1,199 research outputs found
Accurate measurement of ^{13}C - ^{15}N distances with solid-state NMR
Solid-state NMR technique for measureing distances between hetero-nuclei in
static powder samples is described. It is based on a two-dimensional
single-echo scheme enhanced with adiabatic cross-polarization. As an example,
the results for intra-molecular distances in -crystalline form of
glycine are presented. The measured NMR distances ^13 C(2) - ^15 N and ^13 C(1)
- ^15 N are 1.496 0.002 \AA and 2.50 0.02 \AA, respectively.Comment: 12 page
On the Cost-of-Capital Rate under Incomplete Market Valuation
In this paper we discuss the concept of the cost-of-capital (CoC) rate for an insurance company as an equilibrium in the economic triangle of policyholders, shareholders, and the regulator. This provides a possible rationalization and an economic foundation for a quantity that is widely used in practice but whose value is typically neither technically nor economically well justified. We show how it can be well founded in such a triangular equilibrium. Under a simple one-period model and a valuation procedure of a two-price economy for illiquid assets we provide a corresponding economic-theoretical quantification for the CoC rate. The resulting rates are illustrated by a number of concrete numerical examples.ISSN:0022-4367ISSN:1539-697
Antarctic and Arctic populations of the ciliate Euplotes nobilii show common pheromone-mediated cell-cell signaling and cross-mating.
Wild-type strains of the protozoan ciliate Euplotes collected from different locations on the coasts of Antarctica, Tierra del Fuego and the Arctic were taxonomically identified as the morpho-species Euplotes nobilii, based on morphometric and phylogenetic analyses. Subsequent studies of their sexual interactions revealed that mating combinations of Antarctic and Arctic strains form stable
pairs of conjugant cells. These conjugant pairs were isolated and
shown to complete mutual gene exchange and cross-fertilization. The biological significance of this finding was further substantiated by demonstrating that close homology exists among the threedimensional structures determined by NMR of the water-borne signaling pheromones that are constitutively secreted into the extracellular space by these interbreeding strains, in which these molecules trigger the switch between the growth stage and the sexual stage of the life cycle. The fact that Antarctic and Arctic E. nobilii populations share the same gene pool and belong to the same biological species provides new support to the biogeographic
model of global distribution of eukaryotic microorganisms, which had so far been based exclusively on studies of morphological and phylogenetic taxonomy
MetaboLab - advanced NMR data processing and analysis for metabolomics
Background\ud
Despite wide-spread use of Nuclear Magnetic Resonance (NMR) in metabolomics for the analysis of biological samples there is a lack of graphically driven, publicly available software to process large one and two-dimensional NMR data sets for statistical analysis.\ud
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Results\ud
Here we present MetaboLab, a MATLAB based software package that facilitates NMR data processing by providing automated algorithms for processing series of spectra in a reproducible fashion. A graphical user interface provides easy access to all steps of data processing via a script builder to generate MATLAB scripts, providing an option to alter code manually. The analysis of two-dimensional spectra (1H,13C-HSQC spectra) is facilitated by the use of a spectral library derived from publicly available databases which can be extended readily. The software allows to display specific metabolites in small regions of interest where signals can be picked. To facilitate the analysis of series of two-dimensional spectra, different spectra can be overlaid and assignments can be transferred between spectra. The software includes mechanisms to account for overlapping signals by highlighting neighboring and ambiguous assignments.\ud
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Conclusions\ud
The MetaboLab software is an integrated software package for NMR data processing and analysis, closely linked to the previously developed NMRLab software. It includes tools for batch processing and gives access to a wealth of algorithms available in the MATLAB framework. Algorithms within MetaboLab help to optimize the flow of metabolomics data preparation for statistical analysis. The combination of an intuitive graphical user interface along with advanced data processing algorithms facilitates the use of MetaboLab in a broader metabolomics context.\ud
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OR3 operator of bacteriophage lambda in a 23 base-pair DNA fragment: sequence-specific 1H NMR assignments for the non-labile protons and comparison with the isolated 17 base-pair operator
Sequence-specific 1H NMR assignments are presented for a non-selfcomplementary 23-base-pair DNA duplex of molecular weight 15,000 daltons, containing the OR3 repressor binding site of bacteriophage lambda as the central core. The NMR techniques used were mainly phase-sensitive two-dimensional NOE and 2Q spectroscopy, the latter to overcome overlap problems within the spectral region of the deoxyribose spin-systems. Direct sequential NOE connectivities are observed between adenine 2 H and deoxyribose 1' protons. We propose the use of these connectivities as a check of the assignments of C1' and A2 protons, which have independently been derived via other assignment pathways
Application of 13C(ω1)-half-filtered [1H,1H]-NOESY for studies of a complex formed between DNA and a 13C-labeled minor-groove-binding drug
AbstractThe complex formed between the anticancer drug 4-[p-[p-(4-quinolylamino)benzamido]anilino]pyridine (SN 6999) and the decadeoxyribonucleoside nonaphosphate d-(GCATTAATGC)2 was investigated using two-dimensional nuclear Overhauser enhancement spectroscopy (NOESY) with a 13C(ω1)-half-filter. The two quaternary methyl groups in SN 6999 had been labeled with 13C for these experiments. The simplified subspectra of [1H,1H]-NOESY obtained with this procedure greatly facilitate the identification and assignment of intermolecular NOEs. Quite generally, the combined use of isotope labeling and heteronuclear filters in [1H,1H]-NOESY provides an improved experimental basis for structural studies of drug/ DNA complexes
Variations in the in vivo P-31 MR spectra of the developing human brain during postnatal life. Work in progress
With use of a modified surface coil technique, the authors recorded phosphorus-31 magnetic resonance (MR) spectra of the brains of 40 neonates and infants (48 examinations) ranging from 33 weeks postconceptional age to 6 years of age. Signals of phosphorus metabolites were collected in the frontotemporal region of the brain, and various P-31 MR spectral variables were compared at different times during postnatal life. The ratio of the phosphomonoester signal to the phosphodiester signal, which is related to phospholipid synthesis, decreases within the first 6 months of life; during the same time period, the ratio of the phosphocreatine (PCr) signal to the beta-adenosine triphosphate (ATP) signal increases. In addition, a difference was observed between the areas under the alpha- and beta-ATP peaks. This difference increases with age and correlates with the PCr/beta-ATP signal ratio. The variation of the alpha-ATP peak with age might be explained by overlap of the signals of nicotinamide adenine dinucleotide (NAD) and alpha-ATP
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