靖西长喙木兰，广西木兰科一新种（英文）

描述了产自广西木兰科一新种：靖西长喙木兰(Lirianthe jingxiensis Y. H. Tong&N. H. Xia)。本种形态上与绢毛木兰[L. albosericea(Chun&C. H. Tsoong)N. H. Xia&C. Y. Wu]接近,但区别在于该种植株较矮,幼枝、叶柄和幼叶被黄棕色绢毛,叶柄较宽,叶片较宽,倒卵形或倒卵状椭圆形,先端钝或短渐尖,花被片较大,心皮数目较多,被黄棕色绢毛。     

The key residues of active sites on the catalytic fragment for paclitaxel interacting with poly (ADP-ribose) polymerase

Poly(ADP-ribose) polymerase (PARP) is regarded as a target protein for paclitaxel (PTX) to bind. An important issue is to identify the key residues as active sites for PTX interacting with PARP, which will help to understand the potential drug activity of PTX against cancer cells. Using docking method and MD simulation, we have constructed a refined structure of PTX docked on the catalytic function domain of PARP (PDB code: 1A26). The residues Glu327(988), Tyr246(907), Lys242(903), His165(826), Asp105(766), Gln102(763) and Gln98(759) in PARP are identified as potential sites involved in interaction with PTX according to binding energy (E(b)) between PTX and single residue calculated with B3LYP/6-31G(d,p). These residues form an active binding pocket located on the surface of the catalytic fragment, possibly interacting with the required groups of PTX leading to its activity against cancer cells. It is noted that most of the active sites make conatct with the "southern hemisphere" of PTX except for one residue, Tyr246(907), which interacts with the "northern hemisphere" of PTX. The conformation of PTX in complex with the catalytic fragment is observed as being T-shaped, similar to that complexed with β-tubulin. The total Eb of -269.9 kJ/mol represents the potent interaction between PTX and the catalytic fragment, implying that PTX can readily bind to the active pocket. The tight association of PTX with the catalytic fragment would inhibit PARP activation, suggesting a potential application of PTX as an effective antineoplastic agent.     

群体大小和觅食环境变化对东黑冠长臂猿日移动距离的影响

日移动距离是反映动物觅食努力的重要指标之一,相关研究有助于了解动物对生境的适应策略,对濒危物种的保护至关重要.东黑冠长臂猿(Nomascus nasutus)是一种极度濒危的树栖小型类人猿,主要生活在一夫二妻制的群体中,平均群体大小6.3只,目前对于该物种的日移动距离仍然缺乏足够的科学研究.我们以广西邦亮长臂猿国家级自...     

The small molecule CS1 inhibits mitosis and sister chromatid resolution in HeLa cells

Background

Mitosis, the most dramatic event in the cell cycle, involves the reorganization of virtually all cellular components. Antimitotic agents are useful for dissecting the mechanism of this reorganization. Previously, we found that the small molecule CS1 accumulates cells in G2/M phase [1], but the mechanism of its action remains unknown.

Structural insight into the mechanism of epothilone A bound to beta-tubulin and its mutants at Arg282Gln and Thr274Ile

Epothilone A (EpoA) is under investigation as an antitumor agent. To provide better understanding of the activity of EpoA against cancers, by theoretical studies such as using docking method, molecular dynamics simulation and density functional theory calculations, we identify several key residues located on β-tubulin as the active sites to establish an active pocket responsible for interaction with EpoA. Eight residues (Arg276, Asp224, Asp26, His227, Glu27, Glu22, Thr274, and Met363) are identified as the active sites to form the active pocket on β-tubulin. The interaction energy is predicted to be -121.3?kJ/mol between EpoA and β-tubulin. In the mutant of β-tubulin at Thr274Ile, three residues (Arg359, Glu27, and His227) are identified as the active sites for the binding of EpoA. In the mutant of β-tubulin at Arg282Gln, three residues (Arg276, Lys19, and His227) serve as the active sites. The interaction energy is reduced to -77.2?kJ/mol between EpoA and Arg282Gln mutant and to -50.2?kJ/mol between EpoA and Thr274Ile mutant. The strong interaction with β-tubulin is significant to EpoA's activity against cancer cells. When β-tubulin is mutated either at Arg282Gln or at Thr274Ile, the decreased strength of interaction explains the activity reduced for EpoA. Therefore, this work shows that the structural basis of the active pocket plays an important role in regulating the activity for EpoA with a Taxol-like mechanism of action to be promoted as an antitumor agent.     

Molecular dynamics simulation and density functional theory studies on the active pocket for the binding of paclitaxel to tubulin

Paclitaxel (PTX) is used to treat various cancers, but it also causes serious side effects and resistance. To better design similar compounds with less toxicity and more activity against drug-resistant tumors, it is important to clearly understand the PTX-binding pocket formed by the key residues of active sites on β-tubulin. Using a docking method, molecular dynamics (MD) simulation and density functional theory (DFT), we identified some residues (such as Arg278, Asp26, Asp226, Glu22, Glu27, His229, Arg369, Lys218, Ser277 and Thr276) on β-tubulin that are the active sites responsible for interaction with PTX. Another two residues, Leu371 and Gly279, also likely serve as active sites. Most of these sites contact with the “southern hemisphere” of PTX; only one key residue interacts with the “northern hemisphere” of PTX. These key residues can be divided into four groups, which serve as active compositions in the formation of an active pocket for PTX binding to β-tubulin. This active binding pocket enables a very strong interaction (the strength is predicted to be in the range of −327.8 to −365.7 kJ mol⁻¹) between β-tubulin and PTX, with various orientated conformations. This strong interaction means that PTX possesses a high level of activity against cancer cells, a result that is in good agreement with the clinical mechanism of PTX. The described PTX pocket and key active residues will be applied to probe the mechanism of tumor cells resistant to PTX, and to design novel analogs with superior properties.     

Amexanthomycins A–J,pentangular polyphenols produced by Amycolatopsis mediterranei S699∆rifA

Ten new pentangular polyphenols, namely amexanthomycins A–J (1–10) were isolated from the strain Amycolatopsis mediterranei S699∆rifA constructed by deleting the polyketide synthase genes responsible for the biosynthesis of rifamycins. Their structures were elucidated on the basis of 1D and 2D NMR spectroscopic data and high-resolution ESIMS. Amexanthomycins A–C (1–3) showed inhibitory activity against human DNA topoisomerases.