Magnetic and structural aspects of the annealing-induced transformation of rapidly-solidified Mn 55 Al 45 ribbons from the as-quenched metastable antiferromagnetic (AF) ε-phase to the target ferromagnetic (FM) L1 0 τ-phase are investigated. The as-solidified material exhibits a majority hexagonal ε-MnAl phase revealing a large exchange bias shift below a magnetic blocking temperature T B~9 5 K (H ex~1 3 kOe at 10 K), ascribed to the presence of compositional fluctuations in this antiferromagnetic phase. Heat treatment at a relatively low annealing temperature T anneal ≈ 568 K (295 °C) promotes the nucleation of the metastable L1 0 τ-MnAl phase at the expense of the parent ε-phase, donating an increasingly hard ferromagnetic character. The onset of the ε→τ transformation occurs at a temperature that is ~100 K lower than that reported in the literature, highlighting the benefits of applying rapid solidification for synthesis of the rapidly-solidified parent alloy.
Plant cell and tissue cultures are a scalable and controllable alternative to whole plants for obtaining natural products of medical relevance. Cultures can be optimized for high yields of desired metabolites using rapid profiling assays such as HPLC. We describe an approach to establishing a rapid assay for profiling cell culture expression systems using a novel microscale LC-UV-MS-NMR platform, designed to acquire both MS and NMR each at their optimal sensitivity, by using nanosplitter MS from 4 mm analytical HPLC columns, and offline microdroplet NMR. The approach is demonstrated in the analysis of elicited Eschscholzia californica cell cultures induced with purified yeast extract to produce benzophenanthridine alkaloids. Preliminary HPLC-UV provides an overview of the changes in the production of alkaloids with time after elicitation. At the time point corresponding to the production of the most alkaloids, the integrated LC-MS-microcoil NMR platform is used for structural identification of extracted alkaloids. Eight benzophenanthridine alkaloids were identified at the sub-microgram level. This paper demonstrates the utility of the nanosplitter LC-MS/microdroplet NMR platform when establishing cell culture expression systems.
The California poppy, Eschscholzia californica, produces benzophenanthridine alkaloids (BPAs), an important class of biologically active compounds. Cell cultures of E. californica were investigated as an alternative and scalable method for producing these valuable compounds; treatment with yeast extract increased production from low levels to 23 mg/g dry weight (DW) of BPAs. A shotgun proteomic analysis of E. californica cell cultures was undertaken to explore changes in metabolism associated with enhanced BPA production. We implemented differential centrifugation and then shotgun proteomics based on nanoliquid chromatography/mass spectrometry (nano-LC-MS/MS) for peptide separation and analysis. A unigene database available for E. californica was translated and utilized for protein identification. Approximately 646 proteins (3% false discovery rate at the protein level) were identified. Differentially abundant proteins observed with elicitation included enzymes involved in (S)-adenosyl methionine (SAM) biosynthesis and BPA biosynthesis. These results demonstrate (1) the identification of proteins from a medicinal plant using shotgun proteomics combined with a well-annotated, translated unigene database and (2) the potential utility of proteomics for exploring changes in metabolism associated with enhanced secondary metabolite production.
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