Nickel-Catalyzed Carboxylation of Aryl and Vinyl Chlorides Employing Carbon Dioxide

Nickel-catalyzed carboxylation of aryl and vinyl chlorides employing carbon dioxide has been developed. The reactions proceeded under a CO₂ pressure of 1 atm at room temperature in the presence of nickel catalysts and Mn powder as a reducing agent. Various aryl chlorides could be converted to the corresponding carboxylic acid in good to high yields. Furthermore, vinyl chlorides were successfully carboxylated with CO₂. Mechanistic study suggests that Ni­(I) species is involved in the catalytic cycle

Enhanced Electrochemical Performance of LiNi_0.5Mn_1.5O₄ Cathode Material by YPO₄ Surface Modification

Cathode material LiNi_0.5Mn_1.5O₄ (LNMO) for lithium-ion batteries is successfully synthesized by a sol–gel method and is further modified by a thin layer of YPO₄ (1, 3, and 5 wt %) through a simple wet chemical strategy. Physical characterizations indicate that the YPO₄ nanolayer has a little impact on the cathode structure. Electrochemical optimization reveals that the 3 wt % YPO₄-coated LNMO could still deliver a high specific capacity of 107 mAh g^–1 after 240 cycles, with a capacity retention of 77.5%, much higher than that of the pristine electrode. Electrochemical impedance spectroscopy (EIS) analysis proves that the rapid increase of surface impedance could be suppressed by the YPO₄ coating layer and thus facilitates the surface kinetics behavior in repeated cycling. Through further material aging experiments, the improvement of electrochemical performances could be attributed to the formation of Lewis acid YF₃, converted from the YPO₄ coating layer in the LiPF₆-based electrolyte, which not only scavenges the surface insulating alkaline species with a high acidity but also accelerates ion exchange on the material surface and thus helps to generate the solid solution Li–Ni–Mn–Y–O on the surface of YPO₄-coated LNMO

Mutation of the <i>Light-Induced Yellow Leaf 1</i> Gene, Which Encodes a Geranylgeranyl Reductase, Affects Chlorophyll Biosynthesis and Light Sensitivity in Rice

<div><p>Chlorophylls (Chls) are crucial for capturing light energy for photosynthesis. Although several genes responsible for Chl biosynthesis were characterized in rice (<i>Oryza sativa</i>), the genetic properties of the hydrogenating enzyme involved in the final step of Chl synthesis remain unknown. In this study, we characterized a rice <i>light-induced yellow leaf 1-1</i> (<i>lyl1-1</i>) mutant that is hypersensitive to high-light and defective in the Chl synthesis. Light-shading experiment suggested that the yellowing of <i>lyl1-1</i> is light-induced. Map-based cloning of <i>LYL1</i> revealed that it encodes a geranylgeranyl reductase. The mutation of <i>LYL1</i> led to the majority of Chl molecules are conjugated with an unsaturated geranylgeraniol side chain. <i>LYL1</i> is the firstly defined gene involved in the reduction step from Chl-geranylgeranylated (Chl_GG) and geranylgeranyl pyrophosphate (GGPP) to Chl-phytol (Chl_Phy) and phytyl pyrophosphate (PPP) in rice. <i>LYL1</i> can be induced by light and suppressed by darkness which is consistent with its potential biological functions. Additionally, the <i>lyl1-1</i> mutant suffered from severe photooxidative damage and displayed a drastic reduction in the levels of α-tocopherol and photosynthetic proteins. We concluded that <i>LYL1</i> also plays an important role in response to high-light in rice.</p></div

Expression analysis of rice <i>LYL1</i> gene.

<p>(A) Transcript levels of <i>LYL1</i> relative to <i>OsActin</i> in various tissues detected by quantitative real-time PCR. (B) Time-course of <i>LYL1</i> expression in response to light and dark conditions. About 3-week-old seedlings under dark, low-light (LL, 100 µmol photonm m⁻² s⁻¹) and high-light conditions (HL, 400 µmol photon m⁻² s⁻¹) at 27°C were used for expression analysis. T1, 12 hours of dark treatment; T2–T4, 3, 6 and 9 hours after the initiation of light treatment; T5–T8, 3, 6 and 9 hours after dark exposure.</p

A working model of branched pathway starting from GGPP and Chlide to Chl_phy and α-tocopherol in rice.

<p>Geranylgeranyl reductase, encoded by the <i>LYL1</i>, generates PPP and Chl_phy using GGPP and Chlide as substrates. PPP is then directed into the tocopherol-synthesizing pathway.</p

HPLC analysis of the accumulation of Chl derivatives.

<p>The fluorescence intensity at 650(A) HPLC chromatograms of extracts from leaves of ZH11 (top) and <i>lyl1-1</i> (bottom). (B) HPLC chromatograms of extracts from leaves of Nipp (top) and <i>lyl1-2</i> (bottom). Peak 1, Chl <i>b</i>_GG; peak 2, Chl <i>b</i>_DHGG; peak 3, Chl <i>b</i>_THGG; peak 4, Chl <i>b</i>_phy; peak 5, Chl <i>a</i>_GG; peak 6, Chl <i>a</i>_DHGG; peak 7, Chl <i>a</i>_THGG; and peak 8, Chl <i>a</i>_phy. (C) The contents of Chl <i>a</i> derivatives in ZH11 and <i>lyl1-1</i>. (D) The contents of Chl <i>a</i> derivatives in Nipp and <i>lyl1-2</i>. (E) The contents of Chl <i>b</i> derivatives in ZH11 and <i>lyl1-1</i>. (F) The contents of Chl <i>b</i> derivatives in Nipp and <i>lyl1-2</i>. The extracts were isolated from the first, second and third leaves of ZH11, <i>lyl1-1</i>, Nipp and <i>lyl1-2</i> plants grown under natural conditions (high light). Data presented are mean ±SD. ND =  Not Detected. The Chl <i>b</i>_GG of ZH11 and Chl intermediates in Nipp were not detected. ** Significant at the 0.01 level.</p

Effects of different light density on the lipid peroxidation and ROS levels.

<p>The changes in MDA content (A), H₂O₂ content (B) and HO· level (C) between ZH11 and <i>lyl1-1</i> plants under low-light (LL, 100 µmol photonm m⁻² s⁻¹) and high-light (HL, 400 µmol photon m⁻² s⁻¹) conditions. Data presented are mean ±SD. NS =  No significant, ** Significant at the 0.01 level.</p

HPLC analysis of tocopherols and tocotrienols.

<p>(A) HPLC chromatograms of reference standards. Peak 1, δ-tocotrienol; Peak 2, γ-tocotrienol; Peak 3, α-tocotrienol; Peak 4, δ-tocopherol; Peak 5, γ-tocopherol; Peak 6, α-tocopherol. (B) HPLC chromatograms of extracts from the leaves of ZH11 (top) and <i>lyl1-1</i> (bottom), respectively. (C) The contents of α-tocopherol in ZH11 and <i>lyl1-1</i> plants. (D) HPLC chromatograms of extracts from the leaves of Nipp (top) and <i>lyl1-2</i> (bottom), respectively. (E) The contents of α-tocopherol in Nipp and <i>lyl1-2</i> plants. The tocopherols were extracted from the first, second and third leaves of ZH11, <i>lyl1-1</i>, Nipp and <i>lyl1-2</i> plants grown under natural conditions (high light). Data presented are mean ±SD. ** Significant at the 0.01 level.</p

Phenotype of the rice <i>lyl1-1</i> mutant.

<p>(A) wild type ZH11 (left) and <i>lyl1-1</i> mutant (right) at the seeding stage. (B) ZH11 plants at tillering stage. (C) The <i>lyl1-1</i> plants at tillering stage. (D–G), The electron microscopic analysis of ZH11 and <i>lyl1-1</i> leaves. (D) and (E), The mesophyll cells of ZH11 and <i>lyl1-1</i> mutant. Bar  = 1 µm. (F) and (G), The chloroplasts of ZH11 and <i>lyl1-1</i> mutant. g, grana stack; p, plastoglobule; s, starch granule; sl, stroma lamellae. Bar  = 2 µm.</p

Map-based cloning of <i>LYL1</i>.

<p>(A) Rough mapping of the <i>LYL1</i> locus. <i>LYL1</i> is located between two markers, W243 and W226, on the long arm of chromosome 2. (B) Fine mapping of the <i>LYL1</i> locus. The <i>LYL1</i> gene is limited in a 33-kb genomic DNA region between markers W235 and W246, and it co-segregates with marker W247. Six candidate genes are located within this region in the Nipponbare genome, according to the TIGR Rice Genome Annotation Database. LOC_Os02g51080 is the candidate for <i>LYL1</i>. (C) <i>LYL1</i> gene structure at the genomic level. Three exons and the mutation positions are indicated. (D) Confirmation of the splice variation by analysis of the PCR amplicon size in the <i>lyl1-1</i> mutant and 22 rice cultivars. Lane 1, ZH11; lane 2, <i>lyl1-1</i>; lane 3-24, normal rice varieties, Zhongxian 3037, Tianegu, Wuxiangjing 3, Wuyunjing 8, Wuxiangjing 9, 9915, Nantehao, Wu 2661, Nanjing 46, Guandong 194, Nippobare, Guangluai 4, Balillar, Wuyunjing 7, 9516, 3015, Dular, 9311, Wujing 5, Miyang 23, Zhengdao 88 and Fengsizhan. (E) Phenotype of a 3-week-old RNAi transgenic plant. (F) Phenotype of a 2-month-old RNAi plant. (G) Comparison of Chl content between wild type Nipponbare and RNAi line. (H) Examination of <i>LYL1</i> expression level in the RNAi line by RT-PCR. <i>OsActin</i> was amplified as a control. (I) PCR and RT-PCR identification of the Tos17 insertion mutant <i>lyl1-2</i>. D1F was a primer derived from the Tos17 region. The D1R, D2F and D2R primers were derived from the genes examined. For RT-PCR analysis, <i>OsActin</i> was amplified as a control. (J) Phenotype of a 3-week-old <i>lyl1-2</i> mutant. (K) Comparison of Chl content between Nipp and <i>lyl1-2</i>. Data presented are mean ±SD. ** Significant at the 0.01 level.</p