bluuebunny/crossref_metadata_2025 huggingface dataset:
Urban–rural differences in perception of trees described by parents bringing up children in Warsaw and Jedlińsk, Poland
Authors: Wojnowska-Heciak Magdalena , Błaszczyk Magdalena , Suchocka Marzena , Kosno-Jończy Joanna
Published: April 2020

Parents’ attitudes to trees and nature are reflected not only in their children’s outdoor activity, but also in the way they perceive, learn and value the environment. One hundred and eleven respondents, divided into two groups by place of residence, assessed statements in a survey questionnaire. Two groups of questions aimed at evaluating tree benefits and disservices as perceived by urban and rural parents, and identifying their preferences concerning outdoor activity of their children. Tree benefits and disadvantages were grouped into five categories (social, economic, environmental, health and aesthetic). Both urban and rural parents presented similar attitudes to trees as well as to their children’s play environments. Among 37 statements concerning tree benefits, only five revealed statistically significant differences. The most important difference appeared in the way urban and rural parents perceived the aspects of danger. Trees were not perceived as posing any risk on playgrounds for city residents, who—unlike villagers—opposed to the removal of trees from playgrounds.
O espanhol no programa idioma sem fronteiras na Universidade Federal do Maranhão: uma análise de experiência do ensino do espanhol para a internacionalização acadêmica
Authors: Jesus Thiago Augusto Dos Santos de
Published: April 2020

Este artigo tem a finalidade de analisar a experiência recente da implementação da língua espanhola no Programa Idioma Sem Fronteiras na Universidade Federal do Maranhão para atender às necessidades de mobilidade acadêmica dos alunos da graduação, técnicos-administrativos e professores de outras áreas de conhecimento. O curso tem o objetivo de desenvolver as habilidades linguísticas fundamentais para a comunicação em eventos acadêmicos internacionais e a preparação para exames de certificação internacional de aprendizagem do espanhol como o DELE e o SIELE, além de favorecer o contato da comunidade acadêmica com a cultura e a produção científica dos países de língua espanhola. Para tanto, utilizou-se, como metodologia, um estudo de caso situacional, por meio da análise da perspectiva dos sujeitos participantes do curso Bem-Vindo ao Espanhol: língua Internacional, da proposta didática utilizada pelo Núcleo de Línguas da Universidade Federal do Maranhão e do material produzido pelo Núcleo para o desenvolvimento das habilidades linguísticas de nível A1. Para a realização da análise de experiência docente, este trabalho ampara-se nos novos estudos de letramentos para a aprendizagem de línguas, segundo Street (2004) e Heath (2004),  as práticas de letramento são atividades generalizadoras e abstratas no que se referem aos comportamentos relacionados com o uso da leitura e da escrita em contextos específicos de comunicação e na orientação da avaliação das habilidades linguísticas do MCER (2002). Essa experiência permitiu que, no decorrer do processo, houvesse uma percepção de aprendizagem do idioma voltada para a diversidade linguística do espanhol e para as necessidades de integração acadêmica dos estudantes universitários a nível internacional.
Electronic Government Procurement Adoption in Ghana: Critical Success Factors
Authors: Ofori Daniel , Fuseini Osman Issah
Published: April 2020

Aims: The study investigated the critical success factors for adopting an e-procurement in public sector procurement activities in Ghana.

Study Design: The study used descriptive survey design.

Place and Duration of Study: The study was carried out among some selected public sector organisations in Ghana from October 2019-January 2020.

Methodology: A total sample size of 215 procurement staff from public entities including: Department of Feeder Roads, Ghana Cocoa Board, Ghana Health Service, Koforidua Technical University and Tema Metropolitan Assembly. The data collection instruments were interview guide and questionnaires. Both descriptive and inferential statistics were used as the analytical tools. Specifically, Principal Component Analysis (PCA) was used.

Results: The study found that users and stakeholders of the e-procurement perceive the availability of reliable, affordable and fast Internet services as the most critical success factor for the adoption of e-Procurement technologies. Furthermore, the study discovered that the critical success factors (CSFs) for e-procurement adoption can be categorized into organisational support for infrastructure set-up, system features, Monitoring and control and supportive human factors.

Conclusion: For e-Procurement technologies to adequately permeate the fabrics of the Ghanaian public procurement system, the government and stakeholders should put in place mechanisms that can help measure the metrics of physical ICT infrastructure provision; attract adequate internet infrastructure into the country and provide the necessary ICT infrastructure and leadership role in using e-Procurement technologies in their public procurement process.
Role of Agri-input Dealers in Providing Extension Services to the Farmers of Bihar (India) and Their Role Expectation from Government Institutions
Authors: Kumar Subodh , Atal Ravi , Roy Sonam , Panda C. K. , Sohane R. K.
Published: April 2020

The present study was undertaken in Bhagalpur and Vaishali districts of Bihar (India) during 2017-19.The study focused on the farm extension services by agri-input dealers. The data was collected from 120 agri-input dealers through structured schedule. Findings of the study regarding after sale services information showed that the agri-input dealers do farmer’s field visits very often. The agri-input dealers facilitate demonstration of new varieties of seeds, pesticides and herbicides in farmers’ fields in collaboration with the company. They efficiently provide information related to new technologies. Governments’ role in farm extension services to the farmer is unsatisfactory. Dissemination of latest technological information and farm implements through agri-input dealers will reduce the cost of cultivation. Thus agri-input dealers play a significant role in providing information to the farmers. However, most agri-input dealers have in sufficient knowledge so they need training and exposure from government institutions.
Evidence for a three stranded complex between poly I and poly C
Authors: Thiele Danielle , Guschlbauer Wilhelm
Published: July 2002

The conditions for the formation of a triple stranded semi‐protonated complex between polyinosinic (poly (I)) and polycytidylic acid (poly (C)) are described. From potentiometric titrations and mixing curves, the stoichiometry and a phase‐transition diagram is established between the partly protonated triple stranded and the unprotonated and completely protonated double helical complexes.
Über das aminoacylierungsverhalten chemisch modifizierter phenylalaninspezifischer transfer‐ribonucleinsäure aus hefe: (1) Glykolspaltung und reduktion zum diol an der 3′‐terminalen ribose
Authors: Cramer F. , Haar F.v.d. , Schlimme E.
Published: July 2002

The terminal cis‐glycol‐group of phenylalanine specific tRNA (tRNAPhe, I) from yeast was oxidized to the dialdehyde by NaIO4 (tRNAPhe
oxi, II) and subsequently reduced to the diol by NaBH4 (tRNAPhe
oxi‐red, III). In charging experiments it could be shown that tRNAPhe
oxi‐red is still completely specific for phenylalanine. The Michaelis constant of tRNAPhe
oxi‐red remains unchanged when compared with tRNAPhe, while the maximun velocity of charging υmax of tRNAPhe
oxi‐red is decreased to about one half.
Particules ribonucleoproteiques legeres dans le cytoplasme de foie de rat
Authors: Quirin-Stricker C. , Mandel P.
Published: July 2002

The buoyant density and sedimentation properties suggest that these particles are similar to dRNA ribonucleoprotein particles released from polysomes and to those present in rat liver nuclei.
Ein purin nucleosid in ungewöhnlicher konformation: Kristall‐ und molekülstruktur von 5′‐methylammonium‐‐5′‐deoxyadenosin‐jodid‐monohydrat
Authors: Saenger Wolfram
Published: July 2002

5′‐Methylammonium‐5′‐deoxyadenosine is a poor subsrate for adenosine desaminase. The nucleoside was crystallized from aqueous methanol as its iodide monohydrate in space group P21. The structure was solved from three dimensional X‐ray data and refined to R = 4.1%. The structure of the nucleoside is determined by an intramolecular hydrogen bond from N5′ to N3 which implies that (1) the edenine heterocycle is in syn position with respect to the sugar moiety; (2) the ribose pucker is C2′‐exo, C3′‐endo and (3) the conformation about the C4′‐C5′ bond is trans, gauche. The water of hydration is fourfold disordered and forms a linear hydrophilic region which is surrounded by nucleoside molecules in a zigzag arrangement. The adenine heterocycles are not stacked and in closer than Van der Waals distance with iodine ions suggesting a charge transfer type interaction.
The proteins of the inner membrane of rat liver mitchondria
Authors: Tsai Jane H.J. , von Ehrenstein G.
Published: July 2002

Abteilung MolekulareBiologie, Max‐Planck‐Institut Experimentelle Medizin, Gottingen, Germany
Chemical probes for tRNA tertiary structure
Authors: Barciszewski J. , Romby P. , Ebel J.P. , Giegé R.
Published: July 2002

The tertiary structure of tRNA in solution can be proved by chemical modification experiments. Three reagents, N‐ethyl‐N‐nitrosourea, N‐methyl‐N‐nitrosourea and dimethylsulfate which are known to alkylate nucleic acids at nucleophilic centers were compared. It is found that N‐ethyl‐N‐nitrosourea and N‐methyl‐N‐nitrosourea mainly react with phosphate residues and dimethylsulfate only with the bases. With dimethylsulfate the extent of alkylation of guanosines is about one order of magnitude higher than that of the phosphates by the nitrosocompounds.
Potentiating effect of calmodulin and catalytic subunit of cyclic AMP‐dependent protein kinase on ATP‐dependent Ca2+‐transport by cardiac sarcolemma
Authors: Vetter Roland , Haase Hannelore , Will Horst
Published: July 2002

Highly purified sarcolemmal membranes were prepared from pig heart homogenates by differential and density gradient centrifugations. The membrane fragments exhibit ATP‐dependent Ca2+‐transport and Na+/Ca2+‐exchange activities. ATP‐dependent Ca2+‐transport (K
Ca2+

0.5 = 0.3 μM; V
max = 4.6 nmol Ca2+•mg protein−1 •min−1)_is not stimulated by oxalate. Ca2+‐uptake is also not supported by p‐nitrophenylphosphate. Preincubation of sarcolemma with MgATP, calmodulin and catalytic subunit of cyclic AMP‐dependent protein kinase stimulates active Ca2+‐transport 1.8‐fold. The effects of calmodulin and catalytic subunit are potentiating rather than additive. A large portion of the Ca2+ additionally accumulated after prephosphorylation of membranes is exchangable for Na+ via the Na+/Ca2+‐exchange system.
Characteristics of an ATP‐dependent proteolytic system of rat liver mitochondria
Authors: Rapoport S. , Dubiel W. , Müller M.
Published: July 2002

Rat liver mitochondria contain an ATP‐dependent proteolytic system which is localized on the outside of the inner membrane. It is capable of utilizating both the ATP produced within the mitochondria as well as that supplied externally. The system is dependent on Ca2+. Its physiological function is seen in the normal breakdown of mitochondria during their turnover. The system may be selective for the breakdown of the inner membranes.
An obligatory role of protein glycosylation in the life cycle of yeast cells
Authors: Arnold Elisabeth , Tanner Widmar
Published: July 2002

It is postulated that for G1/S phase transition to occur one or more proteins have to be glycosylated.
Interaction between troponin I and troponin C
Authors: Dalgarno D.C. , Grand R.J.A. , Levine B.A. , Moir A.J.G. , Scott G.M.M. , Perry S.V.
Published: July 2002

The spatial proximity on the surface of troponin C for sites specific for peptides CN4 (res. 96–116) and CN5 (res. 1–21) of troponin I has been demonstrated by proton magnetic resonance spectroscopy. The broadened signals from each peptide are at similar radial distances from the paramagnetic spin label bound to Cys 98 of troponin C. A U‐shaped disposition of peptide CN5 about Cys 98 is indicated, the interaction being modulated by calcium binding to the low affinity Ca2+ domains of troponin C. Paramagnetic broadening of signals from peptide CN4 was observed on addition of peptide TR2 (res. 88–159) from spin‐labelled troponin C, a region that contains the higher affinity Ca2+ domains.
Are guanine nucleotide binding proteins a distinct class of regulatory proteins?
Authors: Hughes Simon M.
Published: July 2002

Proteins which bind guanine nucleotides are found in a diverse set of key regulatory positions. They are involved in hormone action, visual transduction, protein synthesis and microtubule assembly. In addition to their ability to bind guanine nucleotides these proteins possess several other common features. (i) They all have similar subunit composition, (ii) they can be ADP‐ribosylated, (iii) their conformation changes depending on the nucleotide bound. These regulatory G‐proteins have close functional homologies. Do they form a general class of regulatory proteins, like the protein kinases? Do they have a common evolutionary ancestry?
Inorganic pyrophosphate‐driven ATP‐synthesis in liposomes containing membrane‐bound inorganic pyrophosphatase and F0‐F1 complex from Rhodospirillum rubrum
Authors: Nyrén Pål , Baltscheffsky Margareta
Published: July 2002

PP1 driven ATP synthesis has been reconstituted in a liposomal system containing the membrane‐bound energy‐linked PP1ase and coupling factor complex, both highly purified from Rhodospirillum rubrum. This energy converting model system was made by mixing both enzyme preparations with an aqueous suspension of sonicated soybean phospholipids and subjecting to a freeze—thaw procedure. In the presence of ADP, Mg2+, P1 and PP1 the system catalyzed phosphorylation by up to 25 nmol ATP formed X mg protein−1 X min−1, at 20°C, which was sensitive to uncouplers and inhibitors of phosphorylation such as oligomycin, efrapeptin and N,N′‐dicyclohexylcarbodiimide.
Vasopressin inhibits the adenylate cyclase activity of human platelet particulate fraction through V1‐receptors
Authors: Vanderwel Marianne , Lum Debra S. , Haslam Richard J.
Published: July 2002

Arg8‐vasopressin inhibited the adenylate cyclase activity of human platelet particulate fraction up to a maximum of 27% (IC
50 = 1.2 nM). This inhibition required the presence of 10 μM GTP and was optimal with 100 mM NaCl. Orn8‐vasopressin had similar effects. 1‐Deamino‐Val4, D‐Arg8‐vasopressin did not by itself affect adenylate cyclase activity but competitively inhibited the action of Arg8‐vasopressin (pA
2 = 7.74). Arg8‐vasopressin did not inhibit adenylate cyclase in intact platelets but instead caused platelet aggregation, an effect that was also competitively inhibited by 1‐deamino‐Val4, D‐Arg8‐vasopressin (pA
2 = 7.82). Thus, platelets possess vasopressin receptors of the V1 type that, under appropriate conditions, can mediate either inhibition of platelet adenylate cyclase or platelet aggregation.
Cyclic AMP‐dependent protein kinase does not phosphorylate cyclic GMP‐dependent protein kinase in vitro
Authors: Hofmann F. , Gensheimer H.-P.
Published: July 2002

The autophosphorylation reaction of purified cGMP‐dependent protein kinase has been studied. Apparent initial rates of autophosphorylation in the absence of cyclic nucleotides and in the presence of cGMP and cAMP are 0.006, 0.04, 0.4 mol. Pi incorp./min−1.mol cGMP‐kinase subunit−1. In the presence of cGMP and cAMP ∼1 and 2 mol P1 are incorporated/mol enzyme subunit. These values are independent of the enzyme concentration. Stimulation of autophosphorylation by cAMP is not due to activation of a contaminating cAMP‐dependent protein kinase since: (a) addition of the heatstable inhibitor protein of cAMP‐kinase does not inhibit autophosphorylation; and (b) catalytic subunit of cAMP‐kinase added at a 10‐fold excess over cGMP‐kinase does not phosphorylate cGMP‐kinase.
Vinblastine‐induced autophagocytosis: effects on liver glycogen
Authors: Hirsimäki Pirrko
Published: July 2002

The possible similarities of the mechanism by which vinblastine induces autophagocytosis in liver were compared with the known effects of glucagon in glucagon‐induced autophagocytosis. A single intraperitoneal injection of vinblastine produced a wave of autophagocytosis in <0.5 h in mouse hepatocytes. Liver glycogen content decreases simultaneously and blood glucose first increased and then decreased below control values. Both liver cAMP concentration and the activity of glycogen phosphorylase remained unchanged. These findings provide evidence tht the induction of autophagocytosis after vinblastine injection is not mediated by cAMP. The increased degradation of glycogen may occur in the lysosomal system by means of increased autophagocytosis.
Primary structure of a novel N‐glycosidic carboyhydrate unit, derived from hen ovomucoid
Authors: Paz-Parente J. , Strecker G. , Leroy Y. , Montreuil J. , Fournet B. , van Halbeek H. , Dorland L. , Vliegenthart J.F.G.
Published: July 2002

This structure is a novel member of the family of N‐glycosidic carbohydrates of glycoproteins.
Glycosaminoglycan synthesis in skin fibroblasts from patients with osteogenesis imperfecta
Authors: Kapoor R. , Bourier S. , Prehm P.
Published: July 2002

Glycosaminoglycans were analysed from skin fibroblasts with osteogenesis imperfecta (OI) IIA and IIB. The content of sulphated glycosaminoglycans was greatly increased over age‐matched controls and to a lesser extent with respect to older age control. Dermatan sulphate in comparison with older control was unaltered in the cells of OI IIA and IIB. The concentration of heparan sulphate was higher in the cells than in the medium, whereas hyaluronic acid, chondroitin sulphate and dermatan sulphate content was higher in the medium. The level of hyaluronic acid was greatly elevated in the medium of OI IIB with respect to both controls.
Microsomal Ca2+‐ and phospholipid‐dependent protein kinase
Authors: Sommarin Marianne , Jergil Bengt
Published: July 2002

A Ca2+‐ and phospholipid‐dependent protein kinase (CaPK) has been identified in rat liver microsomes. CaPK isolated from liver cytosol bound to smooth microsomes in the presence of 100 μM CaCl2. A saturation in binding was observed when a 5‐fold excess of enzyme over that present in microsomes had become bound. The microsomal CaPK and 50% of the enzyme bound in vitro was not removed by EGTA treatment. This suggests that Ca2+ is required for the binding of CaPK to microsomes, but not for the retention of the enzyme on the membrane.
Is Ca2+‐ATPase a water pump?
Authors: Dupont Yves
Published: July 2002

The mechanism of free energy coupling in active transport is discussed with special reference to the sarcoplasmic reticulum Ca2+‐ATPase. In the current working schemes for cation transport ATPases, free energy transduction is nearly always based on enzyme conformational changes. The principal objective of the present article is to examine whether recent experimental results on Ca2+‐ATPase may in fact be better explained by assuming the existence of a direct chemiosmotic process. In the scheme proposed, free energy transduction between ATP and calcium is based on a transfer of solvation water between the acylphosphate bond and the bound calcium ions.
The interaction of fructose 2,6‐bisphosphate with an allosteric site of rat liver fructose 1,6‐bisphosphatase
Authors: Meek D.W. , Nimmo H.G.
Published: July 2002

Rat liver fructose 1,6‐bisphosphatase can be protected against partial inactivation by N‐ethylmaleimide by low concentrations of fructose 2,6‐bisphosphate or high concentrations of fructose 1,6‐bisphosphate. The partially inactivated enzyme has a much reduced sensitivity to high substrate inhibition and has lost the sigmoid component of the inhibition by fructose 2,6‐bisphosphate; this compound is a simple linear competitive inhibitor of the modified enzyme. The results suggest that fructose 2,6‐bisphosphate can bind to the enzyme at two distinct sites, the catalytic site and an allosteric site. High levels of fructose 1,6‐bisphosphate probably inhibit by binding to the allosteric site.
Vanadate stimulates tyrosine phosphorylation of two proteins in Raji human lymphoblastoid cell membranes
Authors: Shelton Earp H. , Rubin Richard A. , Austin Kathy S. , Dy Ruth C.
Published: July 2002

A membrane fraction from Raji human lymphoblastoid cells exhibited tyrosine‐specific kinase activity. Vanadate increased tyrosine phosphorylation up to 5‐fold; serine and threonine phosphorylation were unchanged. The stimulation was detectable within 15 s at 0°C and at concentrations of vanadate (0.3 and 1.0 μM) present in normal tissues and blood. The tyrosine phosphorylation of two substrates, M
1 61 000 and 55 000, was dependent upon vanadate and incorporation into these substrates represented the majority of the vanadate‐sensitive tyrosine phosphorylation.
Messenger RNA—ribonucleoprotein interaction during the initiation of protein synthesis
Authors: Thomas N.S.B. , Arnstein H.R.V.
Published: July 2002

The interaction of globin mRNA with proteins during translation has been investigated in order to establish whether and to what extent messenger‐ribonucleoprotein complexes are involved in protein synthesis. We present evidence for the functional importance of two minor messenger RNA‐associated proteins (55 kDa and 60 kDa) during the initiation of globin mRNA translation in reticulocyte lysates. The formation of an mRNA complex containing the major 78 kDa and 52 kDa messenger‐ribonucleoproteins was not detected.
The sarcoplasmic reticulum calcium pump
Authors: Tanford Charles
Published: July 2002

Free energy transduction in active transport resembles other protein‐catalyzed processes, occurring by an ordered sequence of discrete bond‐breaking and bond‐making steps. The bonds that affect the transported ion directly are chelation bonds, which after the chemical potential of the bound ion, but not its chemical identity. Available data for the sarcoplasmic reticulum Ca pump (admittedly incomplete) suggest that more than 50% of the free energy transfer may be localized to a single step of the reaction cycle.
Protein synthesis by isolated chloroplasts of Chlamydomonas reinhardii
Authors: Leu Stefan , Mendiola-Morgenthaler Leticia , Boschetti Arminio
Published: July 2002

Chloroplasts which have been isolated from the cell wall mutant cw15‐2 of Chlamydomonas reinhardii are active in light‐dependent, in organello protein synthesis. Certain characteristics of protein synthesis in this system were tested, such as time course of amino acid incorporation, sensitivities to Mg2+ as well as to specific inhibitors, and found to be typical of chloroplasts isolated from higher plants. The major products made were identified as the large subunit of ribulose‐1,5‐biphosphate carboxylase and the 32‐kDa rapidly labelled membrane protein.
Evidence for N‐formyl chemotactic peptide‐stimulated GTPase activity in human neutrophil homogenates
Authors: Hyslop Paul A. , Oades Zenaida G. , Jesaitis Algirdas J. , Painter Richard G. , Cochrane Charles G. , Sklar Larry A.
Published: July 2002

Neutropil homogenates contained a high affinity guanosine triphosphatase (GTPase) that was stimulatable (+ 27%) by the addition of 100 nM N‐formyl chemotactic peptide (CHO‐pep), but not by 1 μg·ml−1 phorbolmyristate acetate (PMA). Kinetic analysis of the stimulation demonstrated an apparent lagtime of 14.3 ± 6.9 s between the addition of CHO‐pep and the optimal GTPase stimulation. The GTPase activity (but not CHO‐pep‐stimulated GTPase activity) was preserved in a highly purified plasma membrane fraction of the homogenate. From these observations we suggest that both a high affinity guanine nucleotide binding protein and GTPase are closely associated with the plasma membrane CHO‐pep receptor. The possibility that GTPase activity may influence guanine nucleotide regulation of adenylate cyclase during CHO‐pep stimulation of neutrophils is discussed.
The permeability of the thylakoid membrane for protons
Authors: Schönfeld Mordechay , Schickler Hedva
Published: July 2002

Parallel measurements of light‐induced proton gradients and of electron transport rates were used to characterize proton efflux in lettuce chloroplasts. Proton efflux mediated by the chloroplast H+‐ATPase was resolved from nonspecific leakage, through its dependence on the ratio of internal to external proton concentrations; proton leakage was proportional to the difference between these two concentrations. The proton permeability of the thylakoid membrane was found in these experiments to be 2 × 10−5 cm/s. In spite of this rather high permeability, proton leakage accounted for only ~1% of the total proton flux, due to the low internal proton concentration.
Identification of histidyl and cysteinyl residues essential for catalysis by 5′‐nucleotidase
Authors: Worku Yesehak , Paul Luzio J. , Newby Andrew C.
Published: July 2002

Inactivation of both cytosolic 5′‐nucleotidase and ecto‐5′‐nucleotidase by diethylpyrocarbonate indicated the presence of an essential histidyl residue which in the cytosolic enzyme was conclusively located at the active site. Inactivation by thiol reagents indicated the presence of an essential cysteinyl residue in both enzymes. The data suggest that both 5′‐nucleotidases belong to a group of histidine phosphatases which also includes glucose‐6‐phosphatase and acid phosphatase. A working hypothesis for the catalytic mechanism of these enzymes is proposed.
Differences between uterine and melanoma forms of tissue plasminogen activator
Authors: Pohl Gunnar , Kaplan Lennart , Einarsson Monica , Wallén Per , Jörnvall Hans
Published: July 2002

Tissue plasminogen activator purified from human uterine tissue exhibits differences in N‐terminal starting positions in relation to the melanoma cell plasminogen activator usually studied. A new starting position is compatible with an additional N‐terminal processing apart from those already known. Like the melanoma activator, the uterine activator was found to yield protein chains starting at either of two positions. One of these was identical between uterine and melanoma activators, whereas the other was unique in each case. The most abundant starting position for the uterine preparation was at a valine residue, apparently from cleavage of a Gln‐Val bond, and corresponding to Val‐7 of the longest form of the melanoma activator chain.
NAD‐dependent, PQQ‐containing methanol dehydrogenase: a bacterial dehydrogenase in a multienzyme complex
Authors: Duine J.A. , Frank J. , Berkhout M.P.J.
Published: July 2002

Cell‐free extracts of methanol‐grown Nocardia sp. 239 only show significant dye‐linked methanol‐oxidizing activity when NAD+ is added to the assay mixture. This activity resides in a multienzyme complex which could be resolved into 3 components, namely the methanol dehydrogenase, NAD‐dependent aldehyde dehydrogenase and NADH dehydrogenase. In its dissociated form, the methanol dehydrogenase no longer shows dye reduction and although rises in the absorbance values around 340 nm are seen on addition of methanol plus NAD+ to the enzyme, this is not due to NADH production. However, dye reduction (NAD dependent) could be restored on incubating methanol dehydrogenase with the corresponding NADH dehydrogenase, obtained from the enzyme complex. It is concluded that this novel methanol dehydrogenase transfers the reducing equivalents, derived from methanol, directly to its associated NADH dehydrogenase via a mechanism in which NAD+ and PQQ are involved.
Relationship of lipoamide dehydrogenases from Pseudomonas putida to other FAD‐linked dehydrogenases
Authors: Delaney Robert , Burns Gayle , Sokatch John R.
Published: July 2002

Pseudomonas putida produces two lipoamide dehydrogenases, LPD‐glc and LPD‐val. LPD‐val is specifically required as the lipoamide dehydrogenase of branched‐chain keto acid dehydrogenase and LPD‐glc fulfills all other requirements for lipoamide dehydrogenase. Both proteins are dimers with one FAD per subunit. LPD‐glc has an absorption maximum at 455 nm, but LPD‐val has a maximum at 460 nm. Comparison of amino acid compositions revealed that LPD‐glc was more closely related to Escherichia coli and pig heart lipoamide dehydrogenase than to LPD‐val. LPD‐val did not appear to be closely related to any of the proteins compared with the possible exception of mercuric reductase.
Purification of prostaglandin E2‐9‐oxoreductase from human decidua vera
Authors: Schlegel W. , Krüger S. , Korte K.
Published: July 2002

Prostaglandin E2‐9‐oxoreductase (PGE2‐9‐OR), the enzyme which converts prostaglandin E2 (PGE2) to prostaglandin F2α (PGF2α), has been detected in human decidua vera. A 105‐fold purification was achieved when the centrifuged homogenate was fractionated sequentially by DEAE—Trisacryl, hydroxyapatite—agarose gel, ultrogel AcA 44 and Matrex gel blue A gel chromatographies. The following kinetic constants for PGE2‐9‐OR have been obtained. The equilibrium constant with respect to PGE2 is 83 μM, the Michaelis constant, K
m, for PGE2 is 80 μM, for NADPH 1.6 μM. The maximal velocity for the forward reaction is V
1 = .203 pmol/min. The enzyme was inhibited by progesterone, oestradiol‐17β, cortisol and pharmaceutical drugs. An activating effect could be demonstrated with Ca2+ and oxytocin. The occurrence of PGE2‐9‐OR in the decidua vera suggests that this enzyme may be responsible for the transformation of PGE2 to PGF2α in these tissues. This may be an important mechanism for the initiation and maintenance of uterine contractions.
Endogenous ADP‐ribosylation of elongation factor 2 in polyribosome fraction of rabbit reticulocytes
Authors: Sitikov A.S. , Davydova E.K. , Ovchinnikov L.P.
Published: July 2002

Several polypeptides of about 120, 96, 85, 60 and 38 kDa are shown to be radiolabeled during incubation of the mono‐ and polyribosome fraction of rabbit reticulocytes with [32P]NAD. Among them is a polypeptide coinciding with elongation factor 2 (EF‐2) in its electrophoretic mobility in SDS‐polyacrylamide gel. The addition of pure EF‐2 to the polyribosome fraction results in an increase of the radioactive label in this polypeptide band. From this it is concluded that both endogenous and added EF‐2 is ADP‐ribosylated by an enzyme associated with polyribosomes. A possibility of regulation of protein synthesis through endogenous ADP‐ribosylation in vivo is considered.
Structural transitions of porin, a transmembrane protein
Authors: Schindler Melvin , Rosenbusch Jürg P.
Published: July 2002

Conformational transitions of porin were monitored using 3 independent criteria: (i) oligomeric state as observed by SDS‐polyacrylamide gel electrophoresis; (ii) spectroscopic titrations (ultraviolet and circular dichroism) and (iii) chemical modifications. Four pH‐dependent transitions were observed with half‐maximal changes occurring at pH values of 1.6, 3.5, 11.2 and 12.4. Two of these pH values differ significantly from intrinsic pK values of the constituent amino acids of this membrane protein. Since porin is very polar despite its location predominantly within the outer membranes, this may be due to ion pair formation in the hydrophobic environment of the membrane.
Physico‐chemical principles of cAMP‐dependent protein phosphorylation
Authors: Kochetkov S.N. , Gabibov A.G. , Lukashina T.N.
Published: July 2002

The specificity of pig brain protein kinase towards high‐ and low‐Mr ‘analogs’ of protein substrate was studied. Solvolysis of the phosphoenzyme intermediate by various nucleophilic agents is shown. The transition state structure of the phosphoryl transfer reaction is discussed.
Mass spectral identification of the blocked N‐terminal tryptic peptide of the ATPase inhibitor from beef heart mitochondria
Authors: Dianoux A.C. , Tsugita A. , Przybylski M.
Published: July 2002

The presence of a formyl blocking group at the N‐terminus of the ATPase inhibitor has been identified and the partial sequence of the N‐terminal peptide has been determined by fast atom bombardment and field desorption coupled to mass spectrometry. Minor discrepancies in amino acid sequence of the inhibitor between the present and published data [(1981) Proc. Natl. Acad. Sci. USA 78, 7403‐7407] are reported and its relationships with other inhbitors are briefly discussed.
Localization of a ferricyanide‐reactive site of cytochrome b−c1 complex, possibly of cytochrome b or ubisemiquinone, at the outer face of submitochondrial particles
Authors: Kunz Wolfram S. , Konstantinov Alexander , Tsofina Liliya , Liberman Efim A.
Published: July 2002

When succinate oxidation by submitochondrial particles is blocked by antimycin, NoHOQnO or funiculosin, addition of ferricyanide restores oxygen uptake coupled to membrane potential generation. The effect of ferricyanide is abolished by mucidin or myxothiazol, as well as by KCN. The data strongly favor a cyclic redox loop mechanism in site 2 and show that either heme of the ferrous cytochrome b or ubisemiquinone formed in the QH2‐oxidizing center of complex b−c
1 is accessible to ferricyanide at the outer (M) side of the submitochondrial particle membrane.
A ribosomal protein that is immunologically conserved in archaebacteria, eubacteria and eukaryotes
Authors: Schmid Gerhard , Strobel Olaf , Stöffler-Meilicke Marina , Stöffler Georg , Böck August
Published: July 2002

Eubacteria
Archaebacteria
Eukaryote
Ribosomal protein L2
Immunoblotting
Evolution
Cyclic AMP and anaerobic gene expression in E. coli
Authors: Unden Gottfried , Guest John R.
Published: July 2002

The expression of the fumarate reductase system of Escherichia coli is completely dependent on the presence of adenylate cyclase or cyclic AMP, but the cyclic AMP receptor protein (CRP) is not required. This suggests that cyclic AMP may function as an effector for a second gene activator protein, possibly Fnr, and thus form part of a redox‐sensitive regulatory mechanism controlling the expression of anaerobic respiratory functions.
Synthesis of carbonic anhydrase with messenger RNA isolated from the cells of Chlamydomonas reinhardtii Dangeard C‐9 grown in high and low CO2
Authors: Toguri T. , Yang S.Y. , Okabe K. , Miyachi S.
Published: July 2002

Poly(A)+RNA was isolated from Chlamydomonas reinhardtii cells grown autotrophically in ordinary air (low‐CO2 cells) and in air enriched with 4% CO2 (high‐CO2 cells). In vitro translation products with the messenger RNA showed that the synthesis of the 37‐kDa peptide was greater in low‐CO2 than in high‐CO2 cells. The immunoprecipitate produced by treating the translation products with antiserum against carbonic anhydrase (CA) from this alga was also 37 kDa. Comparison of radioactivities incorporated into these 37 kDA peptides suggested that CA induction by lowering atmospheric CO2 concentration is regulated at the transcriptional level.
In vitro methylation of the elongation factor EF‐Tu from Escherichia coli
Authors: Toledo Héctor , Jerez Carlos A.
Published: July 2002

The in vitro methylation of the elongation factor EF‐Tu from Escherichia coli was investigated. The methylation of newly synthesized EF‐Tu was obtained using λrifd18 DNA as template and S‐adenosyl [methyl‐3H]methionine as methyl donor. About 3 mol methyl residues were incorporated for every 10 mol EF‐Tu synthesized. Analysis of the nature of the methyl‐containing residues by protein hydrolysis followed by paper chromatography showed that both mono‐ and dimethyllysine were present. The methylation of EF‐Tu was also studied separately from its synthesis by using cell‐free systems with artificially undermethylated components.
Detection of NADPH diaphorase activity associated with human neutrophil NADPH‐O2 oxidoreductase activity
Authors: Green Terrence R. , Wu David E.
Published: July 2002

At approximately equimolar concentrations (~70 μM), and in the presence of excess catalase and superoxide dismutase, DCIP, ferricytochrome c and ferricyanide abstracted 21, 6 and 61%, respectively, of the electron equivalents given up by NADPH to the NADPH‐O2 oxidoreductase complex derived from phorbol myristate acetate‐stimulated human neutrophils. With a 10‐fold increase in ferricyanide, all of the electron equivalents given up by NADPH to the oxidoreductase complex were shunted to ferricyanide concomitant with complete inhibition of NADPH‐dependent O2 consumption. These results substantiate the existence of intrinsic diaphorase activity associated with the superoxide generating NADPH‐O2 oxidoreductase of human neutrophils.
Complete primary structure of thermitase from Thermoactinomyces vulgaris and its structural features related to the subtilisin‐type proteinases
Authors: Meloun Bedřich , Baudyš Miroslav , Kostka Vladimïr , Hausdorf Gert , Frömmel Cornelius , Höhne Wolfgang Ernst
Published: July 2002

Thermitase, a thermostable alkaline proteinase, consists of a single polypeptide chain, containing 279 amino acid residues (M
r = 28 369). The enzyme shows remarkable structural features of proteinases of the subtilisin type as shown by pronounced sequential homologies. The amino acid replacements, insertions and deletions observed when the amino acid sequence of the enzyme is compared with the sequences of several subtilisins are discussed with respect to substrate specificity and expected tertiary structure. The existence of a cysteinecontaining subgroup of subtilisin‐like proteinases is postulated.
Activation of a cellular tyrosine‐specific protein kinase by phosphorylation
Authors: Swarup Ghanshyam , Subrahmanyam Gosukonda
Published: July 2002

A tyrosine‐specific protein kinase of M
r 56 000 was purified over 200‐fold from rat spleen. Incubation of this kinase preparation with ATP and Mg2+ results in about 10‐fold increase in the protein kinase activity. The activation of the kinase was unaffected in the presence of soyabean trypsin inhibitor. Polyacrylamide gel electrophoresis of the enzyme preparation after phosphorylation with ATP showed one phosphoprotein band of M
r 56 000. During purification of this kinase a large decrease in enzyme activity was observed which could be prevented by adding 10 μM vanadate, as inhibitor of tyrosine‐specific protein phosphatases. These results suggest that the activation of the protein kinase by ATP is due to phosphorylation of the enzyme.
Surface accessibility of aromatic residues in human lysozyme using photochemically induced dynamic nuclear polarization NMR spectroscopy
Authors: Redfield Christina , Dobson Christopher M. , Scheck Ruud M. , Stob Sijtze , Kaptein Robert
Published: July 2002

1H‐NMR
CIDNP
Lysozyme
Surface accessibility
A chick embryo fibroblast protein kinase recognizing ribosomal protein S6
Authors: Lawen Alfons , Martini Oskar H.W.
Published: July 2002

Protein kinase
Ribosomal protein S6
Chick embryo fibroblast
Growth control
Characterization of the chromosomal protein HMb isolated from Methanosarcina barkeri
Authors: Chartier François , Laine Bernard , Sautiere Pierre , Touze Jean-Pierre , Albagnac Guy
Published: July 2002

Archaebacteria
Methanogen
Chromosomal protein
Folding of single‐stranded DNA on the histone octamer
Authors: Caffarelli E. , Leoni L. , Savino M.
Published: July 2002

A complex between the single‐stranded DNA of the bacteriophage M13 and the histone octamer was analyzed by electron microscopy, low‐angle X‐ray diffraction and nuclease analysis. The morphology and the diffraction pattern of the complex strongly resemble those of the nucleosome. These results, as well as the finding of a protected DNA fragment about 100 nucleotides long following single‐stranded DNA specific nuclease digestion, indicate that ‘a nucleosome‐like’ complex can be formed between single‐stranded DNA and the histone octamer. Competition experiments suggest that under physiological conditions the histone octamer is transferred from single‐ to double‐stranded DNA.
Precursors for peptide hormones share common secondary structures forming features at the proteolytic processing sites
Authors: Rholam Mohamed , Nicolas Pierre , Cohen Paul
Published: July 2002

We have analyzed the amino acid sequences situated around the putative proteolytic cleavage sites in twenty different biosynthetic precursors of peptide hormones by processing enzymes. The prediction of the probability for forming secondary structures around the basic amino acids, constituting the cleavage sites, was made using the modified method of Chou and Fasman. The results indicate that the processing sequences which are cleaved in vivo, are in all cases located inside regions with high β‐turn formation probability or else immediately adjacent to these structures. The β‐turn forming region at the cleavage locus, is flanked on both sides by amino acid sequences with a high probability for forming highly ordered structures, either β‐sheet or α‐helix. These conformational features are not found in precursors around dibasic pairs, i.e. putative cleavage loci, but which are not cleaved in vivo and appear to be conserved. We hypothesize that β‐turns including the basic amino acids doublets, flanked by highly ordered secondary structures (either β‐sheet or α‐helix) may constitute a minimal requirement for the recognition by the endoproteases involved in the processing of these precursors.
Sugar transport in Trypanosoma brucei: a suitable kinetic probe
Authors: Game Stephen , Holman Geoffrey , Eisenthal Robert
Published: July 2002

A transport assay has been developed for use in the investigation of 1‐deoxy‐D‐glucose uptake in trypanosomes. 1‐Deoxy‐D‐glucose has high affinity for the trypanosome sugar transport system (net influx K
m = 4.03 ± 0.42 mM; V = 0.052 ± 0.005 mM·s−. D‐Glucose oxidation is competitively inhibited by 1‐deoxy‐Dglucose. However, we show that 1‐deoxy‐D‐glucose is not a substrate for metabolism and that the competition occurs because of interaction at the transport system. D‐Glucose competitively inhibits 1‐deoxy‐D‐glucose influx.
Mr determination of histones from their electrophoretic mobility in acidic urea gels in the absence of detergents
Authors: Brandt Wolf F. , Sewell B.T. , von Holt Claus
Published: July 2002

The M
r of histones can be determined from their electrophoretic mobility at pH 2.3, 8 M urea in a polyacrylamide gel by correcting for differences in their charge density and properties of the gel matrix. The applicability of this method to other proteins is considered.
Comparison of the internalization efficiency of LDL and transferrin receptors on L2C guinea pig lymphocytes
Authors: Vidal M. , Sainte-Marie J. , Philippot J.R. , Bienvenue A.
Published: July 2002

We demonstrate that L2C lymphocytes have about 10‐times more receptors for transferrin (TO than healthy lymphocytes, as has been shown in the case of LDL receptors. The dissociation constant is the same in the two cell types (about 4 × 10−7 M). In contrast to LDL, Tf enters L2C lymphocytes with very rapid kinetics. It is shown by cross‐reaction that each receptor is internalized independently of the other.
Platelet‐activating factor mobilises intracellular calcium in vascular smooth muscle cells
Authors: Doyle Valerie M. , Creba Judith A. , Rüegg Urs T.
Published: July 2002

The effect of platelet‐activating factor (PAF) on polyphosphoinositide metabolism and 45Ca2+ efflux was examined in a vascular smooth muscle cell line (A7r5). PAF stimulated a rapid but transient production of inositol trisphosphate and inositol bisphosphate which, in the presence of lithium, resulted in an accumulation of inositol monophosphate. In addition, PAF induced a rapid efflux of 45Ca2+ from preloaded cells, an effect which was concentration‐dependent. These data suggest that PAF mobilises intracellular Ca2+ via the production of inositol trisphosphate.
Isolation and amino acid sequence of the 9.5 kDa protein of beef heart ubiquinol:cytochrome c reductase
Authors: Borchart U. , Machleidt W. , Schägger H. , Link T.A. , von Jagow G.
Published: July 2002

The 9.5 kDa protein of beef heart ubiquinol:cytochrome c reductase was isolated by a series of chromatographic steps involving dissociation of the complex by urea and guanidine. A clear distinction between the 9.5 kDa protein and the 9.2 kDa protein described earlier [(1982) J. Biochem. 91, 2077‐2085] by SDS‐PAGE was only achieved when the electrophoresis was performed according to Schägger et al. [(1985) FEBS Lett. 190, 89‐94; (1986) Methods Enzymol. 126, 22] because in this gel system the apparent molecular mass of the 9.5 kDa protein is shifted to 11 kDa. The amino acid sequence was determined by solid‐phase Edman degradation of the whole protein up to amino acid residue 80 and of the proteolytic cleavage fragments. The protein consists of 81 amino acid residues; its M
r was calculated to be 9507. Structure predictions have been made from average and sided hydropathy profiles. The 9.5 kDa protein is either bound to the core proteins within a 9.5 kDa‐core protein subcomplex or else it aggregates easily with the core proteins during the isolation procedure.
An electrogenic sodium‐translocating ATPase in Methanococcus voltae
Authors: Carper S.W. , Lancaster J.R.
Published: July 2002

A membrane potential negative inside generated by the electrogenic efflux K+ via valinomycin was demonstrated to be a driving force for the synthesis of ATP in Methanococcus voltae, but only in the presence of sodium. ATP synthesis was prevented by the addition of external potassium or of the sodium ionophore monensin, but was not inhibited by the protonophore SF6847. ATP synthesis in the absence of potassium in the medium could also be driven by a chemical concentration gradient of sodium directed inwards, but only in the presence of a permeant counterion (tetraphenylborate). These results show that M. voltae contains an electrogenic ATP‐driven ion pump which translocates sodium.
Is thermostability of glucose‐6‐phosphatase indeed dependent on a stabilizing protein?
Authors: Speth Maria , Schulze Hans-Ulrich
Published: July 2002

Partial purification of glucose‐6‐phosphatase from rat liver microsomes by solubilization of the membranes with the non‐ionic detergent Triton X‐144 at pH 6.5 and the removal of inactivating detergent by hydrophobic chromatography results in a thermostable enzyme protein which is not dependent on stabilizing phospholipids or proteins. The readdition of low amounts of detergent immediately causes a conversion into a thermo‐unstable phosphodydrolase protein. Thus these findings present evidence that heatinstability of partially purified glucose‐6‐phosphatase derives from traces of inactivating detergent changing the structural properties of the phosphohydrolase rather than from the absence of the postulated specific stabilizing protein.
A copper‐containing protein that inhibits nitrite reductase from Pseudomonas aeruginosa
Authors: Karapetian A.V. , Kamalian M.G. , Nalbandyan R.M.
Published: July 2002

A non‐blue copper‐containing glycoprotein was isolated from Pseudomonas aeruginosa. The protein has a molecular mass of 10 kDa and contains 1 atom of EPR‐detectable type II copper. The protein inhibits oxidation of both azurin and cytochrome c‐551 catalyzed by nitrite reductase from Ps. aeruginosa. Thus, it may be considered as an endogenous inhibitor of nitrite reductase.
Singlet and triplet absorption spectra of carotenoids bound in the reaction centers of Rhodopseudomonas sphaeroides R26
Authors: Frank Harry A. , Chadwick Barry W. , Taremi Shahriar , Kolaczkowski S. , Bowman M.K.
Published: July 2002

The singlet and triplet state absorption spectra are reported for two carotenoids, methoxyneurosporene and spheroidene, incorporated into the reaction center protein of the photosynthetic bacterial carotenoidless mutant Rhodopseudomonas sphaeroides R26. The spectra for the two different carotenoid molecules are identical suggesting a strong interaction between the protein and the different chromophores. Combined effects of electrochromic band shifts and carotenoid structural changes are invoked to account for the spectral observations.