bluuebunny/crossref_metadata_2025 huggingface dataset:
Purine nucleosides replace cAMP in allosteric regulation of PKA in trypanosomatid pathogens
Authors: Ober Veronica , Githure George B. , Santos Yuri Volpato , Becker Sidney , Moya Gabriel , Basquin Jerôme , Schwede Frank , Lorentzen Esben , Boshart Michael
Published: February 2024

Cyclic nucleotide binding domains (CNB) confer allosteric regulation by cAMP or cGMP to many signalling proteins, including PKA and PKG. PKA of phylogenetically distant
Trypanosoma
is the first exception as it is cyclic nucleotide-independent and responsive to nucleoside analogues (Bachmaier et al. 2019). Here we show that natural nucleosides inosine, guanosine and adenosine are nanomolar affinity CNB ligands and activators of PKA orthologs of the important tropical pathogens
T. brucei
,
T. cruzi
and
Leishmania.
The sequence and structural determinants of binding affinity, -specificity and kinase activation of PKAR were established by structure-activity relationship (SAR) analysis, co-crystal structures and mutagenesis. Substitution of 2-3 amino acids in the binding sites is sufficient for conversion of CNB domains from nucleoside to cyclic nucleotide specificity. In addition, a trypanosomatid-specific C-terminal helix (αD) is required for high affinity binding to CNB-B. The αD helix functions as a lid of the binding site that shields ligands from solvent. Selectivity of guanosine for CNB-B and of adenosine for CNB-A results in synergistic kinase activation at low nanomolar concentration. PKA pulldown from rapid lysis establishes guanosine as the predominant ligand
in vivo
in
T. brucei
bloodstream forms, whereas guanosine and adenosine seem to synergize in the procyclic developmental stage in the insect vector. We discuss the versatile use of CNB domains in evolution and recruitment of PKA for novel nucleoside-mediated signalling.
Disordered regions and folded modules in CAF-1 promote histone deposition in Schizosaccharomyces pombe
Authors: Ouasti Fouad , Audin Maxime , Fréon Karine , Quivy Jean-Pierre , Tachekort Mehdi , Cesard Elizabeth , Thureau Aurélien , Ropars Virginie , Fernández Varela Paloma , Moal Gwenaelle , Soumana-Amadou Ibrahim , Uryga Aleksandra , Legrand Pierre , Andreani Jessica , Guerois Raphaël , Almouzni Geneviève , Lambert Sarah , Ochsenbein Francoise
Published: February 2024

Genome and epigenome integrity in eukaryotes depends on the proper coupling of histone deposition with DNA synthesis. This process relies on the evolutionary conserved histone chaperone CAF-1 for which the links between structure and functions are still a puzzle. While studies of the Saccharomyces cerevisiae CAF-1 complex enabled to propose a model for the histone deposition mechanism, we still lack a framework to demonstrate its generality and in particular, how its interaction with the polymerase accessory factor PCNA is operating. Here, we reconstituted a complete SpCAF-1 from fission yeast. We characterized its dynamic structure using NMR, SAXS and molecular modeling together with in vitro and in vivo functional studies on rationally designed interaction mutants. Importantly, we identify the unfolded nature of the acidic domain which folds up when binding to histones. We also show how the long KER helix mediates DNA binding and stimulates SpCAF-1 association with PCNA. Our study highlights how the organization of CAF-1 comprising both disordered regions and folded modules enables the dynamics of multiple interactions to promote synthesis-coupled histone deposition essential for its DNA replication, heterochromatin maintenance, and genome stability functions.
Mix desing method lightweight concrete
Authors: Pereira Wesley Batista , Galvão Simone Perruci , Veras Juliana Claudino , Mota João Manoel de Freitas
Published: February 2024

There are several methodologies for Portland cement concrete dosage, among these, the method recommended by the Technological Research Institute of the State of São Paulo - IPTUSP, which is widespread in Brazil. Although it does not present dosage factors for lightweight concrete, this paper proposes a dosage method based on the IPT method for lightweight concrete with EPS. The concrete was dosed with CPV ARI cement, sand and EPS, and two volumes of aggregates (m) were made, thus making a rich and a poor trace, for this, two aggregate contents (m) were executed, thus making a rich and a poor mix, being them: 1:1, 1:2 (aggregates mix in real volume (L) per kg of cement),  respectively. Then, each mix (1:m) was dosed with three different levels of EPS (25, 50 and 75%, to each "m"). The properties of the concretes were evaluated in the fresh state, through the slump test [1] and specific mass through the known volume method, and, in the hardened state, by the specific mass test [2] and compressive strength [3].  With the results obtained from this study, it was possible to elaborate a dosage diagram for each "m" analyzed, obtaining the values of the EPS content, projection of compressive and slump resistance, indicated in a dosage abacus made from the test results, these parameters are essential for the determination of the concrete mix.
Determinants of Repayment for Youth Development Fund Loans in Tanzania
Authors: Mwanukizi Donatus Kumbelekubi , Myava Jema Edmund , Kibona Cornel Anyisile
Published: February 2024

The study intended to identify factors influencing youth group loan repayment for the Youth Development Fund (YDF) in Tanzania. This study utilizes cross-sectional primary data from structured questionnaires and interviews with 388 individuals in the Butiama District of the Mara Region. The analysis involved descriptive statistics and econometric estimation using the ordinal logistic regression model. As per descriptive analysis results, this study provides a comprehensive analysis of socio-economic and institutional factors distinguishing loan defaulters from non-defaulters among youth participants in Tanzania's loan programs. Significant variations, supported by p < 0.05, highlight that non-defaulters possess more leadership experience, exhibit superior business performance, undergo increased training, and are in closer proximity to lending institutions. The study reveals noteworthy differences in demographic factors such as marital status, education, belief in societal employment, and types of financed projects between the two groups. Misappropriation of funds, peer pressure, and economic shocks are identified as key contributors to loan defaults, emphasizing the need for targeted interventions and vigilant monitoring for enhanced loan repayment and project success. Moreover, the econometric estimation using the ordinal logistic regression model, with statistical significance at a 5% level, demonstrates that independent factors account for 85.5% of the variation in loan repayment performance among youth groups. The study encounters societal views favoring employment over entrepreneurship, revealing a negative impact on youth loan repayment. Factors like loan diversion, peer pressure, group size, and entrepreneurship training emerge as significant determinants of loan repayment performance, providing valuable insights. In conclusion, the study underscores the critical importance of tailored interventions for addressing challenges faced by youth borrowers. Misappropriation of funds, peer pressure, and economic shocks require nuanced mitigation strategies. Policy recommendations encompass refining loan structures, enhancing training programs, and challenging societal norms favoring employment over entrepreneurship. Tailored interventions with strengthened monitoring, addressing socio-cultural attitudes, and internal control reinforcement are suggested for sustained success in youth-focused financial initiatives through continuous research and policy adaptation.
Effect of Organic Treatments on Growth Parameters of Guava (Psidium guajava L.)
Authors: Sakshi  , Kumar Suresh , Sumit  , Monika
Published: February 2024

A field experiment was conducted during the year 2020-21, at Deen Dayal Upadhyay Centre of Excellence for Organic Farming, CCS Haryana Agricultural University, Hisar. Different combinations of organic and microbial sources of nutrients (Poultry Manure, Vermicompost, FYM, Jeevamrit, Azotobacter and PSB) replicated thrice in Randomized Block Design. The maximum plant height (172.67 cm), plant spread (241.71 cm), stem girth (167.33 mm) and leaf area (62.47 cm2) were recorded at last stage of growth with FYM + Poultry manure + Azotobacter + PSB application followed by plant height (170.24 cm), plant spread (237.32 cm), stem girth (165.46 mm) and leaf area (61.29 cm2) in FYM + Poultry manure + PSB and minimum under control. Therefore, on the basic of results FYM + Poultry manure + Azotobacter + PSB found best for plant growth parameters.
Assessment of Trends of Food Crop Vulnerability to Climatic Fluctuations in the Santa Agro-basin of North-West, Cameroon
Authors: Anumveh Nkemasong Nicasius , Berinyuy Lemnyuy Melanie
Published: February 2024

Santa Subdivision like many highland areas in Cameroon has enormous agricultural potentials. However, climate which plays a vital role in crop production process continues to threaten this agricultural strength through its variability. The study therefore aimed to assess climate variability and its impacts on food crop production in Santa Subdivision. This study used the mixed method and the data collected was both quantitative and qualitative. Rainfall and temperature data for a period of 40 years alongside food crop output data coupled with field observations and interviews were used to assess the link between climatic variations and food crop output in 4 communities. Results showed significant variations in climate with gradual decreasing rainfall trends of -3.7485x and increasing temperature trends of 0.0185x. Regression analysis test showed that there is a direct relationship between climate variability and food crop outputs. This study therefore recommended the provision of climatic data/information and steady early warning systems, development of good techniques to multiply climate variability resistant seeds and the provision of adequate training on sustainable agricultural practices to help farmers cope with climate variability.
Assessing Personality Traits of School Administrators: A Big Five Perspective
Authors: Yıldırım Zeytun , Göksoy Süleyman
Published: February 2024

This research aims to evaluate the personality characteristics of school administrators in terms of the big five personality theory characteristics. With research, in order to bring about positive changes in the education system. It aims to provide guidance on developing effective methods for the development and improvement of school administrators' personality traits. Five factor personality traits of school administrators were examined according to variables such as gender, professional seniority, seniority at school and education level. In this research, the survey model, one of the quantitative research models, was used. It was held in the 2022-2023 academic year in Sakarya province Hendek district with the participation of school principals and deputy principals working at all public primary, secondary and high school levels. 84 school administrators participated in the research. “Five Factor Personality Scale” was used in the research. As a result of the research, it was concluded that school administrators perceived themselves positively at the level of "partially agree" with their personality traits. According to the results of the research, the personality characteristics of school administrators do not differ according to gender variable, and in terms of professional seniority variable; It has been observed that school administrators with 20 years or more of seniority have higher "responsibilities". When looked at in terms of the seniority variable at school, it has been observed that school administrators with 7 years or more of seniority have higher "responsibility" levels than school administrators with 1-3 years and 4-6 years of seniority. When looked at in terms of the education level variable, no significant difference was found between personality traits and education level. It was concluded that there is a positive, moderate, and significant relationship between the big five personality sub-dimensions of school administrators: extraversion, responsibility, agreeableness and openness.
TiO2 Nanoparticle–Photopolymer Composites for Volume Holographic Recording
Authors: Sánchez C. , Escuti M. J. , van Heesch C. , Bastiaansen C. W. M. , Broer D. J. , Loos J. , Nussbaumer R.
Published: September 2005

A new and efficient photopolymer for the recording of volume holograms is presented. The material comprises a mixture of UV‐sensitive acrylates and grafted titanium dioxide nanoparticles with an average size of 4 nm. We report the formation of holographic gratings with refractive‐index modulation amplitudes of up to 15.5 × 10–3—an improvement of more than a factor of four over the base material without nanoparticles—while maintaining a low level of scattering and a high transparency in the visible‐wavelength range. The influence of the composition of the acrylate system on the final properties of the holographic material is also investigated and discussed. The presence of multifunctional monomers favors the compositional segregation of the different components, while the addition of monofunctional acrylate, highly compatible with the grafting of the nanoparticles, favors the dilution of these nanoparticles.
Bonding Polyether onto ZnO Nanoparticles: An Effective Method for Preparing Polymer Nanocomposites with Tunable Luminescence and Stable Conductivity
Authors: Xiong H.‐M. , Wang Z.‐D. , Liu D.‐P. , Chen J.‐S. , Wang Y.‐G. , Xia Y.‐Y.
Published: September 2005

A series of new polymer nanocomposites, ZnO(PEGME), in which ZnO nanoparticles and poly(ethylene glycol methyl ether) (PEGME) molecules are connected by covalent bonds, have been synthesized by a sol–gel route and purified by a non‐solvent method. Various characterization techniques have been employed to determine the compositions and structures of the ZnO(PEGME)s, and their luminescent properties and ionic conductivities (after dissolving lithium salts to form solid polymer electrolytes) have been measured and compared with their counterparts—polymer nanocomposites prepared by mixing PEGME and ZnO nanoparticles physically. These comparisons prove that ZnO(PEGME) hybrids derived from chemical reactions have much better properties and stabilities than their counterparts. As a result, tunable photoluminescence of ZnO nanoparticles and stable conductivity of solid polymer electrolytes have been realized successfully.
2,7‐Carbazolenevinylene‐Based Oligomer Thin‐Film Transistors: High Mobility Through Structural Ordering
Authors: Drolet N. , Morin J.‐F. , Leclerc N. , Wakim S. , Tao Y. , Leclerc M.
Published: September 2005

We have fabricated organic field‐effect transistors based on thin films of 2,7‐carbazole oligomeric semiconductors 1,4‐bis(vinylene‐(N‐hexyl‐2‐carbazole))phenylene (CPC), 1,4‐bis(vinylene‐(N′‐methyl‐7′‐hexyl‐2′‐carbazole))benzene (RCPCR), N‐hexyl‐2,7‐bis(vinylene‐(N‐hexyl‐2‐carbazole))carbazole (CCC), and N‐methyl‐2,7‐bis(vinylene‐(7‐hexyl‐N‐methyl‐2‐carbazole))carbazole (RCCCR). The organic semiconductors are deposited by thermal evaporation on bare and chemically modified silicon dioxide surfaces (SiO2/Si) held at different temperatures varying from 25 to 200 °C during deposition. The resulting thin films have been characterized using UV‐vis and Fourier‐transform infrared spectroscopies, scanning electron microscopy, and X‐ray diffraction, and the observed top‐contact transistor performances have been correlated with thin‐film properties. We found that these new π‐conjugated oligomers can form highly ordered structures and reach high hole mobilities. Devices using CPC as the active semiconductor have exhibited mobilities as high as 0.3 cm2 V–1 s–1 with on/off current ratios of up to 107. These features make CPC and 2,7‐carbazolenevinylene‐based oligomers attractive candidates for device applications.
Evaluation by Chemical Parameters of the Pollution State of the Agricultural‐Industrial Settlement of the Fucino Plain
Authors: Ruggieri Fabrizio , Fanelli Maria , di Pasquale Dorina , Burri Ezio , Petitta Marco , Mazzeo Pietro
Published: September 2005

In the present work are reported the results of a monitoring on a vast scale, carried out through evaluation of opportune chemical parameters, of the pollution state of the agricultural‐industrial settlement of the Fucino Plain. The parameters took into consideration have been the presence of wide consumption pesticides and of ionic species as Cl−, NO2−, NO3−, NH4+, the quantification of the dissolved oxygen, of the temperature, of the conductivity, of pH and eH. Collected data are used for chemometric elaboration. The water systems examined, by means of drawing campaigns carried out at regular intervals in winter, spring, summer, and autumnal seasons, are represented by superficial waters constituting a network of irrigation canals fed by stratum and meteoric waters. In this work are reported the results relative to the drawing campaigns.
Evaluation of Chlorinated By‐Products in Drinking Waters of Clentral Friuli (Italy)
Authors: Goi Daniele , Tubaro Franco , Barbone Fabio , Dolcetti Giuliano , Bontempell Gino
Published: September 2005

Drinkable water supplied by aqueducts undergoes preliminar potabilization which, in Italy, is mainly accomplished by chlorine addition. The bactericidal action involved in this process is always accompanied by chlorination and oxidation of organic species (mainly humic and fulvic acids) naturally present in treated waters, so that many disinfection by‐products (DBPs) are formed, such as trihalomethanes (THMs) and halo‐acetic acids (HAA), which can represent a chemical risk for public health. The aim of this study was the monitoring of DBPs in drinking water disinfected by chlorination, supplied by four different aqueducts of Central Friuli (Italy). DBP evaluations were performed in water samples consisting of both input and output of disinfection plants. The results of analytical determinations were worked out to provide the THM and HAA parameters for disinfected waters, while in feeding waters the following different conventional parameters were adopted : (i) trihalomethanes formation potential (THMFP), (ii) halo‐acetic acids formation potential (HAAFP) and (iii) UV absorbance at 254 nm (UV254). The quite moderate content of chlorinated products found in all samples considered highlighted the excellent quality of potabilized waters available in Central Friuli. Moreover, our results confirmed that the majority of DBPs formed when chlorine is used for water disinfection consists of THMs, while chlorites and chlorates prevailed when potabilization is accomplished by using chlorine dioxide. Finally, simple UV254 monitoring turned out to be a profitable approach for the determination of chlorinated by‐products only when THMs prevail among DBPs.
Determination of Polycyclic Aromatic Hydrocarbons (PAHs) and Total Fats in Human Milk
Authors: del Bubba Massimo , Zanieri Laura , Galvan Paola , Donzelli Gian Paolo , Checchini Leonardo , Lepri Luciano
Published: September 2005

A sensitive and reliable analytical method was developed for the simultaneous extraction of PAHs and total fats and their determination in the human milk. The method involved a liquid‐liquid extraction of PAHs and fats, followed by the gravimetric determination of the latter. PAHs were separated from lipids by size exclusion chromatography eluting with methylene chloride and analysed by gaschromatography coupled with mass spectrometry (GC/MS). The recovery of analytes was in the range of 42‐101 % and agreed well with their boiling temperatures (R2 = 0.779). Precision of the method was found between 7.6 and 19 %. Quantification and detection limits for individual PAHs ranged from 0.011 to 0.032 and from 0.006 to 0.022 μg/Kg milk (wet weight), respectively. Quantification limit for the total fat determination was 0.26 g/Kg milk (wet weight). This procedure, applied to milk samples of ten healthy, non‐smoking, Italian primiparae, living in rural or low‐traffic zones, allowed for the identification and quantitative determination of naphthalene, acenaphthylene, acenaphthene, fluorene, phenanthrene, anthracene, fluoranthene, pyrene, benzo(a)anthracene, benzo(b)fluoranthene and benzo(k)fluoranthene in the mean concentration range 0.114 ‐ 6.95 μg/Kg milk (wet weight). The most volatile compounds, which were not investigated elsewhere, were found at much higher concentrations than those observed for the others. No relation was found between PAH and total fat concentrations.
The Protonation of Polyacrylate in Seawater. Analysis of Concentration Effects
Authors: Battaglia Gianluca , Crea Francesco , Crea Pasquale , Sammartano Silvio
Published: September 2005

The protonation of polyacrylate (PAA, MW 2 kDa) was studied potentiometrically at 25 °C, in mixed electrolyte aqueous solution simulating the composition of seawater, in the salinity range 30 ≤ S ≤ 40. The salt composition of different solutions was varied in order to study its effect on apparent protonation constants. Results were analysed using two fairly different approaches: by simple regression analysis on a combination of concentration parameters and salinity, and by canonical correlation analysis. Unexpectedly we found that variations on protonation constants, due to the different relative component concentrations, are fairly low, revealing a sort of buffering capacity of seawater respect to protonation properties of polyacrylate (and likely for other HMW and LMW polycarboxylates). The intrinsic protonation constant of polyacrylate 2 kDa at 25 °C and 35 salinity is ${\rm log} \bar K^{\rm H^\ast} = {\rm log} K_{\rm int} = 4.399 \pm 0.004$. The use of different pH scales and standard seawater compositions is also discussed.
Use of Multivariate Analysis of MIR Spectra to Study Bread Staling
Authors: Cocch Marina , Foca Giorgia , Marchetti Andrea , Sighinolfi Simona , Tassi Lorenzo , Ulrici Alessandro
Published: September 2005

Different kinds of bread, stored at constant temperature and at controlled humidity conditions for a week since their manufacturing date, were analysed by Attenuated Total Reflectance‐Fourier Transform InfraRed (ATR‐FTIR) spectroscopy. The collected spectra were processed by Principal Component Analysis (PCA), in order to evaluate the changes occurring during bread ageing. For the sake of comparison, the 1060‐950 cm−1‐1 spectral window has been also investigated by curve‐fitting methods. It was observed that the first PC increases monotonically with ageing of samples. Furthermore, the more influential variables on PC1 correspond to spectral regions where are located stretching and bending bands, which are mainly attributed to typical starch bonds vibrations.
Distribution of Heavy Metal Concentrations in Surface Sediments in Dubai Creeks, United Arab Emirates
Authors: Howari Fares M.
Published: September 2005

Dubai is developing rapidly and many developmental activities are concentrated around its Creek. The present study reports the lateral distribution of heavy metals and compares it with local historical record of heavy metal concentrations. For this purpose surface sediment samples were collected and analyzed for metal contents, total organic carbon content (TOC), mineralogy and grain size. The percentages of the different grain size fraction of the collected sediments were as follow 65 % for sand size, 15 % for silt size fraction, and the rest accounted for clay size fraction. The microscopic analyses indicate that the sediment composed mainly from carbonate and quartz with traces of rock fragments. Such mineral composition is not believed to be a potential source of heavy metal. The study found that the average recorded heavy metal concentrations in the collected sediment samples were 87, 96, 127, 38.5, and 279 ppm for Cr, Cu, Ni, Pb, and Zn, respectively. Those values were slightly higher than metal concentrations recoded in 2001 with 1.22 (Cr), 2.5 (Cu), 2.87 (Ni), 0.69 (Pb), and 2.1 (Zn) folds. However, in 2001 and 2003 the measured metal contents, along the creek, were lower than those of the average earth crust. Along the Creek most metals recorded the highest concentrations in the upper reach of the Creek. The distribution of the measured heavy metals was not affected significantly with the TOC values. The present study also documented obvious related point sources of pollution.
Synthesis and Efficiency of a Chelating Fiber for Preconcentration and Separation of Trace Au(III) and Pd(IV) from Solution Samples
Authors: Lian Ning , Chang Xijun , Zheng Hong , Wang Sui , Dong Yuming , Lai Shoujun
Published: September 2005

A novel poly(acryl‐benzoylamidrazone‐acryl‐benzoylhydrazine) chelating fiber was synthesized simply from nitrilon (polyacrylonitrile fiber). The structure of the chelating fiber was verified with the help of FT‐IR spectrum. The parameters influencing the efficiency of the fiber for concentrating trace amounts of Au(III) and Pd(IV) were investigated in detail. Trace Au(III) and Pd(IV) were enriched and separated from real sample solutions and detected using inductively coupled plasma atomic emission spectrometry (ICP‐AES) with satisfactory results. The experiments show that the method is rapid, precise, simple and convenient to use.
Electrochemical determination of 6‐Mercaptopurine at silver microdisk electrodes
Authors: Li Mao‐guo , Wang Yin‐ling , Wang Guang‐feng , Fang Bin
Published: September 2005

The electrochemical behaviour of 6–mercaptopurine (6–MP) at a microdisk electrode is investigated by cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS). The results indicate that 6–MP can be strongly adsorbed on the surface of the static mercury drop electrode (SMDE) and reacts with Ag+ ions which are produced at positive potentials. 6–MP yields a well–defined cathodic stripping signal during the negative scan at about −0.812 V (vs. SCE) in pH 9.0 phosphate buffer solution. The electrode has hence been used for the determination of 6–MP by differential pulse voltammetry (DPV). The linear range is between 2.0 × 10−7 and 5.0 × 10−5 mol/l, with the calculated detection limit (S/N=3) of 8.0 × 10−8 mol/l. The relative standard deviation is 3.0 % for eight successive determinations of 4.0 × 10−5 mol/l 6–MP. The determination of 6–MP in tablets has also been carried out and satisfactory results have been obtained.
Preparation of Poly(Propyleneimine) Dendrimer Immobilized Silica Gel and its Application as Novel Microcolumn Packing for the On‐Line FI Preconcentration and Separation of Platinum
Authors: Liu Peng , Wu Xiongzhi , Pu Qiaosheng , Su Zhixing
Published: September 2005

A G4.0 poly(propyleneimine) dendrimer immobilized silica gel (PPID‐SG) was prepared with a divergent approach from γ‐aminopropyl silica gel (APSG) by repeating the reactions: 1) cyanoethylation of ‐NH2 and 2) reduction of –CN. Then it was successfully applied as the microcolumn packing for the on‐line flow‐injection (FI) preconcentration and separation and flame atomic absorption spectrometry (FAAS) determination of Pt. A limit of detection (LOD) of 0.014 μg/mL was obtained when 0.5 μg/mL Pt in chloride acid of PH = 3 was preconcentrated with a sample flow rate of 4.6 mL/min for 60s and the relative standard deviation (RSD) was 2.65 %. Coexisting metal ions with concentration of 5.0 mg/mL and anion ions of 20.0 mg/ml have no interference in the determination of Pt. The proposed method was successfully applied to the determination of Pt in nickel alloy and anode slime samples.
Ubiquitin in Fox Chase (Nobel‐Vortrag)
Authors: Rose Irwin
Published: September 2005

Der Proteinabbau ist ein genaustens gesteuerter Prozess, bei dem das Eiweißmolekül Ubiquitin eine entscheidende Rolle spielt, indem es an Proteine bindet und sie für ihren Abbau markiert. Die zellulären Mechanismen dieses Vorgangs sind heute dank der Arbeiten der Chemienobelpreisträger 2004, Irwin Rose, Avram Hershko und Aaron Ciechanover (Fotos, von links), weitgehend bekannt. In ihren Nobelvorträgen berichten die Laureaten aus erster Hand.
Intrazellulärer Proteinabbau: von einer ungenauen Vorstellung vom Lysosom und Ubiquitin‐Proteasom‐ System bis hin zu menschlichen Krankheiten und zum Wirkstoff‐Targeting (Nobel‐Vortrag)
Authors: Ciechanover Aaron
Published: September 2005

Zwischen den 50er und 80er Jahren des letzten Jahrhunderts befassten sich Biochemiker und Molekularbiologen in der Hauptsache damit, wie genetische Information der DNA in RNA umgeschrieben und dann in Proteine übersetzt wird – wie diese Proteine abgebaut werden, blieb hingegen eine lange vernachlässigte Frage. Nach der Entdeckung des Lysosoms durch Christian de Duve ging man davon aus, dass zelluläre Proteine in dieser Organelle abgebaut werden. Es gab zwar einige experimentelle Hinweise, dass die intrazelluläre Proteolyse nicht‐lysosomal abläuft, der Mechanismus blieb aber unbekannt. Gelöst wurde das Rätsel mit der Entdeckung des Ubiquitin‐Proteasom‐Systems. Wir wissen heute, dass der Abbau intrazellulärer Proteine an der Regulation zahlreicher zellulärer Prozesse beteiligt ist, darunter Zellzyklus und Zellteilung, Bereitstellung von Transkriptionsfaktoren und zelluläre Qualitätskontrolle. Es überrascht daher nicht, dass Anomalien dieses Systems mit der Pathogenese menschlicher Erkrankungen wie Tumoren und neurodegenerativen Störungen in Verbindung gebracht wurden. Entsprechend intensiviert hat man in der Folge Bemühungen, Wirkstoffe auf Basis dieses Pathogenesemechanismus zu entwickeln.magnified image
Ubiquitin at Fox Chase (Nobel Lecture)
Authors: Rose Irwin
Published: September 2005

Protein breakdown is an exact, controlled process in which the protein molecule ubiquitin plays a decisive role by binding to a protein and labeling it for breakdown. The cellular mechanisms of this process are widely known today thanks to the work of the 2004 Nobel Laureates Irwin Rose, Avram Hershko, and Aaron Ciechanover. The Laureates report at first hand in their Nobel Lectures.
Intracellular Protein Degradation: From a Vague Idea, through the Lysosome and the Ubiquitin–Proteasome System, and onto Human Diseases and Drug Targeting (Nobel Lecture)
Authors: Ciechanover Aaron
Published: September 2005

Between the 1950s and 1980s, scientists were focusing mostly on how the genetic code is transcribed to RNA and translated to proteins, but how proteins are degraded has remained a neglected research area. With the discovery of the lysosome by Christian de Duve it was assumed that cellular proteins are degraded within this organelle. Yet, several independent lines of experimental evidence strongly suggested that intracellular proteolysis is largely non‐lysosomal, but the mechanisms involved remained obscure. The discovery of the ubiquitin–proteasome system resolved the enigma. We now recognize that degradation of intracellular proteins is involved in regulation of a broad array of cellular processes, such as the cell cycle and division, regulation of transcription factors, and assurance of the cellular quality control. Not surprisingly, aberrations in the system have been implicated in the pathogenesis of human disease, such as malignancies and neurodegenerative disorders, which led subsequently to an increasing effort to develop mechanism‐based drugs. chemical structure image
The Ubiquitin System for Protein Degradation and Some of Its Roles in the Control of the Cell‐Division Cycle (Nobel Lecture)
Authors: Hershko Avram
Published: September 2005

Protein breakdown is an exact, controlled process in which the protein molecule ubiquitin plays a decisive role by binding to a protein and labeling it for breakdown. The cellular mechanisms of this process are widely known today thanks to the work of the 2004 Nobel Laureates Irwin Rose, Avram Hershko, and Aaron Ciechanover. The Laureates report at first hand in their Nobel Lectures.chemical structure image
Synthesis of Novel Benzoic Acid Derivatives with Benzothiazolyl Subunit and Evaluation as Aldose Reductase Inhibitors
Authors: Rakowitz Dietmar , Hennig Barbara , Nagano Marietta , Steger Stefan , Costantino Luca , Matuszczak Barbara
Published: September 2005

Several methyl benzothiazolyloxybenzoates, S‐isosters, and the corresponding benzoic acids were synthesized and tested as aldose reductase inhibitors (ARIs). Out of this series, the ester derivative 2a–7 was found to exhibit the highest enzyme‐inhibitoric activity. In order to investigate this unexpected result, further modifications were carried out which allowed us to explain this finding and to open a path to a novel class of ARIs.
Synthesis of Some 2(3H)‐Benzoxazolone Derivatives and their in‐vitro Effects on Human Leukocyte Myeloperoxidase Activity
Authors: Soyer Zeynep , Bas Meral , Pabuccuoglu Aysun , Pabuccuoglu Varol
Published: September 2005

Myeloperoxidase (MPO), a heme protein expressed by polymorphonuclear leukocytes, generates potent oxidants which are proposed to contribute to tissue damage during inflammation and certain pathogenesis such as neurodegenerative disorders. In this study, twenty ω‐[2‐oxo‐3H‐benzoxazol‐3‐yl]‐N‐phenylacetamide and propionamide derivatives having substituents of different lipophilic and electronic nature on the N‐phenyl ring were synthesized to evaluate the inhibitory effects on in vitro leukocyte MPO chlorinating activity. The most active compounds in the series were the derivatives bearing 2‐methyl and 4‐nitro substituent on the N‐phenyl ring.
Synthesis and Antiviral Evaluation of Novel 6′(α)‐Methyl‐Branched Carbovir Analogues
Authors: Kim Jin Woo , Hong Joon Hee
Published: September 2005

A new stereoselective synthesis of 6′‐branched Carbovir analogues was accomplished in this study. The introduction of a methyl group in the requisite 6′(α)‐position was carried out using an ester enolate alkylation (LHMDS, CH3I). The desired cyclopentenol 7 was synthesized via a Felkin‐Anh‐controlled Grignard addition and ring‐closing metathesis using second‐generation Grubbs' catalyst. The natural bases (adenine, cytosine) were efficiently coupled using a Pd(0) catalyst. When the synthesized compounds were examined for their activity against several viruses such as the HIV‐1, HSV‐1, HSV‐2, and HCMV, the adenine analogue 12 exhibited moderate antiviral activity against the HCMV.
On the Synthesis of Bioisosters of O‐Benzothiazolyloxybenzoic Acids and Evaluation as Aldose Reductase Inhibitors
Authors: Rakowitz Dietmar , Muigg Patric , Schröder Nicole , Matuszczak Barbara
Published: September 2005

In continuation of our attempts to develop novel aldose reductase inhibitors (ARIs), a number of compounds characterized by bioisosteric replacement of pharmacophors were prepared. On the one hand, the acidic function was formally replaced by an oxime or a nitro group and on the other hand the lipophilic substituent was modified. The results of the biological evaluation of these derivatives enabled us to gain insight into structural features critical for the aldose reductase inhibition.
A Sensitive and Simple Method for the Determination of Chondroitin Sulfate A with Crystal Violet by Resonance Rayleigh Scattering Technique
Authors: Li Taishan , Liu Shaopu , Liu Zhongfang , Hu Xiaoli
Published: September 2005

Resonance Rayleigh scattering (RRS) spectra resulting from interaction between chondroitin sulfate A (CSA) and crystal violet (CV) have been investigated and applied to the determination of CSA. Though the intensity of RRS has proved very weak for CSA and CV, respectively, it can be greatly enhanced when both interact and form a supramolecular complex. A new RRS spectrum appears with a maximum scattering peak at 328 nm. In this paper, the optimum conditions of the interaction, influencing factors, and the relationship between the relative intensity of RRS (ΔI) and the concentration of CSA have been thoroughly investigated. A new method of determination for the trace amount of CSA has been developed, which combines a simple procedure, high sensitivity, and a low detection limit of 4.8 ng/mL. It has been applied with satisfactory results to the determination of CSA in CSA injection samples and synthetic samples.
Analysis of five HMG‐CoA reductase inhibitors— atorvastatin, lovastatin, pravastatin, rosuvastatin and simvastatin: pharmacological, pharmacokinetic and analytical overview and development of a new method for use in pharmaceutical formulations analysis and in vitro metabolism studies
Authors: Pasha Md. Khalid , Muzeeb Syed , Basha Shaik Jafar Sadik , Shashikumar Dhanya , Mullangi Ramesh , Srinivas Nuggehally R.
Published: September 2005

A specific, accurate, precise and reproducible high‐performance liquid chromatographic (HPLC) method was developed and validated for the simultaneous quantitation of five 3‐hydroxy‐3‐methyglutaryl coenzyme A (HMG‐CoA) reductase inhibitors, viz. atorvastatin, lovastatin, pravastatin, rosuvastatin and simvastatin, in pharmaceutical formulations and extended the application to in vitro metabolism studies of these statins. Ternary gradient elution at a flow rate of 1 mL/min was employed on an Intertisl ODS 3V column (4.6 × 250 mm, 5 µm) at ambient temperature. The mobile phase consisted of 0.01 m ammonium acetate (pH 5.0), acetonitrile and methanol. Theophylline was used as an internal standard (IS). The HMG‐CoA reductase inhibitors and their metabolites were monitored at a wavelength of 237 nm. Drugs were found to be 89.6–105.6% of their label's claim in the pharmaceutical formulations. For in vitro metabolism studies the reaction mixtures were extracted with simple liquid–liquid extraction using ethyl acetate. Baseline separation of statins and their metabolites along with IS free from endogenous interferences was achieved. Nominal retention times of IS, atorvastatin, lovastatin, pravastatin, rosuvastatin and simvastatin were 7.5, 17.2, 21.6, 28.5, 33.5 and 35.5 min, respectively. The proposed method is simple, selective and could be applicable for routine analysis of HMG‐CoA reductase inhibitors in pharmaceutical preparations as well as in vitro metabolism studies. Copyright © 2005 John Wiley & Sons, Ltd.
Antioxidant, pro‐oxidant effect of the thiosemicarbazone derivative Schiff base (4‐(1‐phenylmethylcyclobutane‐3‐yl)‐2‐(2‐hydroxybenzylidenehydrazino) thiazole) and its metal complexes on rats
Authors: Karatepe Mustafa , Karatas Fikret
Published: September 2005

Adverse biological activities of thiosemicarbazone (TSC) and Schiff base (SB) derivatives have been widely studied in rats and in other animal species using different doses, times and routes of administration. However, there are few studies describing changes in some biochemical parameters in vivo which are indicative of oxidative stress in biological systems and of morphological changes of tissues. In this study, the rats were injected subcutaneously with a new thiosemicarbazone thiazole ring containing a Schiff base (LH) and its Cu(L)2 and Zn(L)2 complexes (25 mg kg−1 body weight) and then sacrificed after 1, 2, 4, 8, 16, 32 and 64 days. The aim of this study was to determine the effect of the new compounds on the serum antioxidant vitamins (A, E, C), selenium (Se), malondialdehyde (MDA) levels, erythrocyte GSH‐Px enzyme activity and morphological changes in the liver, kidney and adrenal gland tissues. It was observed that erythrocyte GSH‐Px activity, serum MDA and vitamins A, E concentrations were statistically changed (p < 0.02), but serum levels of selenium, and vitamin C were not changed. In conclusion, the parameters measured show that Cu(L)2 caused considerable oxidative stress and Zn(L)2 behaved as an antioxidant. No oxidative stress in LH was observed compared to the control group. Copyright © 2005 John Wiley & Sons, Ltd.
Effects of the blockade of high voltage‐activated calcium channels on in vitro pineal melatonin synthesis
Authors: Afeche Solange C. , Barbosa Roseli , Scialfa Julieta H. , Terra Ilza M. , Cassola Antonio C. , Cipolla‐Neto José
Published: September 2005

The presence of high voltage‐activated calcium channels in the rat pineal gland is well known. However, their role in pineal metabolism is not completely understood and is even controversial. Better to understand this matter, we investigated the effects of L‐, N‐ or P/Q‐type calcium channel blockers (nifedipine, ω‐conotoxin GVIA, ω‐agatoxin IVA, respectively) on melatonin content and arylalkylamine‐N‐acetyltransferase activity of denervated rat pineal glands kept for 48 h in culture and stimulated with norepinephrine. Melatonin was measured by high performance liquid chromatography with electrochemical detection and arylalkylamine‐N‐acetyltransferase activity was quantified by radiometric assay. Pre‐incubation with any of these high voltage‐activated calcium channel blockers reduced the melatonin production induced by norepinephrine although arylalkylamine‐N‐acetyltransferase activity was reduced only by the N‐type calcium channel antagonist, ω‐conotoxin GVIA. The results indicate that calcium influx through L‐, N‐ or P/Q‐type of high voltage‐activated calcium channels is necessary for the full expression of the metabolic process leading to melatonin synthesis in the rat pineal glands. However, the mechanisms involved in this process are different for the L‐ or P/Q‐ and N‐type calcium channels. Copyright © 2005 John Wiley & Sons, Ltd.
A New Strategy for the Synthesis of Dinucleotides Loaded with Glycosylated Amino Acids—Investigations on in vitro Non‐natural Amino Acid Mutagenesis for Glycoprotein Synthesis
Authors: Röhrig Christoph H. , Retz Oliver A. , Hareng Lars , Hartung Thomas , Schmidt Richard R.
Published: September 2005

The in vitro non‐natural amino acid mutagenesis method provides the opportunity to introduce non‐natural amino acids site‐specifically into proteins. To this end, a chemically synthesised aminoacylated dinucleotide is enzymatically ligated to a truncated suppressor transfer RNA. The loaded suppressor tRNA is then used in translation reactions to read an internal stop codon. Here we report an advanced and general strategy for the synthesis of the aminoacyl dinucleotide. The protecting group pattern developed for the dinucleotide facilitates highly efficient aminoacylation, followed by one‐step global deprotection. The strategy was applied to the synthesis of dinucleotides loaded with 2‐acetamido‐2‐deoxy‐glycosylated amino acids, including N‐ and O‐β‐glycosides and O‐ and C‐α‐glycosides of amino acids, thus enabling the extension of in vitro non‐natural amino acid mutagenesis towards the synthesis of natural glycoproteins of high biological interest. We demonstrate the incorporation of the glycosylamino acids—although with low suppression efficiency—into the human interleukin granulocyte‐colony stimulating factor (hG‐CSF), as verified by the ELISA technique.
A Simple Approach to Well‐Defined Sugar‐Coated Surfaces for Interaction Studies
Authors: Vila‐Perelló Miquel , Gutiérrez Gallego Ricardo , Andreu David
Published: September 2005

Protein–carbohydrate interactions play a crucial role in many relevant biological processes, and the development of simple and reliable tools for their study is a well‐recognized need. Surface‐based methods are particularly attractive because they i ) can effectively mimic cell‐surface recognition events, ii ) allow the identification of low‐affinity binders, iii ) are easily adaptable to high‐throughput screening, and iv ) require minimal sample amounts. We describe here the design and synthesis of a peptide module that efficiently captures glycans through its reducing end, by oxime ligation. Immobilization to carboxyl‐functionalized supports was thereby made possible. Chemically well‐defined surfaces coated with selected glycan targets were generated by this approach for surface plasmon resonance (SPR) studies. The usefulness of the method was demonstrated in the analysis of interactions that covered a five‐orders‐of‐magnitude affinity range; namely, the strong binding (KA∼109 M−1) of a well‐known lectin (wheat germ agglutinin) to chitopentose (GlcNAc5), and that of the same sugar with a weak binder (KA∼104 M−1), HEV32—the smallest hevein domain described.
Crushing the circumflex stent arm in a case of proximal peristent restenosis after kissing stent for the distal left main disease
Authors: Kim Jang‐Young , Yoon Junghan , Jung Hyun‐Sook
Published: September 2005

We present a case of proximal peristent restenosis after kissing stenting in the distal left main lesion. The patient was treated by crushing the proximal portion of the circumflex stent after passing through the stent arm in the left anterior descending. Catheter Cardiovasc Interv 2005; © 2005 Wiley‐Liss, Inc.
A Bayesian online inferential model for evaluation of analyzer performance
Authors: Willis A. J.
Published: September 2005

An iterative Bayesian approach is developed for the inversion of flow instrumentation condition‐monitoring problems. For the case of Gaussian random variables the solution reduces to an iterative weighted least squares approach amenable to online implementation, with a weighting derived from the Bayesian prior. The algorithm is illustrated with reference to a Sulfreen unit in a refinery, where concentrations of H2S and SO2 are measured by a number of input analyzers in parallel, prior to their combination and reaction. This paper discusses approaches to evaluating the performance of each instrument separately by monitoring the inferred bias using output data from the process. Copyright © 2005 John Wiley & Sons, Ltd.
Is BRCA1/BRCA2‐related breast carcinogenesis estrogen dependent?
Authors: Noruzinia Mehadad , Coupier Isabelle , Pujol Pascal
Published: September 2005

Estrogen is a well known promoting factor of sporadic breast carcinoma. With regard to hereditary breast carcinoma, such as in BRCA1/BRCA2 syndromes, to date, the effects of estrogens on risk modification are not clear. Several studies have shown that prophylactic oophorectomy may decrease the risk of breast carcinoma in BRCA1/BRCA2 mutation carriers. Moreover, adjuvant tamoxifen therapy for primary breast carcinoma appears to diminish the risk of a second breast malignancy in BRCA1 mutation carriers. Conversely, exogenous estrogens, such as oral contraceptives, may increase the risk of breast carcinoma in familial breast cancer, as suggested by clinical studies. Paradoxically, the majority of BRCA1‐related breast carcinomas are negative for ER. There is some biologic evidence of interactions between estrogens and BRCA proteins. BRCA1 expression could be induced by estradiol in experimental models, whereas recent studies indicate that BRCA1 modifies the regulatory effects of the estrogen receptor (ER) α (ERα). Prospective studies will be required to estimate the potential benefits of estrogen suppression therapies for the prevention and adjuvant treatment of BRCA1/BRCA2‐related breast carcinomas. Cancer 2005. © 2005 American Cancer Society.