Browsing by Author "Wu, Hui"

Now showing 1 - 7 of 7
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    A Mott insulator continuously connected to iron pnictide superconductors
    (Springer Nature, 2016) Song, Yu; Yamani, Zahra; Cao, Chongde; Li, Yu; Zhang, Chenglin; Chen, Justin S.; Huang, Qingzhen; Wu, Hui; Tao, Jing; Zhu, Yimei; Tian, Wei; Chi, Songxue; Cao, Huibo; Huang, Yao-Bo; Dantz, Marcus; Schmitt, Thorsten; Yu, Rong; Nevidomskyy, Andriy H.; Morosan, Emilia; Si, Qimiao; Dai, Pengcheng; Rice Center for Quantum Materials
    Iron-based superconductivity develops near an antiferromagnetic order and out of a bad-metal normal state, which has been interpreted as originating from a proximate Mott transition. Whether an actual Mott insulator can be realized in the phase diagram of the iron pnictides remains an open question. Here we use transport, transmission electron microscopy, X-ray absorption spectroscopy, resonant inelastic X-ray scattering and neutron scattering to demonstrate that NaFe1−xCuxAs near x≈0.5 exhibits real space Fe and Cu ordering, and are antiferromagnetic insulators with the insulating behaviour persisting above the Néel temperature, indicative of a Mott insulator. On decreasing x from 0.5, the antiferromagnetic-ordered moment continuously decreases, yielding to superconductivity ∼x=0.05. Our discovery of a Mott-insulating state in NaFe1−xCuxAs thus makes it the only known Fe-based material, in which superconductivity can be smoothly connected to the Mott-insulating state, highlighting the important role of electron correlations in the high-Tc superconductivity.
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    Biosynthesis of Medium-Chain ω-Hydroxy Fatty Acids by AlkBGT of Pseudomonas putida GPo1 With Native FadL in Engineered Escherichia coli
    (Frontiers, 2019) He, Qiaofei; Bennett, George N.; San, Ka-Yiu; Wu, Hui; Bioengineering; Chemical and Biomolecular Engineering
    Hydroxy fatty acids (HFAs) are valuable compounds that are widely used in medical, cosmetic and food fields. Production of ω-HFAs via bioconversion by engineered Escherichia coli has received a lot of attention because this process is environmentally friendly. In this study, a whole-cell bio-catalysis strategy was established to synthesize medium-chain ω-HFAs based on the AlkBGT hydroxylation system from Pseudomonas putida GPo1. The effects of blocking the β-oxidation of fatty acids (FAs) and enhancing the transportation of FAs on ω-HFAs bio-production were also investigated. When fadE and fadD were deleted, the consumption of decanoic acid decreased, and the yield of ω-hydroxydecanoic acid was enhanced remarkably. Additionally, the co-expression of the FA transporter protein, FadL, played an important role in increasing the conversion rate of ω-hydroxydecanoic acid. As a result, the concentration and yield of ω-hydroxydecanoic acid in NH03(pBGT-fadL) increased to 309 mg/L and 0.86 mol/mol, respectively. This whole-cell bio-catalysis system was further applied to the biosynthesis of ω-hydroxyoctanoic acid and ω-hydroxydodecanoic acid using octanoic acid and dodecanoic acid as substrates, respectively. The concentrations of ω-hydroxyoctanoic acid and ω-hydroxydodecanoic acid reached 275.48 and 249.03 mg/L, with yields of 0.63 and 0.56 mol/mol, respectively. This study demonstrated that the overexpression of AlkBGT coupled with native FadL is an efficient strategy to synthesize medium-chain ω-HFAs from medium-chain FAs in fadE and fadD mutant E. coli strains.
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    Hydroxy- and dicarboxylic-fat synthsis by microbes
    (2016-11-08) San, Ka-yiu; Xie, Xixian; Tuli, Leepika; Wu, Hui; Rice University; United States Patent and Trademark Office
    Systems, methods and microbes that allow the biological production of hydroxy fatty acids and dicarboxylic fatty acids are provided. Specifically, hydroxy fatty acids and dicarboxylic fatty acids are produced by microbes that have been engineered to overexpress acyl ACP thioesterase plus an alkane degration pathway, such as AlkBGT or AlkJH These can be in separate microbes or the same microbe, and separate microbes can be co-cultured or sequentially cultured. Continuously fed systems transferring secreted fats from one microbial culture to another can also be used.
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    KAS-III free FA synthesis
    (2020-12-01) San, Ka-yiu; Zhang, Xian; Wu, Hui; Wang, Dan; Rice University; United States Patent and Trademark Office
    The present disclosure describes a genetically engineered a KASIII-independent fatty acid biosynthetic pathway that makes use of the promiscuous nature of the rest of the FAS enzymes (3-ketoacyl-ACP synthetase, 3-ketoacyl-ACP reductase, 3-hydroxyacyl ACP dehydrase, enoyl-ACP reductase) to bypass the KASIII step by providing a Co-A precursor of two or higher than two carbons (such as the four carbon butyryl-CoA) as the starting molecule. Since many CoA-based starter molecules can be supplied for the fatty acid synthesis, much more diversified products can be obtained with various carbon-chain lengths. As such, this disclosure will serve as a powerful and efficient platform to produce low to medium chain length products carrying many different functional groups.
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    Metabolic transistor in bacteria
    (2018-07-03) San, Ka-yiu; Bennett, George N.; Wu, Hui; Rice University; United States Patent and Trademark Office
    The disclosure relates to a metabolic transistor in microbes such as bacteria and yeast where a competitive pathway is introduced to compete with a product pathway for available carbon so as to control the carbon flux in the microbe.
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    Metabolic transistor in bacteria
    (2016-09-13) San, Ka-yiu; Bennett, George N.; Wu, Hui; Rice University; United States Patent and Trademark Office
    The disclosure relates to a metabolic transistor in bacteria where a competitive pathway is introduced to compete with a product pathway for available carbon so as to control the carbon flux in the bacteria.
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    Metabolic transistor strategy for controlling electron transfer chain activity in Escherichia coli
    (Elsevier, 2015) Wu, Hui; Tuli, Leepika; Bennett, George N.; San, Ka-Yiu; Bioengineering; Chemical and Biomolecular Engineering
    A novel strategy to finely control a large metabolic flux by using a “metabolic transistor” approach was established. In this approach a small change in the level or availability of an essential component for the process is controlled by adding a competitive reaction that affects a precursor or an intermediate in its biosynthetic pathway. The change of the basal level of the essential component, considered as a base current in a transistor, has a large effect on the flux through the major pathway. In this way, the fine-tuning of a large flux can be accomplished. The “metabolic transistor” strategy was applied to control electron transfer chain function by manipulation of the quinone synthesis pathway in Escherichia coli. The achievement of a theoretical yield of lactate production under aerobic conditions via this strategy upon manipulation of the biosynthetic pathway of the key participant, ubiquinone-8 (Q8), in an E. coli strain provides an in vivo, genetically tunable means to control the activity of the electron transfer chain and manipulate the production of reduced products while limiting consumption of oxygen to a defined amount.