| 1. |
- Zhang, Longhai, et al.
(författare)
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Rational Design of Multinary Metal Chalcogenide Bi0.4Sb1.6Te3 Nanocrystals for Efficient Potassium Storage
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Ingår i: Advanced Materials. - 0935-9648.
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Tidskriftsartikel (refereegranskat)abstract
- Multinary metal chalcogenides hold considerable promise for high-energy potassium storage due to their numerous redox reactions. However, challenges arise from issues such as volume expansion and sluggish kinetics. Here, a design featuring a layered ternary Bi0.4Sb1.6Te3 anchored on graphene layers as a composite anode, where Bi atoms act as a lattice softening agent on Sb, is presented. Benefiting from the lattice arrangement in Bi0.4Sb1.6Te3 and structure, Bi0.4Sb1.6Te3/graphene exhibits a mitigated expansion of 28% during the potassiation/depotassiation process and demonstrates facile K+ ion transfer kinetics, enabling long-term durability of 500 cycles at various high rates. Operando synchrotron diffraction patterns and spectroscopies including in situ Raman, ex situ adsorption, and X-ray photoelectron reveal multiple conversion and alloying/dealloying reactions for potassium storage at the atomic level. In addition, both theoretical calculations and electrochemical examinations elucidate the K+ migration pathways and indicate a reduction in energy barriers within Bi0.4Sb1.6Te3/graphene, thereby suggesting enhanced diffusion kinetics for K+. These findings provide insight in the design of durable high-energy multinary tellurides for potassium storage.
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| 2. |
- Hua, Weijie, et al.
(författare)
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X-ray spectroscopy of blocked alanine in water solution from supermolecular and supermolecular-continuum solvation models : a first-principles study
- 2012
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Ingår i: Physical Chemistry, Chemical Physics - PCCP. - : Royal Society of Chemistry (RSC). - 1463-9076 .- 1463-9084. ; 14:27, s. 9666-9675
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Tidskriftsartikel (refereegranskat)abstract
- The N1s near-edge X-ray absorption fine structure (NEXAFS) and X-ray emission spectra (XES) of blocked alanine in water solution have been investigated at the first-principles level based on cluster models constructed from classical molecular dynamics simulations. The bulk solvent has been described by both supermolecular and combined supermolecular-continuum models. With the former model we show that NEXAFS spectra convergent with respect to system size require at least the inclusion of the second solvation shell and that averaged spectra over several hundreds of snapshots can well represent the statistical effect of different instantaneous configurations of the solvation shells. With the combined model we demonstrate that calculations of a medium-sized peptide-water supermolecule qualitatively predict the NEXAFS spectrum of the solvated peptide even considering a single geometry. Furthermore, sampling over hundreds of snapshots by the combined model, the explicit inclusion of even a few waters yields an averaged spectrum in good quantitative agreement with the discrete model results. In comparison, the XES spectra show little dependence on the structures
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| 3. |
- Li, Hongbao, et al.
(författare)
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A Fragment Based Step-by-Step Strategy for Determining the Most Stable Conformers of Biomolecules
- 2014
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Ingår i: Chemical Physics Letters. - : Elsevier BV. - 0009-2614 .- 1873-4448. ; 610, s. 303-309
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Tidskriftsartikel (refereegranskat)abstract
- For biomolecules of increased size and flexibility, more efficient and reliable strategiesare always needed to determine their stable low-energy conformers. Here, we propose a fragment basedstep-by-step strategy to search for the full conformational space of biomolecules. In this strategy, themolecule is divided into several fragments and each of them is systematically optimized in a step-bystepfashion. It can significantly reduce the computational cost without losing any accuracy asdemonstrated by the conformer search of several representative di-/tri-/tetra- peptides. Such an approachwill be very useful for finding the stable conformers of large biomolecules.
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| 4. |
- Li, Hongbao, 1983-
(författare)
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Conformations of amino acids characterized by theoretical spectroscopy
- 2014
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Amino acids are the basic building blocks of proteins. The determinationof their structures plays an important role in correctly describing the functionsof the proteins. This thesis is devoted to theoretical studies on the potentialenergy surface of amino acids, in particular the infrared and soft X-ray spectralfingerprints of their most stable conformers.The stable structures of amino acids can be explored by different methods.We have used a full space systematic search strategy to determine the potentialenergy surface of deprotonated arginine and revealed several new conformers.With that, the calculated thermodynamic parameters are finally in good agreementwith their experimental counterparts. We have also proposed a molecularfragment based step-by-step strategy to search for the most stable conformers oflarge biomolecules. The high efficiency and good accuracy of this strategy havebeen firmly illustrated by the modeling of several polypeptides.Infrared (IR) spectroscopy has become one of the most applied techniques tocharacterize the structures of gas-phase amino acids. A direct comparison betweenexperimental and calculated infrared spectra provides an efficient way to describethe conformation exchanges of the amino acids. It is found that the conformersof an amino acid are not always necessary to reach the thermal equilibrium undercertain experimental conditions. The local minima could be responsible for theappearance of the measured spectra. This important point has been highlightedby the calculations of deprotonated tyrosine and cysteine, as well as the arginine.The near-edge X-ray absorption fine structure (NEXAFS) spectra and X-rayphotoelectron spectra (XPS) have also been simulated for neutral, deprotonatedand protonated arginine. The influences of intra-, and intermolecular hydrogenbonds on the electronic structure of the arginine have been carefully examined. Itis suggested that the XPS is capable of distinguishing the canonical and zwitterinicisomers of arginine, and works much better than any other tools available.
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| 5. |
- Li, Hongbao, et al.
(författare)
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First-Principles Study on Core-Level Spectroscopy of Arginine in Gas and Solid Phases
- 2012
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Ingår i: Journal of Physical Chemistry B. - : American Chemical Society (ACS). - 1520-6106 .- 1520-5207. ; 116:42, s. 12641-12650
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Tidskriftsartikel (refereegranskat)abstract
- First-principles simulations have been performed for near-edge X-ray absorption fine-structure (NEXAFS) spectra of neutral arginine at different K-edges in the solid phase as well as X-ray photoelectron spectra (XPS) of neutral, deprotonated, and protonated arginines in the gas phase. Influences of the intra- and intermolecular hydrogen bonds (HBs) and different charge states have been carefully examined to obtain useful structure-property relationships. Our calculations show a noticeable difference in the NEXAFS/XPS spectra of the canonical and zwitterionic species that can be used for unambiguously identifying the dominant form in the gas phase. It is found that the deprotonation/protonation always results in red/blue shifts of several electronvolts for the core binding energies (BEs) at all edges. The normal hydrogen bond Y-H center dot center dot center dot X (X, Y = N, O) can cause a blue/red shift of ca. 1 eV to the core BEs of the proton acceptor X/donor Y, while the weak C-H center dot center dot center dot Y hydrogen bond may also lead to a weak red shift (less than 1 eV) of the C1s BEs. Moreover, the influence of intermolecular interactions in the solid state is reflected as a broadening in the sigma* region of the NEXAFS spectra at each edge, while in the pi* region, these interactions lead to a strengthening or weakening of individual transitions from different carbons, although no evident visual change is found in the resolved total spectra. Our results provide a better understanding of the influences of the intra- and intermolecular forces on the electronic structure of arginine.
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| 6. |
- Li, Hongbao, et al.
(författare)
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Gas-phase IR spectroscopy of deprotonated amino acids : Global or Local minima?
- 2014
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Ingår i: Chemical Physics Letters. - : Elsevier BV. - 0009-2614 .- 1873-4448. ; 598, s. 86-90
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Tidskriftsartikel (refereegranskat)abstract
- Density functional theory calculations for the structure and IR spectroscopy of deprotonated tyrosine and cysteine molecules in gas phase have been carried out to resolve the on-going debate about the global minimum of deprotonated amino acids. It is found that the global minimum of the deprotonated specie is not always directly produced from the most stable neutral conformer. Depending on the setup, the experimental IR spectroscopy of deprotonated amino acids could only give the information of the local minima of the deprotonated species.
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| 7. |
- Li, Hongbao, et al.
(författare)
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Identification of the protonation site of gaseous triglycine : the cis-peptide bond conformation as the global minimum
- 2017
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Ingår i: Physical Chemistry, Chemical Physics - PCCP. - : Royal Society of Chemistry. - 1463-9076 .- 1463-9084. ; 19:23, s. 15030-15038
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Tidskriftsartikel (refereegranskat)abstract
- Extensive ab initio investigations have been performed to characterize stable conformers of protonated triglycine (GGGH) in the gas phase. Calculations using the composite CBS-QB3 method confirmed that the most favorable site of protonation on triglycine at 298 K is still the traditional amino nitrogen, rather than the more-recently reported amide oxygen. Furthermore, a non-proline cis-peptide bond conformer is identified for the first time as the global minimum of GGGH. Further transition state calculations considering the temperature effects explained why the previous experimental infrared multiple photon dissociation (IRMPD) spectrum contains a combination of two local minima, rather than a global one. First-principles simulations have been performed for near-edge X-ray absorption fine-structure (NEXAFS) spectra and X-ray photoelectron spectra (XPS) at the C, N and O K-edges to identify the notable spectral differences that enable the unambiguous identification of different protonated forms. The calculated proton affinity (PA) and gas basicity (GB) of triglycine are in excellent agreement with the experimental values. Our study thus provides valuable insights into the protonation of short peptides and illustrates the competition between cis and trans peptide bonds.
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| 8. |
- Li, Hongbao, et al.
(författare)
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The Role of Dimerization on the Structure Transformation of Arginine in Gas Phase
- 2014
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Ingår i: Chemical Physics Letters. - Elsevier : Elsevier BV. - 0009-2614 .- 1873-4448. ; 608, s. 398-403
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Tidskriftsartikel (refereegranskat)abstract
- The equilibrium distribution of arginine molecules in canonical and zwitterionicforms predicted by the theory failed to correctly reproduce the double-peak feature observedin the IR experiment. We have shown from first principles calculations that the energeticallyfavorable dimerization of zwitterions can effectively eliminate the pathway for the structureconversion between two distinct canonical forms and reduce the probability for thesecanonical forms to reach their thermal equilibrium. The role of dispersion effect is discussed.It suggests that the experimental IR spectrum is determined by the way how the conformersof arginine are initially generated.
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