969 resultados para sp-equared sp2 sp^2 hybrid orbital
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Differences in parasite transmission intensity influence the process of acquisition of host immunity to Plasmodium falciparum malaria and ultimately, the rate of malaria related morbidity and mortality. Potential vaccines being designed to complement current intervention efforts therefore need to be evaluated against different malaria endemicity backgrounds. The associations between antibody responses to the chimeric merozoite surface protein 1 block 2 hybrid (MSP1 hybrid), glutamate-rich protein region 2 (GLURP R2) and the peptide AS202.11, and the risk of malaria were assessed in children living in malaria hyperendemic (Burkina Faso, n = 354) and hypo-endemic (Ghana, n = 209) areas. Using the same reagent lots and standardized protocols for both study sites, immunoglobulin (Ig) M, IgG and IgG sub-class levels to each antigen were measured by ELISA in plasma from the children (aged 6-72 months). Associations between antibody levels and risk of malaria were assessed using Cox regression models adjusting for covariates. There was a significant association between GLURP R2 IgG3 and reduced risk of malaria after adjusting age of children in both the Burkinabe (hazard ratio 0.82; 95 % CI 0.74-0.91, p < 0.0001) and the Ghanaian (HR 0.48; 95 % CI 0.25-0.91, p = 0.02) cohorts. MSP1 hybrid IgM was associated (HR 0.85; 95 % CI 0.73-0.98, p = 0.02) with reduced risk of malaria in Burkina Faso cohort while IgG against AS202.11 in the Ghanaian children was associated with increased risk of malaria (HR 1.29; 95 % CI 1.01-1.65, p = 0.04). These findings support further development of GLURP R2 and MSP1 block 2 hybrid, perhaps as a fusion vaccine antigen targeting malaria blood stage that can be deployed in areas of varying transmission intensity.
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Among the huge radiations of haplochromine cichlid fish in Lakes Malawi and Victoria, closely related species are often reproductively isolated via female mate choice although viable fertile hybrids can be produced when females are confined only with heterospecific males. We generated F(2) hybrid males from a cross between a pair of closely related sympatric cichlid fish from Lake Malawi. Laboratory mate choice experiments using microsatellite paternity analysis demonstrated that F(2) hybrid males differed significantly in their attractiveness to females of the two parental species, indicating heritable variation in traits involved in mate choice that may contribute to reproductive isolation between these species. We found no significant correlation between male mating success and any measurement of male colour pattern. A simple quantitative genetic model of reproductive isolation suggests that there may be as few as two chromosomal regions controlling species-specific attractiveness. We propose that adaptive radiation of Lake Malawi cichlids could be facilitated by the presence of genes with major effects on mate choice and reproductive isolation.
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The reaction of [Re6Q8(OH)6]4- (Q = S, Se) with p-tertbutylpyridine (TBP) in water leads to neutral trans-[Re6Q8(TBP)4(OH)2] whose hydroxyl reactivity with carboxylic acid and TBP exchange reaction with functional pyridine have been investigated.
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Fish culture experiments were conducted to compare and evaluate the feeding pattern and strategies, daily ration, gastric evacuation rates, dietary breadth, similarity and overlap of silver barb, Barbodes gonionotus, and tilapia, Oreochromis sp. (natural hybrid of O. mossambicus x O. niloticus) in a rice-fish system. B. gonionotus was found to be a macrophtophagous column feeder while Oreochromis sp. was a detrivorous benthophagic browser. Ontogenic shifts in diet were clearly observed in B. gonionotus while absent in Oreochromis sp. For both species, daily food ration for the small fish was twice as large as that for the large fish. Mean rates of gastric evacuation were 0.18 h super(1) for small and 0.05 h super(1) for large B. gonionotus and 0.09 h super(1) and 0.14h super(1) for small and large Oreochromis sp., respectively. In terms of intraspecific dietary width, the smaller sized individuals of both species had a wider dietary niche than the larger conspecifics. Larger fish increased their specialization and reliance on few food items with increasing size and competitive ability. When both species were reared together, B. gonionotus showed a wider niche width than tilapia. Wider interspecific niche width of B. gonionotus compared to that of tilapia and significant interspecific dietary overlap is likely to result in suppression of the growth of tilapia in mixed culture due to: 1) a high degree of specialization and reliance of tilapia on food of low-nutrient value, and 2) slower gastric evacuation rates as compared to B. gonionotus, which would allow B. gonionotus to outgrow similar sized tilapia.
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A convenient asymmetric total synthesis of the potent HIF-1 inhibitory antitumor natural product, (−)- or (+)-(8R)-mycothiazole (1), is described. Not only does our synthesis confirm the 2006 structural reassignment made by Crews (Crews, P., et al. J. Nat. Prod. 2006, 69, 145), it revises the [α]D data previously reported for this molecule in MeOH from −13.7° to +42.3°. The newly developed route to (8R)-1 sets the C(8)–OH stereocenter via Sharpless AE/2,3-epoxy alcohol reductive ring opening and utilizes two Baldwin–Lee CsF/cat. CuI Stille cross-coupling reactions with vinylstannanes 8 and 3 to efficiently elaborate the C(1)–C(4) and C(14)–C(18) sectors.
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海洋微藻是海洋生态系统中最主要的初级生产者,也是海洋生物资源的重要来源。许多海洋微藻富含对人体具有重要的生理作用与保健功能的长链多不饱和脂肪酸,因此,筛选富含EPA、DHA等长链多不饱和脂肪酸的微藻和利用人工培养方法提高这些脂肪酸的产量是当前海洋生物学研究领域的热点之一。在本研究中,我们对被中科院海洋所定名为“Chlorella sp”(编号为1061)的一种海洋微藻的化学分类、甘油脂及其脂肪酸组成和外源葡萄糖和抗氧化剂(硫代硫酸钠)对这种微藻的脂肪酸含量的影响进行了研究,取得了以下主要结果。 海洋微藻是我固海水养殖中广泛使用的优良饵料藻。脂类物质是微藻最重要的营养指标之一,在本研究中,我们首先分析了被中科院海洋所定名为“Chlorellasp”的海洋微藻中的甘油脂及其脂肪酸种类和组成特点。结果表明,Chlorella sp.中的非极性脂主要为三脂酰甘油,极性甘油脂有10种。其中,一般培养条件下(温度23℃:光照,周期L/D14:10,强度60umolm-2-S-l)三脂酰甘油约占总脂的31 mol%,极性甘油脂约占总脂的69 rriol%。10种极性甘油脂是单半乳糖甘油二脂( monogalactosyldiacylglycerol. MGDG)、 双半乳糖甘油二脂( diagalactosyldiacylglycerol , DGDG)、 硫代异鼠李糖甘油二脂( sulfoquinovosyldiacylglycerol,SQDG)、磷脂酰甘油(phosphatatidylglycerol,PG)、磷脂酰乙醇胺(phosphatidylethanolamine,PE)、磷脂酰胆碱( phosphatidylcholine,PC)、磷脂酰肌醇(phosphatidylinositol,PI)、磷脂酰丝氨醴(phosphatidylserine,Ps)、l,2-二酰基甘油-0-4,.(ⅣMⅣ-三甲基)高丝氨酸(diacylglyceryltrimethylhomoserine,DGTS)以及一种未能完全肯定,但可能是一中氯硫脂( chlorosulfolipid,CSL)。其中MGDG、DGDG、SQDG和PG是构成光合膜的主要成分,也是Chlorella sp中的主要极性脂。甜菜碱脂DGTS和磷脂PC是构成非光合膜的主要组分。Chlorella sp.中的主要脂肪酸为C16:0、C16:1耜C20:5(EPA),后者主要存在于MGDG、DGDG和DGTS中,而三脂酰甘油也含有接近7%的EPA。 海洋微藻Chlorella sp.1061虽然被归属到绿藻纲绿藻目小球藻属,但是我们的研究表明,其色素、极性脂皮其脂肪酸组成与其它小球藻属藻类存在这很大差异Chl b是绿藻纲藻类中最主要的光合色素之一,1 6:4(n-3)和l 8:3(n-3)是绿藻微藻的主要脂肪酸,然而所有这些绿藻的特征化合物均未在Chlorella sp. 1061中检测到。DGTS和20:5(n-3)存在于很多的海洋微藻中,我们从Chlorella sp. 1061 中分离到占总极性甘油脂8 mo1%的DGTS,并从MGDG、DGDG和DGTS等极性甘油脂中检测到大量的20:5(n-3)。但是一般认为,小球藻属藻类中不舍这两种化合物。根据Chlorella sp. 1061的以上特点,这种藻不应该被归到小球藻属中。另外,由于Chlorella sp. 1061在色素、膜脂和脂肪酸组成特征方面大眼藻纲( Eustigmatophyceae)中的微绿球藻(Nannochloropsis)非常相似,因此,我们认为ChloreHa sp. 1061可能是Nannochloropsis中的一个种。但是未得到更进一步的证明和权威的认可之前,本文中我们仍然沿用ChloreHa sp,这一名称。 许多藻类中DGTS和PC -般不会同时存在,或者说一个存在时另外的一个的含量非常低。由此有人认为DGTS和PC之间存在着相互替代的关系。然而本研究中发现正常培养条件下Chlorella sp.中的DGTS和PC含量均较高(约10%)。磷处理实验结果表明,磷缺乏时Chlore Ha sp,中DGTS舍量大幅升高,而同时PC含量相应下降许多:但高浓度的磷并不能提高PC含量和降低DGTS含量,说明Chlorella sp,中DGTS仍可起替代PC的作用,然而PC可能并不能替代DGTS。Chlorella sp.中MGDG和DGTS脂肪酸组成及其位置分布结果显示,它们的组成和分布相似;在老化培养过程中MGDG和DGTS表现出周期性的相反的含量升高、降低的趋势,这进一步说明MGDG和DGTS之间存在着特殊的关系,MGDG可能合成自DGTS。 海洋微藻富含有利于人体健康的长链不饱和脂肪酸,如何提高微藻脂肪酸特别是多不饱和脂肪酸产量是目前研究的热点之一。本文首次报道了同时加入葡萄糖和硫代硫酸钠对Chlorelta sp,的生长、脂类组成和脂肪酸总产量的影响,结果显示葡萄糖和硫代硫酸钠存在明显而且强烈的互作,二者在培养液中的同时存在显著刺激了脂肪酸总产量的积累,在培养液中分别加入2.5 mM的葡萄糖和5mM的硫代硫酸钠,脂肪酸的产量可以比对照提高78%。而低浓度的葡萄糖和硫代硫酸钠对Chlorella sp.脂肪酸组成影响变化不明显,甚至在硫代硫酸钠存在下令人感兴趣的EPA含量还略有升高。显然,在Chlorella sp.培养中同时加入低浓度的葡萄糖和硫代硫酸钠是极具潜力的提高脂产量的方法,也可作为提高培养微藻其它活性物质产量借鉴的方法。在不久的将来,这种培养方法很可能发展成为生产实践中提高Chlore sp.乃至其它微藻脂肪酸、EPA和其它活性物质产量的经济有效的新途径。
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Palladium, iridium, and rhodium complexes of 2-methyleneimidazolines have been synthesized by selective phosphine-assisted activation of the 2-methyl C-H bonds in 2-methylimidazolium compounds. Metallacycles of various sizes were obtained in the reaction of phosphine-tethered 2-methylimidazolium compounds and [{M(cod)X}(2)] (M = Rh or Ir cod = 1,5-cyclooctadiene: X = alkoxyl or Cl). representative complexes were characterized by X-ray crystallography. The selectivity for aliphatic C(sp(3))H versus aromatic C(sp(2))H activation could be adjusted by means of the steric bulk of the OR ligand, whereby a bulky, OR group favors activation of the 2-methyl C(sp(3))-H bond. Experimental results confirmed that a methyl C-H activation product (a seven-membered iridacycle) is the kinetic product, while the aryl C-H activation product (a six-membered iridacycle) is the thermodynamic product.
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This thesis entitled Physicochemical and molecular characterization of bacteriophages ΦSP-1and ΦSP-3, specific for pathogenic Salmonella and evaluation of their potential as biocontrol agent . Salmonella were screened using standard methodologies from various environmental samples including chicken caecum. Salmonella strains, which were previously isolated and stocked in the lab, were also included in this study as host, for screening Salmonella specific lytic phages. The Salmonella strain in this study designated as S49 which helped in phage propagation by acting as host bacteria was identified as Salmonella enterica subsp. enterica by 16S rRNA gene analysis and serotyping . A total of three Salmonella specific phage named as ΦSP-1, ΦSP-2 and ΦSP-3 were isolated from chicken intestine samples via an enrichment protocol employing the double agar overlay method. ΦSP-1 and ΦSP-3 showing consistent lytic nature were selected for further study and were purified by repeated plating after picking of single isolated plaques from the lawns of Salmonella S49 plates. Both the phages produced small, clear plaques indicating their lytic nature. ΦSP-1 and ΦSP-3 were concentrated employing PEG-NaCl precipitation method before further characterization. The focus of present study was to isolate, characterize and verify the efficacy of lytic bacteriophages against the robust pathogen Salmonella, capable of surviving under various hostile conditions. Two phages, ΦSP-1 and ΦSP-3, belonging to two families, Podovoridae and Siphoviridae were isolated.
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Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)
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Hybrid (sp) orbitals are illustrated in various plotting schemes to aid in understaning their structure.
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We present results of the reconstruction of a saccharose-based activated carbon (CS1000a) using hybrid reverse Monte Carlo (HRMC) simulation, recently proposed by Opletal et al. [1]. Interaction between carbon atoms in the simulation is modeled by an environment dependent interaction potential (EDIP) [2,3]. The reconstructed structure shows predominance of sp(2) over sp bonding, while a significant proportion of sp(3) hybrid bonding is also observed. We also calculated a ring distribution and geometrical pore size distribution of the model developed. The latter is compared with that obtained from argon adsorption at 87 K using our recently proposed characterization procedure [4], the finite wall thickness (FWT) model. Further, we determine self-diffusivities of argon and nitrogen in the constructed carbon as functions of loading. It is found that while there is a maximum in the diffusivity with respect to loading, as previously observed by Pikunic et al. [5], diffusivities in the present work are 10 times larger than those obtained in the prior work, consistent with the larger pore size as well as higher porosity of the activated saccharose carbon studied here.