6 results on '"Luning Hao"'
Search Results
2. Improvement of magnetic and cryogenic energy preservation performances in a feeding-power-free superconducting magnet system for maglevs
- Author
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Nan Shao, Zhen Huang, Zhijian Jin, Luning Hao, Fangliang Dong, and Xiaoyong Xu
- Subjects
Superconductivity ,Work (thermodynamics) ,Materials science ,Magnetic energy ,020209 energy ,Mechanical Engineering ,Nuclear engineering ,Energy conversion efficiency ,02 engineering and technology ,Building and Construction ,Superconducting magnet ,Cryogenics ,Pollution ,Industrial and Manufacturing Engineering ,General Energy ,020401 chemical engineering ,Magnet ,0202 electrical engineering, electronic engineering, information engineering ,Energy transformation ,0204 chemical engineering ,Electrical and Electronic Engineering ,Civil and Structural Engineering - Abstract
This work relates to improvement of magnetic and cryogenic energy preservation performances in an on-board high-temperature superconducting magnet system used in linear synchronous motors for ultrahigh speed maglevs. Since maglevs remove all the physical contacts to the ground, the wireless on-board feeding power is rather limited especially for superconducting subassemblies. And it has become one of the development bottlenecks. For the magnet system, realization of on-board feeding-power free is pivotal, which is regarding to two important energy conversions: electrical to magnetic energy by persistent-current mode of superconductivity, and latent heat to effective cooling (or cryogenic) energy by α-β phase transition of solid nitrogen (SN2) in the system. Improvements of the two energy conversions are the main work. Firstly, model and numerical approach of persistent-current mode are proposed, followed by simulation of SN2 cooling. Then performances of persistent-current mode and cryogenic energy preservation are reported. Energy conversion efficiency is also analyzed for a strategy to improve cooling performance. The strategy successfully extends cryogenic energy preservation time to 8.83 h and suppresses thermal non-uniformity to
- Published
- 2020
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3. Human PIR1 of the Protein-tyrosine Phosphatase Superfamily Has RNA 5′-Triphosphatase and Diphosphatase Activities
- Author
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Luning Hao, Stephen Buratowski, Tarangini Deshpande, Toshimitsu Takagi, and Harry Charbonneau
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Molecular Sequence Data ,RNA-binding protein ,Biology ,Heterogeneous ribonucleoprotein particle ,Biochemistry ,Cell Line ,Catalytic Domain ,Escherichia coli ,Humans ,Signal recognition particle RNA ,Amino Acid Sequence ,Molecular Biology ,Glutathione Transferase ,RNA ,Cell Biology ,Non-coding RNA ,Molecular biology ,Acid Anhydride Hydrolases ,Post-transcriptional modification ,RNA editing ,Mutagenesis, Site-Directed ,Dual-Specificity Phosphatases ,Protein Tyrosine Phosphatases ,Sequence Alignment ,Small nuclear RNA - Abstract
A human cDNA was isolated encoding a protein with significant sequence similarity (41% identity) to the BVP RNA 5'-phosphatase from the Autographa californica nuclear polyhedrosis virus. This protein is a member of the protein-tyrosine phosphatase (PTP) superfamily and is identical to PIR1, shown by Yuan et al. (Yuan, Y., Da-Ming, L., and Sun, H. (1998) J. Biol. Chem. 272, 20347-20353) to be a nuclear protein that can associate with RNA or ribonucleoprotein complexes. We demonstrate that PIR1 removes two phosphates from the 5'-triphosphate end of RNA, but not from mononucleotide triphosphates. The specific activity of PIR1 with RNA is several orders of magnitude greater than that with the best protein substrates examined, suggesting that RNA is its physiological substrate. A 120-amino acid segment C-terminal to the PTP domain is not required for RNA phosphatase activity. We propose that PIR1 and its closest homologs, which include the metazoan mRNA capping enzymes, constitute a subgroup of the PTP family that use RNA as a substrate.
- Published
- 1999
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4. The Noncatalytic C-terminal Segment of the T Cell Protein Tyrosine Phosphatase Regulates Activity via an Intramolecular Mechanism
- Author
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Nicholas K. Tonks, Tony Tiganis, Luning Hao, and Harry Charbonneau
- Subjects
RNA Splicing ,T-Lymphocytes ,Proteolysis ,Molecular Sequence Data ,Mutant ,Protein tyrosine phosphatase ,Biology ,Biochemistry ,Catalysis ,Epitope ,medicine ,Humans ,Trypsin ,Amino Acid Sequence ,Molecular Biology ,Chromatography, High Pressure Liquid ,chemistry.chemical_classification ,medicine.diagnostic_test ,Hydrolysis ,C-terminus ,Endoplasmic reticulum ,Antibodies, Monoclonal ,Cell Biology ,Recombinant Proteins ,Enzyme Activation ,Enzyme ,chemistry ,RNA splicing ,Electrophoresis, Polyacrylamide Gel ,Protein Tyrosine Phosphatases - Abstract
Human T cell protein tyrosine phosphatase (TCPTP) is a nontransmembrane enzyme, the first of the protein tyrosine phosphatase family to be cloned. Alternative mRNA splicing results in variation in the sequence at the extreme C terminus of TCPTP and generates a 45-kDa form (TC45) that is targeted to the nucleus and a 48-kDa variant (TC48) associated with membranes of the endoplasmic reticulum. In this report, we assessed the role of the C-terminal, noncatalytic segment of TCPTP in regulating activity, concentrating primarily on the TC45 variant. We have demonstrated that limited tryptic proteolysis of TC45 releases first a 42-kDa fragment, then a 33-kDa catalytic domain. Using reduced carboxyamidomethylated and maleylated lysozyme as substrate (RCML), the catalytic domain displays 20-100-fold more activity than the full-length enzyme. Analysis of the time course of limited trypsinolysis revealed that proteolytic activation occurred following cleavage of a protease-sensitive region (residues 353-387) located at the C terminus of TC45. The activity of truncation mutants illustrated that removal of 20 C-terminal residues was sufficient to activate the enzyme fully. The 33-kDa catalytic domain, but not the full-length enzyme, was inhibited in a concentration-dependent manner by addition of the noncatalytic C-terminal segment of TC45. A monoclonal antibody to TCPTP, CF4, which recognizes an epitope located between residues 350 and 363, was capable of fully activating TC45. These data indicate that the noncatalytic segment of TC45 contains an autoregulatory site that modulates activity via a reversible intramolecular interaction with the catalytic domain. These studies suggest that the C-terminal noncatalytic segment of TC45, and possibly TC48, may not only direct the enzyme to different subcellular locations but may also modulate activity in response to the binding of regulatory proteins and/or posttranslational modification.
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- 1997
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5. A pK change of acidic residues contributes to cation countertransport in the Ca-ATPase of sarcoplasmic reticulum. Role of H+ in Ca(2+)-ATPase countertransport
- Author
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Luning Hao, Giuseppe Inesi, and Xiang Yu
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Carbonyl Cyanide p-Trifluoromethoxyphenylhydrazone ,Time Factors ,Proteolipids ,ATPase ,Fluorescence spectrometry ,Calcium-Transporting ATPases ,Models, Biological ,Biochemistry ,Membrane Potentials ,Adenosine Triphosphate ,Animals ,Molecular Biology ,Ion transporter ,chemistry.chemical_classification ,biology ,Muscles ,Vesicle ,Endoplasmic reticulum ,Cell Biology ,Hydrogen-Ion Concentration ,Membrane transport ,Calcium ATPase ,Kinetics ,Sarcoplasmic Reticulum ,Spectrometry, Fluorescence ,Enzyme ,chemistry ,Liposomes ,biology.protein ,Biophysics ,Calcium ,Rabbits - Abstract
Proteoliposomal vesicles reconstituted with sarcoplasmic reticulum ATPase and exogenous lipids sustain ATP-dependent Ca2+ uptake and H+ ejection, as well as net charge displacement by Ca2+. We have studied the effect of lumenal (inner) and medium (extravesicular) pH variations on the countertransport ratios of H+ and Ca2+. We find that the Ca2+/H+ molar ratio is approximately 1 when the lumenal and medium pH is near neutrality, but changes with a specific pattern when the medium pH is varied in the presence of a constant lumenal pH and when the lumenal pH is varied in the presence of a constant medium pH. Empirical analysis of the experimental data shows that the apparent pK of the residue(s) releasing H+ into the medium is approximately 6.1, whereas the apparent pK of the residue(s) binding lumenal H+ is approximately 7.7. Assuming that the same acidic residues are involved in H+ and Ca2+ countertransport, our findings suggest a lower affinity for H+ in their outward orientation (prevalent in the ground state of the enzyme) and a higher affinity for H+ in lumenal orientation (prevalent in the phosphorylated state of the enzyme). Cyclic pK changes, coupled to ATP utilization, promote cation exchange, Ca2+ uptake, and H+ ejection by the vesicles. The stoichiometry of countertransport and net charge displacement is matched by a corresponding electrogenic behavior. A calculation of voltage development related to initial rates of charge transfer (dV/dt = (dQ/dt)/Cm) is given as a corrective replacement of a previous steady state calculation.
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- 1994
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6. Ca2+/H+ countertransport and electrogenicity in proteoliposomes containing erythrocyte plasma membrane Ca-ATPase and exogenous lipids
- Author
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Luning Hao, Giuseppe Inesi, and J.-L. Rigaud
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Calmodulin ,Proteolipids ,ATPase ,Ionophore ,Calcium-Transporting ATPases ,Biochemistry ,Adenosine Triphosphate ,Humans ,Molecular Biology ,Ion transporter ,Liposome ,Chromatography ,biology ,Chemistry ,Vesicle ,Erythrocyte Membrane ,Biological Transport ,Cell Biology ,Lipid Metabolism ,Kinetics ,Membrane ,biology.protein ,Calcium ,Electrophoresis, Polyacrylamide Gel ,Steady state (chemistry) ,Hydrogen - Abstract
A reconstituted proteoliposomal system was obtained with Ca-ATPase purified from human erythrocyte membrane (plasma membrane, PM ATPase), and liposomes prepared by reverse-phase evaporation. The reconstituted PM ATPase behaved as an electrogenic Ca2+/H+ exchanger and, under optimal conditions, utilization of 1 mol of ATP was accompanied by uptake of one Ca2+ by the vesicles, and ejection of one H+ from the lumen of the vesicles. Ca2+ uptake was greatly (5-fold) stimulated by the addition of calmodulin, and by collapsing the H+ gradient with the ionophore carbonyl cyanide p-trifluoromethoxyphenylhydrazone. In the presence of calmodulin and p-trifluoromethoxyphenylhydrazone, the reconstituted system sustained transport rates of 1.00 +/- 0.12 mumol of Ca2+/mg of protein min-1 (30 degrees C), reaching asymptotic levels of 8.05 +/- 0.41 mumol of Ca2+/mg of protein (i.e. 20 mM lumenal Ca2+). The corresponding net charge transfer produced a maximal electrical gradient of 40.5 +/- 1.8 mV at steady state. Demonstration of the electrogenic behavior of the PM ATPase, obtained for the first time with these experiments, was critically dependent on the detergent used in the reconstitution procedure. The lumenal pH rise had a much greater rate-limiting effect on the pump, than the electrical potential developed by the pump.
- Published
- 1994
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