A universal strategy to prepare sulfur-containing polymer composites with desired morphologies for lithium−sulfur batteries

Lithium–sulfur (Li–S) batteries are probably the most promising candidates for the next-generation batteries owing to their high energy density. However, Li–S batteries face severe technical problems where the dissolution of intermediate polysulfides is the biggest problem because it leads to the degradation of the cathode and the lithium anode, and finally the fast capacity decay. Compared with the composites of elemental sulfur and other matrices, sulfur-containing polymers (SCPs) have strong chemical bonds to sulfur and therefore show low dissolution of polysulfides. Unfortunately, most SCPs have very low electron conductivity and their morphologies can hardly be controlled, which undoubtedly depress the battery performances of SCPs. To overcome these two weaknesses of SCPs, a new strategy was developed for preparing SCP composites with enhanced conductivity and desired morphologies. With this strategy, macroporous SCP composites were successfully prepared from hierarchical porous carbon. The composites displayed discharge/charge capacities up to 1218/1139, 949/922, and 796/785 mA h g–1 at the current rates of 5, 10, and 15 C, respectively. Considering the universality of this strategy and the numerous morphologies of carbon materials, this strategy opens many opportunities for making carbon/SCP composites with novel morphologies

Modeling a New Water Channel That Allows SET9 to Dimethylate p53

SET9, a protein lysine methyltransferase, has been thought to be capable of transferring only one methyl group to target lysine residues. However, some reports have pointed out that SET9 can dimethylate Lys372 of p53 (p53-K372) and Lys4 of histone H3 (H3-K4). In order to understand how p53 can be dimethylated by SET9, we measured the radius of the channel that surrounds p53-K372, first on the basis of the crystal structure of SET9, and we show that the channel is not suitable for water movement. Second, molecular dynamic (MD) simulations were carried out for 204 ns on the crystal structure of SET9. The results show that water leaves the active site of SET9 through a new channel, which is made of G292, A295, Y305 and Y335. In addition, the results of molecular docking and MD simulations indicate that the new water channel continues to remain open when S-adenosyl-L-methionine (AdoMet) or S-adenosyl-L-homocysteine (AdoHcy) is bound to SET9. The changes in the radii of these two channels were measured in the equilibrium phase at the constant temperature of 300 K. The results indicate that the first channel still does not allow water to get into or out of the active site, but the new channel is large enough to allow this water to circulate. Our results indicate that water can be removed from the active site, an essential process for allowing the dimethylation reaction to occur

Representative β-hairpins and β-sheets from REMD of monomeric PrP106–126.

<p>Representative β-hairpins and β-sheets from REMD of monomeric PrP106–126.</p

Distributions and representative structures of dimeric PrP106–126.

<p>Distributions and representative structures of dimeric PrP106–126.</p

Averaged secondary structure contents for the residues included in dimeric PrP106–126.

<p>The secondary structure contents were averaged over the two homologous chains.</p

Last snapshots of the simulations and the detailed illustrations of β-hairpin acquired by the two stable trimers.

<p>The ending structures were colored based on secondary structure. The residues forming the β-hairpin were shown in Licorice and colored according to names of atoms.</p

Interchain contact map of PrP106–126.

<p>Interchain contact map of PrP106–126.</p

The top ten most populated representative conformations of PrP106–126.

<p>The N-terminal region and the C-terminal region are labeled by pink and green balls respectively. α-helices are in purple, extended β-sheets in yellow, 3–10 helices in blue, turns in cyan and coils in white.</p

Ensemble-averaged contact map for PrP106–126.

<p>The (i,i), (i,i±1), and (i,i±2) are not included and result in the dark blue diagonal as shown in this figure.</p

Ensemble-averaged secondary structure fraction for each residue of PrP106–126.

<p>Seven secondary structure elements are turn, β-bridge, α-helix, 3–10 helix, π-helix, coil and β-sheet, respectively.</p