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911.
Modifying the 5′‐Cap for Click Reactions of Eukaryotic mRNA and To Tune Translation Efficiency in Living Cells
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Josephin M. Holstein Lea Anhäuser Prof. Dr. Andrea Rentmeister 《Angewandte Chemie (International ed. in English)》2016,55(36):10899-10903
The 5′‐cap is a hallmark of eukaryotic mRNAs and plays fundamental roles in RNA metabolism, ranging from quality control to export and translation. Modifying the 5′‐cap may thus enable modulation of the underlying processes and investigation or tuning of several biological functions. A straightforward approach is presented for the efficient production of a range of N7‐modified caps based on the highly promiscuous methyltransferase Ecm1. We show that these, as well as N2‐modified 5′‐caps, can be used to tune translation of the respective mRNAs both in vitro and in cells. Appropriate modifications allow subsequent bioorthogonal chemistry, as demonstrated by intracellular live‐cell labeling of a target mRNA. The efficient and versatile N7 manipulation of the mRNA cap makes mRNAs amenable to both modulation of their biological function and intracellular labeling, and represents a valuable addition to the chemical biology toolbox. 相似文献
912.
Laboratory experiments are useful for estimating the carbon and nitrogen isotope discrimination factors and turnover rates that are critical for drawing field-based inferences on consumer diets using stable isotopes. Although the utility of these discrimination factors is widely recognized, work in terrestrial systems has largely been limited to studies involving mammals and birds. In contrast, scant attention has been paid to the application of isotopic techniques to reptiles, despite their broad diversity in terms of numbers of species as well as their trophic roles. Here we estimate carbon and nitrogen isotope discrimination factors and turnover for the tree lizard (Urosaurus ornatus) using a diet-switch experiment. Lizards were collected from a C4-dominated grassland and then switched to C3-based diet (crickets) in the laboratory. We estimated discrimination by lizard claw tissue as Δ13C?=?1.2?±?0.1?‰ for carbon and Δ15N?=?0.7?±?0.1?‰ (mean?±?1 SE) for nitrogen, with 95?% turnover occurring after ~15.5 days. These estimates should be appropriate for use in trophic studies of U. ornatus, and possibly other related small-bodied insectivorous lizards. 相似文献
913.
Vasily A. Vavilin Sergey V. Rytov Natalia Shim Carsten Vogt 《Isotopes in environmental and health studies》2016,52(3):185-202
The non-linear dynamics of stable carbon and hydrogen isotope signatures during methane oxidation by the methanotrophic bacteria Methylosinus sporium strain 5 (NCIMB 11126) and Methylocaldum gracile strain 14 L (NCIMB 11912) under copper-rich (8.9 µM Cu2+), copper-limited (0.3 µM Cu2+) or copper-regular (1.1 µM Cu2+) conditions has been described mathematically. The model was calibrated by experimental data of methane quantities and carbon and hydrogen isotope signatures of methane measured previously in laboratory microcosms reported by Feisthauer et al. [1] M. gracile initially oxidizes methane by a particulate methane monooxygenase and assimilates formaldehyde via the ribulose monophosphate pathway, whereas M. sporium expresses a soluble methane monooxygenase under copper-limited conditions and uses the serine pathway for carbon assimilation. The model shows that during methane solubilization dominant carbon and hydrogen isotope fractionation occurs. An increase of biomass due to growth of methanotrophs causes an increase of particulate or soluble monooxygenase that, in turn, decreases soluble methane concentration intensifying methane solubilization. The specific maximum rate of methane oxidation υm was proved to be equal to 4.0 and 1.3 mM mM?1 h?1 for M. sporium under copper-rich and copper-limited conditions, respectively, and 0.5 mM mM?1 h?1 for M. gracile. The model shows that methane oxidation cannot be described by traditional first-order kinetics. The kinetic isotope fractionation ceases when methane concentrations decrease close to the threshold value. Applicability of the non-linear model was confirmed by dynamics of carbon isotope signature for carbon dioxide that was depleted and later enriched in 13C. Contrasting to the common Rayleigh linear graph, the dynamic curves allow identifying inappropriate isotope data due to inaccurate substrate concentration analyses. The non-linear model pretty adequately described experimental data presented in the two-dimensional plot of hydrogen versus carbon stable isotope signatures. 相似文献
914.
Congjian Sun Yaning Chen Weihong Li Randy L. Stotler Yongqing Zhang 《Isotopes in environmental and health studies》2016,52(3):281-297
By using 233 isotope samples, we investigated the spatial and temporal variations of δ18O and δ2H in precipitation and surface water, and the contribution of different water sources in the rivers within the Tarim River Basin (TRB), which receives snow/glacier meltwater, groundwater, and rainfall. Our study revealed a similar seasonal pattern of precipitation δ18O and δ2H at both the north and south edges of the basin, indicating the dominant effect of westerly air masses in the summer and the combined influence of westerly and polar air masses during the winter, although the southern part showed more complex precipitation processes in the summer. River water in the basin has relatively large temporal variations in both δ18O and δ2H showing a distinct seasonal pattern with lower isotope values in May than in September. Higher d-excess values throughout the year in the Aksu river and the Tizinafu river suggest that water may be intensively recycled in the mountains of the TRB. Based on isotopic hydrograph separation, we found that groundwater is the main water source that discharges the entire basin although individual rivers vary. 相似文献
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919.
Determination of lead in blood by laser ablation ICP-TOF-MS analysis of blood spotted and dried on filter paper: a feasibility study 总被引:1,自引:0,他引:1
Cizdziel JV 《Analytical and bioanalytical chemistry》2007,388(3):603-611
Screening programs for pediatric lead (Pb) poisoning routinely collect blood by finger stick onto specially designed filter
paper (FP) for subsequent laboratory testing. Here, laser ablation inductively coupled plasma time-of-flight mass spectrometry
is evaluated as a novel method for the determination of Pb in blood spotted onto FP cards. The method requires no sample pretreatment
and may be particularly suitable for rapidly screening a large number of samples. Signal intensity from the ICP-MS strongly
correlated (r
2 = 0.996) with Pb target values for five blood cards from a laboratory proficiency testing program. Better precision was obtained
by replicate ablation line scans (<15% rsd) compared to a grid of 25 individual ablation spots (>30% rsd). Because <2% of
the sample is consumed in the laser ablation analysis, selected samples can also be analyzed by traditional techniques or
archived. Lead isotope ratios determined during the same total-Pb analysis appear to be effective for discerning contamination
extraneous to the blood sample. Determining that an elevated result was due to contamination may negate the need for retesting
with invasive pediatric venipuncture. Some elements monitored along with Pb exhibited signal profiles conducive to potential
quantitation (Ca, V, Fe, Cu Zn), whereas others did not (Cr, Mn, Co, Ni, Cd, Hg, Tl, U). Copper, Ca, and V were inversely
correlated with Pb (r = −0.89, −0.90, and −0.92, respectively). Scanning electron microscope images revealed surface modality differences between
FP spotted with fresh whole blood and reconstituted freeze-dried blood reference material.
Figure Image of spotted filter paper blood specimen showing ablation line scans 相似文献
920.
For any , a truncated symmetric α-stable process is a symmetric Lévy process in with a Lévy density given by for some constant c. In this paper we study the potential theory of truncated symmetric stable processes in detail. We prove a Harnack inequality
for nonnegative harmonic functions of these processes. We also establish a boundary Harnack principle for nonnegative functions
which are harmonic with respect to these processes in bounded convex domains. We give an example of a non-convex domain for
which the boundary Harnack principle fails.
The research of Panki Kim is supported by Research Settlement Fund for the new faculty of Seoul National University. The research
of Renming Song is supported in part by a joint US-Croatia grant INT 0302167. 相似文献