bluuebunny/crossref_metadata_2025 huggingface dataset:
A general method for the computation of probabilities in systems of first order chemical reactions
Authors: Zhang Xueying , De Cock Katrien , Bugallo Mónica F. , Djurić Petar M.
Published: March 2005

We present a general method for the computation of molecular population distributions in a system of first-order chemical reactions. The method is based on the observation that the molecules in first-order reactions do not interact with each other. Therefore, the population distributions are a convolution of densities for one molecule. With this method one can study reactions involving any number of molecules. Such analysis is demonstrated on several examples, including an enzyme catalyst reaction and a first-order reaction chain.
Bias-voltage dependence of magnetoresistance in magnetic tunnel junctions grown on Al2O3 (0001) substrates
Authors: Ahn Sung-Jin , Kato Takeharu , Kubota Hitoshi , Ando Yasuo , Miyazaki Terunobu
Published: March 2005

Magnetic tunnel junctions with the structure of Al2O3 (0001)/Pt (111) 20 nm/Ni80Fe20 (111) 50 nm/Al 1.6 nm–O/Co75Fe25 4 nm/Ir22Mn78 10 nm/Ni80Fe20 30 nm were fabricated using UHV sputtering and photolithography process. As the annealing temperature increased up to 250 °C, tunnel magnetoresistance (TMR) ratio at 1 mV bias increased from 28% to 43% for tox=180s plasma oxidation and the V±1∕2, at which the zero bias TMR value is halved, is +640 mV and−650 mV for positive and negative bias voltages, respectively. The bias-voltage dependence of TMR could be explained in terms of the relationship with V±1∕2 and the interface of the ferromagnetic electrode and the Al–O insulating layer. V+1∕2, which reflects the bottom ferromagnetic electrode-barrier interface state, changes with plasma oxidation time, while V−1∕2, which corresponds to top ferromagnetic electrode-barrier interface, hardly changes.
Effects of Eu interfacial mobility on the growth of epitaxial EuBa2Cu3O7−δ films
Authors: Wang H. , Liao X. Z. , Xu H. F. , Zhang X. , Lin Y. , Foltyn S. R. , Arendt P. N. , MacManus-Driscoll J. L. , Zhu Y. T. , Jia Q. X.
Published: March 2005

By inserting a thin YBa2Cu3O7−δ (Y123) seed layer, high quality EuBa2Cu3O7−δ (Eu123) films can grow with epitaxial c-axis orientation on SrTiO3 (STO) substrate without increasing the growth temperature. The interfacial structures of Eu123∕STO and Eu123∕Y123∕STO were investigated using scanning transmission electron microscopy. Results show that the Eu mobility on the STO substrate is very low at the regular deposition temperature. This leads to nonuniform composition distribution at the Eu123∕STO interface and a mixture of c-axis and a-axis growth. A thin Y123 seed layer greatly improves the Eu mobility and therefore facilitates high quality c-axis growth.
Change of the barrier potential shape in magnetic tunnel junctions due to an anneal treatment
Authors: Koller P. H. P. , Swagten H. J. M. , de Jonge W. J. M. , Coehoorn R.
Published: March 2005

A very important process step in the fabrication of magnetic tunnel junctions (MTJs) is the application of a modest anneal step in the presence of a high magnetic field. Roughly, a doubling of the magnetoresistance (MR) ratio is commonly observed. We show that both AlOx as well as TaOx MTJs with Co90Fe10 electrodes have similar oxidation time and anneal temperature dependencies of the MR ratios. In both cases, the maximum MR ratio shifts to higher oxidation times with annealing. TaOx MTJs are, in this sense, good model systems. From photoconductance experiments we find that for TaOx MTJs, this shift in maximum MR is accompanied by a similar shift of the zero crossing of the oxidation time dependent barrier asymmetry. This directly supports the point of view that for obtaining the highest MR ratio one should anneal MTJs that would be characterized as “slightly overoxidized” in the as-deposited state. We argue that this result can be understood by a homogenization of the oxygen distribution in the barrier, and∕or a change of the bottom barrier-electrode interface.
High levels of catalytic antibodies correlate with favorable outcome in sepsis
Authors: Lacroix-Desmazes Sébastien , Bayry Jagadeesh , Kaveri Srini V. , Hayon-Sonsino David , Thorenoor Nithyananda , Charpentier Julien , Luyt Charles-Edouard , Mira Jean-Paul , Nagaraja Valakunja , Kazatchkine Michel D. , Dhainaut Jean-François , Mallet Vincent O.
Published: March 2005

Sepsis is the leading cause of death in intensive care units and results from a deleterious systemic host response to infection. Although initially perceived as potentially deleterious, catalytic antibodies have been proposed to participate in removal of metabolic wastes and protection against infection. Here we show that the presence in plasma of IgG endowed with serine protease-like hydrolytic activity strongly correlates with survival from sepsis. Variances of catalytic rates of IgG were greater in the case of patients with severe sepsis than healthy donors (P< 0.001), indicating that sepsis is associated with alterations in plasma levels of hydrolytic IgG. The catalytic rates of IgG from patients who survived were significantly greater than those of IgG from deceased patients (P< 0.05). The cumulative rate of survival was higher among patients exhibiting high rates of IgG-mediated hydrolysis as compared with patients with low hydrolytic rates (P< 0.05). An inverse correlation was also observed between the markers of severity of disseminated intravascular coagulation and rates of hydrolysis of patients' IgG. Furthermore, IgG from three surviving patients hydrolyzed factor VIII, one of which also hydrolyzed factor IX, suggesting that, in some patients, catalytic IgG may participate in the control of disseminated microvascular thrombosis. Our observations provide the first evidence that hydrolytic antibodies might play a role in recovery from a disease.
Robust
in vitro
activity of RebF and RebH, a two-component reductase/halogenase, generating 7-chlorotryptophan during rebeccamycin biosynthesis
Authors: Yeh Ellen , Garneau Sylvie , Walsh Christopher T.
Published: March 2005

The indolocarbazole antitumor agent rebeccamycin is modified by chlorine atoms on each of two indole moieties of the aglycone scaffold. These halogens are incorporated during the initial step of its biosynthesis from conversion of
l
-Trp to 7-chlorotryptophan. Two genes in the biosynthetic cluster,
rebF
and
rebH
, are predicted to encode the flavin reductase and halogenase components of an FADH
2
-dependent halogenase, a class of enzymes involved in the biosynthesis of numerous halogenated natural products. Here, we report that, in the presence of O
2
, chloride ion, and
l
-Trp as cosubstrates, purified RebH displays robust regiospecific halogenating activity to generate 7-chlorotryptophan over at least 50 catalytic cycles. Halogenation by RebH required the addition of RebF, which catalyzes the NADH-dependent reduction of FAD to provide FADH
2
for the halogenase. Maximal rates were achieved at a RebF/RebH ratio of 3:1. In air-saturated solutions, a
k
cat
of 1.4 min
–1
was observed for the RebF/RebH system but increased at least 10-fold in low-pO
2
conditions. RebH was also able to use bromide ions to generate monobrominated Trp. The demonstration of robust chlorinating activity by RebF/RebH sets up this system for the probing of mechanistic questions regarding this intriguing class of enzymes.
The Impact of Violence Surges on Neighbourhood Business Activity
Authors: Greenbaum Robert T. , Tita George E.
Published: March 2005

Theoretical and empirical arguments suggest that fear of violence will cause consumers, employees and entrepreneurs to alter their routine activities in areas that experience a surge in violent activity. This paper argues that understanding how businesses respond to violence has important implications for understanding community crime cycles and offers further evidence of how crime impacts the choices individuals make with regard to where they live, shop and work. Using newly available longitudinal business data and homicide data disaggregated to the ZIP code level, an examination is made of the impact of violence surges on the creation, destruction and growth of business establishments in five large US cities between 1987 and 1994. Controlling for pre-existing levels of violence, it is found that increased violence has the greatest consequences for service-related establishments in low-crime neighbourhoods. This finding is consistent with the notion that the fear of victimisation imposes additional indirect costs to society through its negative impact on local business establishments.
Poor Places, Poor Prospects? Counterfactual Models of Neighbourhood Effects on Social Exclusion in Stockholm, Sweden
Authors: Brannstrom Lars
Published: March 2005

This study utilises Swedish longitudinal data from the 'golden era' of Swedish welfare policy to evaluate the impact of neighbourhood poverty during adolescence on a wide range of social exclusion outcomes (including but not limited to educational and employment status) within a counterfactual approach based on matched sampling. With certain caveats regarding inter alia the lack of dynamism in the counterfactual methodology, the empirical analyses show that, when two groups of children who are identical according to observed factors before age 10 (including household income, family structure and welfare receipt) live in different types of neighbourhood in adolescence, the outcome for those who grow up in a poor neighbourhood is not more likely to be worse than for those who grow up in a more affluent neighbourhood.
'Colonia' Land and Housing Market Performance and the Impact of Lot Title Regularisation in Texas
Authors: Ward Peter M. , de Souza Flavio , Giusti Cecilia
Published: March 2005

This article analyses performance of the land market in several irregular settlements ( colonias) outside Rio Grande City, Starr County, Texas. Specifically, it explores the impact upon land prices of a major title 'regularisation' initiative to clear property titles of very poor households undertaken by the Community Resources Group (CRG) Receivership Program at the behest of the Texas State government between 1995 and 2002. Land price data and trends are analysed using a major CRG database of over 1400 price records and files, complemented by a questionnaire survey of over 260 households applied by the research team as part of an evaluation of the CRG Program. The data show that prices are relatively 'flat' in real terms over time and that, while there was a spike in prices during the early 1990s, there does not appear to have been any significant increase since regularisation. The data suggest that prices appear to be shaped more by socially determined criteria associated with the developers themselves, rather than by settlement characteristics, location, etc. Regularisation of land title appears to make little difference to land market performance and, while colonias are a vehicle for investment for low-income groups, the rate of return compared with other segments of the (formal) property market is very low. These findings are compared with similar work for less developed countries and also challenge those theories that argue in favour of land regularisation as a means to improve land market performance and integration of the urban poor.
Race and Riots: A Note on the Economic Impact of the Rodney King Riots
Authors: Matheson Victor A. , Baade Robert A.
Published: March 2005

When the four police officers who had been videotaped beating motorist Rodney King were found not guilty of criminal acts in 1992, the city of Los Angeles erupted in the worst rioting seen in the US since the 1960s. The loss of life and destruction of property left a significant scar on the city. Time-series analysis indicates that the Rodney King riots not only reduced taxable sales in the city immediately following the unrest, but that this social catastrophe has had a lasting impact on the economic performance of the city of Los Angeles. In the 10 years since the riots, this continued loss of taxable sales has translated into a cumulative loss of at least $3.8 billion in taxable sales and over $125 million in direct sales tax revenue losses.
ATRIP Binding to Replication Protein A-Single-stranded DNA Promotes ATR–ATRIP Localization but Is Dispensable for Chk1 Phosphorylation
Authors: Ball Heather L. , Myers Jeremy S. , Cortez David
Published: March 2005

ATR associates with the regulatory protein ATRIP that has been proposed to localize ATR to sites of DNA damage through an interaction with single-stranded DNA (ssDNA) coated with replication protein A (RPA). We tested this hypothesis and found that ATRIP is required for ATR accumulation at intranuclear foci induced by DNA damage. A domain at the N terminus of ATRIP is necessary and sufficient for interaction with RPA–ssDNA. Deletion of the ssDNA–RPA interaction domain of ATRIP greatly diminished accumulation of ATRIP into foci. However, the ATRIP–RPA–ssDNA interaction is not sufficient for ATRIP recognition of DNA damage. A splice variant of ATRIP that cannot bind to ATR revealed that ATR association is also essential for proper ATRIP localization. Furthermore, the ATRIP–RPA–ssDNA interaction is not absolutely essential for ATR activation because ATR phosphorylates Chk1 in cells expressing only a mutant of ATRIP that does not bind to RPA–ssDNA. These data suggest that binding to RPA–ssDNA is not the essential function of ATRIP in ATR-dependent checkpoint signaling and ATR has an important function in properly localizing the ATR–ATRIP complex.
Callosal Bisection and Transcallosal Secondary Antiepileptogenesis
Authors: Wada Juhn A.
Published: March 2005

Summary:  More than 28,000 neuroscientists and 3,000 epileptologists gathered at their respective 2001 meetings of the Society for Neuroscience and the American Epilepsy Society. Yet only six articles, one directly and five indirectly, discussed the corpus callosum (CC). Is not this in itself a remarkable finding? Are there no mysteries left? The reality is that considerable uncertainties exist regarding the rationale for callosal bisection (CCB) that causes contrasting effects (i.e., amelioration of generalized seizure, at times leading to freedom from seizure, and intensification of postoperatively fragmented seizure, at times leading to status epilepticus). Similarly, the clinical relevance of EEG mirror focus formation, an experimentally well‐established transcallosal consequence of partial cortical epileptogenesis, continues to be debated. This presentation revisits these unresolved issues (a) to gain insight into the dynamic role played by the CC in medically refractory epilepsy, and (b) to promote the development of antiepileptogenic tools that are currently unavailable.
Study of Antiepileptic Effect of Extracts from Acorus tatarinowii Schott
Authors: Liao Wei‐Ping , Chen Li , Yi Yong‐Hong , Sun Wei‐Wen , Gao Mei‐Mei , Su Tao , Yang Shao‐Qing
Published: March 2005

Summary:  Purpose: To study the antiepileptic properties of extracts from rhizomes of Acorus tatarinowii Schott (ATS).

Methods: The decoction and volatile oil were extracted from rhizomes of ATS by traditional decocting and supercritical CO2 fluid extraction (SFE‐CO2) methods. Maximal electroshock (MES), pentylenetetrazol (PTZ) maximal seizure, and prolonged PTZ kindling models were used to test their anticonvulsive properties. The γ‐aminobutyric acid (GABA) immunohistochemical reaction (IR) was used to study GABAergic neuron changes in the PTZ kindling model and the effects of treatment.

Results: Both decoction (dose; 10–20 g/kg) and volatile oil (1.25 g/kg) of ATS decreased the convulsive rate significantly in the MES model. Decoction of ATS was shown to be effective in the PTZ model with both decreased convulsive and mortality rates. The volatile oil of ATS failed to prevent seizures in the dose range tested, although prolonged seizure latency and decreased mortality were found at a dose of 1.25 g/kg. In the PTZ kindling model, GABA‐IR neurons decreased obviously compared with the normal group. In the groups treated with the decoction and volatile oil, the seizure intensity decreased significantly after treatment. Increased GABA‐IR neurons also were found when compared with PTZ kindling controls. Morphologic observation also showed that GABA‐IR neuron damage was less severe in the drug‐treated groups.

Conclusions: Both decoction and volatile oil extracted from the rhizome of Acorus tatarinowii Schott have anticonvulsive effects. The volatile oil is shown to be less effective for PTZ‐induced convulsions. Both extracts can prevent convulsions as well as convulsion‐related GABAergic neuron damage in the brain in the prolonged PTZ kindling model.
Genetic Malformations of the Cerebral Cortex and Epilepsy
Authors: Guerrini Renzo
Published: March 2005

Summary:  We reviewed the epileptogenic cortical malformations for which a causative gene has been cloned or a linkage obtained. X‐linked bilateral periventricular nodular heterotopia (BPNH) consists of typical BPNH with epilepsy in female patients and prenatal lethality in most males. About 90% of patients have focal epilepsy. Filamin A mutations have been reported in all families and in ∼20% of sporadic patients. A rare recessive form of BPNH also has been reported. Most cases of lissencephaly–pachygyria are caused by mutations of LIS1 and XLIS genes. LIS1 mutations cause a more severe malformation posteriorly. Most children have isolated lissencephaly, with severe developmental delay and infantile spasms, but milder phenotypes have been recorded. XLIS usually causes anteriorly predominant lissencephaly in male patients and subcortical band heterotopia (SBH) in female patients. Thickness of the band and severity of pachygyria correlate with the likelihood of developing Lennox–Gastaut syndrome. Mutations of the coding region of XLIS are found in all reported pedigrees and in 50% of sporadic female patients with SBH. Autosomal recessive lissencephaly with cerebellar hypoplasia; accompanied by severe delay, hypotonia, and seizures, has been associated with mutations of the RELN gene. Schizencephaly has a wide anatomoclinical spectrum, including focal epilepsy in most patients. Familial occurrence is rare. Initial reports of heterozygous mutations in the EMX2 gene need confirmation. Among several syndromes featuring polymicrogyria, bilateral perisylvian polymicrogyria shows genetic heterogeneity, including linkage to Xq28 in some pedigrees, autosomal recessive inheritance in others, and association with 22q11.2 deletion in some patients. About 65% of patients have severe epilepsy, often Lennox–Gastaut syndrome. Recessive bilateral frontal polymicrogyria has been linked to chromosome 16q12.2–21.
The relationship between self‐reported difficulty withT hearing in the worse ear and the better ear
Authors: Okamoto M. , Nakanishi N. , Tatara K.
Published: March 2005

Objectives:  To investigate the relationship of self‐reported hearing difficulty with hearing in the worse ear and the better ear at 1 and 4 kHz.

Design:  Receiver‐operating characteristic (ROC) curve analysis in community‐residing population.

Settings:  The Settsu City Health Center (Osaka, Japan).

Participants:  A total of 919 consecutive participants who were provided health check‐ups.

Main outcomes measures:  Comparison is based on the measurement of the area under the curve (AUC) of ROC.

Results:  At 1 kHz, the area under the curve (AUC) of the worse ear (0.625 ± 0.021) was significantly larger than that of the better ear (0.570 ± 0.021) (P < 0.01). At 4 kHz, the AUC of the worse ear (0.665 ± 0.019) was significantly larger than that of the better ear (0.622 ± 0.020) (P < 0.01). Excluding the subjects with noise exposure, tinnitus and ear disease, at both frequencies, the AUC of the worse ear was not significantly larger than that of the better ear at both 1 and 4 kHz. Hearing in the worse ear was significantly more related to self‐reported hearing difficulty than in the better ear without excluding those with noise exposure, tinnitus and ear disease.

Conclusions:  ROC curve analysis would provide a method to help us judge the difference between the worse hearing ear and the better hearing ear on the subject of hearing loss.
Evidence for correlation of objective and subjective measures of nasal airflow in patients with common cold
Authors: Clarke J.D. , Hopkins M.L. , Eccles R.
Published: March 2005

Objectives:  To utilize posterior rhinomanometry and conductance, as units of measurement, to further investigate the relationship between subjective and objective measures of nasal airflow.

Design:  A prospective, observational study.

Setting:  Common Cold Research Centre.

Participants:  Sixty healthy volunteers from the staff and student population of Cardiff University with an upper respiratory tract infection.

Main outcomes measures:  To determine correlations between visual analogue scores (VAS) and posterior rhinomanometry for total, unilateral, high and low conductance groups.

Results:  No correlation was found between total VAS and total conductance (r = 0.17, P = 0.10). A substantially significant correlation was found between unilateral VAS and unilateral conductance (ρ = 0.50, P < 0.001). The unilateral VAS and conductance were highly correlated for the low total conductance group (ρ = 0.61, P < 0.001).

Conclusions:  Posterior rhinomanometry allows actual measurement of the combined and unilateral conductance of nasal passages. The units of conductance, as opposed to resistance, allow totally obstructed nasal passages to be included in analysis. Visual analogue scores and conductance correlate strongly in unilateral measures for participants with a low total nasal conductance. Posterior rhinomanometry and units of conductance are recommended for future studies investigating the relationship between objective and subjective measures of nasal airflow.
How we do it: Voice therapy to improve vocal constitution and endurance in female student teachers*
Authors: Schneider B. , Bigenzahn W.
Published: March 2005

Keypoints

• Vocal hypofunction should be regarded as risk factor of occupational voice disorders.

• Voice therapy is effective to improve vocal endurance and voice constitution.

• Elucidation of constitutionally weak voices in teachers is recommended prior to their professional career.
Reversible Inactivation of Citrate Lyase: Effect of Metal Ions and Adenine Nucleotides
Authors: Mcd. Blair J. , Datta S. P. , Tate S. S.
Published: March 2005

The inactivation of citrate oxaloacetate‐lyase in dilute solution is complex, at least two processes occurring, one reversible and the other irreversible. Inactivation at low magnesium concentration (0.025–0.1 mM) and reactivation at higher magnesium concentration (2.5 mM) have been investigated. The adenine nucleotides and EDTA exert effects related to the stability constants of their complexes with magnesium. Although unable to activate citrate lyase, Ca2+can protect the enzyme from inactivation in dilute solution.
Synthesis and Use of O‐Stearoyl Polysaccharides in Passive Hemagglutination and Hemolysis
Authors: Hämmerling U. , Westphal O.
Published: March 2005

Lipid‐free polysaccharides generally are not attached to the surface of erythrocytes. In contrast O‐stearoyl derivatives of polysaccharides show a high affinity for red blood cells. By reaction of polysaccharides with stearoyl chloride in dimethyl formamide as a solvent in the presence of pyridine, derivatives are obtained which exhibit marked erythrocyte‐sensitizing activity. The chemical conditions for optimal sensitization of erythrocytes were investigated for a number of polysaccharides, e.g. starch, dextran, and several lipid‐free bacterial cell wall polysaccharides. A content of about 5% by weight of O‐stearoyl groups has been found most suitable for producing erythrocyte‐sensitizing properties without modification of the serological specificity of the polysaccharide.

Sheep erythrocytes coated with O‐stearoyl polysaccharide are specifically agglutinated by antipolysaccharide antibody (passive hemagglutination) or lysed when guinea pig complement is present at the same time (passive hemolysis).

Further applications of the method by using derivatives of O‐stearoyl polysaccharides are mentioned.
The Binding of Calcium at Lipid‐Water Interfaces
Authors: Hauser H. , Dawson R. M. C.
Published: March 2005

Measurements have been made of the binding of radioactive calcium to unimolecular films of purified lipids equivalent to those found in cell membranes.

The adsorption of 45Ca on pure phospholipid films is largely independent of the chemical nature of the phospholipid. The affinity is controlled by Coulombic forces and is directly related to the nett excess negative charge on the lipid molecule.

With pure triphosphoinositide films at collapse pressure on a subphase at pH 5.5 there is evidence that calcium adsorption is lower than that predicted assuming full ionisation of all five anionic sites. This is probably due to the high surface potential suppressing ionisation. After reducing the pressure or after dilution of the triphosphoinositide with lecithin the adsorption of calcium per molecule approaches that predicted from the other phospholipids.

The electrophoretic mobility of lecithin particles containing small amounts of anionic phospholipids indicates that at a bulk pH of pH 5.5 both negative sites on phosphatidic acid and all five negative sites on triphosphoinositide are fully ionized at the ‘lecithin’‐water interface.

The calcium adsorbed on anionic phospholipids and gangliosides is displaced by a large excess of Na+ or K+ but in no instance is one univalent cation significantly more effective than the other. The adsorbed calcium is also displaced by Mg2+ but with all films there is a greater preference for Ca2+ ranging from 4.3 fold with gangliosides to 21 fold with triphosphoinositide.

The adsorption of calcium on stearic acid films is small until the subphase is adjusted to pH values above 9. This and the electrophoretic mobility data indicate that the carboxylic acid group at an interface is only fully ionized or orientated to the aqueous phase at a bulk pH greater than 11. The calcium adsorbed on stearic acid under alkaline conditions is less readily displaced by Na+, K+ and Mg2+ than from other lipids.
Absence of β Globin Synthesis and Excess of α Globin Synthesis in Homozygous β‐Thalassemia
Authors: Bargellesi A. , Pontremoli S. , Conconi F.
Published: March 2005

Globin chain synthesis has been studied in β‐thalassemia by incubating red blood cells of 10 homozygous thalassemic patients with [3H] amino acids, and by measuring the incorporation of radioactivity into the globin chains, separated by column chromatography.

Five of the ten patients were never transfused, five were polytransfused.

The following results were obtained: (a) absence of β chain synthesis in both polytransfused and never trasfused patients; (b) excess of α chain synthesis in the ten cases examined (ratio α synthesis/(γ+δ) synthesis = 3.0).

In three heterozygous subjects β globin synthesis and an excess of α chain synthesis was observed (ratio α/(β+γ+δ) = 1.6). The possible interpretations of these results are presented in the discussion.
A Protein Sequenator
Authors: Edman P. , Begg G.
Published: March 2005

The protein sequenator is an instrument for the automatic determination of amino acid sequences in proteins and peptides. It operates on the principle of the phenylisothiocyanate degradation scheme. The automated process embraces the formation of the phenylthiocarbamyl derivative of the protein and the splitting off of the N‐terminal amino acid as thiazolinone. The degradation proceeds at a rate of 15.4 cycles in 24 hours and with a yield in the individual cycle in excess of 98%. The material requirements are approximately 0.25 μmoles of protein. The thiazolinones are converted to the corresponding phenylthiohydantoins in a separate operation, and the latter identified by thin layer chromatography. The process has been applied to the whole molecule of apomyoglobin from the humpback whale, and it has been possible to establish the sequence of the first 60 amino acids from the N‐terminal end.
Reduced Nicotinamide Dinucleotide Phosphate Diaphorase from Bacillus subtilis
Authors: Avigad G. , Levin N.
Published: March 2005

NADPH‐diaphorase was extensively purified from extracts of Bacillus subtilis N. Y.. FMN is most probably the prosthetic group of this enzyme. NADPH is oxidized by oxygen as the terminal acceptor only in the presence of catalytic amounts of free flavins (Km for FMN was 1.6 × 10−6 M at pH 8.0). NADPH was directly oxidized in the presence of various electron acceptors such as quinones, ferricyanide and tetrazolium salts. Cytochrome c was a very poor acceptor in this system. Km for NADPH was 2.0 × 10−4 M and Ki for NADP+ as a competitive inhibitor was 1.1 × 10−3 M at pH 7.2. Mn++ or Mg++ at mM concentration showed some stimulation of enzyme activity. The enzyme was partially inhibited by various chelating agents and p‐hydroxymercuribenzoate but not by several typical inhibitors of the respiratory chain. It is suggested that this flavoprotein can serve as a useful tool for NADP+ regeneration in coupled enzyme reactions.
Purification and Properties of Fructose Diphosphate Aldolase from Spinach Leaves
Authors: Fluri R. , Ramasarma T. , Horecker B. L.
Published: March 2005

Fructose 1,6‐diphosphate aldolase has been purified from spinach leaves. The preparations are homogeneous on the basis of disc gel electrophoresis and ultracentrifugal analysis. The catalytic properties closely resemble those of the mammalian muscle enzyme. The molecular weight is 120,000 and the enzyme appears to contain three active sites, estimated by reduction of the Schiff base intermediate with borohydride. Three tyrosine residues are liberated by carboxypeptidase. The protein is unusually rich in tryptophan.
Affinité différentielle de la RNA polymérase pour divers polyribonucléotides synthétiques
Authors: Hirschbein L. , Dubert J.‐M. , Babinet C.
Published: March 2005

Using synthetic polyribonucleotides templates as models, the problems of attachment or detachment of DNA dependent‐RNA polymerase to its template have been investigated. In addition, the hypothesis that sites of initiation or termination of transcription might be determined by some specific base sequences was tested with these models.

In order to allow a distinction between the transcription process and its first step, which is the binding of the enzyme to its template, the inhibition by different polyribonucletides of the transcription of DNA was examined. A wide range of relative effects was found (Fig. 3). It is remarkable that the polyribonucleotides Poly G and Poly I showing the highest affinities for the enzyme, as well as the homopolymer pair Poly (G + C) of low affinity could not be transcribed into their complementary sequences when used as template.

When using the polyribonucleotides as template instead of DNA, the Km for triphosphate binding is about 30 fold higher. It was shwon in inhibition experiments that for a given system, a polyribonucleotide was more efficient as an inhibitor as the concentration of its complementary triphosphate was increased (Fig. 4): this result shows that the triphosphate contributes to the stability of the polyribonucleotide‐enzyme complex.

The properties of Poly I or Poly G of having very high affinity for RNA polymerase and of not being transcribed could be used to trap the enzyme not bound to its template at any time before or during the transcription process. Preliminary results are reported in Fig.5.

The fact that Poly (G + C) has barely detectable affinity for RNA polymerase can explain the kinetic results obtained when Poly C is used as a template; the G/C ratio reaches one at the end of the reaction and no further incorporation of GMP is observed when enzyme or GTP is added. Only the addition of Poly C can allow resumption of incorporation of the complementary nucleotides (Fig.2A). Consistent with these results is the observation that the enzyme and the product of the reaction migrate separately in a sucrose gradient centrifugation. Our studies show that the relative affinity of RNA polymerase for different homopolymer pairs Poly (A + U), Poly (G + C) is dependent on the nature of the bases involved in these ordered double helical structures.
Interactions entre pigments et acides nucléiques
Authors: Ohba Y. , Fromageot P.
Published: March 2005

Luteoskyrine, a bis‐polyhydroxyanthraquinone, is a toxic pigment produced by Penicillium islandicum. Its ingestion results in hepatomas and cirrhotic degeneration of the liver in man and the rat. This pigment is able to form in vitro and in the presence of Mg2+ ions two types of complexes with DNA. The first (I) and rapidly formed complex corresponds to an interaction with the purines of the DNA. To react luteoskyrine with the DNA purines, the DNA must be denatured. The interaction is established by the following criteria:

In the presence of denatured DNA the insoluble luteoskyrine‐Mg2+ complex is not formed.

The spectrum of luteoskyrine in aqueous solution is shifted to shorter wave lengths.

When submitted to ultracentrifugation and analysed at 260 mμ, and at 450 mμ the denatured DNA and the luteoskyrine sediment at the same rate, and the sedimentation coefficient of the complex is greater than that of the same sample of DNA alone.

After addition of luteoskyrine and magnesium ions, partially structured DNA is stabilized against further heat denaturation. Similar complexes (type I) are also formed with poly A, poly G and poly I. In each case, the spectra obtained and their stability are characteristic of the polymer utilised. Therefore the complexes of type I are said to be specific.

The second type of complex, type (II), on the contrary, is made slowly with native DNA or paired ribopolymers (poly A:U or poly G:C) irrespective of the nature of the constituent bases. Type II complexes can also be slowly formed from the type I complexes first made with denatured DNA. The spectra of the type II complexes are not characteristic of the nucleic acids involved but are very similar to those corresponding to the aggregated luteoskyrine‐Mg2+ complex.
Sheep Kidney Nuclease
Authors: Kasai K. , Grunberg‐Manago M.
Published: March 2005

An endonuclease showing no apparent base specificity, nor any preference for the sugar moiety has been isolated from sheep kidney. The products of the digestion are 5′‐P‐ended oligonucleotides, and not mononucleotides. Preparation of short oligo A and oligo U (di‐, tri‐, tetra‐) with a good yield is described. The enzyme requires Mg ions, is inhibited at high ionic strength and destroyed by temperatures of 60° and above.

The enzyme displays an extremely rigorous specificity with regard to the secondary structure of its substrate. This structural specificity is apparent from the fact that native DNA, complexes between poly A and poly U, and polyinosinic acid in high salt are completely resistant to the enzyme. Even poly A and poly C, at neutral pH denatured DNA, ribosomal RNA, and especially tRNA, are only slowly attacked.

Preliminary experiments on the effect of addition of poly U on the hydrolysis of a copolymer A, C suggest that the enzyme will hydrolyze the unstructured loop of polyribonucleotide complexes.

The analysis of the hydrolysis of tRNAs by sheep kidney unclease shows that the enzyme attacks all chains and produces mainly large fragments (average chain length, 40 nucleotide units), containing pGp terminal and TpΨpCpG sequences; and small oligonucleotides (average chain length 4.5 nucleotide units), containing a large amount of fragments with a CpCpA terminal.

These results are discussed in relation to the conformation of tRNA.
Préparation de RNA Messager de Réticulocytes de Lapin par Ultracentrifugation en Rotor Zonal
Authors: Huez G. , Burny A. , Marbaix G. , Schram E.
Published: March 2005

Two methods are described for the rapid isolation of 0.6 mg to 1 mg of 9S RNA from rabbit reticulocytes. This RNA has properties expected for messenger RNA.

In the first procedure, reticulocyte polyribosomes are dissolved in 0.5% (w/v) sodium dodecylsulfate and messenger RNA is separated by sucrose gradient centrifugation in a zonal rotor (B IV‐Spinco).

In the second method, messenger RNA is detached from polyribosomes by EDTA (3x10−2M) treatment and separated from ribosomal sub‐particles by sucrose gradient centrifugation using the same rotor.

In both cases, messenger RNA is then concentrated by adsorption on a non‐ionic cellulose column.

Further purification may be obtained by sucrose gradient centrifugations using the rotor S. W. 25.2 (Spinco).
The Localization and Function of Carnitine Acetyltransferase in the Flight Muscles of the Locust
Authors: Beenakkers A. M. T. , Henderson P. T.
Published: March 2005

In order to determine the extent to which carnitine acetyltransferase is restricted to mitochondria, its occurrence in fractions of the flight muscles of Locusta migratoria, obtained by two different procedures, was checked by simultaneous assay of known mitochondrial enzymes.

In one procedure, fractionated extraction of the muscles was achieved by gently stirring the tissue successively in isotonic sucrose and phosphate buffer after which the residue was disrupted in phosphate buffer. In the second procedure fractionation was achieved by differential centrifugation.

In both procedures the partitioning of the carnitine acetyltransferase among all fractions closely paralleled that of the intramitochondrial marker enzymes, thus strongly suggesting that carnitine acetyltransferase is exclusively localized within mitochondria–possibly with the transferase occurring in two intramitochondrial compartments separated from each other by a mimbrane which is impermeable to acetyl CoA.

The last‐named hypothesis is furthermore supported by correlated studies on mitochondrial respiration using acetate derivatives as substrates.
Some Properties of Alkaline Phosphatase of Pseudomonas fluorescens
Authors: Friedberg I. , Avigad G.
Published: March 2005

The formation of alkaline phosphatase in a strain of Pseudomonas fluorescens was found to be induced by limiting quantities of orthophosphate in the extracellular medium. The substrate specificity of this enzyme seemed to be similar to that of Escherichia coli. On the other hand, it had some properties different from those of the E. coli enzyme. The Pseudomonas enzyme was several hundred fold more sensitive to inhibition by EDTA, but was not inhibited by cyanide and by various mercaptans. The apparent Km for p‐nitrophenylphosphate was 2.0x10−4 M and Ki for orthophosphate as a competitive inhibitor was 3.7 × 10−5 at pH 8.6.
The Response of the Respiratory Chain and Adenine Nucleotide System to Oxidative Phosphorylation in Yeast Mitochondria
Authors: Onishi T. , Kröger A. , Heldt H. W. , Pfaff E. , Klingenberg M.
Published: March 2005

Properties and functions of the respiratory chain and of the nucleotide system were studied in mitochondria from Saccharomyces carlsbergensis and compared with those in mitochondria from mammalian tissues.

The composition of the respiratory chain showed a comparatively high content of DPN, ubiquinone, and cytochrome c.

The failure of DPN to become reduced in the controlled state with any substrate confirms the absence of the first phosphorylation site. The redox states of the other components are controlled by the last two phosphorylation sites as in mammalian mitochondria.

Substrates such as lactate, which feed hydrogen into the chain via cytochrome c, reduce ubiquinone in an energy‐dependent reverse electron transport.

The mitochondrial content of nucleotides and of the 32P incorporating components was analysed. The mitochondria were found to have a similar equipment of nucleotides etc. as mammalian mitochondria.

The phosphate transfer system in mitochondria was investigated. The phosphorylation rate of exogenous ADP is even at lower temperatures greater than that of endogenous ADP, in contrast to mammalian mitochondria.

A specific exchange between exogenous and endogenous adenine nucleotides is found with similar properties as the exchange in mammalian mitochondria.
Dye‐sensitized Photooxidation as a Tool for the Elucidation of Critical Amino Acid Residues in Phosphoglucose Isomerase
Authors: Chatterjee G. C. , Noltmann E. A.
Published: March 2005

Rabbit muscle phosphoglucose isomerase was subjected to methylene blue and rose bengal sensitized photooxidation. This treatment caused the enzyme to lose activity quite rapidly with half‐lives of 2 to 10 minutes under the following conditions: pH 7.1; ionie strength, 0.11; temperature, 10°; enzyme concentration, 2 mg per ml. The time progress curve for inactivation was of apparent first order only until approximately 50% of the initial enzyme activity were lost. Quantitative rate studies were therefore restricted to a comparison of rates obtained during this initial period of the inactivation process. The thus obtained pseudo‐first rate constants for inactivation were dependent on reaction volume, enzyme concentration, pH, and ionic strenth.

The loss in enzyme activity was accompanied by an initial decrease in the histidine, cysteine, and methionine content followed, after more prologned oxidation, by a decrease also in tryptophan and tyrosine. Other amino acid residues were not affected, as determined by monitoring the change in total amino acid composition simultaneously with the loss in enzyme activiy as a function of the photooxidation time.

A direct correlation between the rate of activity loss and the oxidation rate of a specific amino acid residue could not be established because of the multiplicity of the photocatalytic modifications. Kinetic studies of the photoinactivation process, however, implicate histidine as the residue whose modification is primarily involved in the loss of catalytic activity. A direct participation of methionine is considered unlikely on the basis of the ionic strength dependency of photoinactivation, while cysteine has been excluded on the basis of other studies with organic mercurials.
4‐Amino‐4,6‐Dideoxyhexoses Isolated from Lipopolysaccharides of Escherichia coli
Authors: Jann B. , Jann K.
Published: March 2005

From the lipopolysaccharides of two Escherichia coli strains (serotypes O 7:K1:(L):H− and O10:K5 (L):H4) two unusual amino sugars were isolated.

By sequential oxidation with periodate and hypoiodite, followed by identification of the reaction products, the aminosugars were characterized as 4‐amino‐4,6‐dideoxy‐d‐hexoses.

The chromatographic properties of the amino sugars and their N‐acetyl derivatives were compared with those of authentic samples of free and N‐acetylated 4‐amino‐4,6‐dideoxy‐d‐glucose and 4‐amino‐4,6‐dideoxy‐d‐galactose. On the basis of the results obtained the unknown amino sugars were tentatively identified as 4‐amino‐4,6‐dideoxy‐d‐glucose (from the lipopoly‐saccharide of E. coli O7:K1:(L):H−) and 4‐amino‐4,6‐dideoxy‐d‐galactose (from the lipopolysaccharide of E. coli O10:K5(L):H4).

This is the first time that 4‐amino‐4,6‐dideoxy‐d‐galactose is described as a constituent of a polysaccharide.
Kinetics and Dissociation Constants of Liver Alcohol Dehydrogenase with 3‐Acetyl Pyridine NAD+ and NADH
Authors: Shore J. D. , Theorell H.
Published: March 2005

Binary complex dissociation constants and kinetic φ values of liver alcohol dehydrogenase were determined for 3‐acetyl pyridine NAD+ and NADH. The reduced analog was bound 24 times less tightly than NADH to liver alcohol dehydrogenase whereas no significant difference was found between the binding of 3‐acetyl pyridine NAD+ and NAD+ to liver alcohol dehydrogenate. The rates of interaction of substrates with binary complexes were one tenth as fast when the acetyl pyridine analogs were used. These results were interpreted with reference to the significance of the pyridine ring amide group in binding, and the interaction of binary complexes with substrates.
The Stimulation of Glycogen Synthesis and of Glycogen Synthetase in the Liver by the Administration of Glucose
Authors: de Wulf H. , Hers H. G.
Published: March 2005

The intravenous administration of glucose to the mouse stimulates 15–20 and up to 40‐fold the conversion of glucose to glycogen in the liver. This effect is observed in the normally fed as well as in the fasted animal and requires 5 min to reach its full development. At that time, the hepatic concentration of glucose 6‐phosphate and of UDPG is markedly lowered whereas the activity of glycogen synthetase, when measured in a concentrated liver homogenate, is greatly increased. The rate of glycogen synthesis is not correlated with the concentration of glucose in the liver but is highly significantly correlated with the activity of liver glycogen synthetase.
The Stimulation of Glycogen Synthesis and of Glycogen Synthetase in the Liver by Glucocorticoids
Authors: de Wulf H. , Hers H. G.
Published: March 2005

In the N.M.R.I. mouse which has been treated by prednisolone the blood glucose level is only slightly increased and its turnover rate is not changed; the conversion of glucose to liver glycogen is greatly stimulated and the activity of glycogen synthetase in the liver is increased in a similar proportion, at least when it is measured in a concentrated liver homogenate. This activation of the glycogen synthetase also accounts for a simultaneous decrease in the concentration of UDPG and of glucose 6‐phosphate in the liver.
Cytolipin H‐Specific Antibodies Obtained with a Synthetic Polypeptide Conjugate
Authors: Arnon R. , Sela M. , Rachaman E. S. , Shapiro D.
Published: March 2005

Antibodies with specificity directed towards the naturally occurring glycolipid, cytolipin H, were elicited by immunization of rabbits with a synthetic antigen. The antigen was a conjugate consisting of a linear copolymer of alanine, glutamic acid and tyrosine, to which lactosyl sphingosine groups were attached. The specificity of the antibodies obtained, as seen from both cross‐precipitation reactions with the parent copolymer and a related conjugate (galactosyl‐sphingosyl‐copolymer), and from inhibition experiments with lactose and lipid derivatives, was towards a region which included — besides the lactose moiety — the lipid part of the molecule as well.
Zur Regulation der Synthese der Malatdehydrogenasen aus Cytosol und Mitochondrien von Rattenleber
Authors: Berkeš‐Tomaševi P. , Holzer H.
Published: March 2005

Nuclei, mitochondria, microsomes and cytosol were obtained from rat liver homogenates in sucrose solution by centrifugal fractionation. Dise electrophoresis exhibits the existence of two separately migrating malate dehydrogenases in these particulate fractions. One of them is preferably found in the mitochondria, the other one in the cytosol. The two malate dehydrogenase separated by disc electrophoresis are probably identical with the mitochondrial and cytoplasmic malate dehydrogenases differentiated earlier by other authors observing their different reaction kinetics with oxaloacetate.

In starvation the malate dehydrogenase activity in the cytoplasm decreased, whereas that in the mitochondria increased. The increase in mitochondrial activity is prevented by actinomycin. The decrease of cytoplasmic malate dehydrogenase caused by starvation is aggravated by actinomycin. All these effects are similar if the malate dehydrogenase activities are expressed as units per g liver fresh weight, per g body weight or per mg protein content in the extract.

The regulation of malate dehydrogenase in the mitochondria is discussed as repression by carbohydrates (or a metabolite originating from carbohydrates). The increase of the enzyme in starvation can therefore be understood as “derepression.” As was found by other authors [2, 16, 17a], mitochondrial malate dehydrogenase participates in gluconeogenesis in the liver; thus a repression of this enzyme by carbohydrates appears “useful for the cell economy”. Probably only the fraction of malate dehydrogenase activity additionally arising in starvation is necessary for gluconeogenesis, whereas the mitochondrial malate dehydrogenase present in normal nutrition is functioning for carbohydrate catabolism in the citric acid cycle.