| 1. |
- Beal, Jacob, et al.
(författare)
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Robust estimation of bacterial cell count from optical density
- 2020
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Ingår i: Communications Biology. - : Springer Science and Business Media LLC. - 2399-3642. ; 3:1
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Tidskriftsartikel (refereegranskat)abstract
- Optical density (OD) is widely used to estimate the density of cells in liquid culture, but cannot be compared between instruments without a standardized calibration protocol and is challenging to relate to actual cell count. We address this with an interlaboratory study comparing three simple, low-cost, and highly accessible OD calibration protocols across 244 laboratories, applied to eight strains of constitutive GFP-expressing E. coli. Based on our results, we recommend calibrating OD to estimated cell count using serial dilution of silica microspheres, which produces highly precise calibration (95.5% of residuals <1.2-fold), is easily assessed for quality control, also assesses instrument effective linear range, and can be combined with fluorescence calibration to obtain units of Molecules of Equivalent Fluorescein (MEFL) per cell, allowing direct comparison and data fusion with flow cytometry measurements: in our study, fluorescence per cell measurements showed only a 1.07-fold mean difference between plate reader and flow cytometry data.
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| 2. |
- Mao, Jiwei, 1990, et al.
(författare)
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Relieving metabolic burden to improve robustness and bioproduction by industrial microorganisms
- 2024
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Ingår i: Biotechnology Advances. - 0734-9750. ; 74
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Forskningsöversikt (refereegranskat)abstract
- Metabolic burden is defined by the influence of genetic manipulation and environmental perturbations on the distribution of cellular resources. The rewiring of microbial metabolism for bio-based chemical production often leads to a metabolic burden, followed by adverse physiological effects, such as impaired cell growth and low product yields. Alleviating the burden imposed by undesirable metabolic changes has become an increasingly attractive approach for constructing robust microbial cell factories. In this review, we provide a brief overview of metabolic burden engineering, focusing specifically on recent developments and strategies for diminishing the burden while improving robustness and yield. A variety of examples are presented to showcase the promise of metabolic burden engineering in facilitating the design and construction of robust microbial cell factories. Finally, challenges and limitations encountered in metabolic burden engineering are discussed.
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| 3. |
- Nelwamondo, Aubrey N., et al.
(författare)
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Uranium assay and trace element analysis of the fourth collaborative material exercise samples by the modified Davies-Gray method and the ICP-MS/OES techniques
- 2018
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Ingår i: Journal of Radioanalytical and Nuclear Chemistry. - : Springer Science and Business Media LLC. - 0236-5731 .- 1588-2780. ; 315:2, s. 379-394
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Tidskriftsartikel (refereegranskat)abstract
- An international group of laboratories participating in CMX-4 subjected three samples to comparative nuclear forensic analysis using uranium assay and trace element analysis techniques to determine if the samples had similar or different origins. Uranium assay indicated that two pellet samples (ES-2 and ES-3) were nearly pure UO 2 while the black powder sample ES-1 was primarily UO 2 with UO 3 and/or U 3 O 8 forms present as impurities. Trace element analysis by five of the six participating laboratories reported molybdenum concentrations below 10 µg/g U in all of the exercise samples, suggesting the same likely facility of origin for all three samples.
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| 4. |
- Qin, Ning, 1990, et al.
(författare)
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Flux regulation through glycolysis and respiration is balanced by inositol pyrophosphates in yeast
- 2023
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Ingår i: Cell. - : Elsevier BV. - 0092-8674 .- 1097-4172. ; 186:4, s. 748-763.e15
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Tidskriftsartikel (refereegranskat)abstract
- Although many prokaryotes have glycolysis alternatives, it's considered as the only energy-generating glucose catabolic pathway in eukaryotes. Here, we managed to create a hybrid-glycolysis yeast. Subsequently, we identified an inositol pyrophosphatase encoded by OCA5 that could regulate glycolysis and respiration by adjusting 5-diphosphoinositol 1,2,3,4,6-pentakisphosphate (5-InsP7) levels. 5-InsP7 levels could regulate the expression of genes involved in glycolysis and respiration, representing a global mechanism that could sense ATP levels and regulate central carbon metabolism. The hybrid-glycolysis yeast did not produce ethanol during growth under excess glucose and could produce 2.68 g/L free fatty acids, which is the highest reported production in shake flask of Saccharomyces cerevisiae. This study demonstrated the significance of hybrid-glycolysis yeast and determined Oca5 as an inositol pyrophosphatase controlling the balance between glycolysis and respiration, which may shed light on the role of inositol pyrophosphates in regulating eukaryotic metabolism.
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| 5. |
- Qin, Ning, et al.
(författare)
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Increased CO 2 fixation enables high carbon-yield production of 3-hydroxypropionic acid in yeast
- 2024
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Ingår i: Nature Communications. - 2041-1723 .- 2041-1723. ; 15:1
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Tidskriftsartikel (refereegranskat)abstract
- CO2 fixation plays a key role to make biobased production cost competitive. Here, we use 3-hydroxypropionic acid (3-HP) to showcase how CO2 fixation enables approaching theoretical-yield production. Using genome-scale metabolic models to calculate the production envelope, we demonstrate that the provision of bicarbonate, formed from CO2, restricts previous attempts for high yield production of 3-HP. We thus develop multiple strategies for bicarbonate uptake, including the identification of Sul1 as a potential bicarbonate transporter, domain swapping of malonyl-CoA reductase, identification of Esbp6 as a potential 3-HP exporter, and deletion of Uga1 to prevent 3-HP degradation. The combined rational engineering increases 3-HP production from 0.14 g/L to 11.25 g/L in shake flask using 20 g/L glucose, approaching the maximum theoretical yield with concurrent biomass formation. The engineered yeast forms the basis for commercialization of bio-acrylic acid, while our CO2 fixation strategies pave the way for CO2 being used as the sole carbon source.
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| 6. |
- Qin, Ning, et al.
(författare)
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Rewiring Central Carbon Metabolism Ensures Increased Provision of Acetyl-CoA and NADPH Required for 3-OH-Propionic Acid Production
- 2020
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Ingår i: ACS Synthetic Biology. - : American Chemical Society (ACS). - 2161-5063. ; 9:12, s. 3236-3244
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Tidskriftsartikel (refereegranskat)abstract
- The central carbon metabolite acetyl-CoA and the cofactor NADPH are important for the synthesis of a wide array of biobased products. Here, we constructed a platform yeast strain for improved provision of acetyl-CoA and NADPH, and used the production of 3-hydroxypropionic acid (3-HP) as a case study. We first demonstrated that the integration of phosphoketolase and phosphotransacetylase improved 3-HP production by 41.9% and decreased glycerol production by 48.1% compared with that of the control strain. Then, to direct more carbon flux toward the pentose phosphate pathway, we reduced the expression of phosphoglucose isomerase by replacing its native promoter with a weaker promoter, and increased the expression of glucose-6-phosphate dehydrogenase and 6-phosphogluconate dehydrogenase by replacing their native promoters with stronger promoters. This further improved 3-HP production by 26.4%. Furthermore, to increase the NADPH supply we overexpressed cytosolic aldehyde dehydrogenase, and improved 3-HP production by another 10.5%. Together with optimizing enzyme expression of acetyl-CoA carboxylase and malonyl-CoA reductase, the final strain is able to produce 3-HP with a final titer of 864.5 mg/L, which is a more than 24-fold improvement compared with that of the starting strain. Our strategy combines the PK pathway with the oxidative pentose phosphate pathway for the efficient provision of acetyl-CoA and NADPH, which provides both a higher theoretical yield and overall yield than the reported yeast-based 3-HP production strategies via the malonyl-CoA reductase-dependent pathway and sheds light on the construction of efficient platform cell factories for other products.
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| 7. |
- Xu, Kai, et al.
(författare)
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Ground-state electron transfer in all-polymer donor-acceptor heterojunctions
- 2020
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Ingår i: Nature Materials. - : Springer Science and Business Media LLC. - 1476-4660 .- 1476-1122. ; 19:7, s. 738-744
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Tidskriftsartikel (refereegranskat)abstract
- Doping of organic semiconductors is crucial for the operation of organic (opto)electronic and electrochemical devices. Typically, this is achieved by adding heterogeneous dopant molecules to the polymer bulk, often resulting in poor stability and performance due to dopant sublimation or aggregation. In small-molecule donor–acceptor systems, charge transfer can yield high and stable electrical conductivities, an approach not yet explored in all-conjugated polymer systems. Here, we report ground-state electron transfer in all-polymer donor–acceptor heterojunctions. Combining low-ionization-energy polymers with high-electron-affinity counterparts yields conducting interfaces with resistivity values five to six orders of magnitude lower than the separate single-layer polymers. The large decrease in resistivity originates from two parallel quasi-two-dimensional electron and hole distributions reaching a concentration of ∼1013 cm–2. Furthermore, we transfer the concept to three-dimensional bulk heterojunctions, displaying exceptional thermal stability due to the absence of molecular dopants. Our findings hold promise for electro-active composites of potential use in, for example, thermoelectrics and wearable electronics.
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| 8. |
- Yue, L., et al.
(författare)
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Novel InGaPBi single crystal grown by molecular beam epitaxy
- 2015
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Ingår i: Applied Physics Express. - : IOP Publishing. - 1882-0786 .- 1882-0778. ; 8:4, s. Art. no. 041201-
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Tidskriftsartikel (refereegranskat)abstract
- InGaPBi crystalline thin films with up to 2.1% bismuth concentration have been grown on GaAs substrates by molecular beam epitaxy. Rutherford backscattering spectrometry confirms that the majority of Bi atoms are located at substitutional lattice sites. The films exhibit good surface, structural, and interface quality, and their strains can be tuned from tensile to compressive by increasing the Bi content. InBi LO and GaBi LO vibrational modes in Raman spectroscopy were observed, and their intensities increased with Bi concentration. A weak photoluminescence signal was observed at 1.78 eV at room temperature for the sample with a Bi content of 0.5%.
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| 9. |
- Zheng, Changcheng, et al.
(författare)
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Behavior of Raman modes in InPBi alloys under hydrostatic pressure
- 2019
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Ingår i: AIP Advances. - : AIP Publishing. - 2158-3226 .- 2158-3226. ; 9:3
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Tidskriftsartikel (refereegranskat)abstract
- Raman spectra of InPBi alloys with bismuth amount 0.3%-2.0% were measured under hydrostatic pressure in diamond anvil cell up to ∼4 GPa at room temperature. Two bismuth related Raman modes were identified and their evolutions under pressure were studied. The linear pressure coefficients of these two modes are determined to be 1.292 and 2.169 cm -1 /GPa, respectively. The different behaviors of these two modes under pressure suggest that they may have distinct origins. InP related Raman modes were also investigated including two InP related modes caused by Bi doping.
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