Browsing by Author "He, LH"
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- ItemAnalysis of monoPEGylated human galectin-2 by small-angle x-ray and neutron scattering: concentration dependence of PEG conformation in the conjugate(American Chemical Society, 2010-12-01) He, LH; Wang, H; Garamus, VM; Hanley, TL; Lensch, M; Gabius, HJ; Fee, CJ; Middelberg, APJProtein conjugation with polyethylene glycol (PEG) is a valuable means for improving stability, solubility, and bioavailability of pharmaceutical proteins. Using human galectin-2 (hGal-2) and 5 kDa PEG as a model system we first produced a PEG-hGal-2 conjugate exclusively at the Cys75 residue, resulting in two monosubstituted subunits per hGal-2 homodimer. Small angle X-ray and neutron scattering (SAXS and SANS) were combined to provide complementary structural information about the PEG-hGal-2 conjugate, wherein signal generation in SAXS depends mainly on the protein while SANS data presents signals from both the protein and PEG moieties. SAXS data gave a constant radius of gyration (Rg = 21.5 Å) for the conjugate at different concentrations and provided no evidence for an alteration of homodimeric structure or hGal-2 ellipsoidal shape upon PEGylation. In contrast, SANS data revealed a concentration dependence of Rg for the conjugate, with the value decreasing from 31.5 Å at 2 mg/mL to 26 Å at 14 mg/mL (based on hGal-2 concentration). Scattering data have been successfully described by the model of the ellipsoidal homogeneous core (hGal-2) attached with polymer chains (PEG) at the surface. Evidently, the PEG conformation of the conjugate strongly depends on conjugate concentration and PEG’s radius of gyration decreases from 24.5 to 15 Å. An excluded volume effect, arising from steric clashes between PEG molecules at high concentration, was quantified by estimating the second virial coefficient, A2, of PEGylated hGal-2 from the SANS data. A positive value of A2 (6.0 ± 0.4 × 10−4 cm3 mol g−2) indicates repulsive interactions between molecules, which are expected to protect the PEGylated protein against aggregation. © 2010 American Chemical Society
- ItemHigh yield expression and efficient purification of deuterated human protein galectin-2(Elsevier, 2012-07-01) Chen, XJ; Wilde, KL; Wang, H; Lake, V; Holden, PJ; Middelberg, APJ; He, LH; Duff, APStructural studies of biological macromolecules often require deuterated proteins, necessitating an effective bioprocessing strategy for high yield deuteration and purification. The fermentation and bioseparation studies reported here concern deuterated human protein galectin-2 mutant C57M (hGal-2), a protein showing potential for therapeutic applications. Using the vector pET-28a and a defined D2O based minimal medium with glycerol as the sole carbon source and kanamycin for selection, we have demonstrated that a high density of Escherichia coli expressing deuterated protein at a bench bioreactor scale (7L) can be achieved, with due attention to prevention of oxygen limitation. Yields achieved were 58 g\L biomass (wet weight) containing 0.7 g/L hGal-2. Affinity chromatography and ion-exchange chromatography were combined to achieve high purity as well as removal of hGal-2 aggregates, giving an overall yield of 1200 mg deuterated hGal-2. The deuterated hGal-2 was characterized and compared with the non-deuterated protein by size exclusion chromatography (SEC), HPLC, N-terminal sequencing, mass spectrometry (MS) and a dot blot immunoassay, showing that deuteration and subsequent purification did not impact the lactose binding and antibody recognition abilities of hGal-2. MS for both intact and trypsin-digested hGal-2 demonstrated that the extent of labeling of non-exchangeable hydrogen atoms by deuterium was (66 +/- 1)%, which provides sufficient contrast variation for structural studies using small angle neutron scattering. The fermentation and bioseparation method established in this work can be applied to process other deuterated proteins with high yield and purity, opening the way to advanced structural studies. © Institution of Chemical Engineers 2014.
- ItemOptimizing the structure of layered cathode material for higher electrochemical performance by elucidating structural evolution during heat processing(Elsevier, 2020-12-01) Huang, ZY; Chu, MH; Wang, R; Zhu, WM; Zhao, WG; Wang, CQ; Zhang, YJ; He, LH; Chen, J; Deng, SH; Mei, LW; Kan, WH; Avdeev, M; Pan, F; Xiao, YGImproving electrochemical performance of cathode materials for lithium-ion batteries requires comprehensive understanding of their structural properties which could facilitate or impede the diffusion of lithium during charge-discharge. In order to optimize the structure and improve the electrochemical performance of layered cathode material, the detailed structural evolution as a function of heat treatment temperature in LiNi0.8Co0.1Mn0.1O2 was investigated by in-situ and ex-situ neutron powder diffraction methods. We show that both cycling stability and rate performance of LiNi0.8Co0.1Mn0.1O2 can be improved by performing heat treatment at 400 °C, which is attributed to the optimization of surface structure and the enlargement of c/a ratio. Heat treatment of LiNi0.8Co0.1Mn0.1O2 at higher temperature induces a layered-to-rock-salt structure phase transition accompanied with the precipitation of lithium oxide. A 3D phase diagram, which correlates the high temperature phases and room temperature phases, is constructed. The presentation of comprehensive phase diagrams up to 1000 °C could provide the basis for further research on not only synthesis strategy but also thermal stability in Ni-rich layered cathode materials. © 2020 Elsevier Ltd.
- ItemStructural and dynamic properties of MgAgSb-based thermoelectric materials studied by neutron scattering(International Conference on Neutron Scattering, 2017-07-12) Li, XY; Wang, BT; Guidi, T; Avdeev, M; He, LH; Zhao, HZ; Wang, FWA breakthrough on thermoelectric materials was recently reported in MgAgSb-based compounds with high ZT value (ZT ~ 1.4 at 450 - 530 K), stimulating the new prospects on the near room temperature (RT) application of thermoelectric generation and solid-state cooling. Here, high resolution neutron powder diffraction (NPD) and inelastic neutron scattering (INS) experiments were performed using ECHIDNA @ ANSTO and MARI @ ISIS, respectively. Rietveld structure refinement of the NPD data indicates that the space group of MgAg0.97Sb0.99 is I-4c2 both at 3 K and 300 K. Combining magnetic and heat-capacity measurements demonstrated that there are no phase transitions between 3 K to RT, in contrast with rich structural phase transitions in the RT - 700 K range. Considering the remarkable crystal-grain-size effect on the thermoelectric performance, we refined the apparent size of ~ 22 nm, validating the TEM result of 10 - 20 nm. We demonstrated that the phonon density of states (PDOS) deduced from MARI data is roughly in agreement with our ab initio calculations. We also analyzed the resonant bonding and LA-TO coupling which are believed to responsible for the low phonon thermal conductivity. Amazingly only 0.5% Ni doping at Ag site reduces the thermal conductivity by more than 8%. High resolution INS experiments to accurately measure the low frequency PDOS will be performed to study the Ni doping effect on the low thermal conductivity mechanism, combining with ab initio calculation.
- ItemThermal batteries based on inverse barocaloric effects(Science Advances, 2023-02) Zhang, Z; Li, K; Lin, SC; Song, R; Yu, DH; Wang, Y; Wang, JF; Kawaguchi, S; Zhang, Z; Yu, CY; Li, XD; Chen, J; He, LH; Mole, RA; Yuan, B; Ren, QY; Qian, K; Cai, ZL; Yu, JG; Wang, MC; Zhao, CY; Tong, X; Zhang, ZD; Li, BTo harvest and reuse low-temperature waste heat, we propose and realize an emergent concept-barocaloric thermal batteries based on the large inverse barocaloric effect of ammonium thiocyanate (NH4SCN). Thermal charging is initialized upon pressurization through an order-to-disorder phase transition, and the discharging of 43 J g-1 takes place at depressurization, which is 11 times more than the input mechanical energy. The thermodynamic equilibrium nature of the pressure-restrained heat-carrying phase guarantees stable long-duration storage. The barocaloric thermal batteries reinforced by their solid microscopic mechanism are expected to substantially advance the ability to take advantage of waste heat. Copyright © 2023 The Authors, some rights reserved; exclusive licensee American Association for the Advancement of Science. No claim to original U.S. Government Works. Distributed under a Creative Commons Attribution NonCommercial License 4.0 (CC BY-NC).
- ItemUltralow thermal conductivity from transverse acoustic phonon suppression in distorted crystalline α-MgAgSb(Springer Nature, 2020-02-18) Li, XY; Liu, PF; Zhao, EY; Zhang, ZG; Guidi, T; Le, MD; Avdeev, M; Ikeda, K; Otomo, T; Kofu, M; Nakajima, K; Chen, J; He, LH; Ren, Y; Wang, XL; Wang, BT; Ren, ZF; Zhao, HZ; Wang, FWLow thermal conductivity is favorable for preserving the temperature gradient between the two ends of a thermoelectric material, in order to ensure continuous electron current generation. In high-performance thermoelectric materials, there are two main low thermal conductivity mechanisms: the phonon anharmonic in PbTe and SnSe, and phonon scattering resulting from the dynamic disorder in AgCrSe2 and CuCrSe2, which have been successfully revealed by inelastic neutron scattering. Using neutron scattering and ab initio calculations, we report here a mechanism of static local structure distortion combined with phonon-anharmonic-induced ultralow lattice thermal conductivity in α-MgAgSb. Since the transverse acoustic phonons are almost fully scattered by the compound’s intrinsic distorted rocksalt sublattice, the heat is mainly transported by the longitudinal acoustic phonons. The ultralow thermal conductivity in α-MgAgSb is attributed to its atomic dynamics being altered by the structure distortion, which presents a possible microscopic route to enhance the performance of similar thermoelectric materials. © The Author(s) 2020.