102,366 research outputs found
COMPARISON OF 4 PULSE SEQUENCES FOR THE ROUTINE APPLICATION OF PROTON CARBON SHIFT CORRELATION
No full textSpeeding-up exchange-mediated saturation transfer experiments by Fourier transform.
No full textProtein motions over various time scales are crucial for protein function. NMR relaxation dispersion experiments play a key role in explaining these motions. However, the study of slow conformational changes with lowly populated states remained elusive. The recently developed exchange-mediated saturation transfer experiments allow the detection and characterization of such motions, but require extensive measurement time. Here we show that, by making use of Fourier transform, the total acquisition time required to measure an exchange-mediated saturation transfer profile can be reduced by twofold in case that one applies linear prediction. In addition, we demonstrate that the analytical solution for R1ρ experiments can be used for fitting the exchange-mediated saturation transfer profile. Furthermore, we show that simultaneous analysis of exchange-mediated saturation transfer profiles with two different radio-frequency field strengths is required for accurate and precise characterization of the exchange process and the exchanging states
NOVEL STRATEGIES FOR SENSITIVITY ENHANCEMENT IN HETERONUCLEAR MULTIDIMENSIONAL NMR EXPERIMENTS EMPLOYING PULSED-FIELD GRADIENTS
No full textNovel strategies for sensitivity enhancement in heteronuclear multidimensional spectra are introduced and evaluated theoretically and experimentally. It is shown that in 3D sequences employing several Coherence Order Selective Coherence Transfer (COS-CT) steps, enhancement factors of up to 2 can be achieved. This sensitivity enhancement is compatible with the use of heteronuclear gradient echoes, yielding spectra with excellent water suppression. HNCO and HCCH-TOCSY pulse sequences are proposed and experimentally tested. These experiments employ recently developed coherence order selective pulse sequence elements, e.g., COS-INEPT and planar TOCSY for antiphase to in-phase transfers 2F(-)S(2) S- or in-phase COS-CT for in-phase transfer F- S-, and the well-known isotropic TOCSY mixing sequences for homo- and heteronuclear in-phase transfer
Magnetically Induced Alignment of Natural Products for Stereochemical Structure Determination via NMR
No full textAnisotropic NMR has gained increasing popularity to determine the structure and specifically the configuration of small, flexible, non‐crystallizable molecules. However, it suffers from the necessity to dissolve the analyte in special media such as liquid crystals or polymer gels. Generally, small degrees of alignment are also caused by an anisotropic magnetic susceptibility of the molecule, for example, induced by aromatic moieties. For this mechanism, the alignment can be predicted via density functional theory. Here we show that both residual dipolar couplings and residual chemical shift anisotropies can be acquired from natural products without special sample preparation using magnetically induced alignment. On the two examples of the novel natural product gymnochrome G and the alkaloid strychnine, these data, together with the predicted alignment, yield the correct configuration with high certainty
Measurement of thrombopoietic levels: clinical and biological relationships
No full textPlatelet production is primarily regulated by the thrombopoietic cytokine thrombopoietin (TPO), In most cases thrombopoietin serum levels are determined by the rate of c-mpl receptor-mediated degradation after TPO uptake into platelets and megakaryocytes. The contribution of increased TPO protein synthesis by a translational mechanism was recently appreciated as the cause for hereditary thrombocythemia and will have to be elucidated in other conditions of thrombocytosis in association with increased TPO levels. (C) 2000 Lippincott Williams & Wilkins, Inc
CONFORMATIONAL-ANALYSIS OF AMINO-ACID SIDE-CHAINS IN PEPTIDES BY QUANTITATIVE-EVALUATION OF CROSS-PEAKS IN COLOC-SPECTRA
No full textLeukemia- and lymphoma-associated genetic aberrations in healthy individuals
No full textIn peripheral blood of at least 50% of healthy individuals, the translocations t(9;22) BCR/ABL, t(14;18) IgH/BCL-2, t(2;5) NPM-ALK and MLL duplications, which characterize chronic myelogenous leukemia and acute lymphoblastic leukemia, follicular lymphoma, anaplastic large cell lymphoma, and acute myelogenous leukemia, respectively, are detectable by sensitive polymerase chain reaction (PCR). No structural differences between these aberrations in normal or disturbed hematopoiesis are apparent. While the total count of t(9;22)- and t(14;18)-positive cells does not exceed 10(4), those with MLL duplications are more frequent and account for approximately 10(7) cells in the total blood pool. t(14;18)-positive cells seem to be immortalized, but the biological consequences of the other aberrations in positive healthy persons have not been studied in detail. Due to the high frequency of positive individuals, most of them will not suffer from the correspondent leukemia or lymphoma, and criteria for subgroups that may be at a higher risk remain to be determined. Most likely, the number of genetic aberrations in healthy individuals, which so far are only associated with hematopoietic disorders, will increase in the near future
Bibliographie Hilarion G. Petzold 1958 – 2009 mit Anhang als Einführung
No full textDieses Archiv enthält die Gesamtbibliographie der Werke des Autors nebst einiger Texte „Über H. G. Petzold“ im Schlussteil der Bibliographie sowie einen Anhang mit einer Einführung in die Architektur des Werkes in seinem wissenslogischen Aufbau als Ausarbeitung seines „Tree of Science Modells“ (2007).This archive contains the complete bibliography of the author and some texts about H. G. Petzold, moreover an epilogue with an introduction to the architecture of the works in its epistemological structure and composition and as an elaborations of Petzold’s „Tree of Science Modell (2007).https://www.fpi-publikation.de/polyloge/01-2009-petzold-h-g-gesamtbibliographie-h-g-petzold-1958-2009-updating-november2009/peerReviewedpublishedVersio
Dispelling the Myths Behind First-author Citation Counts
No full textWe conducted a full-scale evaluative citation analysis study of scholars in the XML research field to explore just how different from each other author rankings resulting from different citation counting methods actually are, and to demonstrate the capability of emerging data and tools on the Web in supporting more realistic citation counting methods. Our results contest some common arguments for the continued
use of first-author citation counts in the evaluation of scholars, such as high correlations between author rankings by first-author citation counts and other citation
counting methods, and high costs of using more realistic citation counting methods that are not well-supported by the ISI databases. It is argued that increasingly available digital full text research papers make it possible for citation analysis studies to go beyond what the ISI databases have directly supported and to employ more
sophisticated methods
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