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Feng G, Xiong YJ, Wei HY, Li Y, Mao LF. Endemic medicinal plant distribution correlated with stable climate, precipitation, and cultural diversity. Plant Divers 2023; 45:479-484. [PMID: 37601541 PMCID: PMC10435908 DOI: 10.1016/j.pld.2022.09.007] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/05/2022] [Revised: 09/24/2022] [Accepted: 09/30/2022] [Indexed: 08/22/2023]
Abstract
Medicinal plants provide crucial ecosystem services, especially in developing countries such as China, which harbors diverse endemic medicinal plant species with substantial cultural and economic value. Accordingly, understanding the patterns and drivers of medicinal plant distribution is critical. However, few studies have investigated the patterns and drivers of endemic medicinal plants distribution in China. Here, we linked endemic medicinal plants distribution with possible explanatory variables, i.e., paleoclimate change, contemporary climate, altitudinal range and ethnic minority human population size at the prefecture city level in China. Our results show that endemic medicinal plants are concentrated in southern China, especially in southwestern China. Notably, both endemic medicinal plant species richness and the ratio of endemic medicinal plant species richness are negatively associated with glacial-interglacial anomaly in temperature, and positively associated with contemporary precipitation and altitudinal range. In addition, we found that endemic medicinal plant species richness is positively associated with ethnic minority population sizes as well as its ratio to the overall population size. These findings suggest that the distribution of endemic medicinal plants is determined by multiple drivers. Furthermore, our findings stress that dramatic future climate changes and massive anthropogenic activities in southern China pose great challenges to the conservation of China's endemic medicinal plants.
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Affiliation(s)
- Gang Feng
- Ministry of Education Key Laboratory of Ecology and Resource Use of the Mongolian Plateau & Inner Mongolia Key Laboratory of Grassland Ecology, School of Ecology and Environment, Inner Mongolia University, Hohhot, China
| | - Ying-Jie Xiong
- Ministry of Education Key Laboratory of Ecology and Resource Use of the Mongolian Plateau & Inner Mongolia Key Laboratory of Grassland Ecology, School of Ecology and Environment, Inner Mongolia University, Hohhot, China
| | - Hua-Yu Wei
- Ministry of Education Key Laboratory of Ecology and Resource Use of the Mongolian Plateau & Inner Mongolia Key Laboratory of Grassland Ecology, School of Ecology and Environment, Inner Mongolia University, Hohhot, China
| | - Yao Li
- Co-Innovation Center for Sustainable Forestry in Southern China, College of Biology and the Environment, Nanjing Forestry University, Nanjing, China
| | - Ling-Feng Mao
- Co-Innovation Center for Sustainable Forestry in Southern China, College of Biology and the Environment, Nanjing Forestry University, Nanjing, China
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2
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Zhang XX, Ye JF, Laffan SW, Mishler BD, Thornhill AH, Lu LM, Mao LF, Liu B, Chen YH, Lu AM, Miller JT, Chen ZD. Spatial phylogenetics of the Chinese angiosperm flora provides insights into endemism and conservation. J Integr Plant Biol 2022; 64:105-117. [PMID: 34773376 DOI: 10.1111/jipb.13189] [Citation(s) in RCA: 7] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/16/2021] [Revised: 07/16/2021] [Accepted: 11/10/2021] [Indexed: 06/13/2023]
Abstract
The flora of China is well known for its high diversity and endemism. Identifying centers of endemism and designating conservation priorities are essential goals for biodiversity studies. However, there is no comprehensive study from a rigorous phylogenetic perspective to understand patterns of diversity and endemism and to guide biodiversity conservation in China. We conducted a spatial phylogenetic analysis of the Chinese angiosperm flora at the generic level to identify centers of neo- and paleo-endemism. Our results indicate that: (i) the majority of grid cells in China with significantly high phylogenetic endemism (PE) were located in the mountainous regions; (ii) four of the nine centers of endemism recognized, located in northern and western China, were recognized for the first time; (iii) arid and semiarid regions in Northwest China were commonly linked to significant PE, consistent with other spatial phylogenetic studies worldwide; and (iv) six high-priority conservation gaps were detected by overlaying the boundaries of China's nature reserves on all significant PE cells. Overall, we conclude that the mountains of southern and northern China contain both paleo-endemics (ancient relictual lineages) and neo-endemics (recently diverged lineages). The areas we highlight as conservation priorities are important for broad-scale planning, especially in the context of evolutionary history preservation.
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Affiliation(s)
- Xiao-Xia Zhang
- State Key Laboratory of Systematic and Evolutionary Botany, Institute of Botany, the Chinese Academy of Sciences, Beijing, 100093, China
| | - Jian-Fei Ye
- State Key Laboratory of Systematic and Evolutionary Botany, Institute of Botany, the Chinese Academy of Sciences, Beijing, 100093, China
- Beijing Botanical Garden, Institute of Botany, the Chinese Academy of Sciences, Beijing, 100093, China
| | - Shawn W Laffan
- School of Biological, Earth and Environmental Sciences, University of New South Wales, Sydney, NSW, 2052, Australia
| | - Brent D Mishler
- University and Jepson Herbaria, and Department of Integrative Biology, University of California, Berkeley, CA, 94720-2465, USA
| | - Andrew H Thornhill
- University and Jepson Herbaria, and Department of Integrative Biology, University of California, Berkeley, CA, 94720-2465, USA
- The University of Adelaide, Environment Institute, Adelaide, SA, 5005, Australia
- State Herbarium of South Australia, Botanic Gardens and State Herbarium, Department for Environment and Water, Adelaide, SA, 5001, Australia
| | - Li-Min Lu
- State Key Laboratory of Systematic and Evolutionary Botany, Institute of Botany, the Chinese Academy of Sciences, Beijing, 100093, China
| | - Ling-Feng Mao
- College of Biology and the Environment, Nanjing Forestry University, Nanjing, 210037, China
| | - Bing Liu
- State Key Laboratory of Systematic and Evolutionary Botany, Institute of Botany, the Chinese Academy of Sciences, Beijing, 100093, China
- Sino-Africa Joint Research Center, the Chinese Academy of Sciences, Wuhan, 430074, China
| | - You-Hua Chen
- Chengdu Institute of Biology, the Chinese Academy of Sciences, Chengdu, 610041, China
| | - An-Ming Lu
- State Key Laboratory of Systematic and Evolutionary Botany, Institute of Botany, the Chinese Academy of Sciences, Beijing, 100093, China
| | - Joseph T Miller
- State Herbarium of South Australia, Botanic Gardens and State Herbarium, Department for Environment and Water, Adelaide, SA, 5001, Australia
- Global Biodiversity Information Facility, Copenhagen, Denmark
| | - Zhi-Duan Chen
- State Key Laboratory of Systematic and Evolutionary Botany, Institute of Botany, the Chinese Academy of Sciences, Beijing, 100093, China
- Sino-Africa Joint Research Center, the Chinese Academy of Sciences, Wuhan, 430074, China
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3
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Li J, Yang Z, Mao LF, Chen RH, Yu XF, Yang XH, Zhang GZ, Wang HQ, Chen SC, Zhao G. Reverse transcription recombinase-aided amplification assay for rapid detection of the influenza A(H1N1)pdm09 H275Y mutation that confers oseltamivir resistance. Mol Cell Probes 2021; 60:101771. [PMID: 34560257 DOI: 10.1016/j.mcp.2021.101771] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/05/2021] [Revised: 05/02/2021] [Accepted: 09/17/2021] [Indexed: 11/30/2022]
Abstract
The emergence of the influenza A(H1N1)pdm09 virus with the NA-H275Y mutation, which confers oseltamivir resistance, must be monitored, especially in patients undergoing neuraminidase inhibitor treatment. In this study, we developed a reverse transcription recombinase-aided amplification assay that has high sensitivity (detection limit: 1.0 × 101 copies/μL) and specificity for detecting the oseltamivir-resistant H275Y mutation; the assay is performed within 30 min at a constant temperature of 39° Celsius using an isothermal device. This method is suitable for the clinical application of targeted testing, thereby providing technical support for precision medicine in individual drug applications for patients with severe infection or immunosuppression.
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Affiliation(s)
- Jun Li
- Microbiology Laboratory, Hangzhou Centre for Disease Control and Prevention, Zhejiang, 310021, China
| | - Zi Yang
- Dali University, Yunnan, 671003, China
| | - Ling-Feng Mao
- Hangzhou Baocheng Biotechnology Co., Ltd., Zhejiang, 310052, China
| | - Ren-Hua Chen
- Department of Infectious Diseases, Hangzhou Centre for Disease Control and Prevention, Zhejiang, 310021, China
| | - Xin-Fen Yu
- Microbiology Laboratory, Hangzhou Centre for Disease Control and Prevention, Zhejiang, 310021, China
| | - Xu-Hui Yang
- Department of Infectious Diseases, Hangzhou Centre for Disease Control and Prevention, Zhejiang, 310021, China
| | - Guo-Zhong Zhang
- Microbiology Laboratory, Hangzhou Centre for Disease Control and Prevention, Zhejiang, 310021, China
| | - Hao-Qiu Wang
- Microbiology Laboratory, Hangzhou Centre for Disease Control and Prevention, Zhejiang, 310021, China
| | - Shu-Chang Chen
- Microbiology Laboratory, Hangzhou Centre for Disease Control and Prevention, Zhejiang, 310021, China
| | - Gang Zhao
- Microbiology Laboratory, Hangzhou Centre for Disease Control and Prevention, Zhejiang, 310021, China.
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4
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Lu LM, Mao LF, Yang T, Ye JF, Liu B, Li HL, Sun M, Miller JT, Mathews S, Hu HH, Niu YT, Peng DX, Chen YH, Smith SA, Chen M, Xiang KL, Le CT, Dang VC, Lu AM, Soltis PS, Soltis DE, Li JH, Chen ZD. Evolutionary history of the angiosperm flora of China. Nature 2018; 554:234-238. [DOI: 10.1038/nature25485] [Citation(s) in RCA: 210] [Impact Index Per Article: 35.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/26/2017] [Accepted: 12/22/2017] [Indexed: 01/03/2023]
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5
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Sun L, Ji A, Hu J, Zhu C, Zhang L, Yang J, Liu Y, Mao LF. A method to measure the distance among scatters and the scatters' diameter in artificial composite materials. Ultrasonics 2016; 67:70-75. [PMID: 26799127 DOI: 10.1016/j.ultras.2016.01.002] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/19/2015] [Revised: 11/15/2015] [Accepted: 01/06/2016] [Indexed: 06/05/2023]
Abstract
A new method to measure the distance among scatters, the density of scatters, and the scatters' diameter in artificial composite materials has been proposed. This method is based on detecting the reflection amplitude change (amp) of the echo signal reflected from scatters. Simulation results show that such a method is valid for the distance less than four times of the acoustic wavelength, because the coupling between the scatters can be neglected for the distance larger than four times of the acoustic wavelength. Therefore, this new measure method can be always valid by choosing appropriate frequency according to the scaling rule discussed in this paper. At the same time, it is found that the diameter of scatters is the half of the wavelength where the curve peak of the amp vs frequency occurs. It implies that such a new method can also be used to measure the diameter of scatters in solids and liquids, and even in PM2.5 pollution particles in air.
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Affiliation(s)
- Li Sun
- Institute of Intelligent Structure and System, Soochow University, Suzhou 215006, PR China
| | - Aiming Ji
- Institute of Intelligent Structure and System, Soochow University, Suzhou 215006, PR China
| | - Jialing Hu
- Institute of Intelligent Structure and System, Soochow University, Suzhou 215006, PR China
| | - Canyan Zhu
- Institute of Intelligent Structure and System, Soochow University, Suzhou 215006, PR China
| | - Lijun Zhang
- Institute of Intelligent Structure and System, Soochow University, Suzhou 215006, PR China
| | - Jianfeng Yang
- Institute of Intelligent Structure and System, Soochow University, Suzhou 215006, PR China
| | - Yongsong Liu
- Department of Physics, Zhejiang Sci-Tech University, Hangzhou 310018, PR China
| | - Ling-Feng Mao
- Institute of Intelligent Structure and System, Soochow University, Suzhou 215006, PR China.
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6
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Mao LF, Ning H, Li X. Effects of Energy Relaxation via Quantum Coupling Among Three-Dimensional Motion on the Tunneling Current of Graphene Field-Effect Transistors. Nanoscale Res Lett 2015; 10:1039. [PMID: 26264688 PMCID: PMC4531885 DOI: 10.1186/s11671-015-1039-4] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 06/18/2015] [Accepted: 08/03/2015] [Indexed: 06/04/2023]
Abstract
We report theoretical study of the effects of energy relaxation on the tunneling current through the oxide layer of a two-dimensional graphene field-effect transistor. In the channel, when three-dimensional electron thermal motion is considered in the Schrödinger equation, the gate leakage current at a given oxide field largely increases with the channel electric field, electron mobility, and energy relaxation time of electrons. Such an increase can be especially significant when the channel electric field is larger than 1 kV/cm. Numerical calculations show that the relative increment of the tunneling current through the gate oxide will decrease with increasing the thickness of oxide layer when the oxide is a few nanometers thick. This highlights that energy relaxation effect needs to be considered in modeling graphene transistors.
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Affiliation(s)
- Ling-Feng Mao
- />School of Computer and Communication Engineering, University of Science and Technology Beijing, Beijing, 100083 China
| | - Huansheng Ning
- />School of Computer and Communication Engineering, University of Science and Technology Beijing, Beijing, 100083 China
| | - Xijun Li
- />Wenzhou Meta Optics Corporate Limited, Wenzhou, 325000 China
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Mao LF, Ning HS, Wang JY. The Current Collapse in AlGaN/GaN High-Electron Mobility Transistors Can Originate from the Energy Relaxation of Channel Electrons? PLoS One 2015; 10:e0128438. [PMID: 26039589 PMCID: PMC4454566 DOI: 10.1371/journal.pone.0128438] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/17/2015] [Accepted: 04/27/2015] [Indexed: 11/18/2022] Open
Abstract
Influence of the energy relaxation of the channel electrons on the performance of AlGaN/GaN high-electron mobility transistors (HEMTs) has been investigated using self-consistent solution to the coupled Schrödinger equation and Poisson equation. The first quantized energy level in the inversion layer rises and the average channel electron density decreases when the channel electric field increases from 20 kV/cm to 120 kV/cm. This research also demonstrates that the energy relaxation of the channel electrons can lead to current collapse and suggests that the energy relaxation should be considered in modeling the performance of AlGaN/GaN HEMTs such as, the gate leakage current, threshold voltage, source-drain current, capacitance-voltage curve, etc.
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Affiliation(s)
- Ling-Feng Mao
- School of Computer & Communication Engineering, University of Science & Technology Beijing, 30 Xueyuan Road, Haidian District, Beijing 100083, P. R. China
| | - Huan-Sheng Ning
- School of Computer & Communication Engineering, University of Science & Technology Beijing, 30 Xueyuan Road, Haidian District, Beijing 100083, P. R. China
| | - Jin-Yan Wang
- Institute of Microelectronics, Peking University, 100871, Beijing, P. R. China
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8
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Li L, Li W, Ji A, Wang Z, Zhu C, Zhang L, Yang J, Mao LF. Anisotropic relaxation of a CuO/TiO2 surface under an electric field and its impact on visible light absorption: ab initio calculations. Phys Chem Chem Phys 2015; 17:17880-6. [DOI: 10.1039/c5cp02010g] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
A CuO/TiO2 layer under a 10.4 MV cm−1 electric field in the [010] direction achieves enhanced absorption of visible light due to the Cu–O bond.
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Affiliation(s)
- Lei Li
- Institute of Intelligent Structure and System
- School of Electronics & Information Engineering
- Soochow University
- Suzhou 215006
- P. R. China
| | - Wenshi Li
- Institute of Intelligent Structure and System
- School of Electronics & Information Engineering
- Soochow University
- Suzhou 215006
- P. R. China
| | - Aimin Ji
- Institute of Intelligent Structure and System
- Soochow University
- Suzhou 215006
- P. R. China
| | - Ziou Wang
- Institute of Intelligent Structure and System
- School of Electronics & Information Engineering
- Soochow University
- Suzhou 215006
- P. R. China
| | - Canyan Zhu
- Institute of Intelligent Structure and System
- Soochow University
- Suzhou 215006
- P. R. China
| | - Lijun Zhang
- Institute of Intelligent Structure and System
- Soochow University
- Suzhou 215006
- P. R. China
| | - Jianfeng Yang
- Institute of Intelligent Structure and System
- School of Electronics & Information Engineering
- Soochow University
- Suzhou 215006
- P. R. China
| | - Ling-Feng Mao
- Institute of Intelligent Structure and System
- Soochow University
- Suzhou 215006
- P. R. China
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9
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Mao LF. Interface traps and quantum size effects on the retention time in nanoscale memory devices. Nanoscale Res Lett 2013; 8:369. [PMID: 23984827 PMCID: PMC3847579 DOI: 10.1186/1556-276x-8-369] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 07/31/2013] [Accepted: 08/23/2013] [Indexed: 06/02/2023]
Abstract
Based on the analysis of Poisson equation, an analytical surface potential model including interface charge density for nanocrystalline (NC) germanium (Ge) memory devices with p-type silicon substrate has been proposed. Thus, the effects of Pb defects at Si(110)/SiO2, Si(111)/SiO2, and Si(100)/SiO2 interfaces on the retention time have been calculated after quantum size effects have been considered. The results show that the interface trap density has a large effect on the electric field across the tunneling oxide layer and leakage current. This letter demonstrates that the retention time firstly increases with the decrease in diameter of NC Ge and then rapidly decreases with the diameter when it is a few nanometers. This implies that the interface defects, its energy distribution, and the NC size should be seriously considered in the aim to improve the retention time from different technological processes. The experimental data reported in the literature support the theoretical expectation.
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Affiliation(s)
- Ling-Feng Mao
- Institute of Intelligent Structure and System, School of Urban Rail Transportation, Soochow University, Suzhou 215006, China.
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10
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Mao LF. Dot size effects of nanocrystalline germanium on charging dynamics of memory devices. Nanoscale Res Lett 2013; 8:21. [PMID: 23305228 PMCID: PMC3576263 DOI: 10.1186/1556-276x-8-21] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 11/27/2012] [Accepted: 01/06/2013] [Indexed: 06/01/2023]
Abstract
The dot size of nanocrystalline germanium (NC Ge) which impacts on the charging dynamics of memory devices has been theoretically investigated. The calculations demonstrate that the charge stored in the NC Ge layer and the charging current at a given oxide voltage depend on the dot size especially on a few nanometers. They have also been found to obey the tendency of initial increase, then saturation, and lastly, decrease with increasing dot size at any given charging time, which is caused by a compromise between the effects of the lowest conduction states and the capacitance of NC Ge layer on the tunneling. The experimental data from literature have also been used to compare and validate the theoretical analysis.
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Affiliation(s)
- Ling-Feng Mao
- Institute of Intelligent Structure and System, School of Urban Rail Transportation, Soochow University, Suzhou, 215006, China.
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11
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Abstract
The finite size effects in nanoribbon graphene field-effect transistors (FETs) make the energy distribution of the channel electrons very different from that when neglecting finite size effects. Such an effect is especially obvious when the width of the graphene ribbon is a few nanometers. Thus, it results in more high-energy electrons in a nanoribbon graphene FET than in a two-dimensional graphene FET for the same device structure and parameters. Furthermore, such an energy distribution of channel electrons results in a change in the gate leakage current of a nanoribbon graphene FET. The numerical calculations demonstrate that the tunneling current rapidly increases with decreasing width of the graphene ribbon. This implies that a workable graphene FET after considering gate oxide reliability should have a channel width larger than 100 nm.
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Affiliation(s)
- Ling-Feng Mao
- School of Electronics and Information Engineering, Soochow University, 178 Gan-jiang East Road, Suzhou 215021, People's Republic of China. mail
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12
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Abstract
The mitochondrial beta-oxidation of 2-methyl fatty acids was studied with coupled rat liver mitochondria and purified enzymes. Measurements of mitochondrial respiration supported by 2-methyl fatty acids, straight chain fatty acids, or their coenzyme A (CoA) thioesters revealed that free short-chain and medium-chain 2-methyl fatty acids are oxidized nearly or as efficiently as are their straight chain analogs. Long-chain 2-methyl hexadecanoyl-CoA is also oxidized, although more slowly than its unbranched counterpart. However, medium-chain 2-methyldecanoyl-CoA, in contrast to its unbranched analog, is not oxidized at all. Of all acyl-CoA dehydrogenases only long-chain acyl-CoA dehydrogenase acts on medium-chain and long-chain 2-methylacyl-CoA thioesters. The resultant 2-methyl-2-enoyl-CoA thioesters are substrates of the mitochondrial trifunctional beta-oxidation complex which catalyzes the sequential hydration, dehydrogenation, and thiolytic cleavage of 2-methyl-substituted substrates to yield chain-shortened acyl-CoA thioesters and propionyl-CoA. The matrix enzymes L-3-hydroxyacyl-CoA dehydrogenase and 3-ketoacyl-CoA thiolase, in contrast to enoyl-CoA hydratase, are inactive with medium-chain and long-chain 2-methyl-substituted chain substrates. The specificity of the beta-oxidation enzymes toward 2-methyl-branched substrates forms the basis for assays of long-chain acyl-CoA dehydrogenase and the trifunctional beta-oxidation complex in the presence of their mitochondrial isozymes. It is concluded that rat liver mitochondria can oxidize 2-methyl fatty acids, but does so most effectively with medium-chain and short-chain ones that can enter mitochondria directly in a carnitine-independent manner.
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Affiliation(s)
- L F Mao
- Department of Chemistry, City College of the City University of New York, New York 10031, USA
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13
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Luo MJ, Mao LF, Schulz H. Short-chain 3-hydroxy-2-methylacyl-CoA dehydrogenase from rat liver: purification and characterization of a novel enzyme of isoleucine metabolism. Arch Biochem Biophys 1995; 321:214-20. [PMID: 7639524 DOI: 10.1006/abbi.1995.1388] [Citation(s) in RCA: 34] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/26/2023]
Abstract
Short-chain L-3-hydroxy-2-methylacyl-CoA dehydrogenase (SC-HMAD), a soluble mitochondrial enzyme, was purified 6000-fold from rat liver in 6% yield by a six-step purification procedure. The purified enzyme was homogenous as judged by gel electrophoresis in the presence of sodium dodecyl sulfate. The molecular mass of this protein was estimated to be 28 kDa under denaturing conditions. Under nondenaturing conditions, the enzyme behaved on Sephacryl S-200 like serum albumin with a molecular mass of 66 kDa. Thus, SC-HMAD seems to be a dimer composed of two, most likely identical 28-kDa subunits. Immunoblotting with antibodies to pig heart L-3-hydroxyacyl-CoA dehydrogenase (HAD) (EC 1.1.1.35) revealed that SC-HMAD and HAD are immunologically unrelated proteins. SC-HMAD, but not HAD, catalyzes the NAD(+)-dependent dehydrogenation of L-3-hydroxy-2-methybutyryl-CoA, a metabolite of isoleucine, to 2-methylacetoacetyl-CoA. Relative activities with 3-hydroxy-2-methylacyl-CoA thioesters having acyl chains with 4, 5, 10, and 16 carbon atoms are 88, 100, 16, and 0%, respectively. Unbranched 3-hydroxyacyl-CoA thioesters are also substrates of SC-HMAD, although poorer ones as evidenced by apparent Km values of 5 and 19 microM for L-3-hydroxy-2-methylbutyryl-CoA and L-3-hydroxybutyryl-CoA, respectively. Maximal velocities observed with these two substrates were similar. It is concluded that SC-HMAD catalyzes the second dehydrogenation step during the beta-oxidation of the isoleucine metabolite 2-methylbutyryl-CoA. This enzyme may also be involved in the beta-oxidation of natural and xenobiotic branched chain carboxylic acids.
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Affiliation(s)
- M J Luo
- Department of Chemistry, City College of the City University of New York, New York 10031, USA
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14
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Abstract
The contribution of peroxisomes to palmitate beta-oxidation in rat heart was estimated by either inhibiting mitochondrial beta-oxidation or measuring the activity of acyl-CoA oxidase. When respiratory inhibitors such as KCN or antimycin plus rotenone, or inhibitors of mitochondrial fatty acid uptake such as 2-tetradecylglycidic acid or 2-bromopalmitate, were used, degrees of inhibitions ranging from 24% to 87% were observed for palmitate beta-oxidation by a rat heart homogenate. Although the oxidation of palmitoyl-L-carnitine by coupled rat heart mitochondria was almost completely (94%) inhibited by KCN, the inhibition by antimycin plus rotenone was incomplete (77%) and was stimulated by L-carnitine. A direct assay of acyl-CoA oxidase, based on the spectrophotometric measurement at 300 nm of 2,4-decadienoyl-CoA formation from 4-trans-decenoyl-CoA, was evaluated with the aim of obtaining reliable values for the activity of this enzyme, which is presumed to catalyse the rate-limiting step of peroxisomal beta-oxidation. Activities determined by use of this assay were much higher than activities obtained by a coupled assay [Small, Burdett and Connock (1985) Biochem. J. 227, 205-210] commonly used to measure the activity of acyl-CoA oxidase. However, both methods yielded the same relative activities with different tissue homogenates. Based on an estimated palmitoyl-CoA oxidase activity of 0.3 nmol/min per mg of protein, the contribution of peroxisomes to palmitate beta-oxidation in a rat heart homogenate would optimally be 4%, and most likely is several-fold lower.
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Affiliation(s)
- C Chu
- Department of Chemistry, City College of City University of New York, NY 10031
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15
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Mao LF, Chu C, Schulz H. Hepatic beta-oxidation of 3-phenylpropionic acid and the stereospecific dehydration of (R)- and (S)-3-hydroxy-3-phenylpropionyl-CoA by different enoyl-CoA hydratases. Biochemistry 1994; 33:3320-6. [PMID: 8136368 DOI: 10.1021/bi00177a024] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/29/2023]
Abstract
The hepatic beta-oxidation of 3-phenylpropionic acid (PPA) was studied by the use of subcellular fractions and purified enzymes with the aim of characterizing intermediates and the subcellular location of this pathway. Respiration measurements with coupled rat liver mitochondria indicate that PPA is efficiently metabolized by mitochondrial beta-oxidation. In contrast, the peroxisomal beta-oxidation of this compound is at best a very slow process, as evidenced by the low activity of peroxisomal acyl-CoA oxidase toward 3-phenylpropionyl-CoA. In mitochondria, 3-phenylpropionyl-CoA is effectively dehydrogenated to cinnamoyl-CoA, which is only slowly converted to benzoylacetyl-CoA due to the unfavorable equilibrium of the hydration of cinnamoyl-CoA to 3-hydroxy-3-phenylpropionyl-CoA. Benzoylacetyl-CoA is a substrate of 3-ketoacyl-CoA thiolase. The dehydration of 3-hydroxy-3-phenylpropionyl-CoA to cinnamoyl-CoA forms the basis for a sensitive and stereospecific assay of enoyl-CoA hydratases. The progress of this reaction, which proceeds to near completion, can be measured spectrophotometrically at 308 nm. Soluble mitochondrial and peroxisomal enoyl-CoA hydratases only act on the (R,L) isomer, whereas the peroxisomal D-3-hydroxyacyl-CoA dehydratase is specific for the (S,D) isomer. Both substrates can be easily prepared from the commercially available enantiomeric acids. It is concluded that PPA, a key compound in Knopp's classical study that led him to formulate the principle of beta-oxidation, is overwhelmingly, if not completely, degraded by mitochondrial beta-oxidation.
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Affiliation(s)
- L F Mao
- Department of Chemistry, City College, City University of New York, New York 10031
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Abstract
The activation of 4-bromocrotonic acid, 4-bromo-2-octenoic acid, valproic acid, and 3-methylglycidic acid by conversion to their CoA thioesters and the effects of these carboxylic acids on palmitoylcarnitine-supported respiration were studied with rat liver and rat heart mitochondria. 4-Bromocrotonic acid was activated by both liver and heart mitochondria, whereas 4-bromo-2-octenoic acid and valproic acid were only activated by liver mitochondria. 3-Methylglycidic acid was not a substrate of mitochondrial activation. All of the carboxylic acids that were activated also inhibited palmitoylcarnitine-supported respiration. 3-Methylglycidoyl-CoA was found to irreversibly inhibit 3-ketoacyl-CoA thiolase in a concentration-dependent and time-dependent manner. Together, these results lead to the conclusion that substituted medium-chain carboxylic acids, which enter mitochondria directly, may inhibit beta-oxidation as long as they are activated and perhaps further metabolized in the mitochondrial matrix to compounds that sequester CoA and/or inhibit beta-oxidation enzymes. Liver is more susceptible to inhibition by such xenobiotic carboxylic acids due to the broader substrate specificity of its mitochondrial medium-chain acyl-CoA synthetase (EC 6.2.1.2).
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Affiliation(s)
- K W Yao
- Department of Chemistry, City College of the City University of New York, NY 10031
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Mao LF, Millington DS, Schulz H. Formation of a free acyl adenylate during the activation of 2-propylpentanoic acid. Valproyl-AMP: a novel cellular metabolite of valproic acid. J Biol Chem 1992; 267:3143-6. [PMID: 1737769] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/28/2022] Open
Abstract
A study of the activation of valproic acid (2-n-propylpentanoic acid) by a soluble extract of rat liver mitochondria in the presence of ATP, CoASH, and MgCl2 revealed that, in addition to valproyl-CoA, an unknown UV-absorbing compound is formed which is the sole product when CoASH is omitted from the incubation mixture. The unknown compound, which was purified by high performance liquid chromatography, was identified as valproyl adenylate (valproyl-AMP) by mass spectrometry and by its enzymatic conversion to valproyl-CoA in the presence of CoASH. Valproyl-AMP exists, at least partially, in a free, not-enzyme-bound form. Its rate of formation is linear with time and increases 5-fold when the pH is decreased from 8 to 6.8. Valproyl-AMP was also identified when the metabolism of valproate was investigated with rat liver mitochondria and rat hepatocytes. Since the synthesis of valproyl-AMP is inhibited by octanoate, medium-chain acyl-CoA synthetase (EC. 6.2.1.2) may be responsible for its formation. This study establishes that during the activation of valproic acid to valproyl-CoA free valproyl-AMP is formed which is a novel cellular metabolite of valproic acid.
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Affiliation(s)
- L F Mao
- Department of Chemistry, City College, City University of New York, New York 10031
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18
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Abstract
The beta-oxidation of valproic acid (2-propylpentanoic acid), an anticonvulsant drug with hepatotoxic side effects, was studied with subcellular fractions of rat liver and with purified enzymes of beta-oxidation. 2-Propyl-2-pentenoyl-CoA, a presumed intermediate in the beta-oxidation of valproic acid, was chemically synthesized and used to demonstrate that enoyl-CoA hydratase or crotonase catalyzes its hydration to 3-hydroxy-2-propylpentanoyl-CoA. The latter compound was not acted upon by soluble L-3-hydroxyacyl-CoA dehydrogenases from mitochondria or peroxisomes but was dehydrogenated by an NAD(+)-dependent dehydrogenase associated with a mitochondrial membrane fraction. The product of the dehydrogenation, presumably 3-keto-2-propylpentanoyl-CoA, was further characterized by fast bombardment mass spectrometry. 3-Keto-2-propylpentanoyl-CoA was not cleaved thiolytically by 3-ketoacyl-CoA thiolase or a mitochondrial extract but was slowly degraded, most likely by hydrolysis. The availability of 2-propylpentanoyl-CoA (valproyl-CoA) and its beta-oxidation metabolites facilitated a study of valproate metabolism in coupled rat liver mitochondria. Mitochondrial metabolites identified by high-performance liquid chromatography were 2-propylpentanoyl-CoA, 3-keto-2-propylpentanoyl-CoA, 2-propyl-2-pentenoyl- CoA, and trace amounts of 3-hydroxy-2-propylpentanoyl-CoA. It is concluded that valproic acid enters mitochondria where it is converted to 2-propylpentanoyl-CoA, dehydrogenated to 2-propyl-2-pentenoyl-CoA by 2-methyl-branched chain acyl-CoA dehydrogenase, and hydrated by enoyl-CoA hydratase to 3-hydroxy-2-propylpentanoyl-CoA.(ABSTRACT TRUNCATED AT 250 WORDS)
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Affiliation(s)
- J Li
- Department of Chemistry, City College of the City University of New York, New York 10031
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