bluuebunny/crossref_metadata_2025 huggingface dataset:
Nachweis von Konformationsisomeren im Hämoglobin(III) von Chironomus th. thummi mit Hilfe der Elektronen‐Spin‐Resonanz
Authors: Gersonde Klaus , Sick Hinrich , Wollmer Axel
Published: March 2005

The magnetic properties of oxidized haemoglobins from Chironomus th. thummi in the pH range, pH 5 to pH 10, are described.

The results of magnetostatic susceptibility at room temperature show that the high spin part decreases from 80% to 70% during transformation of the H2O‐Hb(III) into OH‐Hb(III). Chromatographically purified individual haemoglobins do not differ in this regard from the complex material.

The esr signals of the Hb(III) measured at 77° K, can be separated into three groups, according to their common pH behaviour. Each group of signals can be ascribed to one type of iron complexes each: (a) g⊥= 6, g= 2,00; (b) g1= 2.88, g2= 2.35, g3= 1.95; (c) g′1= 2.68, g′2= 2.16, g′3= 1.82.

g is split into two signals with g1 = 2.03 and g2 = 1.98. g1 has a N‐hyperfine structure with five lines, g2 with three lines. These two g′ ‐signals are ascribed to two different conformation isomers of the native H2O‐Hb(III), which, dependent on the pH, can be transformed into each other. The half transformation point of this change of conformation at pH 7.2 is the allosteric pK value.

The pH‐dependency of the g⊥ signal shows a biphasic curve, with inflection points at pH 6.9 and pH 8.9.

By aid of a thermodynamic circuit process, the interaction between allosteric transformation and protolysis is described and the corresponding pK values are calculated from the pH dependency of g⊥.

The mechanism of this allosteric interaction, that means of a proton binding site in the protein with the 6th ligand is discussed as a trans‐effect of the 5th ligand.
Echanges de lipides entre mitochondries, microsomes et surnageant cytoplasmique de cellules de pomme de terre ou de chou‐fleur
Authors: Benabdelkader Ahmed , Mazliak Paul
Published: March 2005

The incorporation rates of [1‐14C]acetate in vivo into the lipids of different subcellular fractions of potato or cauliflower tissues are consistent with a flow of radioactive lipids from microsomes to mitochondria.

When potato tuber microsomes, containing phospholipids labelled from [1‐14C]acetate, [32P]‐phosphate or [1‐14C]glycerol, are incubated in vitro with unlabelled mitochondria and cytoplasmic supernatant, the radioactivity of the microsomes decreases strongly within 2 hours; the lipids of the mitochondria and those of the supernatant become radioactive, taking up to 40% of the initial radioactivity. The same transfer of labelled lipids is observed when one incubates labelled mitochondria with unlabelled microsomes.

During these experiments, one can observe a marked decrease of the specific radioactivities of the phospholipids present in the initially labelled fractions. This may be explained by a departure of labelled phospholipids from the radioactive fraction towards the other cellular fraction and by an arrival of unlabelled lipids from the initially unlabelled fraction to the radioactive fraction. The results obtained with three different precursors are roughly similar, suggesting that there is an exchange of entire phospholipidic molecules between the cellular fractions. However, the rates of exchange of the lipids labelled from [1‐14C]acetate are a little higher than those observed with the other precursors thus suggesting an exchange of free fatty acids in addition to the exchange of phospholipids.

Phosphatidylcholine and phosphatidylethanolamine represent the most important fraction of the exchanged phospholipids.

The cytoplasmic supernatant acts as an intermediate in these exchanges. When a volume of supernatant containing radioactive lipids is incubated with unlabelled mitochondria or unlabelled microsomes, the radioactivity of the supernatant lipids decreases. The lipids of the mitochondrial and microsomal fractions, particularly the phospholipids, become labelled.

The results obtained when mixing cauliflower subcellular fractions in vitro are very similar.

The same flows of lipid exchanges (in vitro) can be observed between potato mitochondria and cauliflower microsomes, or reciprocally. However, a great part of the lipids liberated by the cellular fraction from one species remains blocked in the cytoplasmic supernatant from the other species, which may indicate that the exchange are limited, in this case, by a specific requirement for certain kinds of lipids for the biogenesis of membranes.
Effects of Trialkyltin and Triphenyltin Copounds on Mitochondrial Respiration
Authors: Stockdale Martin , Dawson Alan P. , Selwyn Michael J.
Published: March 2005

In a sucrose medium, free from anions which are effective in the anion‐hydroxide exchange catalysed by trialkyltins, the effects of these compounds on mitochondrial respiration are similar to those of oligomycin, i.e. inhibition of respiration coupled to phosphorylation, and of arsenate stimulated respiration. They do not inhibit respiration stimulated by uncouplers nor respiration stimulated by uptake of divalent cations. They do not induce significant light scattering changes in this medium.

In a medium containing potassium chloride similar oligomycin‐like effects are observed but in addition some release of respiratory control and marked swelling of the mitochondria are observed. A time‐dependent inhibition of uncoupler stimulated respiration appears to be a secondary effect consequent upon extensive swelling. The maximal rate of respiration attainable by the uncoupling effect of the trialkyltin compounds is independent of which compound is used. The concentration of trialkyltin compound required to produce uncoupling is correlated with the concentration required to mediate the chloride hydroxide exchange.

In media containing other anions the maximal rate of respiration produced by trialkyltin compounds is correlated with the rate of electrogenic uniport of the anions through the mitochondrial membrane.

Uncoupling by trialkyltin compounds is attributed to the action of the anion‐hydroxide exchange followed by leakage of the anion out of the mitochondria. These two processes result in the discharge of both the pH differential and electrical potential difference across the mitochondrial membrane.

Apart from a lytic action of triphenyltin chloride and a potent respiratory inhibition in the presence of iodide or thiocyanate ions, it is proposed that all the observed effects of those compounds can be accounted for by the oligomycin‐like inhibition and the mediation of an anion hydroxide‐exchange across the mitochondrial membrane.
Structure du virescenoside C, nouveau métabolite de Oospora virescens (Link) Wallr.
Authors: Cagnoli‐Bellavita Nera , Ceccherelli Paolo , Mariani Raffaele , Polonsky Judith , Baskevitch Zoïa
Published: March 2005

Chemical investigation of the glycosidic constituents of Oospora virescens (Link) Wallr. resulted in the isolation of several glycosides. We have shown recently [1] that two of them, named virescenoside A (I) and B (II) are β‐d‐altropyranosides of virescenol A and B; these diterpenic aglycones have been found to have the structure of isopimaradien‐2α,3β‐19‐triol (IV) and isopimaradien‐3β,19‐diol (V), respectively [2].

In this paper we describe the isolation and structure of virescenoside C, a new metabolite of Oospora virescens. The results obtained show that virescenoside C (IIIa), C26K40O7, m. p. 160—162°, [α]d− 71,4°, is a β‐d‐altropyranoside of virescenol C, which is found to have the structure of 3‐keto 19‐hydroxy isopimaradiene (VIa).

These results are based on physical evidence (infra‐red, nuclear magnetic resonance and mass spectra) and particularly on the chemical correlation with virescenol B and virescenoside B.

Virescenoside C seems to be the third example of an altroside found in nature.
Studies on Human Erythrocyte IMP: Pyrophosphate Phosphoribosyltransferase
Authors: Craft John A. , Dean Betty M. , Watts Richard W. E. , Westwick Wendy J.
Published: March 2005

Some kinetic properties of the enzyme, IMP: pyrophosphate phosphoribosyltransferase have been investigated.

The effect of varying the concentration [S] of the purine substrate (hypoxanthine or guanine) on the initial velocity v of the reaction was studied at constant concentrations of P‐Rib‐PP and Mg2+. The velocity curves (plots of v against [S]) were hyperbolic.

The velocity curves were sigmoid when the P‐Rib‐PP concentration was varied at constant concentrations of purine and Mg2+.

Sigmoid velocity curves also resulted when the Mg2+ concentration was varied in the presence of constant concentrations of P‐Rib‐PP and purine.

Mn2+ could not replace Mg2+ in the system, but low concentrations of Mn2+ were stimulatory and high concentrations were inhibitory in the presence of low concentrations of Mg2+ and P‐Rib‐PP.

The shape of the curves obtained by plotting the P‐Rib‐PP concentration against the initial velocity at constant concentrations of purine and Mg2+ was pH dependent, being hyperbolic at pH 8.5 and sigmoid at pH 7.5 or less.

Inorganic orthophosphate had a slight activating effect when the P‐Rib‐PP concentration was varied at constant concentrations of purine and high concentrations of Mg2+ (6 mM). However, if the Mg2+ concentration was low (1 mM), high concentrations of inorganic phosphate (12 mM) were inhibitory.

The activity of the enzyme was reduced disproportionately with respect to the amount of protein present when it was highly diluted.

The possibility that these findings are due to the enzyme having allosteric properties, and their bearing on the possible function of IMP: pyrophosphate phosphoribosyltransferase in the regulation of de novo purine biosynthesis are discussed.
Étude comparative des DNA de phages 2C, SP 8*, SP 82, φe, SP 01 et SP 50
Authors: Truffaut Nicole , Revet Bernard , Soulie Marie‐Odile
Published: March 2005

The following Bacillus subtilis phages: SP8*, SP82, φe, SP01, 2C and SP50, were studied and compared for morphological characteristics as well as for physico‐chemical properties of their DNA. All the determinations were effected under identical conditions for the six different phages. The aspect and variety of plaques formed by them with susceptible strain B. subtilis 168–2 (as indicator host), on Difco nutrient agar plates, are slightly different from phage to phage, but do not allow differenciation.

As shown by electron microscopy measurements, the five phages SP8*, SP82, SP01, φe, and 2C are morphologically identical and easily distinguishable from SP50, but not from each other.

As for the physico‐chemical properties of their DNA, the first five phages are clearly different from SP50 DNA which was taken as a reference: (a) their analytical base composition is consistently the same, all of them containing hydroxymethyluracil instead of thymine in their DNA, and the analyzed percentage guanine plus cytosine is 39%, as compared to 41.6% for SP50 DNA which has no unusual bases; (b) sedimentation coefficients for all the DNA (including SP50 DNA) are about 51 S, at a concentration of 20 μg/ml (s20, w); (c) the melting point in 0.15 M NaCl, 0.015 M Na citrate is 77.5°, without any significant variation among the first group (as compared to 87.3°, for SP50, which is approximately the same as the host Bacillus subtilis 168–2); (d) in a cesium chloride gradient, the buoyant densities of the native DNA of the first group are all 1.742 g/cm3. Since the complementary strands differ in average base composition, two bands of buoyant density 1.752 and 1.762 g/cm3 are obtained following denaturation; (e) all denatured DNA become associated with polyriboguanylic acid [poly(G)], which is preferentially bound to the heavy component, although a slight binding to the light component also occured. Preparative centrifugation in CsCl density gradients in the presence of poly G results in good separation of the two components; (f) the extent of homologous base sequence among the six phages has been determined by DNA/DNA hybridization: hybridization of 2C DNA, SP01 DNA and SP82 DNA with 2C DNA is experimentally identical and assumed to represent 100% homology. However for SP8 DNA/2C DNA and φe DNA/2C DNA, the percentage is lower, amounting to 92% and 83%, respectively. With SP50 and B. subtilis DNA it is only 7%.

On the whole, there are no apparent properties, peculiar to one of the 2C, SP8*, SP82, φe, and SP01 phages, allowing its differentiation from the others, whereas SP50 is morphologically distinct, particularly by the length of its tail. It also differs by diverse physical and biological properties. All the common characteristics possessed by the first group of phages, particularly the high extent of DNA/DNA hybridization among them, and the fact that the phages and their DNA are serologically related, demonstrate their close relationship.
Incorporation de l'acide shikimique dans le noyau des naphtoquinones d'origine bactérienne et végétale
Authors: Leduc Mireille M. , Dansette Patrick M. , Azerad Robert G.
Published: March 2005

Degradation of Mycobacterium phlei dihydromenaquinone‐9 biosynthesized from [1,2‐14C2]‐shikimic acid or [5‐3H]shikimic acid shows that the ring junction of the naphthoquinonic part originates from the ethylenic carbons (C‐1,6) of these precursors. The same results are found with lawsone (from Impatiens balsamina) and juglone (from Juglans regia). Tentative schemes for the naphthoquinonic ring biosynthesis are presented, involving o‐carboxyphenylpyruvic acid as an intermediate. A possible derivative of this intermediate, o‐carboxy[1‐14C]phenylacetic acid was synthesized, but could not be incorporated in dihydromenaquinone‐9, lawsone or juglone.
Identification of Sulfur‐Containing Bases in Transfer Ribonucleic Acids by Phosphorescence Spectroscopy
Authors: HÉLÈNE Claude , Yaniv Moshe
Published: March 2005

The phosphorescence spectra and phosphorescence excitation spectra of tRNAVal, tRNATyr, tRNAPhe and total tRNA from Escherichia coli have been rcorded at 77° K in the presence and absence of magnesium ions. The main phosphorescence of these tRNA species originates from sulfur‐containing nucleosides which have very high phosphorescence quantum yields as compared to their oxygenated analogs.

The phosphorescence of 4‐thiouridine excited at 345 nm has a very short lifetime (about) 3 msec). The phosphorescence spectrum and quantum yield of 4‐thiouridine in tRNATyr are shown to differ from those of 4‐thiouridine in tRNAVal and tRNAPhe (lower quantum yield and red‐shift). These differences are attributed to interactions between two adjacent 4‐thiouridine residues in tRNATyr. The phosphorescence spectrum of 2‐methylthio‐N6‐(Δ2‐isopentenyl)‐adenosine excited at 280 nm has a characteristic shape which is observed for many adenine on the phosphorescence spectra of the tRNA species used in this study. The phosphorescence quantum yields of thionucleosides in tRNATyr are increased in the presence of Mg2+ions.

Phosphorescence measurements provide a convenient method to determine the presence of and identify sulfur‐containing nucleosides in pure species of tRNA. The possible use of thionucleoside phosphorescence to study conformational changes in tRNA and interactions involving tRNA molecules is suggested.
Preparation of Nascent RNA Strands of the Bacteriophage M12
Authors: Francke Bertold , Ward Richard , Konings Rund N. H. , Hofschneider Peter Hans
Published: March 2005

Nascent M12 RNA has been isolated in large quantities from Replicative Intermediate and denatured by a short heat treatment. After sucrose gradient centrifugation of the denatured Replicative Intermediate in a zonal rotor, the nascent RNA strands were divided into six fractions with increasing sedimentation values. Each fraction was further purified by sedimentation conventional sucrose gradients. In this manner, a set of M12 nascent RNA strands with fairly uniform lengths, ranging from about 15 nucleotides to almost 90% of the complete phage RNA genome, have been obtained. The molecules in these fractions, all containing the same 5′‐end as complete phage RNA but an increasing portion of the phage genome, provide suitable tools for studies of the structure and function of phage RNA.
The Diagram, a Method for Comparing Sequences
Authors: Gibbs Adrian J. , Mcintyre George A.
Published: March 2005

A simple method for detecting similarities in sequences is described. It is used:

To provide similarity measures for classifying 25 cytochromes by their amino acid sequences,

to detect repetitions in the amino acid sequences of various proteins,

to detect regions of possible base‐pairing in the nucleotide sequence of a nuclei acid.
Coupled Endogenous Respiration in Brown Adipose Tissue Mitochondria
Authors: Ppedersen Jan I.
Published: March 2005

Carnitine + ATP were required for oxidation of endogenous substrates in brown adipose tissue mitochondria from newborn guinea‐pigs when the reaction medium lacked serum albumin. There was no evidence of phosphorylation linked to this oxidation.

When the reaction medium contained 2% serum albumin endogenous substrates were oxidized provided that phosphate and ADP were present. Carnitine did not influence the respiration. This oxidation was coupled to phosphorylation, P/O ratios between 2.4 and 2.8 being found.

Evidence is presented that the substrates responsible for the coupled endogenous respiration are mainly fatty acids, probably derived from an internal pool and activated in an internal mitochondrial compartment.

Brown adipose tissue mitochondria from newborn animals respiring on endogenous substrates could rapidly be brought into the controlled state (state 4) provided that high energy nucleotides were added to the reaction medium. In their absence, addition of ADP was followed by a slower and more gradual transition into state 4.

With brown adipose tissue from foetuses and weaned animals the endogenous respiration was under phosphate acceptor control in absence of high energy compounds.

The results suggest that the highly loose coupled state of brown adipose tissue mitochondria in thermogenic phases is related to lowered amounts of endogenous high energy phosphates.
Horse Liver Alcohol Dehydrogenase
Authors: Jørnvall Hans
Published: March 2005

The [14C]carboxymethylated protein of the ethanol‐active isoenzyme of horse liver alcohol dehydrogenase has been treated with trypsin (with and without previous maleylation of the substrate), chymotrypsin, pepsin and cyanogen bromide, respectively. Peptide mixtures obtained have been fractionated and analysed.

Data are given for those peptides originating from a C‐terminal region comprising about 60% of the protein chain, and the amino acid sequence of this segment, containing the last 234 residues, is deduced. The N‐terminal part was known previously and the primary structure of the whole protein chain is therefore established.

The ethanol‐active isoenzyme is found to be a dimer of two completely identical protein chains, each 374 residues long. The N‐terminal part of the molecule contains the reactive cysteine residue, six out of the seven histidine residues in the whole chain, the majority of the mutations between the isoenzyme chains of different substrate specificities, and a region homologous to another dehydrogenase.

Serine residues that reacted during maleylation of the protein were found to undergo O → N maleyl shift when they became N‐terminal residues in peptides. Evidence was obtained suggesting that carboxymethylmethionyl peptide bonds are labile.
Horse Liver Alcohol Dehydrogenase
Authors: Jörnvall Hans
Published: March 2005

Tryptic digests of the [14C]carboxymethylated derivatives of the three isoenzymes EE, ES and SS of horse liver alcohol dehydrogenase have been compared in “fingerprint” experiments.

Eight peptide spots present in the digest of the carboxymethylated EE enzyme were not detected in the digest of the carboxymethylated SS enzyme; and seven spots found in the latter were not discovered in the former. No other differences were noticed. The ES derivative yielded both types of spots but in reduced amounts. It is concluded that the E‐ and S‐types of subunits are very similar and that the ES isoenzyme is a hybrid molecule.

From the carboxymethylated SS and ES isoenzymes the S‐chain peptides that differ from their counterparts in the E‐chain were prepared and their structures analysed. They were compared to the known structures [1–3] of the corresponding E‐chain peptides. It is concluded that all the differences between the two sets of peptides are accounted for by amino acid changes at only six positions along the protein chains of the E‐ and S‐types of subunits, and an ancestral geneduplication is suggested. The differences at five positions (17, 94, 101, 110 and 366) are amino acid exchanges compatible with one‐base mutations, while the nature of the sixth difference (position 115) is not fully established.

The six differences make the S‐chain more hydrophobic and three units of charge more positive than the E‐chain. These properties fit the solubilities and electrophoretic mobilities of the three isoenzymes. The difference in substrate specificity between the E‐ and S‐chains might be explained by a direct participation in the substrate binding site of some of the residues exchanged, but other explanations cannot be excluded.
Construction of Isokinetic Sucrose Gradients for Rate‐Zonal Centrifugation
Authors: Steensgaard Jens
Published: March 2005

An isokinetic gradient is a density and viscosity gradient, in which the particles during the centrifugation sediment with constant velocity. A numerical method for construction of isokinetic sucrose gradients for gradient centrifugation in B XIV zonal rotors is described, and several examples of gradients for separation of soluble proteins, nucleic acids, ribosomes and polysomes are given. The general usefulness of isokinetic gradients is illustrated by experimental separations of soluble immune complexes and of rat brain RNA.
β‐Methylcrotonyl‐CoA‐Carboxylase
Authors: Apitz‐Castro Rafael , Rehn Kurt , Lynen Feodor
Published: March 2005

β‐Methylcrotonyl‐CoA‐carboxylase was purified 120‐fold from an Achromobacter species. When the cells were grown on isovaleric acid, the enzyme was formed mainly during exponential growth. The enzyme can be labeled by addition of radioactive biotin to growing cells. A former procedure of purification was improved by using adsorption to calcium phosphate gel and chromatography on Sephadex G‐200. Enzyme homogeneous by both sedimentation and Tiselius electrophoresis was thus obtained in a yield of 40–70% and was crystallized in a form resembling crystalline propionyl‐CoA‐carboxylase.

The molecular weight of the enzyme as determined by sedimentation velocity is 760000 daltons. The biotin content of 1,27 μmoles/g indicates 4 moles of biotin are bound to 1 mole of protein as is also the case for propionyl‐CoA‐carboxylase and pyruvate carboxylase.

Glutamic and aspartic acid comprise 23% of the amino acids in the enzyme. Extrapolation of electrophoretic mobility as a function of pH indicates the isoelectric point of the enzyme is in the vicinity of pH 3.5. Such a value would mean that most of the carboxyl groups of the acidic residues are free.

The usual methods of preparations for electron microscopy, even with preceding fixation steps, cause degradation of the enzyme since only particles of about 1/4 of the expected size could be seen. However, ultracentrifugation did not indicate any dissociation of the enzyme into subunits.
Hemmung der Trypsinkatalyse durch kationische Carbonsäureester und Amide
Authors: Hartmann Hermann , Holler Eggehard
Published: March 2005

In paper [5] a simplified model for the hydrophobic binding sites of trypsin was proposed, showing where 1‐amino‐n‐alkanes and α,ω‐diamino‐n‐alkanes are bound while they competitively inhibit the catalyzed hydrolysis of a substrate ester. In the model, the enzyme has two hydrophobic binding sites separated by an aqueous region which presumably contains the catalytic important residues. The first site binds up to 4 methylene groups of the aliphatic side chain adjacent to the ω‐amino group; additional –CH2 groups in the chain extend into the aqueous region. If the chain is larger than 7 carbon atoms, the additional methylene or methyl groups are bound to the second hydrophobic site. This site is found to bind less strongly than the first site.

This paper presents a thermodynamic investigation of the binding properties of trypsin in the formation of complexes with cationic esters and amids which bear an ammonium group on either the end of the acid side chain or the end of the alcohol or amine component. Free energy and in addition enthalpy and entropy of binding were measured as a function of the length of the inhibitor molecule and as a function of the position of the ester or amide carbonyl group. It was found that the stability of a complex increases linearly with length of the molecule, and that the magnitude of increase depends on the position of the carbonyl group. Amides always exhibit a smaller increase than esters. Inhibitors with the ammonium group on the alcohol component were bound with about the same stability than the corresponding ω‐aminoacidesters. The results are consistent with the model. Positioning of the carbonyl group within the first or second binding site reduces stability due to restricted interaction of the hydrophobic residues on enzyme and inhibitor. Only when the carbonyl group falls into the aqueous region, the free energy for an inhibitor containing the ester group is similar to that for a 1‐amino‐n‐alkane with identical chain length.

Enthalpy and entropy as functions of the position of the carbonyl group show minima for the position within the aqueous region. This observation is correlated with the jump of enthalpy and entropy of complex formation of trypsin in the series of 1‐amino‐n‐alkanes reported earlier.

It is shown that the magnitude of free energy of complex formation with specific substrates is well estimated on basis of the model. As a consequence, the alternative binding of either the 2‐N‐acyl group or the alcohol or amine component to the second hydrophobic site may imply a mode of less productive binding. It is emphasized that unproductive binding should be reflected in the Michaelis Menten constants for substrate amides whereas the Michaelis Menten constant for a substrate ester is normally not perturbed.
Methionine Synthetase
Authors: Rüdiger Harold , Jaenicke Lothar
Published: March 2005

A purification procedure is described which permits the isolation of the vitamin B12‐de‐pendent methionine synthetase (5‐methyl‐tetrahydrofolate‐homocysteine‐transmethylase) from Escherichia coli largely in its native, i. e. methylated form. The enzymatic activity of this species does not depend on the presence of S‐adenosylmethionine. The native enzyme can be demethylated and thus made dependent on S‐adenosylmethionine; this reaction is reversible. The inter‐conversions of the enzyme can be recognized by the spectra. The demethylation is effected by a macromolecular factor present in E. coli cells. By gel filtration, both methylated and demethylated enzyme have been found to possess a molecular weight of about 255000.
Substrate Specificity of Ribosomal Peptidyl Transferase
Authors: Rychlík Ivan , ČErná Jiřina , Chládek Stanislav , Pulkrábek Petr , ŽEmlička Jiří
Published: March 2005

The effect of the nature of the amino acid residue on the acceptor activity of substrates of ribosomal peptidyl transferase was investigated. We tested 2′(3′)‐O‐aminoacyladenosines containing the following amino acid residues: l‐alanine, l‐glutamine, glycine, l‐3‐(1‐benzyl‐4‐imidazolyl)‐alanine, l‐leucine, l‐lysine, l‐methionine, l‐methionine S‐oxide, l‐phenylalanine, d‐phenylalanine, l‐proline, l‐serine and l‐valine as acceptors of the acylaminoacyl residue transferred from peptidyl‐tRNA. The acceptor activity of these compounds was dependent on the nature of the side chain of the amino acid residues bound to adenosine. The acceptor activity was also affected by the nature of the donor tRNA derivative. With l‐acetylphenylalanyl‐tRNA or l‐acetylleucine npetanucleotide fragments derived from l‐acetylleucyl‐tRNA donating the acetylphenylalanyl and the acetylleucyl residue, respectively, a high acceptor activity was shown by the basic 2′(3′)‐O‐l‐lysyladenosine or 2′(3′)‐O‐l‐3‐(1‐benzyl‐4‐imidazolyl)‐alanyladenosine which acted only as weak acceptors of lysine peptides from (Lys)n‐tRNA. The transfer reaction catalyzed by peptidyl transferase was stereospecific with respect to acceptor substrates. The acylaminoacyl residue was transferred from tRNA to 2′(3′)‐O‐l‐phenylalanyladenosine, whereas 2′(3′)‐O‐d‐phenylalanyladenosine, containing a d‐phenylalanine residue, was completely inactive as acceptor.
A Kinetic Study of Saccharopine Dehydrogenase Reaction
Authors: Fujioka Motoji , Nakatani Yoichi
Published: March 2005

Kinetic studies were carried out on saccharopine [ɛ‐N‐(l‐glutaryl‐2)‐l‐lysine] dehydrogenase which catalyzed a reversible reaction according to the following equation.

Saccharopine + NAD++ H2O ⇌ lysine +α‐ketoglutarate + NADH + H+.

Initial velocity kinetics of the reverse direction showed that the saccharopine dehydrogenasecatalyzed reaction was consistent with a mechanism that the addition and release of reactants to and from the enzyme follow an obligatory order. The product inhibition studies in the forward direction also revealed kinetic patterns consistent with the ordered mechanism where the sequence of addition of substrates being NAD+ and saccharopine, and that of release of products being lysine, α‐ketoglutarate and NADH. The various kinetic parameters determined at pH 6.8 and 22° are also described.
The Identification of 4‐Deoxy‐d‐arabino‐hexose as a Constituent in Lipopolysaccharides of Four Citrobacter Species
Authors: Keleti Juraj , Mayer Hubert , Fromme Inge , Lüderitz Otto
Published: March 2005

4‐Deoxy‐d‐arabino‐hexose has been identified as a constituent of the four Citrobacter sero‐types 4, 23, 27 and 36a. Its structure was evaluated by the aid of mass spectrometry and gas liquid chromatography in comparison with known deoxyhexoses.
Concentration of Cyclic 3′: 5′‐Adenosine Monophosphate and Glycogen Metabolism in the Liver
Authors: Van den Berghe Georges , De Wulf Henri , Hers Henri‐Géry
Published: March 2005

The increase in the concentration of cyclic adenosine 3′: 5′‐phosphate in the liver after the administration of a small dose of glucagon precedes the inactivation of glycogen synthetase by 1–2 min. This sequence of events is in agreement with the role of the nucleotide as second messenger in the hormonal action. The increase is dose dependent and is the same in control and prednisolone treated mice.

Treatment of mice with glucose or prednisolone causes a slight decrease in the concentration of cyclic adenosine 3′: 5′‐phosphate in the liver. The minuteness of this effect is in contrast with the large activation of glycogen synthetase that occurs under the same conditions.
Cinétique des réactions catalysées par la polynucléotide phosphorylase de Escherichia coli
Authors: Bon Suzanne , Godefroy Thérèse , Grunberg‐Manago MARIANNE
Published: March 2005

A systematic study of the effect of deoxy‐ADP on the reactions catalyzed by polynucleotide phosphorylase from Escherichia coli confirmed its behavior as a monofunctional analog of ADP.

The polymerization reaction is limited to the addition of one (or two at the most) residues of dAMP to a primer oligonucleotide. The Km of oligonucleotides in this reaction have been studied as a function of chain length, from (pA)2 to (pA)6, and for (pA)40. The Km and Vmax decrease with the chain length, as in the phosphorolysis reaction, but the variation is quantitatively different. (pA)2pdA is not a good substrate for the limited elongation, due to its poor Vmax, while it is a substrate for phosphorolysis.

The dADP/Pi exchange occurs only in the presence of oligonucleotide. Comparison of ADP/Pi exchange and dADP/Pi exchange in the presence of (pA)2 seems to indicate an interaction between binding sites of the oligonucleotide and the nucleoside diphosphate. This interaction is larger with ADP than with dADP.

The inhibitory properties of dADP in both polymerization of ADP and phosphorolysis were studied. In the absence of oligonucleotide, dADP increases the lag phase of polymerization, and also increases the concentration of oligonucleotide necessary to remove the lag phase. In the presence of saturating oligonucleotide, dADP behaves like a competitive inhibitor of ADP. Similarly, dADP is a competitive inhibitor of both phosphate and oligonucleotide in the phosphorolysis reaction. In the phosphorolysis of poly A it is only competitive with phosphate.

The results presented here are consistent with a complete reversibility of polymerization and phosphorolysis. Namely, the oligonucleotide, when used in the phosphorolysis reaction, covers the nucleoside diphosphate binding site. The importance of the 2′OH in the different positions of the substrates is discussed.
Oxidation of 5β‐Cholestane‐3α, 7α, 12α‐triol by Rat Liver Microsomes
Authors: Cronholm Tomas , Johansson Gunnar
Published: March 2005

The oxidation of 5β‐cholestane‐3α, 7α, 12α‐triol by different subcellular fractions of rat liver homogenate was studied. The most efficient oxidation was observed with the microsomal fraction fortified with the 100000 ×g supernatant fluid. Efficient oxidation occurred also with the microsomal fraction fortified with NADPH. The main products were identified as a number of cholestanetetrols. 5β‐Cholestane‐3α, 7α, 12α,25‐tetrol and 5β‐cholestane‐3α, 7α, 12α, 26‐tetrol accounted for about 60% of the cholestanetetrols. The oxidation of 5β‐cholestane‐3α, 7α, 12α‐triol by the microsomal fraction fortified with NADPH was stimulated about five‐fold by administration of phenobarbital. Phenobarbital treatment stimulated hydroxylations at C‐23, C‐24 and C‐25 to a much greater extent than that at C‐26. Carbon monoxide inhibited all the side‐chain hydroxylations and the most marked inhibition was observed for the 26‐hydroxylation.

5β‐Cholestane‐3α, 7α, 12α, 26‐tetrol was found to be a much more efficient precursor of cholic acid than either 5β‐cholestane‐3α, 7α, 12α, 25‐tetrol or the two C‐24 epimers of 5β‐cholestane‐3α, 7α, 12α, 24‐tetrol.
Immunochemistry of R Lipopolysaccharides of Escherichia coli
Authors: Schmidt Günter , Jann Barbara , Jann Klaus
Published: March 2005

Acapsular (K−) forms were isolated from Escherichia coli strain E56b (serotype O8 :K27(A): H−). A number of different R strains were obtained from the K− forms by selection of spontaneous mutants and by phage selection.

The lipopolysaccharides of these R strains (consisting of core and lipid A) were subjected to mild acid degradation and, after removal of insoluble lipid A, the mixtures were fractionated by gel chromatography. Results of chemical analyses showed that the core oligosaccharides of different R mutants differed with respect to their sugar constituents as well as to the molar ratios of these constituents. A group of R mutants did not contain phosphate in their core oligosaccharides (P− mutants).

Enzyme determinations indicated that one R mutant had a block involving UDP glucose pyrophosphorylase, whereas the enzymes of activation and interconversion of component sugars were intact in the other R mutants.

By allelic exchange (mating with S‐form Hfr strains) it could be demonstrated that with one exception the chromosomal site of the SR mutation of all mutants maps close to mtl (mannitol utilization). In Salmonella the rfa locus maps in the same region. All R mutants had an unimpaired (his‐linked) rfb locus.

The groups of mutants which differed in the sugar composition of their core oligosaccharides could also be differentiated serologically and by their sensitivity to phages. There was serological cross reactivity between the lipopolysaccharides of some R mutants with R mutants of Salmonella minnesota which also have a very incomplete core.

It is concluded that the lipopolysaccharides of the R mutants described in this paper have incomplete core structures which result from blocks at successive stages in the synthesis of the coli R1 core. In analogy to Salmonella these E. coli R mutants should, with one exception, be termed rfa type mutants.
Méthode d'estimation de la concentration des cytochromes dans les cellules entières de levure
Authors: Claisse Maurice L. , Péré‐Aubert Geneviève A. , Clavilier Léa P. , Slonimski Piotr P.
Published: March 2005

A method for the estimation of cytochrome concentrations in whole yeast cells was worked out with strains of Saccharomyces cerevisiae obtained in the laboratory. Differences of cytochrome c content were due to mutations affecting the nature or the quantity of synthetized cytochrome c. Respiratory deficient mutants (without cytochromes a+a3 and b) were also used. Spectra were measured directly on yeast pastes (up to 3 mm thick) with a Cary 15 recording spectrophotometer provided with a Xenon lamp.

Absorption differences between the maxima of α and β peaks of cytochrome c in relation to two base lines were measured. The mean value so obtained was in accordance with Lambert's law when the thickness of the sample of the same yeast paste was changed. For a constant optical path, Beer's law has been verified with the strains of different cytochrome c contents due to genotypical differences. There is a linear relation between quantities of cytochrome c extracted and absorptions measured on whole cells pastes.

A device for liquid nitrogen temperature recordings is described and the extension of the method to low temperature measurements, and to the estimation of cytochromes a+a3 concentration is discussed.
Structure primaire de la caséine αs1 bovine
Authors: Grosclaude François , Mercier Jean‐Claude , Ribadeau‐Dumas Bruno
Published: March 2005

Our earlier publications on the primary structure of bovine αs1 casein, which contains 198 amino acid residues in a single polypeptide chain, dealt with the sequence of forty‐eight residues from the COOH‐terminal and also with the various approaches utilised for the elucidation of the primary structure of the molecule: amino acid composition of tryptic peptides, composition and arrangement of the peptides obtained by selective hydrolysis at the arginyl or methionyl bonds and identification of the tryptic peptides in these two series of peptide fragments.

In the present communication we report the sequence of sixty amino acid residues from the NH2‐terminal of the bovine αs1 casein with the exception of a fragment consisting of seven amino acid residues (from position 46 to 52) and three phosphate groups whose sequence will be reported in our final publication.

The NH2‐terminal of bovine αs1 casein contains markedly different zones which are successively basic (position 1 to 10), non‐polar (position 20 to 33) and acid (position 45 to 60).

We will report in another paper that the A variant of αs1 casein is characterised by a deletion of thirteen amino acid residues in this part of the NH2‐terminal.
The Covalent Structure of Beef Heart Myoglobin
Authors: Han Kia‐Ki , Dautrevaux Michel , Chaila Xavier , Biserte Gérard
Published: March 2005

The covalent structure of beef myoglobin is being investigated through different experimental approaches. The globin was cleaved by cyanogen bromide. The resulting fragments were fractionated and submitted to tryptic and chymotryptic digestions. The complete amino acid sequence of these peptides has been established. From the overlaps in sequence between chymotryptic and tryptic peptides, it is possible to place most of these peptides of 153 residues of beef myoglobin in unique sequence. The remaining residues have been ordered on the basis of the apparent homology in sequence between beef and horse myoglobins. The horse protein differs from that of beef in 18 positions. All of the amino acid replacements, except three, were confined to amino acid interchange caused by the change of one base in the coding triplet leaving 135 of 153 positions in the sequence invariant in the two proteins. The relations of these data to other is discussed.
Über den Einfluß von Insulin auf die Alaningluconeogenese in der isoliert perfundierten Leber von New Zealand Obese Mice
Authors: Rudorff K.‐H. , Huchzermeyer H. , Windeck R. , Staib W.
Published: March 2005

The influence of insulin and fat‐rich diet on the alanine gluconeogenesis was investigated on isolated perfused livers of 3 1/2–4 month‐old male New Zealand obese mice (NZO‐mice). White mice were taken as controls for an insulin effect. Glucose tolerances of NZO‐mice were distinctly changed compared with those of white mice. Insulin inhibited gluconeogenesis in the livers of white mice in the same way as in the livers of rats. No insulin effect could be demonstrated out in livers of NZO‐mice, however. This result shows that only the periphery but also the livers of these animals are insusceptible to insulin. Fat‐rich diet over 6 weeks had no influence on gluconeogenesis. Under the influence of this diet the production of ketone bodies was distinctly increased, the β‐hydroxybutyrate/acetoacetate ratio was unchanged, however. Fat‐rich diet increased body weight significantly, but the liver contents of total lipids and esterified fatty acids was clearly decreased as well as 14C‐incoporation from [U‐14C]alanine in total lipids. This suggests that fat is broken down in the liver at a higher rate to meet the energy requirement.
Cooperative Binding of Manganese (II) to Transfer RNA
Authors: Danchin Antoine , Guèron Maurice
Published: March 2005

We have measured the binding of manganse ions to tRNA in the concentration range of 1 to 28 bound Mn2+ per tRNA at 23°. The free Mn2+ concentration was monitored by electron spin resonance. The Scatchard plot shows that the first four Mn2+ bind cooperatively, at a free Mn2+ concentration of 3 μM. The cooperativity presumably reflects a conformational change of tRNA. A resulting structure with 6–10 strong binding sites (ks= 1.8 × 105M−1), and 21–25 weak binding sites (kw= 5 × 103 M−1) is suggested.

From the bound Mn2+ electron spin resonance we estimate a minimal distance between the strong sites of about 1.5 nm; this shows that the binding sites are spread on the molecule and not clustered together.
The Fine Structure of Glycogen from Type IV Glycogen‐Storage Disease
Authors: Mercier Christiane , Whelan William J.
Published: March 2005

The structure of glycogen isolated from a male child suffering from type IV glycogenosis (amylopectinosis) has been examined. It is confirmed that the polysaccharide is superficially similar to plant amylopectin. However, a more searching analysis involving the examination and comparison of the pullulanase‐debranched polysaccharides, revealed marked differences between the profiles of unit chains that make up the macromolecules. The type IV glycogen contains a significant proportion of short branches. The occurrence of these branches is consistent with a recent hypothesis advanced to explain why a branched polysaccharide should be synthesized in the absence of branching enzyme, this being the enzyme deletion that characterizes this type of glycogenosis.
Electron Spin Resonance of Pteridine Radicals and the Structure of Hydropteridines
Authors: Ehrenberg Anders , Hemmerich Peter , Müller Franz , Pfleiderer Wolfgang
Published: March 2005

Cations of monohydropteridine radicals have been obtained in solution and investigated by electron spin resonance. The hyperfine pattern of these signals as well as that of previously described trihydropteridine radical cations has been computed to agreement with experiment. The first mentioned radicals are shown to have 5,8‐H2Pter+‐structure, whereas the latter are 5,6,7,8‐H4Pter+. Substitutions in the pyrimidine part of the system (positions 1–4) do not affect the spin distribution essentially in any case. In monohydropteridine the unpaired electron is delocalized over the whole pyrazine part of the system (positions 5–8), whereas in trihydropteridines it is mainly confined to N(5) and possibly to the bridge carbons.

The biochemical implications of pteridine radicals are discussed. While two‐electron oxidoreduction, implying 7,8‐dihydropteridine, is thermodynamically irreversible, one‐electron oxidoreduction appears to be intermediate in the systems Pter/5,8‐H2Pter on the one hand, and 6,7‐H2Pter/H4Pter on the other hand, thus permitting rapid electron transfer. Hence, it is reasonable to assume that trihydropteridine radicals might be of biological importance, though clearly not as the strongly acidic cations described here, but maybe in the stabilized form of metal complexes.

In this context, existence, stability and eventual biological importance of the various dihydropteridine isomers is discussed.
Acid Protease from Germinated Sorghum
Authors: Garg Govind K. , Virupaksha Tumkur K.
Published: March 2005

A protease has been isolated from germinated sorghum seeds in a highly purified, crystalline form. A molecular weight of about 80 000 has been obtained for the enzyme from gel filtration experiments. The protease does not require serine or cysteine (sulfhydryl) at the active site and has no requirement for metal ions. This enzyme has been classified as an “acid protease”, since it has its pH optimum at acidic pH range (pH 3.6). Effects of enzyme concentration and substrate concentration on the rate of catalysis have been studied and an apparent Km of 0.76 mM and 0.19 mM has been obtained against bovine serum albumin and N,N‐dimethyl albumin as substrates, respectively.
The Biosynthesis of Polyunsaturated Fatty Acids by Photosynthetic Tissue
Authors: Gurr Michael I. , Brawn Peter
Published: March 2005

Phosphatidyl choline acts as a “carrier molecule” for oleic acid during its conversion into linoleic acid in the green alga Chlorella vulgaris. Chlorella contains 7 molecular species of phosphatidyl cholines, having from one to five double bonds per molecule. No one oleate‐containing species is involved in the desaturation of oleate into linoleate, but dioleoyl‐phosphatidyl choline may be quantitatively the most important “carrier molecule” in this reaction.
Inability of Escherichia coliB to Incorporate Added Deoxycytidine, Deoxyadenosine, and Deoxyguanosine into DNA
Authors: Karlström H. Olle
Published: March 2005

It is known that Escherichia coli can incorporate labeled thymidine into its DNA, but it has not been previously possible to measure the incorporation of the other deoxyribonucleosides deoxycytidine, deoxyadenosine, and deoxyguanosine because of degradation of these compounds.

The present experiments utilize a mutant of E. coli B lacking deoxyribonucleoside‐catabolizing enzymes. This strain, OK441, has mutations affecting the following enzymes: thymidine phosphorylase, purine nucleoside phosphorylase, eytidine deaminase, and adenosine deaminase.

The results with OK441 show that E. coli, in contrast to lactobacilli and mammalian cells, does not incorporate any deoxyribonucleoside other than thymidine into its DNA.E. coli may be unable to phosphorylate deoxyeytidine, deoxyadenosine, and deoxyguanosine. In agreement with this suggestion, only thymidine kinase but no other deoxyribonucleotide kinase could be detected in extracts of OK441.