Studies on Fusarium-Gladiolus Interactions

Using standardized conditions, 65 genotypes of Gladiolus were screened for Fusarium resistance. High levels were found in 'large-flowered" types, Primulinus hybrids, G. callianthus, G. garnierii , and G. dalenii. Some accessions of G. dalenii exhibited no disease symptoms when inoculated with two standard test isolates. No resistance was found in 'small-flowered' types. To estimate race-specifity of the resistance, eight highly resistant Gladiolus genotypes were tested in an in vitro test against 43 isolates of F. oxysporum f.sp. gladioli. Two isolates were able to partially infect the G. dalenii accessions and this was confirmed using whole plants. Implications for resistance breeding are discussed.     

Bleomycin-DNA interactions: fluorescence and proton magnetic resonance studies.

The interaction of bleomycin A2 with DNA has been examined by fluorescence spectroscopy and proton magnetic resonance techniques. Fluorescence bands observed at 353 and 405 nm in the spectrum of bleomycin were assigned to the bithiazole and 4-aminopyrimidine rings, respectively. Quenching of bithiazole fluorescence by DNA was used to determine apparent equilibrium constants for the complex which, in 2.5 mM tris(hydroxymethyl)aminomethane buffer, pH 8.4, are 1.2 X 10(5) M-1 for bleomycin and 1.4 X 10(5) M-1 for tripeptide S, a partial acid hydrolysis product of the antibiotic. Uner these conditions, one molecule of bleomycin binds for every five to six base pairs in DNA. In the proton magnetic resonance spectrum of bleomycin, resonances emanating from the bithiazole rings and dimethylsulfonium groups are preferentially broadened and reduced in intensity in the presence of DNA, suggesting that these moieties bind most tightly to the polymer.     

Studies on Plant Viruses-soil Colloids Interactions

Stability and infectivity of cucumber mosaic virus, strain D (CMV-D), associations with kaolinite and montmorillonite were determined, as affected by: i) nature of clay minerals; ii) nature of clay saturating cations; iii) exposure to dissociating salt solutions (2 M LiCl). Infectivity experiments carried out with sediments following centrifugation of the virus-clay mixtures (sd fractions), showed that, in absence of LiCl, the highest values were obtained with kaolinite, in the order Li⁺= K⁺ > NH₄⁺= Mg⁺⁺ > Na⁺ > Ca⁺⁺ clay saturating cations, ranging between 91 and 30 % of the untreated control, whereas comparable montmorillonite fractions gave infectivity values with all cations about 10–15 % of the control. In presence of 2 M LiCl, montmorillonite preserved infectivity of the same fraction (Lsd fraction), which, in the case of Li⁺- or Ca⁺⁺ -saturated samples, was higher when compared with the corresponding sd values, thus revealing for these cations an amplifying effect on infection. This did not occur with kaolinite which, however, gave a Lsd fraction more infectious than the other clay. The results confirmed that clay minerals preserve infectivity of virus preparations exposed to critical conditions, thus providing an explanation for the persistence in soil of infectivity of viruses which are normally not soil-borne. Under appropriate soil conditions these viruses may form complexes with clay minerals thus retaining an infectivity which may be enhanced by addition of cations as those contained in fertilizers.     

NIRF对P53蛋白泛素化作用的研究

HEK293和HeLa细胞分别被Np95/ICBP90-likeRINGfingerprotein(NIRF)和P53转染后,细胞上清和免疫沉淀产物用SDS-聚丙烯酰胺凝胶电泳免疫印迹法分析;细菌合成GST-P53后,用GSTpull-down技术检测NIRF与P53相互作用;在GST-P53、E1、E2和NIRF体外泛素化反应系统中,检测NIRF对P53的体外泛素化.结果表明:NIRF能与P53相互作用,NIRF不仅能与P53特异性结合,而且还会将P53泛素化,这种相互作用在细胞内和细胞外均能发生.推测NIRF可能是P53的一个新的负调节蛋白.     

植物与病原菌互作的蛋白质组学研究进展

深入认识植物与病原菌的识别方式、亲和性或非亲和性的互作模式,对于揭示植物-病原菌互作机制研究具有重要意义.利用蛋白质组学方法研究病原菌侵染植物过程,分析相关的基因和蛋白,有助于从分子水平上探究植物-病原菌相互作用机制.本文概述了植物-病原菌的互作机制,系统介绍了差异蛋白质组学分析方法在植物-病原真菌、植物-病原细菌两类互作系统中的应用,分析了植物与病原菌互作过程中可能涉及的差异表达功能蛋白,并对当前蛋白质组学技术在植物与病原菌互作研究中存在的诸多问题进行了探讨.     

Studies on plant growth-regulating substances: Interactions between auxins and inactive analogues

Applications of streptomycin sulphate or protectant fungicides reduced numbers of secondary infections in severely infected hop plantings. When primary infected shoots treated with streptomycin were left on plants for 3 weeks no significant increase in secondary disease resulted. Streptomycin, which was absorbed rapidly by hop plants, could not be detected in expressed shoot sap by early June and had no effect on crop yield or quality.     

应用平衡透析法分析药物小分子与蛋白质相互作用

蛋白质的相关信息一直是生命科学研究的重点,其中药物小分子与蛋白质的相互作用成为近年来的研究热点。平衡透析法是研究药物小分子与蛋白质相互作用的经典方法,通过该方法可以定量的讨论药物小分子与蛋白质结合的结合数量、结合常数。就平衡透析法用于分析药物小分子与蛋白质的作用方式、作用模型及国内外研究进展进行综述。     

Gene-Gene and Gene-Environment Interactions in Meta-Analysis of Genetic Association Studies

Extensive genetic studies have identified a large number of causal genetic variations in many human phenotypes; however, these could not completely explain heritability in complex diseases. Some researchers have proposed that the “missing heritability” may be attributable to gene–gene and gene–environment interactions. Because there are billions of potential interaction combinations, the statistical power of a single study is often ineffective in detecting these interactions. Meta-analysis is a common method of increasing detection power; however, accessing individual data could be difficult. This study presents a simple method that employs aggregated summary values from a “case” group to detect these specific interactions that based on rare disease and independence assumptions. However, these assumptions, particularly the rare disease assumption, may be violated in real situations; therefore, this study further investigated the robustness of our proposed method when it violates the assumptions. In conclusion, we observed that the rare disease assumption is relatively nonessential, whereas the independence assumption is an essential component. Because single nucleotide polymorphisms (SNPs) are often unrelated to environmental factors and SNPs on other chromosomes, researchers should use this method to investigate gene–gene and gene–environment interactions when they are unable to obtain detailed individual patient data.     

微量热泳动技术原理及其在研究生物分子互作方面的应用

微量热泳动(MST)技术是近年来兴起的一项用于研究生物分子间互作的新技术。其检测是基于热泳动现象,即分子在温度梯度中的定向运动及由此引起分子性质的变化,如分子大小、电荷和水化层及构象等。该方法把精确的荧光检测与灵敏的热泳动相结合,从而提供了一个灵敏的、快速的精确分析生物分子间互作的检测方法。就MST的工作原理和检测过程及其在生物学研究中的应用作以综述。     

Interactions of Isophorone Derivatives with DNA: Spectroscopic Studies

Interactions of three new isophorone derivatives, Isoa Isob and Isoc with salmon testes DNA have been investigated using UV-Vis, fluorescence and circular dichroism spectroscopic methods. All the studied compounds interact with DNA through intercalative binding mode. The stoichiometry of the isophorone/DNA adducts was found to be 1:1. The fluorescence quenching data revealed a binding interaction with the base pairs of DNA. The CD data indicate that all the investigated isophorones induce DNA modifications.     

Computational Studies of Ligand-Receptor Interactions in Bitter Taste Receptors

Phenylthiocarbamide tastes intensely bitter to some individuals, but others find it completely tasteless. Recently, it was suggested that phenylthiocarbamide elicits bitter taste by interacting with a human G protein-coupled receptor (hTAS2R38) encoded by the PTC gene. The phenylthiocarbamide nontaster trait was linked to three single nucleotide polymorphisms occurring in the PTC gene. Using the crystal structure of bovine rhodopsin as template, we generated the 3D structure of hTAS2R38 bitter taste receptor. We were able to map on the receptor structure the amino acids affected by the genetic polymorphisms and to propose molecular functions for two of them that explained the emergence of the nontaster trait. We used molecular docking simulations to find that phenylthiocarbamide exhibited a higher affinity for the target receptor than the structurally similar molecule 6-n-propylthiouracil, in line with recent experimental studies. A 3D model was constructed for the hTAS2R16 bitter taste receptor as well, by applying the same protocol. We found that the recently published experimental ligand binding affinity data for this receptor correlated well with the binding scores obtained from our molecular docking calculations.     

Apolipoprotein/Lipid Interactions: Studies with Synthetic Polypeptide

Abstract

The understanding of complex interactions which occur in the serum lipoproteins has been greatly aided by using peptide synthesis to obtain fragments of the apolipoproteins which are unobtainable by other means. The results from lipid-binding studies with these synthetic materials have generally supported the amphipathic helical hypothesis of Segrest et a1.¹² for the interaction of phospholipid with the apolipoprotein. However, CD results from these same experiments suggest that the amphipathic helices may not be as large as originally proposed. The contribution of other protein structural features, e.g. β-sheets and β-turns, to lipid binding has not been systematically investigated. The importance of hydrophobicity to lipid-protein interaction is strongly supported by the experimental data. Indeed, there is preliminary evidence^44,60 that the hydrophobic residues positioned beneath the paired acidic and basic residues on the amphipathic helix are extremely critical to the interaction with phospholipid. The role of charged residues in binding is less clear and needs further investigation. The importance of the structural features previously mentioned can be elucidated through the synthesis of appropriately substituted peptides. However, the final proof of the protein structural features involved in protein-lipid interaction must await x-ray diffraction analysis and detailed NMR measurements.

As more peptides are synthesized and studied, the authors feel that the complexities of lipid transport and metabolism will be better understood. The surface properties of peptide fragments of the apoproteins are presently being investigated and could lead to important findings on the exchange of apoproteins between lipoprotein classes. The interactions of synthetic peptides with the enzymes which control lipid synthesis and degradation have increased the understanding of protein-protein and protein-lipid interactions which control these important processes. The ability of a synthetic peptide to accelerate lipolysis in an apoC-II deficient lipoprotein offers the potential for treating these patients with synthetic material to reduce their hypertriglyceridemia. The ability to model the amphipathic helix opens new vistas for the study of the role of hydrophobicity, peptide length, helix potential, and charged residues in lipid binding. The observation of Pownall et al.⁷¹ and Yokayama et al.⁷⁴ that phospholipid-cholesterol complexes of these model peptides can serve as substrates for LCAT suggests several exciting avenues for further study of cholesterol metabolism and transport. As these studies increase knowledge of lipid transport, the potential exists to intervene therapeutically with potent synthetic lipid-binding peptides to reduce serum cholesterol or to remove cholesterol from arterial lesions.     

Computational Studies on Sirtuins from Trypanosoma cruzi: Structures,Conformations and Interactions with Phytochemicals

Background

The silent-information regulator 2 proteins, otherwise called sirtuins, are currently considered as emerging anti-parasitic targets. Nicotinamide, a pan-sirtuin inhibitor, is known to cause kinetoplast alterations and the arrested growth of T. cruzi, the protozoan responsible for Chagas disease. These observations suggested that sirtuins from this parasite (TcSir2rp1 and TcSir2rp3) could play an important role in the regulation of the parasitic cell cycle. Thus, their inhibition could be exploited for the development of novel anti-trypanosomal compounds.

Methods

Homology modeling was used to determine the three-dimensional features of the sirtuin TcSir2rp1 from T. cruzi. The apo-form of human SIRT2 and the same structure solved in complex with its co-substrate NAD⁺ allowed the modeling of TcSir2rp1 in the open and closed conformational states. Molecular docking studies were then carried out. A library composed of fifty natural and diverse compounds that are known to be active against this parasite, was established based on the literature and virtually screened against TcSir2rp1 and TcSir2rp3, which was previously modeled by our group.

Results

In this study, two conformational states of TcSir2rp1 were described for the first time. The molecular docking results of compounds capable of binding sirtuins proved to be meaningful when the closed conformation of the protein was taken into account for calculations. This specific conformation was then used for the virtual screening of antritrypanosomal phytochemicals against TcSir2rp1 and TcSir2rp3. The calculations identified a limited number of scaffolds extracted from Vismia orientalis, Cussonia zimmermannii, Amomum aculeatum and Anacardium occidentale that potentially interact with both proteins.

Conclusions

The study provided reliable models for future structure-based drug design projects concerning sirtuins from T. cruzi. Molecular docking studies highlighted not only the advantages of performing in silico interaction studies on their closed conformations but they also suggested the potential mechanism of action of four phytochemicals known for their anti-trypanosomal activity in vitro.     

Chromosome Interactions in DROSOPHILA MELANOGASTER. I. Viability Studies

The nature of fitness interactions is an important, yet unsolved, question in population genetics. We compare the egg-to-adult viability of individuals homozygous for either a second or a third chromosome with the viability of individuals homozygous for both chromosomes simultaneously. On the average, the viability of the two-chromosome homozygotes is somewhat greater than expected assuming that the fitnesses of the single-chromosome homozygotes interact in a multiplicative fashion. This result differs from previous observations that indicate either no significant deviations from the expectation or lower-than-expected average fitnesses for the double homozygotes.     

Diversity of Interactions: A Metric for Studies of Biodiversity

Multitrophic interactions play key roles in the origin and maintenance of species diversity, and the study of these interactions has contributed to important theoretical advances in ecology and evolutionary biology. Nevertheless, most biodiversity inventories focus on static species lists, and prominent theories of diversity still ignore trophic interactions. The lack of a simple interaction metric that is analogous to species richness is one reason why diversity of interactions is not examined as a response or predictor variable in diversity studies. Using plant–herbivore–enemy trophic chains as an example, we develop a simple metric of diversity in which richness, diversity indices (e.g., Simpson's 1/D), and rarefaction diversity are calculated with links as the basic unit rather than species. Interactions include all two-link (herbivore–plant and enemy–herbivore) and three-link (enemy–herbivore–plant) chains found in a study unit. This metric is different from other indices, such as traditional diversity measures, connectivity and interaction diversity in food-web studies, and the diversity of interaction index in behavioral studies, and it is easier to compute. Using this approach to studying diversity provides novel insight into debates about neutrality and correlations between diversity, stability, productivity, and ecosystem services.