Latest ArticlesThe deletion of the C-terminal arginine of the anaphylatoxin protein C5a reduces it receptor binding affinity. Understanding how C-terminal arginine affects the structure and bioactivity of C5a is important for the development of C5a C-terminal mimics as drug candidates. Herein, we report the total chemical synthesis of rat C5a and its D-enantiomer with its C-terminal arginine deleted, namely L-rC5a-desArg and D-rC5a-desArg. The structure of rC5a-desArg was then determined by racemic crystallography for the first time. The C-terminal residues of rC5a-Arg were found to expand from the fourth helix in a continuous helical conformation. This C-terminal conformation is significantly different from that of the previously reported full-length of C5a, indicating that the deletion of C-terminal arginine residue could result in the destruction of a positively charged surface formed by two adjacent Arg residues in C5a.
Absolute one-handed chiral quinoline tetramers andoctamers containing different oxazolylanilines at the C-terminus have been synthesized. The absolute one-handed sense and diastereomeric excess values were valued by 1H NMR. X-ray crystal diffractionand CD studies reveal that the S-oxazolylaniline always induces a P-handed helicity and the absolute helicity is driven by the stable three-center hydrogen bonding between protons in the amide and N atoms in oxazolylaniline and adjacent quinoline ring. CPL investigations demonstrated that S-CQn-a~d are CPL active and its glum values are dependent on its length. Interestingly, the sizes of the substituents in the chiral centers are different, however, they exert no effect on the dissymmetric factors gabs and glum of quinoline oligoamide foldamers.
We report on the synthesis of two acentric and one centrosymmetric Zn metal-organic complexes with 3-tetrazolemethyl pyridine spacers obtained in situ by hydrothermal routes. X-ray diffraction structural analysis reveals that they have the same equivalent nodes but with dissimilar topologies. The two acentric frameworks[Zn(Tzmp)Cl]n (1) and ([Zn(Tzmp)Br]n (2), HTzmp=3-tetrazolemethyl pyridine) are isomorphism which exhibit an acentric 3D framework with (10, 3)-b net called "ths", while the centrosymmetric complex ([Zn(Tzmp)N3]n (3)) features a distinctive 2D sheet with Shubnikov hexagonal plane net. Photo-luminescent studies suggest the ligand-field strength of coordinated negative ions (Cl- > Br- > N3-) has ordered adjusting effects on the emission redshift. The second harmonic generation (SHG) measurement shows that compounds 1 and 2 are nonlinear optically active, with SHG responses being 2/3 and half of the standard potassium dihydrogen phosphate (KDP), respectively.
Deposition of platinum (Pt) monolayers (PtML) on Au substrate represents a robust strategy to maximally utilize the Pt atoms and meanwhile achieve high catalytic activity towards methanol oxidation reaction for direct methanol fuel cells owing to a substrate-induced tensile strain effect. However, recent studies showed that PtML on Au substrate are far from perfect smooth monoatomic layer, but actually exhibited three-dimensional nanoclusters. Moreover, the PtML suffered from severe structural instability and thus activity degradation during long-term electrocatalysis. To regulate the growth of PtML on Au surface and also to improve its structural stability, we exploit dealloyed AuCu core-shell nanoparticles as a new substrate for depositing PtML. By using high-resolution scanning transmission electron microscopy and energy dispersive X-ray elemental mapping combined with electrochemical characterizations, we reveal that the dealloyed AuCu core-shell nanoparticles can effectively promote the deposition of PtML closer to a smooth monolayer structure, thus leading to a higher utilization efficiency of Pt and higher intrinsic activity towards methanol oxidation compared to those on pure Au nanoparticles. Moreover, the PtML deposited on the AuCu core-shell NPs showed substantially enhanced stability compared to those on pure Au NPs during long-term electrocatalysis over several hours, during which segregation of Cu to the Au/Pt interface was revealed and suggested to play an important role in stabilizing the PtML catalysts.
It is of a great challenge to develop semiconductor photocatalysts with potential possibilities to simultaneously enhance photocatalytic efficiency and inhibit generation of toxic intermediates. In this study, we developed a facile method to induce the La doping and cationic vacancie (VZn) on ZnO for the highly efficient complete NO oxidation. The photocatalytic NO removal efficiency increases from 36.2% to 53.6%. Most importantly, a significant suppressed NO2 production also has been realized. According to the DFTcalculations, ESR spectra and in situ FTIR spectra, the introduction of La3+ induce the redistribution of charge carriers in La-ZnO, which promote the production of·O2- and lead to the formation of VZn for the formation of·OH, contributing to the complete oxidation of NO to nitrate. Besides, the conversion pathway of photocatalytic NO oxidation has been elaborated. This work paves a new way to simultaneously realize the photocatalytic pollutants removal and the inhibition of toxic intermediates generation for efficient and safe air purification.
Herein, the origin of the diastereoselectivity of N-heterocyclic carbene (NHC)-catalyzed cross-benzoin reactions between an α-amino aldehyde and furfural was studied by density functional theory. The computational results showed that the reaction proceeded through four steps:nucleophilic addition of NHC onto furfural, formation of a Breslow intermediate, cross-coupling reaction between Breslow intermediate and α-amino aldehyde, and dissociation of the catalyst. The cross-coupling was identified as the diastereoselectivity-determining step, with the R-configured product generated preferentially. Noncovalent interaction (NCI) analysis showed that the C-H ··· O and C-H ··· F interactions were responsible for determining the diastereoselectivity.
Antimony-based materials have become promising anodes within lithium-ion batteries (LIBs) due to their low cost and the high theoretical capacity. However, there is a potential to further enhance the electrochemical performance of such antimony-based materials. Herein, Sb2Se3@C nanofibers (Sb2Se3@CNFs) are designed and obtained via a novel electrospinning method. Upon electrochemically testing as an anode within LIBs, the Sb2Se3@CNFs (annealed at 600 ℃) delivers a remarkably good cycling performance of 625 mAh/g at 100 mA/g after 100 cycles. Moreover, it still remains at 490 mAh/g after 500 cycles with an applied current density of 1.0 A/g. The excellent performance of the Sb2Se3@CNFs can be attributed to the fact that the N-doped C matrices not only remit the volume expansion of materials, but also enhance the electrical and ionic conductivity thusly increasing the lithium-ion diffusion. The obtained Sb2Se3@CNFs are promising anode for LIBs in the future.
β-Elemene is a volatile oil used for the treatment of cancer, but poor solubility, low bioavailability, and various adverse reactions limit its application. For ameliorating risks of the venous toxicity of β-elemene, intravenously injectable micelle of β-elemene was prepared using the thin-film hydration method. The results pointed out the micelles were uniformly spherical with about 20.96 ± 0.1966 nm in average diameter and exhibited high entrapment efficiency (99.02% ± 0.88%). As revealed by drug release studies in vitro, β-elemene micelles had sustained drug release. Compared with free β-elemene, the micelles increased the drug cellular uptake and enhanced the anti-tumor effect in vitro through retarding cell cycle and inducing apoptosis. Meanwhile, the elevated serum stability of β-elemene micelles implied less drug leakage and reduced toxicity. The wound healing and tube formation assay in vitro demonstrated the anti-metastasis and anti-angiogenesis effects of β-elemene micelles. Moreover, the pharmacokinetics study showed the AUC and T1/2 of β-elemene in micelle group were 1.79 and 1.62 times of that in free β-elemene group, suggesting the circulation time of β-elemene in the blood had been prolonged. In addition, β-elemene micelles showed a favorable antitumor response compared with the β-elemene solution on C26 colon cancer-bearing mice model. Local irritation study investigated in rabbits indicated that the β-elemene micelles strikingly mitigated the irritation to the injection sites compared with free β-elemene. These results proved that the micelle could be a good candidate as an auspicious drug delivery system of β-elemene for the prospective clinical treatment of carcinoma.
In this paper, norbornene imidazolium hexafluorophosphate (NM-MIm-PF6) was modified on the surface of aminopropyl silica by ring-opening metathesis polymerization (ROMP), and then oligo(ethylene glycol) methacrylate (OEGMA) were grafted on the surface by atom transfer radical polymerization (ATRP). Some characterizations in this article confirmed that the synthesis of P(NM-MIm-PF6)-SiPOEGMA (P1-Si-P2) is successful. The P1-Si-P2 can separate sugars, amino acids, sulfonamides in a hydrophilic interaction mode and alkyl benzene, polycyclic aromatic hydrocarbon in a reverse phase mode. The experiment also found that the column has typical characteristics of hydrophobic/hydrophilic separation mechanism. Compared to single hydrophobic C18 column and single hydrophilic Si-NH2 column, this P1-Si-P2 shows certain advantages.
A ferrocene-initiated radical reaction of benzoquinone with amines has been successfully developed for the direct access to diaminobenzoquinone imines in high yields, in which the commercially available and cheap ferrocene was employed as a radical initiator and TBHP was used as an oxidant. Moreover, this reaction could be achieved with low loading of ferrocene (0.5 mol%). This protocol is highly efficient with good substrate tolerance and provides a new approach for the construction of benzoquinone imines with potential pharmaceutical interest.
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