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.     

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.     

Studies on Bleomycin-DNA and Bleomycin-Iron Interactions

Abstract

The bleomycins, a group of antitumor antibiotics (Figure 1), cause the degradation of DNA by a process requiring iron(II) and dioxygen (1,2). DNA degradation appears to involve two steps: association of the drug with the nucleic acid and degradation of the DNA. As part of studies directed toward achieving an understanding of how the bleomycins degrade DNA, we have examined various properties of the drug using a variety of chemical and physico- chemical techniques, including NMR and Mössbauer spectroscopy. We have studied both the interaction of the antibiotic with its target (DNA) as well as its association with its metal ion cofactor. This work has been performed on the intact drug and its derivatives as well as on synthetic models of the parent drug. This paper reviews and updates the recent work from this laboratory on the bleomycins.     

Lateral Ordering of Lipid Chains in Cholesterol-Containing Membranes: High-Field Spin-Label EPR

High-field (i.e., 94 GHz) electron paramagnetic resonance is used to characterize the nonaxial ordering of spin-labeled lipid chains in membranes containing cholesterol. Employing high magnetic fields (and microwave frequencies) allows investigation of both the lateral and transverse ordering of the phospholipid chains by cholesterol, from the x-y and z-elements, respectively, of the spin-label g-tensor. Transverse ordering is described by the conventional order parameter, P₂(cosβ), where β is the instantaneous inclination of the chain axis to the membrane normal; and lateral ordering is described by the order parameter cos2( − ), where is the azimuthal angle about the chain axis and is the mean azimuthal orientation about which angular fluctuations take place. To obtain high positional resolution, phosphatidylcholines spin labeled at all odd and even positions from n = 4 to n = 14 in the sn-2 chain (1-acyl-2-[n-(4,4′-dimethyloxazolidine-N-oxyl)]stearoyl-sn-glycero-3-phosphocholine) are used at probe amounts in membranes of dimyristoyl phosphatidylcholine containing either high (40 mol %) or low (5 mol %) concentrations of cholesterol. At high-cholesterol content, lateral ordering of the spin-labeled lipid chains is detected over a wide range of temperature throughout the liquid-ordered phase. The transverse profile of lateral -ordering with position, n, of chain labeling follows the profile of the rigid steroid nucleus of cholesterol. It becomes progressively averaged toward the terminal methyl group of the sn-2 chain, in the region of the flexible hydrocarbon chain of cholesterol. At low-cholesterol content, lateral chain ordering is prominent at low temperature, but diminishes at progressively higher chain positions with increasing temperature. The nonaxial lipid ordering may be related to the formation of in-plane lipid domains in membranes containing cholesterol and saturated lipids.     

A Spin-Label Study on Lipids in Dough Formed at Various Concentrations of Oxygen

The effect of oxygen on wheat flour lipids during dough mixing was investigated by analysis of the lipid composition and by an ESR technique with a fatty acid spin-label (4,4’-dimethyl-oxazolidine-N-oxyl derivative of 5-ketostearic acid). Dough was prepared in the presence of the spin-label under an atmosphere of air, nitrogen, 95% nitrogen—5% oxygen or oxygen, and the gluten was obtained by washing out the starch. ESR spectra of the spin-label incorporated into the gluten showed decreases in the order parameter, rotational correlation time and activation energy for rotational viscosity with increasing atmospheric oxygen concentration. During dough mixing in oxygen, oxidation of lipids proceeded and bound lipids slightly decreased. These data indicate that modification of lipids by incorporated oxygen leads to an increase in their fluidity and to a decrease in their hydrophobic interaction with protein in dough.     

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.     

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.     

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.     

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.     

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.     

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.     

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。     

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.     

fMRI Studies of Opponent Interregional Interactions in the Macaca mulatta Brain

Journal of Evolutionary Biochemistry and Physiology - In neurophysiological studies, functional magnetic resonance imaging (fMRI) is most commonly used to map brain functions by locating areas of...     

A General Model for Multilocus Epistatic Interactions in Case-Control Studies

Background

Epistasis, i.e., the interaction of alleles at different loci, is thought to play a central role in the formation and progression of complex diseases. The complexity of disease expression should arise from a complex network of epistatic interactions involving multiple genes.

Methodology

We develop a general model for testing high-order epistatic interactions for a complex disease in a case-control study. We incorporate the quantitative genetic theory of high-order epistasis into the setting of cases and controls sampled from a natural population. The new model allows the identification and testing of epistasis and its various genetic components.

Conclusions

Simulation studies were used to examine the power and false positive rates of the model under different sampling strategies. The model was used to detect epistasis in a case-control study of inflammatory bowel disease, in which five SNPs at a candidate gene were typed, leading to the identification of a significant three-locus epistasis.