Enantioselective Dearomative [3 + 2] Umpolung Annulation of N-Heteroarenes with Alkynes.

Enantioselective [3 + 2] annulation of N-heteroarenes with alkynes has been developed via a cobalt-catalyzed dearomative umpolung strategy in the presence of chiral ligand and reducing reagent. A variety of electron-deficient N-heteroarenes, including quinolines, isoquinolines, quinoxaline, and pyridines, and internal or terminal alkynes are employed in this reaction, showing a broad substrate scope and good functionality tolerance. Annulation of electron-rich indoles with alkynes is also developed. This protocol provides a straightforward access to a variety of N-spiroheterocyclic molecules in excellent enantioselectivities (76 examples, up to 99% ee).

Synthesis of Polymer Single-Chain Nanoparticle with High Compactness in Cosolvent Condition: A Computer Simulation Study.

Polymeric single-chain nanoparticles (SCNPs) are soft nano-objects synthesized by intramolecular crosslinking of isolated single polymer chains. Syntheses of such SCNPs usually need to be performed in a dilute solution. In such a condition, the bonding probability of the two active crosslinking units at a short contour distance along the chain backbone is much higher than those which are far away from each other. Such a reaction condition often results in local spheroidization and, therefore, the formation of loosely packed structures. How to inhibit the local spheroidization and improve the compactness of SCNPs is thus a major challenge for the syntheses of SCNPs. In this study, computer simulations are performed and the fact that a precollapse of the polymer chain conformation in a cosolvent condition can largely improve the probability of the crosslinking reactions at large contour distances is demonstrated, favoring the formations of closely packed globular structures. As a result, the formed SCNPs can be more spherical and have higher compactness than those fabricated in ultradilute good solvent solution in a conventional way. It is believed this simulation work can provide a insight into the effective syntheses of SCNPs with spherical conformations and high compactness.

[Protein composition analysis and cytotoxicity of gulbulin hydrolysates of Brucea javanica seeds].

To analyze the protein composition of Brucea javanica seeds and evaluate the cytotoxicity of its gulbulin hydrolysates. Four protein fractions of albumin, gulbulin, prolamin and glutelin were sequentially extracted and then quantified by Kjeldahl method. Different kinds of proteases were applied to hydrolyze B.javanica gulbulin, and MTT assay was used to evaluate the cytotoxicity of low molecular weight hydrolysates (≤3 kDa) on human breast cancer MCF-7 cell. The results showed that： the total protein content of B.javanica seeds was 17.47%, albumin, gulbulin, coxin, glutelin and residue protein accounted for 15.01%, 8.11%, 2.47%, 44.92% and 23.62% of the total protein content, respectively. The hydrolysates (≤3 kDa) of B.javanica globulin produced by pepsin showed significant growth inhibitory activity on MCF-7 cells, and the IC50 value was（6.52±0.01） mg•L⁻¹ after 72 h of incubation. Protein was abundant in B.javanica seeds, and its peptides demonstrated specific cytotoxicity on MCF-7 cell line in vitro, suggesting antitumor active ingredient can be further generated from B.javanica seeds.

[Effects of Arsenic Trioxide on K562 Cell Proliferation and Its Mechanisms].

OBJECTIVE: To investigate the effects of arsenic trioxide (As2O3) on K562 cell proliferation by regulating cell cycle protein D1 and cyclin-dependent kinase inhibitor p27kip1. METHODS: MTT was used to detect the effect of As2O3 on K562 cell proliferation, so as to screen out the appropriate drug concentration. Furthermore, the K562 cell apoptosis was observed by microscopy. The expression of CyclinD1 and p27kip1 in K562 cells treated with As2O3 was analyzed by reverse transcription-polymerase chain reaction(RT-PCR), immunohistochemistry and Western blot. RESULTS: As2O3 could inhibit the proliferation of K562 cells in a dose- and time- dependent manner (r= 0.967). And the apoptosis cell number in As2O3 group was significantly higher than that in the control group(P<0.05). As2O3 could markedly inhibit the expression of CyclinD1 in K562 cells(P<0.05), but the expression of P27kip1 was not significantly changed after As2O3 treatment. CONCLUSIONS: As2O3 can induce K562 cell apoptosis and inhibit K562 cell proliferation by regulating the expression of CyclinD1.