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971.
Predominant Information Quality Scheme for the Essential Amino Acids: An Information‐Theoretical Analysis 下载免费PDF全文
Prof. Rodolfo O. Esquivel Dr. Moyocoyani Molina‐Espíritu Prof. Sheila López‐Rosa Prof. Catalina Soriano‐Correa Prof. Carolina Barrientos‐Salcedo Prof. Miroslav Kohout Prof. Jesús S. Dehesa 《Chemphyschem》2015,16(12):2571-2581
In this work we undertake a pioneer information‐theoretical analysis of 18 selected amino acids extracted from a natural protein, bacteriorhodopsin (1C3W). The conformational structures of each amino acid are analyzed by use of various quantum chemistry methodologies at high levels of theory: HF, M062X and CISD(Full). The Shannon entropy, Fisher information and disequilibrium are determined to grasp the spatial spreading features of delocalizability, order and uniformity of the optimized structures. These three entropic measures uniquely characterize all amino acids through a predominant information‐theoretic quality scheme (PIQS), which gathers all chemical families by means of three major spreading features: delocalization, narrowness and uniformity. This scheme recognizes four major chemical families: aliphatic (delocalized), aromatic (delocalized), electro‐attractive (narrowed) and tiny (uniform). All chemical families recognized by the existing energy‐based classifications are embraced by this entropic scheme. Finally, novel chemical patterns are shown in the information planes associated with the PIQS entropic measures. 相似文献
972.
Dr. Carolina Fontana Prof. Dr. Andrej Weintraub Prof. Dr. Göran Widmalm 《ChemistryOpen》2015,4(1):47-55
Shiga-toxin-producing Escherichia coli (STEC) is an important pathogen associated to food-borne infection in humans; strains of E. coli O181, isolated from human cases of diarrhea, have been classified as belonging to this pathotype. Herein, the structure of the O-antigen polysaccharide (PS) from E. coli O181 has been investigated. The sugar analysis showed quinovosamine (QuiN), glucosamine (GlcN), galactosamine (GalN), and glucose (Glc) as major components. Analysis of the high-resolution mass spectrum of the oligosaccharide (OS), obtained by dephosphorylation of the O-deacetylated PS with aqueous 48 % hydrofluoric acid, revealed a pentasaccharide composed of two QuiNAc, one GlcNAc, one GalNAc, and one Glc residue. The 1H and 13C NMR chemical shift assignments of the OS were carried out using 1 D and 2 D NMR experiments, and the OS was sequenced using a combination of tandem mass spectrometry (MS/MS) data and NMR 13C NMR glycosylation shifts. The structure of the native PS was determined using NMR spectroscopy, and it consists of branched pentasaccharide repeating units joined by phosphodiester linkages: →4)[α-l-QuipNAc-(1→3)]-α-d-GalpNAc6Ac-(1→6)-α-d-Glcp-(1→P-4)-α-l-QuipNAc-(1→3)-β-d-GlcpNAc-(1→; the O-acetyl groups represent 0.4 equivalents per repeating unit. Both the OS and PSs exhibit rare conformational behavior since two of the five anomeric proton resonances could only be observed at an elevated temperature. 相似文献
973.
Paving the Way to Novel Phosphorus‐Based Architectures: A Noncatalyzed Protocol to Access Six‐Membered Heterocycles 下载免费PDF全文
Dr. Carlos Romero‐Nieto Alicia López‐Andarias Dr. Carolina Egler‐Lucas Florian Gebert Jens‐Peter Neus Oliver Pilgram 《Angewandte Chemie (International ed. in English)》2015,54(52):15872-15875
Phosphorus‐based heterocycles provide access to materials with properties that are inaccessible from all‐carbon architectures. The unique hybridization of phosphorus gives rise to electron‐accepting capacities, a large variety of coordination reactions, and the possibility of controlling the electronic properties through phosphorus postfunctionalization. Herein, we describe a new noncatalyzed synthetic protocol to prepare fused six‐membered phosphorus heterocycles. In particular, we report the synthesis of novel phosphaphenalenes. These fused systems exhibit the benefits of both five‐ and six‐membered phosphorus heterocycles and enable a series of versatile postfunctionalization reactions. This work thus opens up new horizons in the field of conjugated materials. 相似文献
974.
Results in Mathematics - We consider continuous solutions $${f : \mathbb{R}_{+} \rightarrow \mathbb{R}_{+}=(0,\infty )}$$ of the functional equation $${f(xf(x))=\varphi (f(x))}$$ where... 相似文献
975.
Simeon Reich 《Applicable analysis》2013,92(4):349-352
We prove a convergence theorem for an implicit iterative scheme and then apply it to an explicit one. 相似文献
976.
Carolina Cândida de Queiroz Brito-Cunha Ivan Torres Nicolau de Campos Fabrícia Paula de Faria Luiz Artur Mendes Bataus 《Applied biochemistry and biotechnology》2013,170(3):598-608
Xylanases have raised interest because of their potential applications in various industrial fields, including the pulp and paper industries, bioethanol production, and the feed industry. In bioethanol production from lignocellulosic compounds, xylanase can improve the hydrolysis of cellulose into fermentable sugars, since the xylan restricts the cellulases from acting efficiently. In this work, a new thermophilic Streptomyces sp. was selected for its ability to produce xylanase. Carbon source selection is an important factor in the production of hemicellulases. The highest activity was obtained when Streptomyces sp. I3 was grown in the presence of wheat bran. Xylanase activity was partially characterized concerning the effect of pH and temperature on activity and thermostability, and the effects of different metal ions were also tested. The pH and temperature profile showed optimal activity at pH 6.0/70 °C. Zymogram analysis showed multiple xylanases (39, 21, 18, and 17 kDa). Xylanases studied in this work are thermophilic, thermostable, and active in a wide pH range; they have potential to be used in the development of new processes of biotechnological interest. 相似文献
977.
Andreas D. Merrem Frank G. Zöllner Marcel Reich Arvid Lundervold Jarle Rorvik Lothar R. Schad 《Magnetic resonance imaging》2013
Kidney function can be accessed by dynamic contrast-enhanced magnetic resonance imaging (DCE-MRI) measurements which yield spatially resolved maps of physiological parameters like perfusion or filtration. The motion of the kidneys during the scan is a dominant limitation of the measurement quality, and image registration is necessary for accurate quantification. We analyzed the feasibility of applying an algorithm, originally developed for multimodal registration, to kidney perfusion time series. The algorithm uses a variational calculation scheme to align the images. In four out of five data sets, kidney motion could be reduced to below the spatial resolution of the images of 1.6 mm while preserving the enhancement pattern of kidney perfusion. Fitting a pharmacokinetic model to the data showed an average reduction of the Akaike fit error of 10% for the registered data, suggesting more stable parameters. We conclude that this image registration algorithm is feasible for correcting kidney motion in renal DCE-MRI. 相似文献
978.
H. Kreis W. Baldin E. Laves Frédéric Seiler Robert Heuss Rudolf Hefelmann R. Wollny Carl Zeiss J. H. Annacker und Edgar Reich 《Fresenius' Journal of Analytical Chemistry》1895,34(1):474-479
Ohne Zusammenfassung 相似文献
979.
We study holomorphic solutions f of the generalized Dhombres equation f(zf(z))=φ(f(z)), z∈C, where φ is in the class E of entire functions. We show, that there is a nowhere dense set E0⊂E such that for every φ∈E?E0, any solution f vanishes at 0 and hence, satisfies the conditions for local analytic solutions with fixed point 0 from our recent paper. Consequently, we are able to provide a characterization of solutions in the typical case where φ∈E?E0. We also show that for polynomial φ any holomorphic solution on C?{0} can be extended to the whole of C. Using this, in special cases like φ(z)=zk+1, k∈N, we can provide a characterization of the analytic solutions in C. 相似文献
980.