Wax synthase (WS, fatty acyl-coenzyme A [coA]: fatty alcohol acyltransferase) catalyzes the final step in the synthesis of linear esters (waxes) that accumulate in seeds of jojoba (Simmondsia chinensis). We have characterized and partially purified this enzyme from developing jojoba embryos. A protein whose presence correlated with WS activity during chromatographic fractionation was identified and a cDNA encoding that protein was cloned. Seed-specific expression of the cDNA in transgenic Arabidopsis conferred high levels of WS activity on developing embryos from those plants. The WS sequence has significant homology with several Arabidopsis open reading frames of unknown function. Wax production in jojoba requires, in addition to WS, a fatty acyl-CoA reductase (FAR) and an efficient fatty acid elongase system that forms the substrates preferred by the FAR. We have expressed the jojoba WS cDNA in Arabidopsis in combination with cDNAs encoding the jojoba FAR and a -ketoacyl-CoA synthase (a component of fatty acid elongase) from Lunaria annua.13 C-Nuclear magnetic resonance analysis of pooled whole seeds from transgenic plants indicated that as many as 49% of the oil molecules in the seeds were waxes. Gas chromatography analysis of transmethylated oil from individual seeds suggested that wax levels may represent up to 70% (by weight) of the oil present in those seeds.
NASICON-type
of solid-state electrolyte, Na3Zr2Si2PO12 (NZSP), is one of the potential solid-state
electrolytes for all-solid-state Na battery and Na–air battery.
However, in solid-state synthesis, high sintering temperature above
1200 °C and long duration are required, which led to loss of
volatile materials and formation of impurities at the grain boundaries.
This hampers the total ionic conductivity of NZSP to be in the range
of 10–4 S cm–1. Herein, we have
reduced both the sintering temperature and time of the NZSP electrolyte
by sintering the NZSP powders with different amounts of Na2SiO3 additive, which provides the liquid phase for the
sintering process. The addition of 5 wt % Na2SiO3 has shown the highest total ionic conductivity of 1.45 mS cm–1 at room temperature. A systematic study of the effect
of Na2SiO3 on the microstructure and electrical
properties of the NZSP electrolyte is conducted by the structural
study with the help of morphological and chemical observations using
X-ray diffraction (XRD), scanning electron microscopy, and using focused
ion-beam-time of flight-secondary ion mass spectroscopy. The XRD results
revealed that cations from Na2SiO3 diffused
into the bulk change the stoichiometry of NZSP, leading to an enlarged
bottleneck area and hence lowering activation energy in the bulk,
which contributes to the increment of the bulk ion conductivity, as
indicated by the electrochemical impedance spectroscopy result. In
addition, higher density and better microstructure contribute to improved
grain boundary conductivity. More importantly, this study has achieved
a highly ionic conductive NZSP only by facile addition of Na2SiO3 into the NZSP powder prior to the sintering stage.
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