Modeling the spontaneous initiation of the polymerization of methyl methacrylate

The mechanism of the spontaneous initiation of the polymerization of methyl methacrylate (MMA) was investigated theoretically. The six minimum energy paths (MEP) of the possible reactions were calculated using the density functional theory (DFT) in conjunction with the B3LYP functional and 6-31G* basis set. The Diels-Alder initiation mechanism (path (I) and path (II)) with remarkably high energy barriers is not applicable to MMA. Four favorable paths were found (path (III), path (IV), path (V) and path (VI)), which are supporting the Flory mechanism. Path (V) has the lowest active energy. Therefore this path is considered as the main path for the spontaneous polymerization of MMA. Figure The mechanism of the spontaneous initiation of the polymerization of methyl methacrylate (MMA) was investigated theoretically. The six minimum energy paths (MEP) of the possible reactions were calculated using the density functional theory (DFT) in conjunction with the B3LYP functional and 6-31G* basis set.     

Diet composition of post-metamorphic bullfrogs (Rana catesbeiana) in the Zhoushan archipelago, Zhejiang Province, China

Bullfrogs (Rana catesbeiana) are listed as one of the 100 worst invasive alien species in the world. They are generalist predators and thus may affect native species through predation. In previous studies, the food contents of bullfrogs were mostly examined at a single site. In the present study, the diet composition of post-metamorphic bullfrogs on eight islands (Daishan, Liuheng, Xiushan, Fodu, Taohua, Xiashi, Cezi, and Putuoshan) in the Zhoushan Archipelago, Zhejiang Province of China, were examined by using the stomach flushing method from June 30 to August 11 in 2005. A total of 391 individual frogs were measured, including 113 adults and 278 juveniles. The analysis of the stomach contents shows that, for adult bullfrogs, the most important prey (by diet volume) overall were Decapoda, Coleoptera, Odonata, Mesogastropoda, Raniformes, and Cypriniformes. For juvenile bullfrogs, these were Decapoda, Coleoptera, Cypriniformes, Odonata, Orthoptera, Hymenoptera, Lepidoptera larvae, Mesogastropoda, and Raniformes. Moreover, the prey size and diet volume increased with the body size of both adult and juvenile bullfrogs. The diet composition of primary preys of bullfrogs was significantly different among the islands. The results indicate that bullfrogs exert different predatory influences on native fauna at different sites and that bullfrogs are generalist predators with extensive ecological impacts on native fauna. __________ Translated from Biodiversity Science, 2006, 14 (5): 363–371 [译自: 生 物多样性]     

Effects of lanthanum on rumen fermentation, urinary excretion of purine derivatives and digestibility in steers

The objective of this study was to evaluate the effects of LaCl₃ supplementation on rumen fermentation, urinary excretion of purine derivatives and feed digestibility in the total tract of steers. Eight ruminally cannulated Simmental steers (420 ± 20 kg) were used in a replicated 4 × 4 Latin square experiment. The treatments were control (without LaCl₃); La-low; La-medium and La-high with 450, 900 and 1800 mg LaCl₃ per steer per day, respectively. Diet consisted of 600 g/kg corn stover and 400 g/kg concentrate (dry matter [DM] basis). Dry matter intake (averaged 9 kg/day) was restricted to a maximum of 90% of ad libitum intake. Ruminal pH (range of 6.59–6.42) was quadratically (P<0.04) changed, whereas total volatile fatty acids (VFA) concentration (range of 74.16–88.61 mM) was linearly (P<0.01) and quadratically (P<0.01) increased with increasing La supplementation. Ratio of acetate to propionate decreased linearly (P<0.01) from 3.28 to 1.79 as La supplementation increased due to the increased in propionate production. In situ ruminal neutral detergent fibre (aNDF) degradation of corn stover was improved but the crude protein (CP) degradability of soybean meal was decreased with increasing La supplementation. Urinary excretion of purine derivatives was quadratically (P<0.01) changed with altering La supplementation (75.5, 81.0, 82.4 and 70.6 mmol/day for control, low-, medium- and high-LaCl₃ supplementation, respectively). Similarly, digestibilities of organic matter, aNDF and CP in the total tract were also linearly and quadratically increased with increasing La supplementation. The present results indicate that supplementation of diet with LaCl₃ improved rumen fermentation and feed digestion in beef cattle. It was suggested that the La stimulated the digestive microorganisms or enzymes in a dose-dependent manner. In the experimental conditions of this trial, the optimum La dose was about 900 mg LaCl₃ per steer per day.     

An affinity-enhanced neutralizing antibody against the membrane-proximal external region of human immunodeficiency virus type 1 gp41 recognizes an epitope between those of 2F5 and 4E10

The membrane-proximal external region (MPER) of human immunodeficiency virus type 1 (HIV-1) gp41 bears the epitopes of two broadly neutralizing antibodies (Abs), 2F5 and 4E10, making it a target for vaccine design. A third Ab, Fab Z13, had previously been mapped to an epitope that overlaps those of 2F5 and 4E10 but only weakly neutralizes a limited set of primary isolates. Here, libraries of Fab Z13 variants displayed on phage were engineered and affinity selected against an MPER peptide and recombinant gp41. A high-affinity variant, designated Z13e1, was isolated and found to be approximately 100-fold improved over the parental Fab not only in binding affinity for the MPER antigens but also in neutralization potency against sensitive HIV-1. Alanine scanning of MPER residues 664 to 680 revealed that N671 and D674 are crucial for peptide recognition as well as for the neutralization of HIV-1 by Z13e1. Ab competition studies and truncation of MPER peptides indicate that Z13e1 binds with high affinity to an epitope between and overlapping with those of 2F5 and 4E10, with the minimal peptide epitope WASLWNWFDITN. Still, Z13e1 remained about an order of magnitude less potent than 4E10 against several isolates of pseudotyped HIV-1. The sum of our molecular analyses with Z13e1 suggests that the segment on the MPER of gp41 between the 2F5 and 4E10 epitopes is exposed on the functional envelope trimer but that access to the specific Z13e1 epitope within this segment is limited. Thus, the ability of MPER-bearing immunogens to elicit potent HIV-1-neutralizing Abs may depend in part on recapitulating the particular constraints that the functional envelope trimer imposes on the segment of the MPER to which Z13e1 binds.     

Expression and purification of an FGF9 fusion protein in E. coli,and the effects of the FGF9 subfamily on human hepatocellular carcinoma cell proliferation and migration

Fibroblast growth factor (FGF) 9 has oncogenic activity and plays an important role in the development of ovarian, lung, prostate, and gastric cancers. In the present study, with the aim of reducing the cost of utilizing growth factors in cancer research, a simple and efficient method for the preparation of recombinant human (rh)FGF9 in Escherichia coli was established. The rhFGF9 fusion protein (6 × His-TEV-rhFGF9) and the native protein released by tobacco etch virus (TEV) protease were obtained using a Ni-NTA system, with > 95% purity. Both purified forms of rhFGF9, with and without fusion tags, significantly stimulated the proliferation of NIH3T3 cells. The FGF9 subfamily, including FGF9, FGF16, and FGF20, in addition to rhFGF16, rhFGF9, and rhFGF20, were shown to stimulate the proliferation and migration of HuH7 human hepatocellular carcinoma (HCC) cells. Mechanistic studies revealed that the stimulation of HuH7 cell proliferation and migration with rhFGF9 and rhFGF20 were associated with the activation of the extracellular signal-regulated kinase (ERK) and nuclear factor κB (NF-κB) pathways and matrix metalloproteinase-26 (MMP26). Inhibition of the ERK and NF-κB pathways blocked cell migration, and NF-κB was demonstrated to be regulated by ERK. Therefore, the present study demonstrates a simple method for the preparation of biologically active rhFGF9 protein. Furthermore, the results indicate that exogenous rhFGF9- and rhFGF20-activated ERK/NF-κB signal transduction pathways play important roles in the regulation of HCC cell proliferation and migration, and this discovery helps to find the potential for new solutions of the treatment of liver cancer.

     

Quantitative detection of BCR–ABL fusion gene and its application in monitoring chronic myeloid leukemia treatment

The BCR–ABL fusion gene in chromosome translocation, t (9; 22), and its product, p210BCR/ABL oncogenic tyrosine kinase, is the underlying molecular mechanism that leads to the development of CML. Quantitative detection of BCR–ABL fusion gene has become a reliable approach to diagnose and monitor CML. The aim of this study was to evaluate a Roche t (9; 22) kit in CML diagnosis, monitoring treatment responses, and identification of relapse. Using BCR–ABL fusion gene-expressing K562 cells, a series of standard samples were prepared and used to establish a curve for the calculation of BCR–ABL fusion gene expression in patient samples. Our results indicate that PCR detection system with aforementioned kit has good reproducibility. In addition, the relative concentration of BCR–ABL measured by PCR was in agreement with the patient’s response to the Imatinib treatment and bone marrow morphology remission. Furthermore, we found that the relative concentration of BCR–ABL fusion gene increased 1–3 months before CML relapse was clinically and cytogenetically diagnosed, suggesting that the PCR-based BCR–ABL fusion gene detection with t (9; 22) kit is able to diagnose the recurrence of CML at least 1 month earlier than the classic cytogenetic analysis. In conclusion, detection of BCR–ABL fusion gene expression in CML using Roche t (9; 22) kit has great clinical value in the primary diagnosis, monitoring treatment responses, and identification of relapse in CML patients.     

Enhanced chilling tolerance in Zoysia matrella by pre-treatment with salicylic acid, calcium chloride, hydrogen peroxide or 6-benzylaminopurine

Following leaf application of salicylic acid (SA), calcium chloride, hydrogen peroxide and 6-benzylaminopurine (BA), Manila grass (Zoysia matrella) plants were exposed to day/night temperature of 7/2 °C for 120 h in a growth chamber. The lower content of malondialdehyde (MDA) and H₂O₂ and higher activities of ascorbate peroxidase (APX), guaiacol peroxidase (POD) and catalase (CAT) during exposure to low temperature in pre-treated plants in comparison with control plants demonstrated that these compounds improved the chilling tolerance of Manila grass.     

冀东地区西伯利亚白刺开发利用价值研究

西伯利亚白刺是华北沿海地区仅有的一个白剌种,在冀东滨海地区有一定的野生群落分布。研究结果表明,西伯利亚白刺具有极强的耐盐能力,0—50cm土体平均全盐含量最高达到1．97％,极端最高值达到3．99％。其果汁含有非常丰富的维生素C,高达444．07mg／100g,仅次于酸枣,排在各类蔬菜、水果的第二位,是开发功能饮料的上好原料。果实成熟后的嫩茎叶含粗蛋白28．80％,粗纤维8．86％,粗脂肪2．24％,是优质的饲料。种子脂肪含量17．2％,其中油酸含量25．02％,亚油酸含量69．02％,是生产优质保健食用油的好原料。所以,西伯利亚白刺是开发利用重盐碱地和沿海滩涂的优良植物,极具开发价值。