Amino acid and chlorin based degradation indicators in freshwater systems

Lakes cover a global area that is about 35 times smaller than the oceans, but carbon burial in lakes and oceans are on the same order of magnitude. Hence, understanding the processes for such high organic carbon burial in lacustrine systems is essential. We applied proxies typically used for marine environments including amino acid (AA) content and their nitrogen stable isotope composition to the water columns and sediments of three lakes that differ in their trophic states and depositions rates of sedimentary terrestrial organic matter. Additionally, we used carbon isotope fingerprinting of AAs to characterise their sources and fates. We show that this set of proxies tracks sources and degradation processes in eutrophic lakes with high sedimentary total organic carbon and nitrogen content. Those lakes also have a high total hydrolysable amino acid (THAA) content as well as higher pigment concentrations. While the Chlorin degradation Index (CI) showed increasing values with depth, the patterns were less consistent for the Degradation Index (DI). In general, all parameters failed to describe degradation in the most oligotrophic lake due to the very low organic carbon and nitrogen content in the sediment. We show that AAs are mostly of autochthonous origin and that AA contribute 5–45% to the organic material in plankton, POM, and sediment. Proxies based on AA for bacterial reworking (ΣV) or trophic level (TL) showed increasing values in the water column but relatively stable values in the sediments. Furthermore, we show that methanotrophic bacteria led to increased values for the bacterial reworking proxy (ΣV) and extraordinarily low δ13C AA values (−30 to −60‰).1. Introduction 2. Experimental 2.1. Sample locations and collection 2.2. Elemental and isotopic composition 2.3. Chlorin Index 2.4. Hydrolysation, derivatisation and quantification of amino acids 2.5. Compound specific stable isotope analysis of amino acids 2.6. Degradation index 2.7. Trophic level calculation 2.8. Statistical methods 3. Results 3.1. Bulk properties 3.2. Composition of total hydrolysable amino acids (THAA) 3.3. Degradation indicators 3.4. Compound specific stable nitrogen isotope analysis 3.5. Compound specific stable carbon isotope analysis 4. Discussion 4.1. Degradation indicators 4.2. Amino acids as source markers 4.3. Bacterial reworking 4.4. Trophic level 4.5. Carbon isotopes of amino acids 4.6. Implications 5. Conclusion

Antiferromagnetism and Its Relation to the Superconducting Phases of UPt3

Using magnetic x-ray and neutron diffraction in UPt3, we find that a suppression of the antiferromagnetic scattering intensity in the superconducting phase is due to a reduction in the magnitude of the staggered moment with no change in symmetry. The existence of the suppression as well as the magnetic correlation lengths are not affected by the presence or absence of a visible splitting in the superconducting transition. The simplest models wherein antiferromagnetic order provides the symmetry-breaking field for the splitting do not provide a compete explanation of our results

CelloSelect – A synthetic cellobiose metabolic pathway for selection of stable transgenic CHO cell lines

Current protocols for generating stable transgenic cell lines mostly rely on antibiotic selection or the use of specialized cell lines lacking an essential part of their metabolic machinery, but these approaches require working with either toxic chemicals or knockout cell lines, which can reduce productivity. Since most mammalian cells cannot utilize cellobiose, a disaccharide consisting of two β-1,4-linked glucose molecules, we designed an antibiotic-free selection system, CelloSelect, which consists of a selection cassette encoding Neurospora crassa cellodextrin transporter CDT1 and β-glucosidase GH1-1. When cultivated in glucose-free culture medium containing cellobiose, CelloSelect-transfected cells proliferate by metabolizing cellobiose as a primary energy source, and are protected from glucose starvation. We show that the combination of CelloSelect with a PiggyBac transposase-based integration strategy provides a platform for the swift and efficient generation of stable transgenic cell lines. Growth rate analysis of metabolically engineered cells in cellobiose medium confirmed the expansion of cells stably expressing high levels of a cargo fluorescent marker protein. We further validated this strategy by applying the CelloSelect system for stable integration of sequences encoding two biopharmaceutical proteins, erythropoietin and the monoclonal antibody rituximab, and confirmed that the proteins are efficiently produced in either cellobiose- or glucose-containing medium in suspension-adapted CHO cells cultured in chemically defined media. We believe coupling heterologous metabolic pathways additively to the endogenous metabolism of mammalian cells has the potential to complement or to replace current cell-line selection systems.ISSN:1096-7176ISSN:1096-718

Spin gap and antiferromagnetic correlations in the kondo insulator CeNiSn

Neutron scattering measurements show that the crossover (at T≈≤10 K) from metallic heavy-fermion to semiconducting behavior coincides with the formation of a gap in the magnetic excitation spectrum of CeNiSn. In contrast to the simple band picture of an insulator, the gap is well defined only at particular values of the momentum transfer Q. While substantial anti ferromagnetic correlations in the a-c plane characterize the low-T state, the corresponding zero-frequency response function is Q independent