Heterotic string on the CHL orbifold of K3

We study N = 2 compactifications of heterotic string theory on the CHL orbifold (K3 x T-2)/Z(N) with N = 2, 3, 5, 7. Z(N) acts as an automorphism on K3 together with a shift of 1/N along one of the circles of T-2. These compactifications generalize the example of the heterotic string on K3 x T-2 studied in the context of dualities in string theories. We evaluate the new supersymmetric index for these theories and show that their expansion can be written in terms of the McKay-Thompson series associated with the Z(N) automorphism embedded in the Mathieu group M-24. We then evaluate the difference in one-loop threshold corrections to the non-Abelian gauge couplings with Wilson lines and show that their moduli dependence is captured by Siegel modular forms related to dyon partition functions of N = 4 string theories.

Heterotic string on the CHL orbifold of K3

We study N = 2 compactifications of heterotic string theory on the CHL orbifold (K3 x T-2)/Z(N) with N = 2, 3, 5, 7. Z(N) acts as an automorphism on K3 together with a shift of 1/N along one of the circles of T-2. These compactifications generalize the example of the heterotic string on K3 x T-2 studied in the context of dualities in string theories. We evaluate the new supersymmetric index for these theories and show that their expansion can be written in terms of the McKay-Thompson series associated with the Z(N) automorphism embedded in the Mathieu group M-24. We then evaluate the difference in one-loop threshold corrections to the non-Abelian gauge couplings with Wilson lines and show that their moduli dependence is captured by Siegel modular forms related to dyon partition functions of N = 4 string theories.

Infiltração microbiana por Enterococcus faecalis em canais retrobturados com MTA, iRoot SP e Endo CPM Sealer

O objetivo deste trabalho consistiu na análise da infiltração apical em dentes retrobturados por três materiais: MTA, iROOT SP e Endo CPM Sealer. Para tal, foram utilizados 51 dentes humanos extraídos, incisivos centrais superiores, que foram instrumentados manualmente com limas tipo K, pela técnica Crown-down, obturados com compactação lateral e, após serem apicectomizados a 3mm aquém do ápice foram submetidos à retrobturação, com os três materiais propostos. As amostras foram divididas, randomicamente, em três grupos: GI MTA, GII iROOT SP e GIII Endo CPM Sealer, cada grupo com 15 amostras. Os dentes foram inseridos em tubos de eppendorfs, e feitos a impermeabilização do remanescente radicular utilizando duas camadas de cianocrilato, epóxi, e outra camada de esmalte. Em cada eppendorf foi adicionado caldo TSB estéril e uma suspensão de Enterococcos faecalis e adaptado ao frasco de vidro com meio de cultura enterococcosel. A infiltração bacteriana foi verificada pela turvação do meio de cultura. Após a análise no período de 60 dias, podemos concluir que durante esse tempo ocorreram infiltrações no Grupo I, 43,75 % das amostras apresentaram turvamento do meio de cultura demonstrando persistência da infecção. Já no Grupo II, 31,25 % das amostras tiveram crescimento bacteriano. Por fim no Grupo III, 25,00 % houve a infiltração. Grupos controle positivo e negativo para crescimento bacteriano foram realizados (n=3, cada). Os cimentos testados comportaram-se de maneira semelhante frente à infiltração bacteriana durante o período testado.

槐花提取化合物K3体外抗HIV-1活性的研究

目的:研究槐花提取化合物K3的体外抗HIV-1活性,并对其抗HIV-1机制进行初步探讨.方法:采用MTT比色法检测化合物对各种细胞的毒性.用合胞体形成计数法,p24抗原捕获ELISA法及RT-PCR等多种方法研究化合物体外抗HIV-1活性.结论:槐花提取化合物K3体外有较好的抗HIV-1活性,能够抑制病毒实验株(HIV-1ⅢB,耐药株(HIV-1 74v)和临床分离株(HIV-1KM018)等多种病毒株的复制,且其作用机制是多靶点的,不仅可以抑制病毒的进入,还可以抑制HIV-1逆转录酶活性.

灯盏花乙素和槐花化合物K3 体外抗HIV-1 活性研究

由于目前抗HIV 药物价格昂贵且有较强的毒副作用，传统药物将成为未来 HIV 治疗的主流药物。许多植物来源的天然化合物体外具有较好的抗HIV 活性， 有些化合物甚至可以作用在病毒复制周期的不同阶段。HIV 侵入抑制剂目前成 为抗HIV 药物研发的热点。HIV 侵入抑制剂靶定在病毒复制周期的结合或融合 位点，对临床中已产生耐药性突变的病毒株也有较好的抑制作用。该类抑制剂 的出现将为HARRT 疗法提供更多新的药物组合。开发新一代的HIV-1 侵入抑制 剂，与逆转录酶或蛋白酶抑制剂联合使用将增加治疗的有效性并减少毒副作用 的产生。 灯盏花乙素（Scutellarin）与槐花化合物K3 均从天然植物资源中提取，且 前者在我国临床上一直有着广泛应用。我们对这两种化合物的抗HIV-1 活性进 行了研究，检测了其对实验室适应病毒株（HIV-1ⅢB）、耐药株（HIV-174V）和临 床分离病毒株（HIV-1KM018）的抑制活性。灯盏花乙素是从植物滇黄芩中分离出 来的具有多种生物活性的黄酮类化合物，该化合物抑制HIV-1ⅢB 诱导C8166 细 胞合胞体形成的EC50 为26μM，选择指数为36。灯盏花乙素对耐药病毒株和临 床分离株也表现出良好的抑制作用。从槐花中提取的硫酸酯类化合物K3 体外研 究证实也有很好的抗HIV-1 活性，它不仅可以抑制HIV-1 致细胞病变效应，也 可以抑制感染细胞中的HIV-1 特异性抗原表达，该化合物的半数有效抑制浓度 EC50 为5～54μM。 灯盏花乙素与槐花化合物K3 的抗HIV-1 机制研究结果表明：两种化合物均 能有效抑制病毒进入细胞。灯盏花乙素在54μM 时抑制45%的病毒粒子进入细 胞，槐花化合物K3 在40μM 时能够有效抑制56％的HIV-1 进入细胞；灯盏花乙 素与槐花化合物K3 也可以抑制C8166 细胞与慢性感染的H9/HIV-1ⅢB 细胞间的融合，灯盏花乙素的EC50 为15μM，而槐花化合物K3 的EC50 为5μM；两种化 合物对体外重组的HIV-1 逆转录酶有微弱的抑制作用，在433μM 时，灯盏花乙 素可以抑制48％的逆转录酶活性，槐花化合物K3 在300μM 时能够抑制80％的 HIV-1 逆转录酶活性；这两种化合物体外对HIV-1 均无直接杀伤作用，也不能抑 制慢性感染细胞中的病毒复制和HIV-1 蛋白酶活性。因此，灯盏花乙素与槐花 化合物K3 的体外抗HIV-1 作用机制主要源于其能够抑制HIV-1 RT 活性和阻止 HIV-1 进入细胞。 灯盏花乙素和槐花化合物K3的有效抗病毒活性和多种作用途径使其成为具 有发展潜力的抗病毒先导化合物。

PURIFICATION AND PARTIAL CHARACTERIZATION OF AN ENDO-POLYGALACTURONASE FROM ASPERGILLUS NIGER

A pectinase was identified and isolated from a commercial Aspergillus niger pectinase preparation. The crude enzyme preparation, which was prepared by precipitation of the water extract of the culture of A. niger with ammonium sulfate, was further fractionated by three steps of chromatography, i. e., cation exchange, hydrophobic interaction and onion exchange, to obtain an electrophoretically homogeneous pectinase. The molecular weight of the purified enzyme was estimated by SDS-PAGE to be about 40.4 kDa under both nonreducing and reducing conditions, with the optimum pH at 5.0 and the optimum temperature at 36C. The enzyme was stable at temperatures below 35C. The partial N-terminal ammo acid sequence data analysis of the first 19 amina acids of the obtained pectinase revealed 94.7% and 89.5% homology with two reported pectinases from A. niger.

Palladium catalysed formal 6-endo-trig approaches to pumiliotoxin alkaloids: interception of the elusive cyclopropyl intermediate

Intramolecular Heck cyclisation of (E)-vinyl bromides leads to indolizidines, related to pumiliotoxin alkaloids, in which the stereochemistry of the trisubstituted double bond undergoes inversion. A cyclopropyl intermediate, which is believed to be responsible for the double bond inversion, has been intercepted by forcing an 'early' beta-hydride elimination on this species. The relative stereochemistry of this cyclopropyl intermediate determines the regioselectivity of the final beta-hydride elimination. In this case all three beta-hydride eliminations were stereochemically permitted, giving rise to a mixture of three isomeric products, differing in the position of a double bond. (Z)-Vinyl bromides were found to be less reactive than (E)-vinyl bromides, but on cyclisation gave the required conjugated diene, with inversion of the vinyl bromide stereochemistry, as the sole reaction product. This methodology will allow rapid stereoselective access to the diene-based pumiliotoxin alkaloids.

Feleucin-BO1: A Novel Antimicrobial Non-Apeptide Amide from the Skin Secretion of the Toad, Bombina orientalis, and Design of a Potent Broad-Spectrum Synthetic Analogue, Feleucin-K3

Feleucins-BV1 and -BV2 are recently-described prototypes of a novel antimicrobial nonapeptide (AMP) family identified in the skin secretion of the bombinid toad, Bombina variegata. They are encoded on different precursors that also encode a novel bombinin. Here we describe the identification of feleucin-BO1 (FLGLLGSLLamide) which is co-encoded with a different novel bombinin, named feleucin precursor-associated bombinin (FPA-bombinin-BO), from the skin secretion of Bombina orientalis. Synthetic feleucin-BO1 displayed activity against a reference Gram-positive bacterium. Staphylococcus aureus (MIC 34 μM) but was inactive (> 250 μM) against the Gram-negative bacterium, Escherichia coli, and the yeast, Candida albicans. This pattern of activity was similar to that of the prototypes. Design and synthesis of a cationicity-enhanced analogue, feleucin-K3 (F-K3), in which the amino acid residues at positions 3 (G), 6 (G) and 7 (S) of feleucin-BO1 were substituted with Lys (K) residues, resulted in a peptide with significantly-enhanced potency and spectrum of activity. The MICs of F-K3 against the reference microorganisms were 7 μM (S. aureus), 14 μM (E. coli) and 7 μM (C. albicans). These data indicate that the skin secretions of amphibians can continue to provide novel peptide templates for the rational design of analogues with possible therapeutic utility.

The Role of Membrane Lipid Composition on Sarco(endo)plasmic Reticulum Calcium ATPase Function in Rat Soleus Muscle

Sarco(endo)plasmic reticulum calcium ATPase (SERCA) is a transmembrane protein whose function is regulated by its immediate lipid environment (annulus). The composition of the annulus is currently unknown or it’s susceptibility to a high saturated fat diet (HSFD). Furthermore it is uncertain if HSFD can protect SERCA from thermal stress. The purpose of the study was to determine SERCA annular lipid composition, resulting impact of a HSFD, and in turn, influence on SERCA activity with and without thermal stress. The major findings were annular lipids were shorter and more saturated compared to whole homogenate and HSFD had no effect on annular lipid composition or SERCA activity with and without thermal stress. Both average chain length and unsaturation index were positively correlated with SERCA activity with and without thermal stress. These findings suggest that annular lipid composition is different than whole homogenate and its composition appears to be related to SERCA function.

Caracterización de una endo-xilanasa producida por bacillus flexus NJY2.

Tesis (Maestría en Ciencias con Orientación en Microbiología Industrial) UANL, 2012.

endo-Selective (3+2) cycloaddition polymerizations of nitrone monomers with olefins utilising high pressure conditions

A high pressure mediated (3+2) cycloaddition polymerization strategy has been employed to afford linear poly(isoxazolidine) architectures. Under these high pressure conditions this cycloaddition process was found to afford primarily endoheterocycles which when translated to the polymerization should ultimately affect the tacticity and resultant properties of the polymer. The stereoselectivity occurred as a result of a lower volume of activation for the endo-transition state and the application of a 'type-I' regime (HOMODipole-LUMODipolarophile) cycloaddition process that features secondary orbital interactions within the extended molecular orbitals. A variety of linker segments were employed in an attempt to affect the physical properties of the polymeric cycloadducts such as T-g and solubility in order to tailor these materials for use in coating applications. (C) 2007 Elsevier Ltd. All rights reserved.