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| Registros recuperados: 603 | |
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| Xuri Wu; Nan Liu; Yunmian He; Yijun Chen. |
| Various ketoreductases exclusively participate in all common biological events, and they are a class of important biocatalysts for the production of chiral alcohols. While many types of ketoreductase have been extensively studied and their functions, properties and utilities have been well known, the capability of stereoselectively reducing two carbonyl groups in the same diketohexanoate ester molecule to form a dihydroxy product by a single ketoreductase has not been evidently characterized. Here we show that a unique and novel enzyme, diketoreductase, was cloned from Acinetobacter baylyi, heterogeneously expressed in _Escherichia coli_ and purified to homogeneity. The diketoreductase is up to 78% homologous to bacterial 3-hydroxyacyl coenzyme-A... |
| Tipo: Manuscript |
Palavras-chave: Biotechnology; Chemistry; Microbiology. |
| Ano: 2008 |
URL: http://precedings.nature.com/documents/1697/version/1 |
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| Xuri Wu; Nan Liu; Yunmian He; Yijun Chen. |
| Various ketoreductases exclusively participate in all common biological events, and they are a class of important biocatalysts for the production of chiral alcohols. While many types of ketoreductase have been extensively studied and their functions, properties and utilities have been well known, the capability of stereoselectively reducing two carbonyl groups in the same diketohexanoate ester molecule to form a dihydroxy product by a single ketoreductase has not been evidently characterized. Here we show that a unique and novel enzyme, diketoreductase, was cloned from Acinetobacter baylyi, heterogeneously expressed in _Escherichia coli_ and purified to homogeneity. The diketoreductase is up to 78% homologous to bacterial 3-hydroxyacyl coenzyme-A... |
| Tipo: Manuscript |
Palavras-chave: Biotechnology; Chemistry; Microbiology. |
| Ano: 2010 |
URL: http://precedings.nature.com/documents/1697/version/2 |
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| Sierra Rayne; Kaya Forest. |
| New experimental data is available in the literature regarding the octanol-water distribution behavior of representative straight chain perfluoroalkyl carboxylate (PFCA) and sulfonate (PFSA) congeners. The current study provides the first investigation into the predictive ability of various software programs for estimating the corresponding octanol-water partitioning (log P) and distribution (log D) constants of PFCAs and PFSAs. Wide predictive variation was found within and between the various methods. Several programs were able to accurately estimate the log P/D fragmental contributions of a -CF~2~- group for PFCAs, as well as the associated Gibbs free energies for partitioning into octanol from water due to the hydrophobic character of the... |
| Tipo: Manuscript |
Palavras-chave: Chemistry; Earth & Environment. |
| Ano: 2009 |
URL: http://precedings.nature.com/documents/3282/version/1 |
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| Sierra Rayne; Kaya Forest. |
| New experimental data is available in the literature regarding the octanol-water distribution behavior of representative straight chain perfluoroalkyl carboxylate (PFCA) and sulfonate (PFSA) congeners. The current study provides the first investigation into the predictive ability of various software programs for estimating the corresponding octanol-water partitioning (log P) and distribution (log D) constants of PFCAs and PFSAs. Wide predictive variation was found within and between the various methods. Several programs were able to accurately estimate the log P/D fragmental contributions of a -CF~2~- group for PFCAs, as well as the associated Gibbs free energies for partitioning into octanol from water due to the hydrophobic character of the... |
| Tipo: Manuscript |
Palavras-chave: Chemistry; Earth & Environment. |
| Ano: 2009 |
URL: http://precedings.nature.com/documents/3282/version/2 |
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| Sierra Rayne; Kaya Forest. |
| Gas phase enthalpies of formation at 298.15 and 1 atm (Δ~f~H~(g),298K~) were calculated using the atomization approach at the G4MP2 composite method level of theory for 86 polyaromatic hydrocarbons (PAHs) and other C~10~ through C~20~ unsaturated hydrocarbons. Where available, good agreement with prior experimental data and/or high level theoretical estimates was obtained. Linear regressions between semiempirical MNDO, MNDO-d, AM1, PM3, RM1, and PM6 estimated Δ~f~H~(g),298K~ and the corresponding G4MP2 values were employed to obtain G4MP2 corrected semiempirical Δ~f~H~(g),298K~ for a suite of 156 C~11~ through C~42~ unsaturated hydrocarbons and PAHs. |
| Tipo: Manuscript |
Palavras-chave: Chemistry. |
| Ano: 2011 |
URL: http://precedings.nature.com/documents/6450/version/1 |
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| Sierra Rayne; Kaya Forest. |
| Enthalpies of formation (Δ~f~H~(g)~) at 298.15 K and 0 K were calculated for various potential high energy materials (HEMs) using the high-level Gaussian-4 (G4) and W1BD methods with the atomization approach. Where prior high level estimates are available in the literature, the G4 and W1BD Δ~f~H~(g)~ are in good agreement. The results presented herein represent the highest level calculations performed to date on this suite of HEMs. These G4/W1BD enthalpies of formation should provide utility among the research community as a benchmark set of values against which to assess future experimental and/or theoretical data. |
| Tipo: Manuscript |
Palavras-chave: Chemistry. |
| Ano: 2011 |
URL: http://precedings.nature.com/documents/6461/version/1 |
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| D. V. Williams; Bipasha Barua; Niels H. Andersen. |
| The effects of alanine substitutions in each helical segment of the structure, and Gly to D-Ala mutations at sites where glycines have positive phi angles in the Trp-cage miniprotein are reported. The effects of the stabilizing mutation were additive, yielding a 20-residue construct (Tm = 83^o^C). Gly to L-Ala substitutions were uniformly destabilizing ([DELTA][DELTA]G~F~ > 11 kJ/mol): the preference for a D-Ala can be as large as 16 kJ/mol. Glycine to D-Ala mutations are validated as a strategy for the design of hyperstable miniprotein scaffolds suitable for stereospecific pharmacophore display. |
| Tipo: Manuscript |
Palavras-chave: Chemistry. |
| Ano: 2008 |
URL: http://precedings.nature.com/documents/2074/version/1 |
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| Saheeb Ahmed Kayani. |
| In this research report, X-ray diffraction (XRD) and X-ray fluorescence (XRF) spectrometry have been used to determine the mineralogical and elemental composition of a stone sample recovered from a location near village Lehri in district Jhelum, Pakistan. The test data is compared with previous findings (as reported in literature and included in references) to identify this sample stone as part of a prehistoric meteorite ablation debris.
Further to this, carbon content of a specimen of the meteorite debris has been determined through combustion analysis. This carbon abundance has been compared with carbon wt% value of a certain type of meteorites to establish the origin and nature of the parent body of this particular meteorite debris. |
| Tipo: Manuscript |
Palavras-chave: Chemistry; Earth & Environment. |
| Ano: 2010 |
URL: http://precedings.nature.com/documents/5450/version/1 |
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| Domenico P. R. O. F. Fuoco. |
| In order to study and develop an economic solution to environmental pollution in water, a wide variety of materials were investigated. Natural zeolites emerge from that research as the best in class of this category. Zeolites are natural materials relatively abundant and non biodegradable, economic and good to perform processes of environmental remediation. This paper contains a full description of a new method to characterize superficial properties of natural zeolites of exotic provenience (Caribbean Islets) with atomic force microscopy (AFM). AFM works with the optical microscope simplicity and the high resolution typical of a transmission electron microscope (TEM). Structural information of mesoporous material is obtained using scanning and transmission... |
| Tipo: Manuscript |
Palavras-chave: Chemistry. |
| Ano: 2012 |
URL: http://precedings.nature.com/documents/6828/version/1 |
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| Jian-She Yang; Bo-Zhang Yu; Wen-Xin Li. |
| Radiotherapy plays a very important role in cancer treatment. Radiosensitizers have been widely used to enhance the radiosensitivity of cancer cells at given radiations. Here we fabricate multi-walled carbon nanotubes with ammonium persulfate, and get very short samples with 30-50 nanometer length. Cell viability assay show that f-WCNTs induce cell death significantly. We hypothesize that free radicals originated from hydroxyl and carbonyl groups on the surface of f-WCNTs lead cell damage. |
| Tipo: Manuscript |
Palavras-chave: Biotechnology; Cancer; Chemistry. |
| Ano: 2007 |
URL: http://precedings.nature.com/documents/1421/version/1 |
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| Rodrick Wallace. |
| A spontaneous symmetry breaking argument is applied to the problem of protein folding, via a Rate Distortion analysis of the relation between genome coding and the final condensation of the protein molten globule. In the 'energy' picture, the average distortion between codon message and protein structure, under constraints driven by evolutionary selection, serves as a temperature analog, so that low values limit the possible distribution of protein forms, producing the canonical folding funnel. A dual 'developmental' perspective sees the rate distortion function itself as the temperature analog, and permits incorporation of chaperons or toxic exposures as catalysts, driving the system to different possible outcomes or... |
| Tipo: Manuscript |
Palavras-chave: Chemistry; Molecular Cell Biology; Bioinformatics. |
| Ano: 2010 |
URL: http://precedings.nature.com/documents/4280/version/2 |
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| Ilie Fishtik. |
| Background: Flux balance and network-based pathway analyses are theoretical tools aimed to find optimal steady state flux distributions in a metabolic network subject to additional constraints on the rates of the reaction steps. Although these methods are mathematically accurate, there are several physicochemical and computational aspects that are questionable and misleading. In particular, it is well known that the flux balance analysis may result in multiple flux distributions for the same objective function. 

Results: The flux balance and network-based pathway analyses are reformulated in terms of reaction routes (RRs), a theoretical framework that has been developed by Horiuti over 50 years ago. Not only does the... |
| Tipo: Manuscript |
Palavras-chave: Biotechnology; Chemistry; Bioinformatics. |
| Ano: 2009 |
URL: http://precedings.nature.com/documents/2788/version/1 |
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| Sosale Chandrasekhar. |
| It is argued that the Carnot cycle is a highly inaccurate representation of a steam engine, and that the net work obtained in its operation would be zero. This conclusion is also supported by an elementary mathematical approach, which re-examines the work done in the four individual steps of the cycle. An important consequence of this is that the concept of entropy, originally proposed on the basis of the Carnot theorem, may not be a fundamentally valid thermodynamic quantity. Also, the experimental approach generally adopted in the determination of entropy is questionable, and the importance of increasing randomness in natural processes not universally valid. In fact, a more viable basis, at least vis-à-vis chemical reactions, appears to be the... |
| Tipo: Manuscript |
Palavras-chave: Chemistry. |
| Ano: 2008 |
URL: http://precedings.nature.com/documents/1852/version/1 |
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| Nigel Wheatley. |
| The conventional definition of amount of substance _n_ is as a quantity proportional to number of entities _N_. This implies that n is discrete for small _N_ while _n_ is considered to be continuous at the macroscopic scale, leading to a sorites paradox. A practical criterion is proposed for distinguishing between amount of substance and number of entities, and the implications for the conventional definition of amount of substance are discussed. |
| Tipo: Manuscript |
Palavras-chave: Chemistry. |
| Ano: 2011 |
URL: http://precedings.nature.com/documents/5568/version/1 |
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| Registros recuperados: 603 | |
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