Controlling Properties and Cytotoxicity of Chitosan Nanocapsules by Chemical Grafting

The tunability of the properties of chitosan-based carriers opens new ways for the application of drugs with low water-stability or high adverse effects. In this work, the combination of a nanoemulsion with a chitosan hydrogel coating and the following poly (ethylene glycol) (PEG) grafting is proven to be a promising strategy to obtain a flexible and versatile nanocarrier with an improved stability. Thanks to chitosan amino groups, a new easy and reproducible method to obtain nanocapsule grafting with PEG has been developed in this work, allowing a very good control and tunability of the properties of nanocapsule surface. Two different PEG densities of coverage are studied and the nanocapsule systems obtained are characterized at all steps of the optimization in terms of diameter, Z potential and surface charge (amino group analysis). Results obtained are compatible with a conformation of PEG molecules laying adsorbed on nanoparticle surface after covalent linking through their amino terminal moiety. An improvement in nanocapsule stability in physiological medium is observed with the highest PEG coverage density obtained. Cytotoxicity tests also demonstrate that grafting with PEG is an effective strategy to modulate the cytotoxicity of developed nanocapsules. Such results indicate the suitability of chitosan as protective coating for future studies oriented toward drug delivery.     

Mariner 9 television reconnaissance of Mars and its satellites: preliminary results

At orbit insertion on 14 November 1971 the Martian surface was largely obscured by a dust haze with an extinction optical depth that ranged from near unity in the south polar region to probably greater than 2 over most of the planet. The only features clearly visible were the south polar cap, one dark, spot in Nix Olympica, and three dark spots in the Tharsis region. During the third week the atmosphere began to clear and surface visibility improved, but contrasts remained a fraction of their normal value. Each of the dark spots that apparently protrude through most of the dust-filled atmosphere has a crater or crater complex in its center. The craters are rimless and have featureless floors that, in the crater complexes, are at different levels. The largest crater within the southernmost spot is approximately 100 kilometers wide. The craters apparently were formed by subsidence and resemble terrestrial calderas. The south polar cap has a regular margin, suggsting very flat topography. Two craters outside the cap have frost on their floors; an apparent crater rim within the cap is frost free, indicating preferentia loss of frost from elevated ground. If this is so then the curvilinear streaks, which were frost covered in 1969 and are now clear of frost, may be low-relief ridges. Closeup pictures of Phobos and Deimos show that Phobos is about 25 +/-5 by 21 +/-1 kilometers and Deimos is about 13.5 +/- 2 by 12.0 +/-0.5 kilometers. Both have irregular shapes and are highly cratered, with some craters showing raised rims. The satellites are dark objects with geometric albedos of 0.05.     

A small molecule Smac mimic potentiates TRAIL- and TNFalpha-mediated cell death

We describe the synthesis and properties of a small molecule mimic of Smac, a pro-apoptotic protein that functions by relieving inhibitor-of-apoptosis protein (IAP)-mediated suppression of caspase activity. The compound binds to X chromosome- encoded IAP (XIAP), cellular IAP 1 (cIAP-1), and cellular IAP 2 (cIAP-2) and synergizes with both tumor necrosis factor alpha (TNFalpha) and TNF-related apoptosis-inducing ligand (TRAIL) to potently induce caspase activation and apoptosis in human cancer cells. The molecule has allowed a temporal, unbiased evaluation of the roles that IAP proteins play during signaling from TRAIL and TNF receptors. The compound is also a lead structure for the development of IAP antagonists potentially useful as therapy for cancer and inflammatory diseases.     

Predictive thresholds for plague in Kazakhstan

In Kazakhstan and elsewhere in central Asia, the bacterium Yersinia pestis circulates in natural populations of gerbils, which are the source of human cases of bubonic plague. Our analysis of field data collected between 1955 and 1996 shows that plague invades, fades out, and reinvades in response to fluctuations in the abundance of its main reservoir host, the great gerbil (Rhombomys opimus). This is a rare empirical example of the two types of abundance thresholds for infectious disease-invasion and persistence- operating in a single wildlife population. We parameterized predictive models that should reduce the costs of plague surveillance in central Asia and thereby encourage its continuance.     

硅酸盐细菌代谢产物对植物生长的促进作用

从根际微生物的角度研究了硅酸盐细菌对植物生长的促进作用。代谢产物对植物生长促进作用最好的是１３８＃菌,处理５０天,水稻株高比对照增加２７．７％,生物量比对照增加４０．２％,硅酸盐细菌的代谢产物对植物生长的刺激作用与浓度有关,低浓度的代谢产物对植物生长有明显的促进作用,高浓度的代谢产物则有一定的抑制作用,代谢产物的作用对根系生长的影响尤为明显。     

佛香茶香气成分的研究

 佛香茶是云南名茶,具有香高持久、带板栗香的香型特点。用GC／MS法分析了佛香茶的香气组成,共鉴定出30种香气成分。其主要成分如下:芳樟醇、α-松油醇、香叶醇、橙花醇、橙花叔醇、α-[HT6”,5”SS]律[HT5”]草烯、氧化长叶松烯、氧化石竹烯、丁酸-4-已烯酯、四甲基-十六碳-2-烯-Ⅰ-醇。     

广东鲂(♀)×团头鲂()杂交子一代及其双亲同工酶的比较

采用聚丙烯酰胺垂直平板电泳法对广东鲂、团头鲂及其杂交子一代肌肝眼 3种组织的 4种同工酶(EST、LDH、MDH、SOD)进行电泳 ,分析其酶谱组成和活性差异。结果显示父母本同种组织中大部分同工酶的表达酶谱较相似 ,尤其以眼组织的LDH、肝组织的MDH以及 3种组织的SOD同工酶的表型最为相似 ,表明两种鱼的亲缘关系较近 ,是本远缘杂交成功的遗传物质基础。同时父母本的某些同工酶谱又存在有稳定的种间差异 ,如肝组织的LDH。杂交子一代同工酶表型有些具有来自双亲的区带总和 ,有些则单独表达父本或母本的基因 ,更有些出现父母本没有的表型     

A high-resolution radiation hybrid map of the human genome draft sequence

We have constructed a physical map of the human genome by using a panel of 90 whole-genome radiation hybrids (the TNG panel) in conjunction with 40,322 sequence-tagged sites (STSs) derived from random genomic sequences as well as expressed sequences. Of 36,678 STSs on the TNG radiation hybrid map, only 3604 (9.8%) were absent from the unassembled draft sequence of the human genome. Of 20,030 STSs ordered on the TNG map as well as the assembled human genome draft sequence and the Celera assembled human genome sequence, 36% of the STSs had a discrepant order between the working draft sequence and the Celera sequence. The TNG map order was identical to one of the two sequence orders in 60% of these discrepant cases.     

蛋白质与淀粉对挂面和方便面品质及微观结构的影响

以小麦淀粉、小麦活性面筋粉和标准面粉为原料 ,通过控制各原料比例的方法 ,结合扫描电子显微镜技术 ,观察与分析了不同淀粉与蛋白质含量的混合粉在制作面条和方便面过程中微观结构、加工特性及食用品质的变化情况。结果表明 ,蛋白质和淀粉含量对面条和方便面的品质都有重要影响 ,相对而言 ,蛋白质的作用大于淀粉。只有蛋白质和淀粉间比例及其在面粉中含量处于比较合适的水平时 ,才能制成高品质的挂面和方便面。蛋白质经吸水或变性后形成的网络结构是使面团具有可塑性、熟面条具有弹性和部分韧性、方便面具有良好复水性的主要原因 ;也是束缚淀粉颗粒 ,防止其从面条中失落的主要因素。淀粉通过缓解面筋强度、添补蛋白质网络空隙等途径 ,有增大面团和面带延伸性、改善面带表面光滑性、增加面条白度等作用。