authors: Roebke W. , Schöneshöfer M. , Henglein A. 
Published: February 2015

A polymer (CHS2)n and sulfate are formed in the γ-irradiation of deaerated aqueous carbon disulfide solutions. The G-values are 3.6 and 0.41, respectively. In the presence of N,O, G (polymer) is decreased while G(SO4
-) is increased. G(SO4
-) can be decreased by isopropanol. G(polymer) is increased by H+ ions and reaches a value of 5 below pH = 2. Formic acid, hydrogen sulfide and carbonate are formed in the hydrolysis of the polymer. Pyrolysis at first leads to a red oil consisting of oligomer (HCS2)n and finally to H2S, CS2 plus a residue containing much carbon. The structure of the polymer is discussed.
Pulse radiolytic experiments show that CS2 reacts with eaq (3.1 × 1010M-1s-1) and OH(7.4 × 109M-1s-1) in a diffusion controlled manner. The first product of the reaction with OH is SC(OH)S. The pK of the electrolytic dissociation
SC(OH)Ṣ ⇄ SC(O-)S + H+

is 4.4. The absorption spectra of SC(OH)S and SC(O-)S were measured. SC(OH)S disappears by second order with 2k = 1.6 × 109M-1s-1 at pH = 6. The product is a bivalent acid, the spectrum of which was measured. The second pK of this acid is 5.7, its first pK is lower than 4.
Both eāq and H react with CS2 to form SCS-. The absorption spectrum of this radical anion was measured. The pK of the equilibrium
SCSH ⇄SCS- + H+

is about 1.6. In solutions of low H+-concentration, SCS- disappears by second order with 2k = 6.4 × 109M-1s-1. The structure of dithioformic acid is attributed to the resulting product. In solutions of high H+-concentration, SCS- (or SCSH) disappears by a fast first order process, the rate constant of which increases with H+-concentration. The carbeniat neutralization

is believed to be responsible for this process. The rate constant is 5.1 × 107M-1S-1. The spectrum of SC(H)S was measured. This radical disappears by second order with 2k = 7.4 × 109M-1s-1. The spectrum of the resulting product was also determined.
It is concluded that the formation of the polymer and of SO4
- occurs in processes in which the first products from the attack of eāq, H and OH on CS2 as well as molecules which were built up from these products are involved.
Hydration, Schichtsolvatbildung und Kationenaustauschreaktionen nichtstöchiometrischer ternärer Sulfide des Titans / Hydration, Layer Solvate Formation and Cation Exchange of Nonstoichiometric Ternary Sulfides of Titanium
Authors: Schöllhorn Robert , Weiss Armin 
Published: February 2015

Nonstoichiometric ternary phases (MI)x[TiS2] with MI = Li, Na, K were prepared by reaction of TiS2 in salt melts of the corresponding alkali halides under H2S/CS2 atmosphere. The compounds form hexagonal crystal plates with negatively charged [TiS2]x--layers of the CdJ2-type and alkali cations located between the metal sulfide sheets. They react with water to form hydrates, whose layer distances depend on the radius of the alkali cation and on the ambient water vapour pressure. A variety of layer solvate complexes is obtained by partial or total replacement of the water with polar molecules, which are able to solvate the metal sulfide layers and the interlayer cations. The latter may be exchanged with mono- and divalent inorganic and organic cations.
Similar reactions were observed with a number of ternary layer chalcogenides (MI)x⁻ [(MII)yXz] with MI = Li, Na. K, Rb, Cs; MII = Zr, Hf, V. Nb, Ta, Cr, Ni, Pd, Pt and X = S, Se.
Photoelectron Spectra and Molecular Properties. XVII
Authors: Stafast H. , Bock H. 
Published: February 2015

Photoelectron spectra, hyperconjugation, methylene derivatives
The photoelectron (PE) spectra of dicyano methane and of its dimethyl derivative are tentatively assigned on the basis of a simple MO model. The interactions defined therein between the two cyano groups as well as with the R2C-framework can be parametrized using the PE data. Thus the hyperconjugation πCN/πCR₂ is estimated to amount to 1.7 eV in both compounds. Hyperconjugative effects in methane derivatives H3CX and H2CX2 with X = Br, Cl and CN are compared.
The Coordination Chemistry of Phosphoryl Compounds Containing the -N(CH3)2 Group, XII.
Authors: Bolster M.W.G. De , Nieuwenhuijse B. , Reedijk J. 
Published: February 2015

Room temperature electron spin resonance powder spectra have been recorded for some compounds of the type Mn(ligand)p(anion)2 with hexamethylphosphoramide and nonamethylimidodiphosphoramide as ligands (p = 1 - 4) and BF-4, NO-3, Cl-, Br-, I- and NCS-as anions.
The values for the zero-field parameters, D and λ, have been determined and are compared with literature data. It is shown that ESR spectroscopy can be very helpful in elucidating the structures of manganese(II) complexes.
The high values for the hyperfine coupling constant of the solvates suggest that in these complexes the bonding between the ligands and the metal ion is essentially ionic.
Photochemischer Abbau N-substituierter O-Alkylurethane / The Photolysis of N-Substituted O-Alkylurethanes
Authors: Schultze Hartmut 
Published: February 2015

The photolysis of N-aryl-carbamic acid alkyl esters in methanol was investigated. The primary products, amino-benzoic acid esters and aromatic amines, result from photo-Fries rearrangements and splitting processes.
2,4,6-Trimethylphenyl-carbamic acid ethyl ester and N-alkyl-carbamic acid alkyl esters form photolysis products only through homolytic splitting reactions.
The photooxidation of N-substituted urethanes has been investigated in tert.-butanol. The main products are primary amines and CO2.
These initially formed compounds are then further oxidized. In the aliphatic substituted derivatives, oxidation of the N-alkyl group results followed homolytic bond splitting.