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[en] Designing experiments with fruit trees, using isotopic techniques, is different from the classical isotopic field experiments. This article summarizes the procedures to set up such experiments, explains the necessary calculations and ways to relate the data. Several examples of already conducted experiments are presented
[en] Methods are described for exposing to 15N2 systems ranging in complexity from free-living microorganisms to complex associations in the rhizosphere. The simplest chambers for the anaerobic incubation of soil, leaf litter, rotting wood etc. require only an oxygen-scavenging system, but when defined oxygen tensions are required, some system of oxygen control must be incorporated to compensate for respiratory losses. For simple photosynthetic organisms such as blue-green algae illumination must be provided but because incubation periods are short, little if any control of CO2 or O2 is necessary. The most complex asymbiotic system, the higher plant rhizosphere association, requires a protracted exposure to 15N2 with adequate control of CO2, temperature, light intensity, soil moisture and plant transpiration to maintain normal plant growth over sufficiently long periods to give a valid estimate of nitrogen fixation. (author)
[en] Encodable lanthanide binding tags (LBTs) have become an attractive tool in modern structural biology as they can be expressed as fusion proteins of targets of choice. Previously, we have demonstrated the feasibility of inserting encodable LBTs into loop positions of interleukin-1β (Barthelmes et al. in J Am Chem Soc 133:808–819, 2011). Here, we investigate the differences in fast dynamics of selected loop-LBT interleukin-1β constructs by measuring 15N nuclear spin relaxation experiments. We show that the loop-LBT does not significantly alter the dynamic motions of the host protein in the sub-τc-timescale and that the loop-LBT adopts a rigid conformation with significantly reduced dynamics compared to the terminally attached encodable LBT leading to increased paramagnetic alignment strength. We further analyze residual dipolar couplings (RDCs) obtained by loop-LBTs and additional liquid crystalline media to assess the applicability of the loop-LBT approach for RDC-based methods to determine structure and dynamics of proteins, including supra-τc dynamics. Using orthogonalized linear combinations (OLCs) of RDCs and Saupe matrices, we show that the combined use of encodable LBTs and external alignment media yields up to five linear independent alignments.
[en] The low-energy bare-nucleus cross section for 15N(p,α)12C is extracted by means of the Trojan-horse Method applied to the 2H(15N,α)12C)n reaction at Ebeam = 60 MeV. The astrophysical S-factor is deduced and compared to the direct data in the same energy region. A fair agreement with direct data down to 80 keV is found if energy resolution effects are taken into account
[en] The study was performed in an inceptisol at the ''San Jorge'' experimental station (altitude 2.900 m), Bogota, Colombia. The influence of phosphate and the application of split doses of nitrogen on the nitrogen fertilizer use efficiency of a potato crop. (Solanum tuberosum, L.) cv Tequendama, was evaluated. The phosphate was applied at levels of 100, 150 and 200 Kg P2O5 ha-1 in the form of triple super phosphate. The nitrogen (100 Kg N. ha-1) was applied in split doses at seeding and 60 days after emergence (DAE) in the following proportions: 1/3: 2/3 or 1/2. The N source used was Urea labelled with 1.5 atom % 15N excess. The results showed that: a) The maximum tuber yield (41 t.ha-1) was experience with 100 Kg P2O5Ha-1 and this was significantly higher than a zero phosphate control (24t. ha-1) even though the soluble soil phosphorus (Bray II) was high. b) The phosphate favoured the productivity of the crop and increased the N fertilizer use efficiency (% FUE) from 28 to 51%.c). The different splitting of the N fertilizer application had no detectable effect on yield % FUE. d) The tubers represented 76% of the total dry matter and contained 63% of the total nitrogen and fertilizer N accumulated by the crop