bluuebunny/crossref_metadata_2025_split huggingface dataset:
Structural Investigations on the Core Polysaccharide of Escherichia coli 0100
Authors: Hämmerling Günter , Lüderitz Otto , Westphal Otto , Mäkelä P. Helena 
Published: March 2005

In order to investigate the core structure of the lipopolysaccharide from an Escherichia coli 0100 strain, two derivatives were prepared from this strain by introducing genetic material from Salmonella abony. One, an SR hybrid, contained a lipopolysaccharide with short side chains consisting of simple repeating units of Salmonella group B specificity attached to the E. coli core. The other, an R form, contained only the E. coli core and no O side chains, due to a mutation in the Salmonella rfb chromosomal region, which determines the synthesis of the O repeating units.By partial acid hydrolysis of the SR and R lipopolysaccharides, oligosaccharide fragments were obtained which made it possible to reconstruct the hexose region of the core (see formula below). Methylation studies performed on the dephosphorylated polysaccharides confirmed and extended these results. It was found that only about 60% of the distal glucose units of the core chains were substituted by N‐acetylglucosamine residues. Further, the heptose region was shown to form a branched trisaccharide.On mild acid hydrolysis of both lipopolysaccharide preparations a Gal‐α1,7(8)‐KDO disaccharide was formed, indicating that a galactose unit is linked to the 2‐keto‐3‐deoxyoctonate (KDO) portion of the lipopolysaccharide.After Smith degradation of the SR lipopolysaccharide, the oligosaccharide Gal‐β1,4‐Glc‐glycerol was identified which derived from the linkage region between the Salmonella type repeating unit and the E. coli core. Only the core stubs substituted by N‐acetylglucosamine residues carried an O‐specific unit.On the basis of the these findings the partial structure of the E. coli 0100 core polysaccharide with a Salmonella group B‐specific unit attached to it is proposed as given below. The relationships to core structures identified in lipopolysaccharides of other representatives of Enterobacteriaceae are discussed.
A Calorimetric Study of the Denaturation of Lysozyme by Guanidine Hydrochloride and Hydrochloric Acid
Authors: Lapanje Savo , Wadsö Ingemar 
Published: March 2005

The denaturation of lysozyme by guanidine hydrochloride and hydrochloric acid at several temperatures, and by guanidine hydrochloride alone at 25°C was studied using a microcalorimetric technique. From results of the calorimetric measurements at 25, 29.5 and 34.6°C enthalpies of denaturation by hydrochloric acid at constant guanidine hydrochloride concentration were calculated. From these ΔH values corresponding ΔCp values were calculated.An approximate value for the enthalpy of denaturation at 25°C of lysozyme by guanidine hydrochloride alone has also been obtained. It is shown that microcalorimetry is a sensitive method for following the two denaturation processes.
A Study of Mitochondrial Protein Synthesis in Intact HeLa Cells
Authors: Brega Agnese , Baglioni Corrado 
Published: March 2005

Mitochondrial protein synthesis has been studied in intact HeLa cells by utilizing specific inhibitors. We have observed that in the presence of pederine, an inhibitor of cytoplasmic protein synthesis in mammalian cells, protein synthesis continues for at least 1 h at approximately 0.5% of the rate of untreated cells. When control cells and cells treated with pederine are fractionated after an incubation with labeled amino acids into a mitochondrial and a supernatant fraction, it is found that incorporation into the mitochondrial fraction is higher in the presence of the inhibitor. Mitochondrial protein synthesis has been shown to take place on aggregates of mitochondrial ribosomes.The synthesis of mitochondrial proteins has been studied by incubating HeLa cells with labeled amino acids and either pederine or chloramphenicol, an inhibitor of mitochondrial protein synthesis. We have been able to establish that the structural protein of mitochondrial ribosomes is synthesized on cytoplasmic ribosomes and its synthesis is thus inhibited by pederine, but not by chloramphenicol. Mitochondrial proteins have been analyzed by acrylamide gel electrophoresis after fractionation of the mitochondria into inner and outer membranes. Proteins synthesized by mitochondria in the presence of pederine are located predominantly on the inner mitochondrial membranes. Only few protein species synthesized by mitochondria are resolved by gel electrophoresis. This finding is discussed in relationship to the information content of mitochondrial DNA.
Photoreactions of Chloroplasts in a Glycine Medium
Authors: Walz Dieter , Schuldiner Shimon , Avron Mordhay 
Published: March 2005

The rate of photoinduced electron transport in a medium containing glycine as the major salt was very low. It was dramatically increased by low concentrations of monovalent salts (2–4 mM) to rates typical of uncoupled systems. Further increase in salt concentration (beyond 15–20 mM) cause a sharp decrease back to “coupled” values. Salts of divalent ions, like Mg2+ were even more effective in the “recoupling” process (0.1 mM).When low amounts of Mg2+, phosphate and ADP were added to the glycine medium, photophosphorylation proceeded initially at high rates but stopped after a certain amount of ATP was accumulated. This effect was traced to a complete inhibition by the ATP formed of any further phosphorylation. The concentration of ATP needed to inhibit increased sharply with an increase of the salt concentration in the medium. ADP exhibited a similar inhibitory effect but higher concentrations were required.At concentrations where ATP inhibited phosphorylation, proton uptake was not affected.
Effects of Iodination and Acetylation of Tyrosyl Residues on the Activity and Structure of Arginine Kinase from Lobster Muscle
Authors: Fattoum Abdellatif , Kassab Ridha , Pradel Louise‐Anne 
Published: March 2005

The iodination and O‐acetylation of tyrosyl residues in arginine kinase from lobster muscle (Homarus vulgaris) with iodine and N‐acetylimidazole have been studied after reversible blocking of the thiol groups.The conversion of one tyrosyl residue to monoiodotyrosine, as measured by spectrotitration and by radioactive iodine labeling, resulted in a total loss of activity.The extent of the conformational changes occurring after nitration by tetranitromethane and iodination was studied by the optical rotary dispersion and the hydrogen‐tritium exchange techniques.The functional properties of this tyrosyl residue were underlined by the inhibition of arginine kinase after o‐acetylation and the ability of the modified protein to recover full activity upon tyrosyl de‐o‐acetylation with neutral hydroxylamine.
Studies on Lichen Enzymes
Authors: Mosbach Klaus , Schultz Joachim 
Published: March 2005

Orsellinate decarboxylase, catalyzing the decarboxylation of orsellinic acid (2,4‐dihydroxy‐6‐methyl benzoic acid) to orcinol has been isolated from the lichen Lasallia ptulata.The substrate specificity of the enzyme has been tested: only orsellinic acid, 3‐chloro‐, 5‐chloro‐orsellinic acids, homo‐orsellinic acid (2,4‐dihydroxy‐6‐ethyl benzoic acid) and everninic acid (4‐methoxy‐2‐hydroxy‐6‐methyl benzoic acid) were decarboxylated.The obtained degree of purification was 400‐fold with a hal specific activity of 14.1 units/mg of protein. The purified enzyme has a molecular weight of about 72000 (±10%) as determined by dodecyl sulphate‐polyacrylamide gel electrophoresis. The Kmfor orsellinic acid has been determined as 211 μM, the Ki of the inhibitor β‐resorcylic acid (2,4‐dihydroxy benzoic acid) as 800 μM. A spectrophotometric method suitable for the assay of orsellinate decarboxylase is described.
Fingerprint Maps of Tryptic Peptides from Subunits of Escherichia coli and T4‐Modified DNA‐Dependent RNA Polymerases
Authors: Schachner Melitta , Zillig Wolfram 
Published: March 2005

DNA‐dependent RNA polymerase from bacteriophage T4‐infected Escherichia coli cells differs in all its subunits from the host's core enzyme.T4‐modified α differs from E. coliα by 1 or 2 additional peptides. One additional tyrosine positive peptide and the displacement of one histidine containing peptide is characteristic for T4‐modified β'. T4‐modified β is significantly different from E. coliβ in its histidine and tryptophan containing peptides, whereas differences in the tyrosine peptide pattern are less obvious.No common features were observed among the peptide patterns of the subunits from E. coli RNA polymerase.
Coenzyme Binding in Yeast Pyruvate Decarboxylase
Authors: Wittorf John H. , Gubler Clark J. 
Published: March 2005

A kinetic investigation of the behavior of apopyruvate decarboxylase from Saccharomyces carlsbergensiswith thiamine pyrophosphate analogues gave the values of 23 μM as the Km for thiamine pyrophosphate and 20 μM as the Km for 2′‐ethylthiamine pyrophosphate. The Vfor the latter compound was 25%, that of thiamine pyrophosphate. Inhibitor constants, Ki, were determined for the following competitive inhibitors of thiamine pyrophosphate with the apoenzyme, (the values are for the pyrophosphate esters): tetrahydrothiamine, 6.5 μM; oxythiamine, 20 μM; 2′‐n‐butyIthiamine, 45 μM; 2′‐methoxythiamine, 70 μM; pyrithiamine, 78 μM; 2′‐demethylthiamine, 220 μM; 2′‐hydroxythiamine, 380 μM. None of the inhibitors exhibited coenzyme activity.A hydrophobic interaction of the 2′‐methyl group of thiamine pyrophosphate with the apoenzyme has been proposed and a model for the coenzyme binding site of pyruvate decarboxylase, consisting of a pyrophosphate and a pyrimidine binding region, is discussed.
An Improved Technique for the Analysis of Ribonucleoprotein Fragments from Escherichia coli 30S Ribosomes
Authors: Brimacombe Richard , Morgan Joan M. , Cox Robert A. 
Published: March 2005

30S ribosomal subunits from Escherichia coli were hydrolyzed with ribonuclease T1, and the ribonucleoprotein fragments produced were fractionated on a 5% polyacrylamide/0.5% agarose composite gel. Two main breakdown products were observed corresponding in size to about 20% and 60% of the intact 30S particle.
Each fraction from the 5% composite gel was subjected to protein analysis on a periodatesoluble 15% polyacrylamide gel, run in the detergent Sarkosyl. The smaller ribonucleotprotein fragment was found to contain only four of the 30S ribosomal proteins, and these were present in equimolar amounts. The larger fragment had a complex protein composition; it was deficient in the four proteins contained in the smaller fragment, and was considerably enriched in the largest 30S protein.
The results show a striking correlation with Nomura's “assembly map” of the 30S particle.
Inactivation of 50S Ribosomal Subunits by 2‐Methoxy‐5‐nitrotropone
Authors: Suzuka Iwao 
Published: March 2005

Treatment of 50S ribosomal subunits with 2‐methoxy‐5‐nitrotropone results in extensive loss of their ability to synthesize polyphenylalanine, display ribosome‐dependent GTPase activity, or bind GTP to ribosomes. In contrast, 5‐nitrotroponyl 50S subunits are fully active for diphenylalanine synthesis. Thus, 2‐methoxy‐5 nitrotropone‐reactable ribosomal protein groups on the 50S subunit may be associated with translocation activity of ribosomes.
Sedimentation analysis of 5‐nitrotroponyl 50S subunits at 0.02 M Mg2+ shows a slightly faster sedimenting component (54S) and their dimerized form (79S). Furthermore, the particles which are reassociated with 30S and 5‐nitrotroponyl 50S subunits are dissociated into each subunit under conditions of Mg2+ concentration (5 mM) where most of 30S‐associated control 50S particles are still present as a 70S particle. These results appear to reflect the structural alteration of the 50S subunits caused by the treatment of 2‐methoxy‐5‐nitrotropone.
A Quantitative Analysis of Proflavine Binding to Polyadenylic Acid, Polyuridylic Acid, and Transfer RNA
Authors: Dourlent Maurice , Hélène Claude 
Published: March 2005

Absorbance measurements show that the binding of proflavine to poly (A) and poly(U) can be quantitatively resolved (within ± 10% relative error) by the consideration of two bound species whose spectral properties and mechanisms of interaction are similar to those found in the DNA. proflavin systems: cooperative binding along the phosphate backbone (process I) and interaction between the aromatic rings of base and dye resulting presumably from some kind of interacalation of the ligand between consecutive bases (process II). The comparison with a simple theoretical model shows that process I and process II are not independent but coupled.The spectrophotometric method is able to resolve the binding of proflavine to a tRNA species with the same accuracy as that obtained for poly(A) and poly(U). Accordingly, it is proposed that the mode of interaction between proflavine and all classes of polynucleotides (DNA, RNA, synthetic polymers) is similar in nature. From the differences observed in the distribution of the bound dye between the two complexes, the existence of a close correlation between the secondary structure of the polymer and its ability for binding the dye in complex II is proposed.
Fate of Exogenous DNA in Arabidopsis thaliana
Authors: Ledoux Lucien , Huart Raoul , JACOBS Michel 
Published: March 2005

It has been shown that when Arabidopsis seeds are incubated with different heteropycnic labelled DNA during the first 4 days of germinating, large fragments of exogenous DNA are taken up by the seedling plant tissues (cotyledons and rootlet) and remain polymerized and double‐stranded during the entire growth period. Only a small percentage of the population of exogenous DNA molecules appears to be destroyed and reutilized for DNA synthesis de novo. Most of the exogenous DNA remains free or becomes integrated with the Arabidopsis DNA as double‐stranded molecules, not separable by alkali denaturation, but easily separable by ultrasonication.Analysis of different tissues and organs of growing plants reveals that a large amount of foreign DNA remains in the cotyledons during the vegetative growth phase, but is redistributed at the flowering stage (when cotyledons etiolate). At this time, the foreign DNA leaves the cotyledons and migrates towards the flowering buds where it accumulates as a highly molecular and double‐stranded material. In the F1 progeny, radioactive molecules are found which do not correspond to the endogenous material and which have a density depending on that of the foreign DNA used.
Hydride Transfer in the Biosynthesis of Uridine Diphospho‐Apiose from Uridine Diphospho‐d‐glucuronic Acid with an Enzyme Preparation of Lemna minor
Authors: Kelleher William J. , Grisebach Hans 
Published: March 2005

The fate of the hydrogen atoms at C‐3 and C‐4 of uridine diphospho‐d‐glucuronic acid (UDP‐GlcUA) in the course of its conversion to uridine diphospho‐apiose (UDP‐api) was investigated. The specifically labeled UDP‐GlcUA substrates were prepared enzymatically from d‐[3‐3H]glucose and d‐[4‐3H]glucose by the combined action of hexokinase, phosphoglucomutase, UDPG‐pyrophosphorylase, and UDPG dehydrogenase. UDP‐[U‐14C, 3‐3H]GlcUA, UDP‐[U14C, 4‐3H]‐GlcUA, and UDP‐[14C, 3,4‐3H2]GlcUA were separatelly converted to UDP‐Api by an enzyme preparation from Lemna minor. In order to obtain an apiose (3‐C‐hydroxymethyl‐d‐erythro‐furanose) derivative which was reasonably stable and which could be produced without passing through the aldehydo form, the apiosyl radical of UDP‐Api was enzymatically transferred to 7‐glucosylapigenin by an enzyme preparation from parsley. The product of this reaction, apiin (7‐O‐[β‐d‐apiofuranosyl‐(1→2)‐β‐d‐glucosyl‐5,7,4′‐trihydroxyflavone), was subjected to mild periodate oxidation to convert the branch hydroxymethyl group of the apiosyl residue to formaldehyde.Approximately 14–16% of each of the substrates was converted to UDP‐Api. The transfer of the apiosyl moiety to 7‐glucosylapigenin was essentially quantitative in all cases. The isolated apiin was shown to have retained 53.5% of the tritium from the substrate labeled at C‐3, 99% from the substrate labeled at C‐4, and 73% from the substrate labeled at C‐3,4. All of the tritium and one‐fifth of the 14C of apiin produced from the variously labeled substrate was accounted for in the formaldehyde‐dimedone derivative. These results establish the occurrence of a hydride shift from C‐4 of UDP‐GlcUA to C‐3′ of apiose in the biosynthesis of UDP‐Api from UDP‐GlcUA.
Steady‐State Kinetics of Mitochondrial Nicotinamide Nucleotide Transhydrogenase
Authors: RydstrÖM Jan , Ernster Lars , Texixeira Da Cruz António 
Published: March 2005

The steady‐state kinetics of the nonenergy‐linked nicotinamide nucleotide transhydrogenase reaction catalyzed by submitochondrial particles from beef heart were investigated.
From the relationship found between reaction velocities and concentrations of substrates, and from the observed of product inhibition, it is concluded that the reaction involves a ternary‐complex, Theorell‐Chance mechanism.
Maximal velocities of the forward and reverse reactions, Michaelis constants for the four substrates, dissociation constants of the binary enzyme. substrate complexes, and rate constants of the partial reactions are calculated.
The results are discussed in relation to earlier information concerning the mechanism of the reaction.
Steady‐State Kinetics of Mitochondrial Nicotinamide Nucleotide Transhydrogenase
Authors: RydstrÖM Jan , Ernster Lars , Texixeira Da Cruz António 
Published: March 2005

The stedy‐state kinetics of the energy‐linked nicotinamide nucleotide transhydrogenase reaction catalyzed by submitochondrial particles from beef heart were investigated.
From the relationship between reaction velocities and concentrations of substrates, patterns of product inhibition, and isotope exchange data, it is concluded that the energy‐linked trans‐hydrogenase reaction involves a ternary‐complex, Theorell‐Chance mechanism, i.e a mechanism identical to that found for the nonenergy‐linked transhydrogenase reaction.
Maximal velocities of the forward and reverse reactions, Michaelis constants for the four substrates, disociation constants of the binary enzyme. substrate complexes, and rate constants of the partial reactions are calculated and compared with those found for the nonenergy‐linked reaction.The effect of energization is reflected primarily in an increase in the maximal velocity of the forword reaction and a decrease and increase, respectively of the dissociation constants of the binary enzyme. substrate and enzyme. product complexes.
Inhibition of the reverse reaction upon energization is shown to be competitive with respect to the substrates NAD+ and NADPH. These findings are interpreted in terms of an energy‐ and substrate‐controlled conformational change of the enzyme between an active and an inactive form.
Reaction mechanisms for the transhydrogenase reaction and its relationship to the mitochondrial energy transfer system are proposed and discussed inrelation to current hypotheses.
Fatty‐Acid Composition of Arthrobacter simplex Grown on Hydrocarbons
Authors: Yano Ikuya , Furukawa Yoshiya , Kusunose Masamichi 
Published: March 2005

Fatty acids of Arthrobacter simplex cells grown on various n‐alkanes or 1‐alkanes as the sole carbon ource have been investigated.

The lipid pattern of the hydrocarbon‐grown cells was alsmost identical with that of the cells grown on the glucose‐yeast‐extract medium reported earlier. The phospholipids of both the cells consisted largely of cardiolipin and two types of phosphatiylglycerols. In one phosphatidyl‐glycerol, α‐hydroxy fatty acids, together with nonhydroxylated fatty acids, occurred as major fatty‐acid components.
Total fatty acids from the cells grown on 1‐octadecene were separated into several groups with different thin‐layer chromatographic characteristics, and analyzed by gas chromatography. C16, C16:1Δ15, C17:1Δ9, t‐C18, C18:1Δ9, C18:1Δ17, t‐C19, C18:2Δ9,17, t‐C19:1Δ17, α‐OH‐C16 and α‐OH‐C16:1Δ15 acids were revealed to be presented as major fatty acids: (t) = 10‐methylstearic). Among them, C18:2Δ9,17 and α‐OH‐C16:1Δ15 acids were further characerized by use of mass spectrometry, and chemical oxidation and reduction. As the growth proceeded from the early phase to the stationary phase, it was noted that the content of odd‐numbered α‐hydroxy fatty acids increased markedly.
Fatty‐acid compositions of the cells grown on C13 to C19 alkanes and C16, C18 and C20 1‐alkenes were determined by gas chromatography. The results suggested that the hydrocarbongrown cells were capable of utilizing hydrocarbon skeletons without degradation for the synthesis of fatty acids. Furthermore, it was proposed that both the α and β oxidation of fatty acids operated equally substantially in A. simplex cells.
Sub‐Units of Citrate Oxaloacetate‐Lyase
Authors: Bowen T. John , Mortimer Michael G. 
Published: March 2005

Citrate lyase has been shown to have values for S°20,W and D°20,W of 17.6 S and 3.02 × 10−7 cm2 sec−1, respectively. Using the Svedberg equation a value of 533000 was assigned for the molecular weight of the active preparation. The meniscus depletion sedimentation equilibrium method led to a value of 550000 while the transient state method gave a value of 566000. The partial specific volume was determined by the 2H2O method of Edelstein and Schachman to be 0.73 ml g−1.The enzyme was also studied in a variety of denaturing solvents. Molecular weights were measured in the analytical ultracentrifuge and also using dodecylsulphate‐polyacrylamide‐gel electrophoresis with marker proteins of known molecular weight. A range of particles resulted suggesting that there could be 16 sub‐units in the active enzyme preparation.
Biogenesis of the Crystalline Inclusion of Bacillus thuringiensis during Sporulation
Authors: Lecadet Marguerite‐M. , Dedonder Raymond 
Published: March 2005

The biogenesis of the crystalline inclusion of Bacillus thuringiensis has been studied in the more general context of sporulation and in regard to the formation of some spore constituents. It has been shown that crystal protein is essentially formed during stages III and IV, before the acquisition of octanol resistance. One fraction of protein spore coats which is solubilized by a reducing agent associated with urea or guanidine hydrochloride, is synthesised at the same time; a more insoluble cystine‐rich fraction is formed later, during stage V, just before the heat resistance is reached.The analysis of bacterial extracts at intervals during sporogenesis indicates preferential synthesis of insoluble proteins (or proteins bound to membraneous structures), crystal protein represents a large proportion of these proteins. Immunological characterisation of crystal protein, with autoradiographic experiments reveals at least three antigens produced simultaneously after t4 and continuously throughout the biogenesis.The sporulation of a mutant non crystal bearing strain was studied; it has been shown that this mutant accumulates soluble proteins having some of the properties of crystal constituents; in this case the synthesis and maturation of spore coats arise earlier in the course of sporulation than in the wild strain.All results suggest a relation between crystal protein and a protein fraction of the spore coats.