Synthesis of 3′,4′-difluoro-3′-deoxyribonucleosides and its evaluation of the biological activities: Discovery of a novel type of anti-HCV agent 3′,4′-difluorocordycepin

Upon reacting 3′,4′-unsaturated cytosine (8 and 9) and adenine nucleosides (13 and 14) with XeF₂/BF₃·OEt₂, the respective novel 3′,4′-difluoro-3′-deoxyribofuranosyl nucleosides (10–12 and 15–18) could be obtained. Formation of anti-adducts (11, 16 and 18) revealed that the fluorination involved oxonium ions as incipient intermediates. TBDMS-protected 3′,4′-unsaturated adenosine provided the β-face adducts as sole stereoisomers whereas α-face-selectivity was observed with the TBDPS-protected adenosine 14. The evaluation of the novel 3′-deoxy-3′,4′-difluororibofuranosylcytosine-(19–21) and adenine nucleosides (22–25) against antitumor and antiviral activities revealed that 3′,4′-difluorocordycepin (24) was found to possess anti-HCV activity. The SI of 24 was comparable to that of the anti-HCV drug ribavirin. However, sofosbuvir, FDA-approved novel anti-HCV drug, showed better SI value. Our finding revealed that the introduction of the fluoro-substituent into the 4′-position of cordycepin derivatives decreased the cytotoxicity to the host cell with retention of the antiviral activity.     

中华绒螯蟹蜕壳过程中肌肉的组织学、超微结构及主要蛋白质含量的变化

为探讨中华绒螯蟹(Eriocheir sinensis)蜕壳前后肌肉组织的形态特征变化, 采用石蜡切片、电镜及生物化学方法, 研究了中华绒螯蟹蜕皮过程中步行足和腹部肌肉的组织学、超微结构及主要蛋白质含量的变化。结果显示: 相对于蜕皮间期, 步行足在蜕皮前后组织学形态特征无明显变化; 超微结构在蜕皮前无明显变化, 蜕皮后可见肌原纤维纵裂及肌小节横裂现象, 表明蜕皮后外骨骼硬化的过程伴随着肌肉的生长。相对于蜕皮间期, 腹部肌肉在蜕皮前后组织学特征变化明显: 蜕皮前肌束间隙增大, 蜕皮后肌束内肌纤维间隙增大。电子显微镜观察显示, 蜕皮前肌原纤维在内部降解, 出现空洞, 肌原纤维边缘降解, 导致肌原纤维间隙增大; 蜕皮后肌原纤维重新组装、重建, 恢复到间期正常形态。生物化学研究发现, 蜕皮前后步行足和腹部肌肉中肌原纤维蛋白和可溶性蛋白含量的变化同其结构特征的变化相一致。以上研究结果表明, 中华绒螯蟹肌肉组织的结构特征同蜕皮周期密切相关。     

Arg-Gly-Asp (RGD) sequence conjugated in a synthetic copolymer bearing a sugar moiety for improved culture of parenchymal cells (hepatocytes)

A copolymer, including a Gly-Arg-Gly-Asp-Ser (GRGDS) sequence and sugar moieties, was synthesized for the culturing of parenchymal cells (hepatocytes). Hepatocyte cells attached to poly[N-p-vinylbenzyl-d-maltonamide-co-6-(p-vinylbenzamido)-hexanoic acid-GRGDS] [poly(VMA-co-VBRGD)]-coated dishes grew approximately 60% better than on other polymer-coated surface for 12 h. Also, about 80% greater albumin secretion (0.38 pg ml^–1) and about 70% greater urea synthesis (0.495 pg ml^–1) from hepatocytes were produced in this matrix as compared with unstimulated cells. The behaviour of hepatocytes on poly(VMA-co-VBGRGDS)-coated dishes was not distinct from those attached to a collagen. The conjugation of the adhesion molecules of the RGD peptide in the poly(VMA-co-VBGRGDS) copolymer therefore specifically interacts with integrin families on the hepatocyte cell membrane.     

喜树叶、枝水溶性糖提取的研究

用正交实验结果作方差分析表明：溶剂用量对试验结果有较显著的影响（a=0.10)，提取温度对试验结果也有较大的影响，而提取时间对试验结果的影响不显著。喜树叶中水溶性糖的提取最优方案是A3C2B3，即溶剂用量为60ml，提取温度80℃，提取时间60min；喜树叶水溶性糖的提取最优方案是A2C2B1，即溶剂用量为40ml，提取温度80℃，提取时间20min。通过对喜树叶与枝的成对比较分析，叶与枝的水溶性糖含量无显著差异。     

Nucleotide sequence of the gene encoding the Corynebacterium glutamicum mannose enzyme II and analyses of the deduced protein sequence

Abstract The complete nucleotide sequence of the gene encoding the Corynebacterium glutamicum mannose enzyme II (EII^Man) was determined. The gene consisted of 2052 base pairs encoding a protein of 683 amino acid residues; the molecular mass of the protein subunit was calculated to be 72570 Da. The N-terminal hydrophilic domain of EII^Man showed 39.7% homology with a C-terminal hydrophilic domain of Escherichia coli glucose-specific enzyme II (EII^Glc). Similar homology was shown between the C-terminal sequence of EII^Man and the E. coli glucose-specific enzyme III (EIII^Glc), or the EIII-like domain of Streptococcus mutans sucrose-specific enzyme II. Sequence comparison with other EIIs showed that EII^Man contained residues His-602 and Cys-28 which were homologous to the potential phosphorylation sites of EIII^Glc, or EIII-like domains, and hydrophilic domains (IIB) of several EIIs, respectively.     

Relationship between the concentration of sugars in the roots and VA mycorrhizal infection

Summary The VA-infected wheat varieties showed an increase of total (Lozano var.) and reducing (Lozano and Pane vars.) sugars in their root extracts. However, no clear relationship between sugar concentration in the root and VA mycorrhizal infection level could be established.In addition, the VA mycorrhizal hosts sorghum, alfalfa, sunflower and maize, and non-host radish and cabbage plants were tested for sugar content in their root extracts after fifteen days of growth. Sugars present in the root extracts of these plants did not seem to be a decisive factor in plant susceptibility to VA infection.     

Pyrophosphate-dependent phosphofructokinase from pollen: properties and possible roles in sugar metabolism

To evaluate the role of pyrophosphate-dependent phosphofructokinase (PFP. EC 2.7.1.90) in the sugar metabolism of pollen. its occurrence and properties were studied in pollen grains of several plants including camellia ( Camellia japonica L.). In all pollen samples, PFP was strongly activated by fructose-2,6-bisphosphate (F2,6BP), and the activity of F2,6BP-activated PFP was higher than that of phosphofructokinase (PFK. EC 2.7.1.11). PFP partially purified from camellia pollen required Mg²⁺ for activity with an optimum at 1 m M . and was almost unaflected by a variety of metabolites at 1 m M . Its molecular mass was around 220 kDa, and apparent K_m values for F6P, PP_i. F1, 6BP and P_i were 294, 4, 20 and 580 u M , respectively. The levels of F2.6BP. PP_i and F6P in camellia pollen were sufficent to support the forward reaction by PFP, and PFP, was 20- to 40-fold more active than PFK during pollen growth. These results suggest that pollen PFP plays a role in glycolysis but not gluconeogenesis. and the possible relevance of this to pollen tube growth is discussed.     

Possible correlation between high temperature-induced floret sterility and endogenous levels of IAA,GAs and ABA in rice (<Emphasis Type="Italic">Oryza sativa</Emphasis> L.)

In order to explore the possible physiological mechanism of high temperature induced sterility in rice, we examined the floret sterility and endogenous plant growth regulator contents in pollens of two hybrid rice cultivars Shanyou63 and Teyou559 that are tolerant and susceptible to high temperature, respectively. Indexes of floret sterility, pollen activity, and variation of endogenous indole-3-acetic acid (IAA), gibberellic acids (GAs), abscisic acid (ABA), free proline and soluble proteins in anthers were measured. We found that during the course of high temperature treatment, both cultivars exhibited a marked decrease in pollen activity, pollen germination and floret fertility; however, the high temperature tolerant Shanyou63 showed a much slower rate of decrease than the high temperature susceptible Teyou559. In addition, anthers of both cultivars displayed a decrease in the contents of IAA, GAs, free proline and soluble proteins but an increase in the ABA content. Yet compared to Teyou559, Shanyou63 retained significantly higher levels of free praline and GAs and a lower level of ABA, along with higher pollen vigour and pollen germination rate even after prolonged high temperature treatment. Our study suggests a possible correlation between pollen viability/floret sterility and high temperature-caused changes in IAA, GAs, ABA, free proline and soluble protein contents. The severity in these changes may reflect the variation of rice cultivars in their heat stress sensitivities for floret development.     

Physiological manipulation and formulation of the biocontrol yeast Pichia anomala for control of Penicillium verrucosum and ochratoxin A contamination of moist grain

The major hurdle in the production of commercial biocontrol agents (BCAs) has been the lack of production of appropriate formulations. Of particular importance is the conservation of viability and ecological competence after application. With this in mind studies were conducted to develop formulations of P. anomala which would have these attributes. Cells were grown in molasses-based medium modified with proline to different water availability levels (0.98 and 0.96) which significantly increased (up to 50%) the content of trehalose and arabitol in the yeast cells during liquid broth fermentation. The use of isotonic solutions for harvesting the yeast cells further increased the endogenous content of these compatible solutes as well as glycerol. Fluidised bed drying of cells at 30–80°C was carried out for 10 and 20 min and showed that viability was significantly decreased at 70–80°C. A temperature of 50°C for 20 min was found to be best for viability (70%) and moisture content of <10%. Several additives for conservation of viability showed that cotton seed flour+skimmed milk was the best treatment when dried at 50°C. The biocontrol efficacy of formulated P. anomala cells was tested in laboratory scale studies and this showed that they inhibited growth of Penicillium verrucosum and reduce ochratoxin A production in moist wheat grain under some combinations of water availability. Physiologically modified formulated yeast cells with increased levels of trehalose and arabitol gave similar efficacy as fresh cells. This suggests that ecophysiological manipulation of such BCAs can result in improved ecological competence of such formulations and effective biocontrol.     

Dinitrogen fixation and infection of grass leaves byPseudomonas rubrisubalbicans andHerbaspirillum seropedicae

Bacteria causing mottled stripe disease in sugar cane, known asPseudomonas rubrisubalbicans, were shown to be able to fix molecular N₂ and to grow on it. The root associated diazotroph known asHerbaspirillum seropedicae, after artificial inoculation caused mottled stripe disease symptoms on sorghum and Napier grass but not on sugar cane. Both bacteria could be reisolated from leaves even 60 days after. Sugar cane leaves contained large numbers of these bacteria even in the uninoculated controls. Additional physiological characteristics of six strains ofP. rubrisubalbicans were compared with those of twoH. seropedicae strains and were shown to be very similar.