bluuebunny/crossref_metadata_2025_split huggingface dataset:
Eyes Absent Proteins: Characterization of Substrate Specificity and Phosphatase Activity of Mutants Associated with Branchial, Otic and Renal Anomalies
Authors: Musharraf Amna , Markschies Nicole , Teichmann Kathleen , Pankratz Susann , Landgraf Kathrin , Englert Christoph , Imhof Diana 
Published: August 2008

AbstractThe eyes absent (Eya) genes encode a family of proteins that combine the functions of transcriptional cofactors, signal transducers and enzymes, namely protein tyrosine phosphatases. The latter activity resides in the highly conserved C‐terminal Eya domain (ED). Here, we investigated the substrate specificity of the Arabidopsis thaliana homologue (AtEya) by using low‐molecular‐weight compounds and synthetic phosphotyrosine (pY)‐containing peptides that correspond either to phosphorylation sites in proteins or to peptides that were selected through the screening of a combinatorial peptide library. AtEya displayed modest peptide substrate specificity and was sensitive to charges adjacent to pY. In general, the presence of acidic residues on the N‐terminal side of the phosphorylation site was critical for catalysis, whereas basic amino acids seemed to be preferred with respect to high‐affinity binding. We also detected significant acyl phosphatase activity of AtEya; this suggests that Eya proteins might have further substrates in vivo. In addition, we analysed the phosphatase activity of a number of variants of the mouse Eya1 protein that harbours single point mutations that were associated with branchio–oto–renal syndrome (BOR), branchio–oto syndrome (BO) and ocular defects, respectively, in humans. While BOR mutations led to a significantly reduced phosphatase activity, BO mutants as well as those that are associated with ocular defects only displayed activity that was similar to wild‐type levels.
Chemical Genetic Analysis of FOXO Nuclear–Cytoplasmic Shuttling by Using Image‐Based Cell Screening
Authors: Zanella Fabian , Rosado Aranzazú , García Beatriz , Carnero Amancio , Link Wolfgang 
Published: August 2008

AbstractFOXO proteins are direct targets of PI3K/Akt signaling and they integrate the signals of several other transduction pathways at the transcriptional level. FOXO transcription factors are involved in normal cell homeostasis and neoplasia, and they are regulated by multiple post‐transcriptional modifications. In cancer research, the regulation of the FOXO factors is receiving increasing attention as their activation has been linked to cell‐cycle arrest and apoptosis. Hence, FOXO proteins have been proposed to act as tumor suppressors. Here, we applied a chemical biology approach to study the mechanisms that influence the intracellular localization of the FOXO family member FOXO3a. We established a high‐throughput cellular‐imaging assay that monitors the nuclear–cytoplasmic translocation of a GFP–FOXO3a fusion protein in tumor cells. Nuclear accumulation of fluorescent signals upon treatment with the known PI3K inhibitors LY294002, wortmannin, PIK‐75, and PI‐103 was dose dependent and agreed well with the IC50 values reported for PI3Kα inhibition in vitro. Additionally, we identified 17 compounds from a panel of 73 low‐molecular‐weight compounds capable of inducing the nuclear accumulation of GFP–FOXO. These compounds include chemicals known to interfere with components of the PI3K/Akt signaling pathway, as well as with nuclear export and Ca2+/calmodulin (CaM)‐dependent signaling events. Interestingly, the therapeutic agent vinblastine induced efficient nuclear translocation of the FOXO reporter protein. Our data illustrate the potential of chemical genetics when combined with robust and sensitive high‐content‐screening technology.
Molecular Evolution of a Defined DNA Sequence with Accumulation of Mutations in a Single Round by a Dual Approach to Random Chemical Mutagenesis (DuARCheM)
Authors: Mohan Utpal , Banerjee Uttam Chand 
Published: August 2008

AbstractDirected evolution has paved the way to a new era of protein and nucleic acid molecules with improved and enhanced properties. The utmost important component of directed evolution is random mutations in a defined DNA sequence. The utility of random chemical mutagenesis in directed evolution studies is dwindling due to the inherent flaws with whole‐organism mutagenesis and the in vitro approach. Here, we report a novel Dual Approach to Random Chemical Mutagenesis (DuARCheM) to introduce random mutations in a defined DNA fragment. DuARCheM involves in vivo chemical mutagenesis and in vitro genetic manipulations. The resulting library revealed an accumulation of mutations in its members. These results imply that the parent mutation is carried in the further generations within the same library. This method might help to change random chemical mutagenesis because the combination of in vivo and in vitro approaches mimics the amplification and mutation that is performed by PCR‐based mutagenesis, and at the same time the mutations are confined to the desired gene. Moreover, the mutagen pressure is greater in chemical mutagenesis than in a Taq‐polymerase‐based error‐prone system. Concomitant amplification and mutation in the DuARCheM method leads to a better spectrum of mutants because the plasmid construct is exponentially amplified in the presence of mutagen pressure, unlike in the in vitro chemical mutagenesis system in which the template molecule does not replicate. This work is able to nullify all the disadvantages that are associated with random chemical mutagenesis, and could make random chemical mutagenesis an indispensable tool in directed evolution studies.
Screening the Structural and Functional Properties of Bicyclo‐DNA: bcox‐DNA
Authors: Luisier Samuel , Leumann Christian J. 
Published: August 2008

AbstractThe synthesis of two novel pyrimidine bicyclonucleosides (bcox‐nucleosides) has been accomplished. These bicyclonucleosides each carry a lipophilic benzyloxime substituent on the carbocyclic ring and show improved conformational similarity to 2′‐deoxyribonucleosides as shown by their X‐ray structures. The thymine‐containing bcox‐nucleoside was converted into the corresponding phosphoramidite building block and incorporated into oligodeoxyribonucleotides by standard phosphoramidite chemistry. Tm data with complementary RNA and DNA were measured and compared to corresponding cases of natural and unfunctionalized bc‐DNA. It was found that single incorporations of bcox residues destabilize duplexes by roughly 5 °C per modification. The destabilization was found to be due to the oxime substituent and not to the bicyclic scaffold itself. No significant alteration of the base‐pairing selectivity as a function of the modification was observed. With RNA (but not with DNA) as a complement the relative thermal destabilization of bcox‐oligothymidylates was gradually reduced and converted into a stabilizing interaction with increasing numbers of consecutive modifications. While no cellular uptake of bcox‐oligonucleotides into HeLa cells occurred without transfecting agents, a significant increase in the transfection rate relative to unmodified DNA was observed in complexation with lipofectamine.
On the Mechanism of d–f Energy Transfer in RuII/LnIII and OsII/LnIII Dyads: Dexter‐Type Energy Transfer Over a Distance of 20 Å
Authors: Lazarides Theodore , Sykes Daniel , Faulkner Stephen , Barbieri Andrea , Ward Michael D. 
Published: August 2008

AbstractWe have used time‐resolved luminescence methods to study rates of photoinduced energy transfer (PEnT) from [M(bipy)3]2+ (M=Ru, Os) chromophores to LnIII ions with low‐energy f–f states (Ln=Yb, Nd, Er) in d–f dyads in which the metal fragments are separated by a saturated CH2CH2 spacer, a p‐C6H4 spacer, or a p‐(C6H4)2 spacer. The finding that d→f PEnT is much faster across a conjugated p‐C6H4 spacer than it is across a shorter CH2CH2 spacer points unequivocally to a Dexter‐type energy transfer, involving electronic coupling mediated by the bridging ligand orbitals (superexchange) as the dominant mechanism. Comparison of the distance dependence of the Ru→Nd energy‐transfer rate across different conjugated spacers [p‐C6H4 or p‐(C6H4)2 groups] is also consistent with this mechanism. Observation of Ru→Nd PEnT (as demonstrated by partial quenching of the RuII‐based 3 MLCT emission (MLCT=metal‐to‐ligand charge transfer), and the growth of sensitised NdIII‐based emission at 1050 nm) over approximately 20 Å by an exchange mechanism is a departure from the normal situation with lanthanides, in which long‐range energy transfer often involves through‐space Coulombic mechanisms.
An Enolisable Barbiturate with Adjustable Hydrogen‐Bonding Structure for UV/Vis Detection of Nucleic Acid Bases and Related Compounds
Authors: Bolz Ina , Spange Stefan 
Published: August 2008

AbstractThe use of hydrogen‐bonding patterns in the same way as is known from DNA building blocks is a challenge for the construction of novel types of suitable chromophoric probes. This feature has been utilised for the construction of a novel type of UV/Vis probe for detection of supramolecular AAD or DAD sequences (A=hydrogen bond acceptor, D=hydrogen bond donor). Here we report on the structure of the enolisable chromophore 1‐n‐butyl‐5‐(4‐nitrophenyl)barbituric acid (1), which has an adjustable hydrogen‐bonding pattern. The position of the keto–enol equilibrium of this dye is strongly influenced both by the solvent polarity and by the chemical environment. Furthermore, the recognition properties of the barbiturate were examined by the use of seven artificial receptors: the pyridine bases 2,6‐diaminopyridine (DAP), 2,6‐diacetamidopyridine (DAC) and 2,6‐bis(trifluoroacetamido)pyridine (TFA), as well as the nucleic acid bases 9‐ethyladenine (EtAd), 9‐ethylguanine (EtGu), 1‐n‐butylcytosine (BuCy) and 1‐n‐butylthymine (BuTy). It was found that 1 can interact with these bases either through acid–base interaction or by hydrogen‐bonding complexation. The balance between the interactions is dependent both on the basicity strength and on the presence of a suitable recognition sequence in the base. The induced formation of the enol form of 1 thus causes a significant UV/Vis shift as function of the nature of the base.
Discovery of Water‐Soluble Antioxidant Flavonols without Vasorelaxant Activity
Authors: Yap Suwan , Loft Karen J. , Woodman Owen L. , Williams Spencer J. 
Published: August 2008

Abstract3′,4′‐Dihydroxyflavonol (DiOHF) is a cardioprotective flavonol that can decrease ischaemia/reperfusion injury in the heart. DiOHF exhibits antioxidant and vasorelaxant properties that are thought to underlie its cardioprotective activity. A major limitation to its use for the treatment or prevention of cardiovascular disease is its poor water solubility, preventing intravenous administration at the required dosage. In this study, three novel flavonols were synthesised that bear an ionisable succinamic acid substituent at the 6‐position of the A ring with zero, one, or two hydroxy groups on the B ring. The ionised compounds possess improved aqueous solubility, dissolving at concentrations up to 10−1 m, whereas DiOHF is insoluble in water (<10−7 m). Pharmacological analysis revealed that the DiOHF‐6‐succinamic acid derivative was the best antioxidant, possessing activity similar to DiOHF, whereas vasorelaxant activity was attenuated. This compound was able to effectively scavenge superoxide from the autoxidation of pyrogallol, preventing oxidant‐induced endothelial dysfunction. DiOHF‐6‐succinamic acid represents the first antioxidant flavonol that lacks vasorelaxant activity and in the future will enable studies to cast light on the specific biological activity required for cardioprotection.
Chemotherapy with 5‐fluorouracil and a platinum compound improves outcomes in metastatic small bowel adenocarcinoma
Authors: Overman Michael J. , Kopetz Scott , Wen Sijin , Hoff Paulo M. , Fogelman David , Morris Jeffrey , Abbruzzese James L. , Ajani Jaffer A. , Wolff Robert A. 
Published: August 2008

AbstractBACKGROUND.Metastatic small bowel adenocarcinoma (SBA) has a poor prognosis. Because of the rarity of SBA, only a few studies have evaluated the role of chemotherapy in the treatment of metastatic SBA; thus, the benefit, if any, of adding a platinum compound to fluorouracil (5‐FU) is unknown. The objective of this retrospective study was to determine whether the addition of a platinum compound to 5‐FU provided any benefit in the treatment of patients with metastatic SBA.METHODS.The authors identified 80 patients with metastatic SBA who were treated with chemotherapy at the University of Texas M. D. Anderson Cancer Center between 1978 and 2005. Response rates, progression‐free survival (PFS), and overall survival (OS) were compared between patients who received 5‐FU and a platinum compound and patients who received other chemotherapy combinations.RESULTS.The median patient age was 53 years. The primary tumor site was the jejunum in 35 patients (43%), duodenum in 30 patients (38%), ileum in 6 patients (8%), and nonspecified small bowel in 9 patients (11%). Of all 80 patients, 29 patients (36%) received 5‐FU and a platinum compound, 41 patients (51%) received 5‐FU without a platinum compound, and 10 patients (13%) received non‐5‐FU–based treatment. Compared with other chemotherapy regimens, treatment with 5‐FU and a platinum agent resulted in a higher response rate (46% vs 16% with other regimens; P = .01) and longer median PFS (8.7 months vs 3.9 months; P ≤ .01) but not better OS (14.8 months vs 12 months; P = .1). In multivariate analysis, treatment with 5‐FU and a platinum compound was a significant predictor of response (odds ratio, 4.5; 95% confidence interval [CI], 1.3‐15.8; P = .02) and PFS (hazard ratio. 0.49; 95% CI, 0.29‐0.84; P = .01) but only reached borderline significance for OS (hazard ratio, 0.63; 95% CI, 0.37‐1.07; P = .08).CONCLUSIONS.To the authors' knowledge, the current analysis represents the largest number of patients with metastatic SBA treated with chemotherapy in the literature, and the results suggested that the combination of 5‐FU and a platinum compound leads to a higher response rate and PFS compared with other chemotherapy regimes. The authors concluded that prospective investigation of platinum analogues in the treatment of SBA is warranted. Cancer 2008. © 2008 American Cancer Society.
Pyrenyl Excimers Induced by the Crystallization of POSS Moieties: Spectroscopic Studies and Sensing Applications
Authors: Bai Hua , Li Chun , Shi Gaoquan 
Published: August 2008

AbstractAn ester (PBPOSS) of 1‐pyrenebutyric acid (PBA) and 1‐(2,3‐propanediol)propoxy‐3,5,7,9,11,13,15‐isobutylpentacyclo‐[9.5.1.1(3,9).1(5,15).1(7,13)]octasiloxane (a polyhedral oligomeric silsesquioxane, POSS) is synthesized by simple one‐step esterification. Thin films of PBPOSS fabricated by the spin‐coating technique exhibit strong excimer emissions of visible light. Upon exposure to the vapours of nitroaromatic compounds, including trinitro‐ toluene and dinitrotoluene, the films show fast fluorescence quenching. The high performance of these gas sensors is due to the high excimer contents and good vapour permeability of the PBPOSS films. Spectroscopic studies indicate that the crystallization of the POSS moieties in PBPOSS films induce the formation of pyrenyl excimers.
Increased concentrations of soluble CD40 ligand may help to identify type 1 diabetic adolescents and young adults at risk for developing persistent microalbuminuria
Authors: Chiarelli F. , Giannini C. , Verrotti A. , Mezzetti A. , Mohn A. 
Published: August 2008

AbstractBackgroundRecent studies on the pathogenesis of diabetic complications have demonstrated the important role of a number of aberrantly expressed molecules acting together in the development of early diabetic microvascular complications. Soluble CD40 ligand (sCD40L) is supposed to be one of the most likely candidates for both retinopathy and nephropathy.MethodsIn January 1989, sCD40L was measured in 340 normoalbuminuric diabetic adolescents and young adults. Participants were examined at baseline and biannually thereafter. sCD40L was measured every 2 years during a 16‐year follow‐up period. sCD40L was also measured in parents.ResultsOver 16 years, 32 out of 340 patients developed persistent microalbuminuria; no patient developed overt diabetic nephropathy. The risk of developing microalbuminuria was higher in children with increased sCD40L at the beginning of the study (using 6 ng/mL as the arbitrary cut‐off value) (group A) compared with those with normal sCD40L (group B). Sex did not influence predictive value, sensitivity, or specificity. sCD40L was not significantly correlated with duration of diabetes. The percentage of offspring with both parents having sCD40L above the mean values was significantly higher in group A than in group B. The odds ratio (OR) for the occurrence of microalbuminuria after adjustment for confounding variables in patients with elevated baseline sCD40L was 4.2 (95% CI, 2.1–10.7).ConclusionsPersistently increased sCD40L levels from the onset of diabetes might help to identify those normotensive and normoalbuminuric young patients at increased risk of developing incipient nephropathy later in life. Copyright © 2008 John Wiley & Sons, Ltd.
A Theoretical Study on the Reactivity of a Rhenium Hydroxo‐Carbonyl Complex Towards β‐Lactams
Authors: Yeguas Violeta , Campomanes Pablo , López Ramón 
Published: August 2008

AbstractThe mechanism of the reaction between the complex [Re(OH)(CO)3(N2C2H4)] and azetidin‐2‐one or 3‐formylamino‐N‐sulfonatoazetidin‐2‐one was investigated by using the B3LYP density functional theory methodology in conjunction with the PCM‐UAHF model to take into account solvent effects. According to our calculations, the rate‐determining energy barrier for the azetidin‐2‐one case of 38.8 kcal mol−1, becomes 25.7 kcal mol−1 in the case of the 3‐formylamino‐N‐sulfonatoazetidin‐2‐one species. The presence of the sulfonato group is crucial for the cleavage of the β‐lactam N1–C2 bond by the Re complex thanks to the interaction of the sulfonato group with the hydroxy and bidentate ligands of the complex. This could be of interest for the synthesis of β‐amino acids and their derivatives from β‐lactams under mild conditions and in solvents of low polarity promoted by organometallic complexes. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2008)
A Ferrocene–Peptide Conjugate as a Hydrogenase Model System
Authors: de Hatten Xavier , Bothe Eberhardt , Merz Klaus , Huc Ivan , Metzler‐Nolte Nils 
Published: August 2008

AbstractThis work introduces a bis(cysteine) ligand to build a small peptidic model system of hydrogenase enzymes. Fe(C5H4CO–Cys–OMe)2 (LH2) has been employed as a chelate for an iron–carbonyl complex, which mimics two essential structural properties of the hydrogenase class of enzymes, namely the coordination of the iron–carbonyl core to peptide ligands and the presence of an electrochemical relay in spatial proximity. The treatment of LH2 with Fe3(CO)12 yields LFe2(CO)6 (3a), which is the first peptide‐coordinated iron hydrogenase active‐site model complex. Compound 3a was fully characterized spectroscopically (1H NMR, 13C NMR, IR and Mössbauer spectroscopy, mass spectrometry and elemental analysis). A single‐crystal X‐ray analysis confirms the proposed structure and reveals a staggered conformation of the Fe2(CO)6S2 core. Fourier transform infrared (FTIR) spectroelectrochemistry reveals an electronic interaction between the peptide backbone and the iron–carbonyl cluster, but not with the ferrocene subsite. The introduction of this peptidic cysteine‐based ligand into hydrogenase model chemistry helps to confirm the proposed cofactor biosynthesis and understand the electronic interplay between the metal–carbonyl active site and the protein environment in this important class of enzymes.(© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2008)
Some biophysical properties of castor oil esterified with some acid anhydrides
Authors: Saied Mona A. , Mansour Samia H. , Eweis Mohamed , El‐Sabee Maher Z. , Saad Azima L. G. , Nour Kamal N. Abdel 
Published: August 2008

AbstractA series of castor oil adducts were synthesized by esterification of castor oil with acid anhydrides: phthalic, maleic and succinic anhydrides. The chemical structure of castor oil and the prepared adducts were characterized by means of IR and 1H NMR spectroscopy. The number‐average and weight‐average molecular weights were measured by gel permeation chromatography. The electrical properties were studied through the permittivity, dielectric loss and conductivity measurements, which are considered to be in the range of electrical insulation. The electrical conductivity, which describes the ionic mobility of the systems, was found to be in the range of 10–9 to 10–12 S/cm. This indicates that castor oil and its esters could be used for antistatic applications. The viscosity η and the activation energy Eη, obtained from the dependency of viscosity on temperature using the Arrhenius equation, were found to increase with increasing molecular weight of the system. The effect of different concentrations of castor oil and its esters on the growth activities of the sugar beet pathogens R. solani and S. rolfsii was studied through the determination of percent germination, average length of hyphal extensions, dry mass yield and the production of sclerotia. The obtained data indicate that the esterification of castor oil with anhydrides improves the antifungal activity.
Kinetic study for the development of an accelerated oxidative stability test to estimate virgin olive oil potential shelf life
Authors: Mancebo‐Campos Vanessa , Fregapane Giuseppe , Desamparados Salvador María 
Published: August 2008

AbstractThis study proposes an accelerated test performed at mild temperature (40–60 °C) to measure oxidative stability and estimate the potential shelf life of extra‐virgin olive oil (EVOO). The kinetic behavior of normalized oxidation indices (PV, K232 and K270) and the oxidizing substrate [unsaturated fatty acids (UFA)] during storage of different virgin olive oil samples in darkness and at different temperatures (25–60 °C) is reported for the first time. PV and K232 followed an apparent pseudo zero‐order kinetics (R2 >0.951) at all the experimental temperatures in all samples, whereas the evolution of K270 apparently better fitted a pseudo first‐order kinetics (R2 >0.926). The temperature‐dependent kinetics of the oxidation indices and the UFA were well described by the linear Arrhenius equation between 25 and 60 °C (0.960< R2 <0.999, p <0.05). The best correlation between loss of PUFA and increase of oxidation product indices was K232 (0.581< R2 <0.924). The time required to reach the upper limits for PV, K232 and K270 established for the EVOO category in the current EU legislation correlated well with temperature using a potential equation, making it possible to set up an accelerated stability test at temperatures below 60 °C to estimate the potential shelf life under normal storage temperature conditions.