bluuebunny/crossref_metadata_2025_split huggingface dataset:
Physico‐Chemical Properties of Mitochondrial Ribosomal RNA from Fungi
Authors: Edelman Marvin , Verma Inder M. , Herzog Rita , Galun Esra , Littauer Uriel Z. 
Published: March 2005

Several physico‐chemical properties of mitochondrial and cytoplasmic ribosomal RNA from the filamentous fungi, Trichoderma viride and Neurospora crassa were determined and compared with those for Aspergillus nidulans.

The thermal denaturation patterns of the mitochondrial rRNAs differed markedly from those of their homologous cytoplasmic rRNAs. The two rRNAs, therefore, possess distinct conformations in solution.
The guanine + cytosine content of Trichoderma mitochondrial rRNA was shown to be very low (31.5 and 35.5% for the heavy and light components) and to differ considerably from that of its cytoplasmic rRNA (50 and 49%). Such nucleotide compositions are characteristic of fungal mitochondrial rRNA and account, at least in part, for the unusual physical characteristics which these polynucleotides exhibit.
Polyacrylamide gel electrophoresis of mitochondrial and cytoplasmic rRNA was performed in buffers of different ionic strenghts. In low‐salt buffer, the relative mobilities of the mitochondrial rRNAs were severely retarded, causing mitochondrial rRNA to migrate more slowly than cytoplasmic rRNA. In Mg buffer, mitochondrial and cytoplasmic rRNA co‐electrophoresed and were easily distinguished from Escherichia coli rRNA. Thus, under certain conditions, the conformational peculiarities of fungal mitochondrial rRNAs are expressed with this technique as well. It is concluded that accurate extrapolations from electrophoretic mobilities to molecular weight values cannot be made for these rRNA samples.
Mitochondrial rRNAs sediment more slowly than their corresponding cytoplasmic rRNAs. However, under the same experimental conditions the sedimentation velocity patterns for the various mitochondrial rRNAs are not identical.
While the above measurements clearly distinguish mitochondrial rRNAs, as a group, from cytoplasmic and bacterial rRNAs, they also point out a considerable physical heterogeneity among the fungal mitochondrial rRNAs.
Excretion of Endogenous Steroids and Metabolites of [4‐14C]Pregnenolone in Bile of Female Rats
Authors: Cronholm Tomas , Eriksson Håkan , Gustafsson Jan‐Åke 
Published: March 2005

Gas‐liquid chromatography, gas chromatography‐mass spectrometry and radio‐gas chromatography were used to identify endogenous steroids and metabolites of [4‐14C]pregnenolone in bile from female bile fistula rats.About 70% of the administered radioactivity was recovered in the bile during the first 24 h, and less than 1% during the following three days. 76% of the biliary radioactivity was extracted and was separated according to conjugation. The free steroid fraction contained 2%, the glucuronide fraction 22%, the monosulphate fraction 45%, and the disulphate fraction 28% of this radioactivity. The following steroids were identified by gas chromatography‐mass spectrometry and were found to be labelled: glucuronide fraction: 3α‐hydroxy‐5α‐androstan‐17‐one, 3α‐hydroxy‐5α,17β‐pregnan‐20‐one and 3α,16α‐dihydroxy‐5α‐pregnan‐20‐one; monosulphate fraction: 3α,7α‐dihydroxy‐5α‐androstan‐17‐one and/or 3α,15α‐dihydroxy‐5α‐androstan‐17‐one, 3α,11β‐dihydroxy‐5α‐androstan‐17‐one and 3α,16α‐dihydroxy‐5α‐pregnan‐20‐one; disulphate fraction: 3α,7α‐dihydroxy‐5α‐androstan‐17‐one, 3α,11β‐dihydroxy‐5α‐androstan‐17‐one, 5α‐pregnane‐3β,20β‐diol and 3α,21‐dihydroxy‐5α‐pregnan‐20‐one. The main part of radioactivity in the steroid monosulphate fraction was associated with pregnenolone that had a very high specific activity. The amount of steroids excreted during the first 24 h after bile duct cannulation was about 700 μg, when no correction for losses was made. The large quantity of steroid metabolites excreted in the bile confirms the importance of this excretory pathway also for endogenous steroids. The quantitatively most important steroids were found to be unlabelled corticosterone metabolites: 3α‐ and 3β,11β,21‐trihydroxy‐5α‐pregnan‐20‐one and 3α,11β,15α,21‐tetrahydroxy‐5α‐pregnan‐20‐one. Several other unlabelled steroids were identified. The heterogenous distribution of radioactivity among the metabolites is in contrast to the more uniform labelling previously obtained with intact rats. This shows that the metabolism of injected labelled steroids in bile fistula rats is not representative of the conditions in the intact animal, where enterohepatic circulation results in a continuous labelling of precursor steroid(s).
The Peroxidase Activity of Deuterohemin
Authors: Portsmouth David , Beal Elizabeth A. 
Published: March 2005

The reaction of hydrogen peroxide with deuterohemin and the reaction of the products with peroxidase substrates in neutral aqueous solution have been investigated. Qualitative observations indicate that, prior to oxidative degradation of the porphyrin ring system, a peroxidatic hemeperoxide complex is formed which can react with hydrogen donors to regenerate free deuterohemin. Quantitative data support this conclusion and show that this complex formation can account for the peroxidase activity of deuterohemin. The kinetics of formation of this complex and its reaction with peroxidase substrates have been studied and indicate that the principal difference between the catalytic mechanisms of deuterohemin and peroxidase is the very much more rapid rate of formation of the primary active complex in peroxidase. The overall rate of conversion of the primary active complex to the free catalyst is approximately the same in both enzyme and model systems, although in the latter case no intermediate analogous to compound II of peroxidase is formed.The mechanism of action of peroxidases and the nature of their active peroxide complexes is discussed in the light of these findings.
Massenspektrometrische Identifizierung substituierter Phenylthiohydantoine aus dem Edman‐Abbau von Petiden
Authors: Weygand Friedrich , Obermeier Rainer 
Published: March 2005

The mass spectroscopic identification of substituted phenylthiohydantoins from the Edman degradation of peptides is described. For better recognition of the PTH peaks within the spectrum, p‐bromophenylisothiocyanate was used predominantly. The mass numbers, characteristic for each of the common amino acid PTH derivatives, are shown. The whole procedure, named MS‐Edman degradation was tested by degradation of the octapeptide Pro‐Phe‐Phe‐Leu‐Ile‐Ile‐Leu‐Val and the N‐terminal sequence of glucagon (16 cycles). This procedure has the following advantages:a) Direct identification of phenylthiohydantoins by mass numbers instead of indirect, e.g. chromatographic comparison.b) Unequivocal assignment of the amide groups by differences between the phenylthiohydantoins of Asn and Asp, or Gln and Glu and easy differentiation of Leu and Ile.c) High sensitivity.d) Simultaneous observation of side reactions and peptide fragmentation during the Edman procedure.
Optical Rotatory Dispersion and Circular Dichroism of Cytochrome Oxidase
Authors: King Tsoo E. , Bayley Peter M. , Yong Fook Choy 
Published: March 2005

Optical rotatory dispersion of the oxidized and the reduced cytochrome oxidase has been measured from 196 to 550 nm. The experimental data have been analyzed in order to separate the extrinsic cotton effects from the rotations of the protein backbone. From the resolution, two cotton effects of similar sign are obtained in the Soret region. For the reduced enzyme, the cotton effect centered at 446.5 nm shows a molar amplitude of 192 k‐degrees with a band width of 5.3 nm and rotational strength of 0.25 Debye magneton; the second cotton effect centered at 444 nm shows a molar amplitude of 45 k‐degrees with a band width of 12.9 nm and rotational strength of 0.14 Debye magneton. Upon oxidation, the centers of these cotton effects shift to 432 and 423.7 nm. The amplitudes become 114 and 122 k‐degrees with band widths of 6.1 and 11.2 nm and rotational strengths of 0.18 and 0.35 Debye magneton, respectively. In addition, a less defined third cotton effect centered at 376 nm appears with an amplitude of 28 k‐degrees, band width of 18 nm, and rotational strength of – 0.15 Debye magneton. The circular dichroic curves constructed from the optical rotatory dispersion data by the Kronig‐Kramers transform are in general agreement with the experimentally determined spectra.The backbone rotations are analyzed and expressed in the terms of Shechter‐Blout's parameters. The effective helicity thus computed is 50% for the reduced and 44.5% for the oxidized form.The sources of the Soret cotton effects are discussed along with the possibilities of the components present (cytochromes a and a3 and copper), the intrinsic property of the Soret transition, possible splitting of the Soret band, interactions with the protein helix, and heme‐heme and heme‐copper couplings. The fact that the optical rotatory dispersion and circular dichroism behavior is dependent upon the oxidation state of cytochrome oxidase could arise either from an altered conformation of the protein backbone and/or from an altered interaction with the heme group. Regardless of the possibilities, the geometrical conformation of cytochrome oxidase and the electronic relation between the prosthetic group and the apoenzyme is dependent upon the oxidation state of the enzyme.
Light‐Induced Structural Transitions of Chloroplasts Studied by the Spin‐Probe Method
Authors: Tzapin A. I. , Mmolotkovsky Y. G. , Ggoldfield M. G. , Dzjubenko V. S. 
Published: March 2005

The light‐induced structural state changes of chloroplast (swelling and shrinkage) are compared with the change of activity (ferrcyanide reduction and photophosphorylation) and the state of hydrophobic membrane parts, characterised by the electron spin resonance spectra of iminoxyl radical‐probe, introduced in the membrane.Shrinkage of chloroplasts in sodium acetate medium is accompanied by non‐essential changes of activity and conformational state. Moreover light‐induced swelling in sodium chloride medium is accompanied by transition of chloroplasts to the uncoupled state and by change of conformational state.The regulatory function of conformational transitions in the chloroplasts is discussed and the corresponding scheme of regulation of photophosphorylation is suggested.
Ribosomal Proteins
Authors: Homann Heide E. , Nierhaus Kund H. 
Published: March 2005

The 43 S precursor of the 50 S ribosomal subunit shows a protein pattern very similar to that of a “core” particle derived from 50 S subunits on CsCl gradients.
A comparison of the protein patterns of “core” particles from 50 S subunits after CsCl equilibration runs or incubation with increasing LiCl concentrations over the molarity range 0.4–6 M revealed that the proteins are successively released from the “core” in five distinct groups.
The protein pattern of the 21 S precursor of 30 S ribosomal subunits was compared with that of the reconstituted intermediate particle and LiCl‐treated “core” particles of 30 S subunits. The 21 S is similar to both the reconstituted intermediate and the “core” particles derived by a 1 M LiCl treatment, whereas the reconstituted intermediate and this core particle differ rather more.
Synthetic Antigens with Sequential and Conformation‐Dependent Determinants Containing the Same l‐Tyrosyl‐l‐alanyl‐l‐glutamyl Sequence
Authors: Schechter Bilha , Schechter Israel , Ramachandran Janakiraman , Conway‐jacobs Abigail , Sela Michale , Benjamini Eli , Shimizu Meikyo 
Published: March 2005

Two synthetic copolymers have been used in order to investigate the role of conformation in immunogenicity and antigenic specificity. The first one is a high molecular weight ordered copolymer composed of the repeating sequencel‐tyrosyl‐l‐alanyl‐l‐glutamyl. This polymer exists as an α‐helix under physiological conditions. In the second polymer, the tripeptide l‐tyrosyl‐l‐alanyl‐l‐glutamic acid is attached to branched poly‐dl‐alanine. In this branched polymer the tripeptide exists as a random coil. These polymers elicit the formationof antibodies with distinct specificities, since there was no cross‐precipitation reaction between the two systems. Furthermore, antibodies against the branched polymer were efficiently inhibited by the tripeptide l‐tyrosyl‐l‐alanyl‐l‐glutamic acid, whereas antibodies against the helical polymer were inhibited neither by the tripeptide, nor by other small peptides of sequences related to the primary structure of the helical polymer. However, inhibition was obtained with oligopeptides possessing the general formula (Tyr‐Ala‐Glu)n (with n = 3, 4, 7, and 9), the inhibitory capacity increasing with the value of n. Peptides with n values of 7 and 9 were efficient inhibitors, whereas (Tyr‐Ala‐Glu)13 precipitated with the antibodies. The dependence of inhibitory capacity on a suggests that the peptides with n = 2–9 undergo transconformation (from random coil to α‐helix) upon reaction with the antibody combining site.The immunological studies showed that the antigenic determinats of the α‐helical polymer are conformation‐dependent, whereas the branched polymer contains sequential determinants.
pH Dependence of the Activity of β‐Galactosidase from Escherichia coli
Authors: Tenu Jean‐Pierre , Viratelle Odile M. , Garnier Jean , Yon Jeannine 
Published: March 2005

The “specific reactivity” of β‐galactosidase from Escherichia coli for different substrates has been studied at the optimal pH value. The pH dependence of the enzyme activity has been reinvestigated in highly controlled conditions with respect to Mg2+ and Na+ concentrations and ionic strength. The different kinetic parameters kcat, km and the kcat/km ratio have been determined with o‐nitrophenyl‐β‐d‐galactoside and o‐nitrophenyl‐β‐d‐fucoside, at different pH values between 5.16 and 10, for both Mg2+‐enzyme and Mg2+‐free enzyme, since a residual activity has been found in the absence of Mg2+.The activity of both types of enzyme is controlled by a protonated group which ionizes in the alkaline range and by at least one unprotonated group which ionizes in the acidic range. This latter group has a pK smaller than 6 in both types of enzyme; it is plausible to assume that this group is a carboxylate.In the alkaline range, the pK of the involved group shifts from about 6.5 in Mg2+‐free enzyme to 8.4 in the Mg2+ enzyme. Either the substrate or the Mg binding induces this shift in the ionization of the group.The β‐galactosidase catalyzed reactions proceed via two intermediary complexes. For o‐nitrophenyl‐β‐d‐galactoside substrate the limiting process is not the same for the Mg2+ enzyme and for the Mg2+‐free enzyme.
Studies on “Nonspecific” Binding
Authors: Andersson Lars‐Olov , Rehnström Ann , Eaker David L. 
Published: March 2005

The binding of flourescein to bovine serum albumin was studied by equilibrium dialysis under various conditions. At pH 8.0 and 5°C there are three binding sites with association constants of 2.8 × 104 M−1. Specific labelling of the binding sites using fluorescein‐isothiocyanate showed that two of the binding sites are immediately adjacent. The labelled peptides were isolated and the sequence around one of the binding regions was determined revealing the presence of three lysines in this eight amino acid sequence. The binding is mainly casused by hydrophobic interactions and to lesser extent by electrostatic forces. The electrostatic contribution is much less than expected compared with other substances which are bound to bovine serum albumin. This is probably related to the fact that fluorescein is a nonphysiological compound and is “nonspecifically” bound to bovine serum albumin.Studies on binding properties of various peptic fragments of bovine serum albumin were performed. They showed that even slight fragmentation caused a drastic decrease in the ability to bind fluorescein.
Coordination de la transcription des RNA 5 S et 23 S et coordination de la maturation du RNA 5 S et de la sous‐unité reibosomique 50 S chez Escherichia coli
Authors: Galibert Francis , Tiollais Pierre , Sanfourche Françoise , Boiron Michel 
Published: March 2005

The stepwise biosynthesis of Escherichia coli ribosomes can be characterized by a number of precursor ribonucleoprotein particles. It has been shown that 5 S RNA exists as a precursor, pre‐RNA 5 S, prior to its integration into the 40 S relax particle. The present study is concerned with the regulation of 5 S RNA biosynthesis. We report here that:a) the pre‐5‐S‐RNA fraction containing the precursor of 5 S RNA is heterogeneous and consists of a mixture of three (or possibly four) RNA's each precursor to 5 S RNA and each corresponding to a different step in the pathway of 5 S RNA biosynthesis;b) amino acid starvation of an auxotrophic strain of Escherichia coli arrests the maturation of ribonucleoprotein and of 5 S RNA. 23 S and 16 S ribosomal RNA appear in 25 S and 18 S particles and in 38 S and 21 S particles, depending on whether RCrelaxed or RCstringent strains were used. 5 S RNA accumulates as 5 S relax RNA or 5 S stringent RNA. The electrophoretic, chromatographic and denaturation analysis of these accumulated RNA's reveal that 5 S relax RNA is less mature than 5 S stringent RNA. The results demonstrate that the maturation of ribosomal particles and 5 S RNA are coordinated together, as the arrest of ribosomal particle maturation is accompained by the arrest of 5 S RNA maturation at a comparable stage;c) by utilizing different methods of cell lysis one can demonstrate that the precursor of 5 S RNA and the immature ribonucleoprotein particles are not found free in the cell but are attached to cellular structures which may be involved in the coordination of the maturation of 5 S RNA and ribosomes;d) kinetic studies of uridine incorporation into RNA during amino acid starvation of an Escherichia coli RCstringent auxotrophic strian reveals that an equimolar amount of 23 S RNA and 5 S RNA are synthesized and one may conclude that these syntheses are coordinated.
The meta Cleavage of Catechol by Azotobacter Species
Authors: Sala‐trepat Jose M. , Evans W. Charles 
Published: March 2005

Catechol was metabolized through 2‐hydroxymuconic semialdehyde by cell‐free extracts of benzoate‐grown Azotobacter Strains. Some properties of catechol 2,3 oxygenase preparations from Azotobacter vinelandii 206 are described.
Two different enzymatic activities able to attack 2‐hydroxymuconic semialdehyde have been found in crude extracts from benzoate‐grown cells; one catalyses a hydrolytic release of formate from the semialdehyde and the other a dehydrogenation of this compound to 4‐oxalocrotonate. However, the low, non‐inducible levels of 2‐hydroxymuconic semialdehyde hydrolase activity appear negligible for metabolic purposes and the semialdehyde seems to be dissimilated almost exclusively via 4‐oxalocrotonate, by the action of a NAD+‐dependent dehydrogenase, in Azotobacter strains.
A tautomerase activity responsible for the interconversion of the enol and keto forms of 4‐oxalocrotonic acid was found in extracts from benzoate‐grown cells.
4‐Oxalocrotonate was stoicheiometrically converted to CO2 and 4‐hydroxy‐2‐oxovalerate by a partially purified extract, with the transient formation of a compound that appears to be 2‐oxopent‐4‐enoic acid. The 4‐oxalocrotonate decarboxylase activity was stimulated by Mg2+ or Mn2+ ions and was inhibited by EDTA.
Cell‐free extracts from Azotobacter strains converted synthetic 4‐hydroxy‐2‐oxovalerate to acetaldehyde and pyruvate.
A reaction sequence, termed the 4‐oxalocrotonate pathway, for the dissimiation of catechol to acetaldehyde and pyruvate by Azotobacter species is presented. All the enzymes operative in this pathway were inducible, except the 4‐hydroxy‐2‐oxovalerate aldolase.
The findings described here are discussed in connection with the two previously reported meta cleavage pathways for the oxidation of catechol in Pseudomonas strains.
Anaerobic Oxidation‐Reduction Titrations of Human Ceruloplasmin
Authors: Carrico Robert J. , Malmström Bo G. , Vänngård Tore 
Published: March 2005

Anaerobic oxidation‐reduction titrations of human ceruloplasmin were performed with ascorbate and NADH as reductants. Under most conditions examined one electron per copper ion was required to diminish completely the electron paramagnetic resonance (EPR) signals and the 330 and 610 nm optical absorption bands. In sodium phosphate buffer at pH 7.4 the same changes were attained by addition of only 0.5 electron per copper ion. However, one equivalent NADH was oxidized per g‐atom of copper indicating that the electron accepting capacity of the protein was unchanged. Three kinds of electron acceptors were apparent from titration curves based on optical absorption and EPR parameters. One acceptor is the “blue” copper which gives the Type 1 EPR signal. The second is the remaining paramagnetic copper, Type 2, and this does not have detectable absorption bands in the visible spectrum. The third is a chromophore with an optical absorption maximum near 330 nm and is probably associated with the diamagnetic copper.A temperature‐dependent electron shift caused the 610 nm absorbance of partially reduced ceruloplasmin to decrease when the temperature was lowered. Fluoride ion prevented this shift and brough about marked changes in the titration behavior of the electron acceptors.
Studies of Glutamate Dehydrogenase
Authors: Pilz Ingrid , Sund Horst 
Published: March 2005

The size and shape of beef liver glutamate dehydrogenase in the presence of the allosteric effectors GTP and NADH were investigated by X‐ray small‐angle measurements. These nucleotides cause a dissociation of the associated particles into oligomers. The radius of gyration (R) of the oligomer was found to be 47 Å and a pronounced subsidiary maximum was obtained as is the case with the associated particles. Comparison with theoretical scattering curves shows that the overall shape of the oligomer corresponds well to a rounded cylinder with a ratio diameter to length of 1:1.5, a length of 12.6 nm and a diameter of 8.4 nm. The relatively high value of the volume (V= 668 nm3) indicates that the oligomer is loosely built and from the height of the subsidiary maxima it must be assumed that the oligomer contains larger voids. It is concluded that after interaction with GTP and NADH the conformation of glutamate dehydrogenase is not changed to a great extent although these nucleotides favor the dissociation into the oligomers.Based on the comparison of calculated scattering curves the eclipsed model for the oligomer proposed by Eigenberg and Reisler can be excluded. The calculated curve for the more staggered model has some similarities but does not coincide completely with the experimental scattering curve.