192 Computer-aided search for novel anti-HIV-1 agents presenting peptidomimetics of broadly neutralizing antibodies against the virus envelope GP120 V3 loop

Computer-aided search for novel anti-HIV-1 agents that are able to imitate the pharmacophore properties of the antigen-binding site of a broadly neutralizing mAb 3074 against the envelope gp120 V3 loop was carried out followed by evaluation of their potential inhibitory activity by molecular modeling. In doing so, the following problems were solved: (1) the mAb 3074 amino acid residues responsible for specific binding to the HIV-1 V3 loop were identified from the X-ray structures of this antibody Fab in complexes with the MN, UR29, and VI191 V3 peptides (Jiang et al., 2010); (2) using these data, 2039 possible mAb-3074 peptidomimetics were found by pepMMsMIMIC presenting a public, web-oriented virtual screening platform (Floris et al., 2011); (3) the complexes of these compounds with the above V3 peptides were built by molecular docking and, based on their analysis, the four molecules exhibiting a high affinity to V3 in the in silico studies were selected as the most probable peptidomimetics of mAb 3074 (Figure 1); and (4) stability of the complexes of these molecules with the MN, UR29, and VI191 V3 peptides was estimated by molecular dynamics and free energy simulations. As a result, a key role in specific binding of the selected compounds to the V3 loop was shown to belong to π-π interactions between their aromatic rings and the conserved Phe20 and/or Tyr21 of the V3 immunogenic crown. Similarly to mAb 3074, these compounds were found to block the tip of the V3 loop forming its invariant structural motif, which contains residues critical for cell tropism (Andrianov et al., 2011; Andrianov et al., 2012). In addition, the complexes of interest do not undergo significant changes within the molecular dynamics calculations, exhibiting the low values of free energy of their formation. In this context, the compounds given in Figure 1 are considered as the promising basic structures for the design of novel, potent, and broad anti-HIV-1 drugs.     

Structural analysis of the envelope gp120 V3 loop for some HIV-1 variants circulating in the countries of Eastern Europe

The V3 loop on gp120 from human immunodeficiency virus type 1 (HIV-1) is a focus of many research groups involved in anti-AIDS drug development because this region of the protein is a principal target for neutralizing antibodies and a major determinant for cell tropism and syncytium formation. In this study, the nucleotide sequences of the env gene region coding the V3 loop were determined by DNA sequencing methods for four novel HIV-1 strains that circulate in the countries of Eastern Europe, such as Russia, Belarus, Ukraine, etc. Based on the empirical data obtained, the 3D structures of the V3 loops associated with these viral modifications were generated by computer modeling and then compared to discover similarities in the spatial arrangement of this functionally important site of gp120. Despite the HIV-1 genetic variety, several regions of the V3 loop that contain residues critical for cell tropism were shown to be structurally invariant, which may explain its exceptional role in a co-receptor usage. These data together with those on the biological activity of the V3 individual residues clearly show that these conserved structural motifs of gp120 represent potential HIV-1 weak points most suitable for therapeutic intervention.     

Explicit Solvent Molecular Dynamics Simulation of Duplex Formed by the Modified Oligonucleotide with Alternating Phosphate/Phosphonate Internucleoside Linkages and its Natural Counterpart

Abstract

Impact of the internucleoside linkage modification by inserting a methylene group on the ability of the modified oligonucleotide to hybridize with a natural DNA strand was studied by fully solvated molecular dynamics (MD) simulations. Three undecamer complexes were analyzed: natural dT₁₁.dA₁₁ duplex as a reference and two its analogs with alternating modified and natural linkages in the deoxyadenosine chain. The isopolar, non-isosteric modified linkages were of 5′-O-PO₂-CH₂-O-3′ (5′PC3′) or 5′-O-CH₂-PO₂-O-3′ (5′CP3′) type. Simulations were performed by using the AMBER 5.0 software package with the force field completed by a set of parameters needed to model the modified segments. Both modifications were found to lead to double helical complexes, in which the thymidine strand as well as deoxyriboses and unmodified linkages in the adenosine strand adopted conformations typical for the B-type structure. For each of the two conformational richer modified linkages two stable conformations were found at 300 K: the -ggt and ggt for the 5′PC3′ and ggg, tgg for the 5′CP3′, respectively. Both modified chains adopted helical conformations with heightened values of the inclination parameter but without affecting the Watson-Crick hydrogen bonds.     

Unique features of the motility and structures in the flagellate polar region of Campylobacter jejuni and other species: an electron microscopic study

Similarly to Helicobacter pylori but unlike Vibrio cholerae O1/O139, Campylobacter jejuni is non‐motile at 20°C but highly motile at ≥37°C. The bacterium C. jejuni has one of the highest swimming speeds reported (>100 μm/s), especially at 42°C. Straight and spiral bacterial shapes share the same motility. C. jejuni has a unique structure in the flagellate polar region, which is characterized by a cup‐like structure (beneath the inner membrane), a funnel shape (opening onto the polar surface) and less dense space (cytoplasm). Other Campylobacter species (coli, fetus, and lari) have similar motility and flagellate polar structures, albeit with slight differences. This is especially true for Campylobacter fetus, which has a flagellum only at one pole and a cup‐like structure composed of two membranes.     

Physiology and toxicology of hormone-disrupting chemicals in higher plants

Higher plants are exposed to natural environmental organic chemicals, associated with plant–environment interactions, and xenobiotic environmental organic chemicals, associated with anthropogenic activities. The effects of these chemicals result not only from interaction with metabolic targets, but also from interaction with the complex regulatory networks of hormone signaling. Purpose-designed plant hormone analogues thus show extensive signaling effects on gene regulation and are as such important for understanding plant hormone mechanisms and for manipulating plant growth and development. Some natural environmental chemicals also act on plants through interference with the perception and transduction of endogenous hormone signals. In a number of cases, bioactive xenobiotics, including herbicides that have been designed to affect specific metabolic targets, show extensive gene regulation effects, which are more in accordance with signaling effects than with consequences of metabolic effects. Some of these effects could be due to structural analogies with plant hormones or to interference with hormone metabolism, thus resulting in situations of hormone disruption similar to animal cell endocrine disruption by xenobiotics. These hormone-disrupting effects can be superimposed on parallel metabolic effects, thus indicating that toxicological characterisation of xenobiotics must take into consideration the whole range of signaling and metabolic effects. Hormone-disruptive signaling effects probably predominate when xenobiotic concentrations are low, as occurs in situations of residual low-level pollutions. These hormone-disruptive effects in plants may thus be of importance for understanding cryptic effects of low-dosage xenobiotics, as well as the interactive effects of mixtures of xenobiotic pollutants.     

Metabolic impact assessment for heterologous protein production in Streptomyces lividans based on genome-scale metabolic network modeling

The metabolic impact exerted on a microorganism due to heterologous protein production is still poorly understood in Streptomyces lividans. In this present paper, based on exometabolomic data, a proposed genome-scale metabolic network model is used to assess this metabolic impact in S. lividans. Constraint-based modeling results obtained in this work revealed that the metabolic impact due to heterologous protein production is widely distributed in the genome of S. lividans, causing both slow substrate assimilation and a shift in active pathways. Exchange fluxes that are critical for model performance have been identified for metabolites of mouse tumor necrosis factor, histidine, valine and lysine, as well as biomass. Our results unravel the interaction of heterologous protein production with intracellular metabolism of S. lividans, thus, a possible basis for further studies in relieving the metabolic burden via metabolic or bioprocess engineering.     

Cooperation between osteoblastic cells and endothelial cells enhances their phenotypic responses and improves osteoblast function

Osteogenesis requires close co-operation with angiogenesis to create vascularized bone tissue. In this study, an indirect co-culture model using osteoblasts (OBs), primary endothelial cells (ECs) and Matrigel interlayer was established to understand the impact of each cell type on the other. ECs synergistically enhanced osteoblastic gene expression by OBs, while OBs were capable of supporting tubule-like structures formed by ECs on Matrigel, enhancing mean tubule length from 146.5 ± 23.5 μm in ECs alone to 192 ± 28.6 μm in co-culture (p < 0.05). Similar improvements were noted in terms of tubule number. An applicability study of the co-culture model to bone tissue engineering, performed on a biopolymer fibrous membrane, showed substantially enhanced deposition of calcified nodules. These results demonstrate the efficacy of co-culture with ECs to improve osteogenesis for bone tissue engineering.     

Internal ethnicity in the ethnic economy

Internal ethnicity refers to ethnic subgroups within an immigrant group. An ‘ethnic economy’ includes the self‐employed and their co‐ethnic workers. Although most research treats the boundaries of ‘ethnic economy’ and its variant, the ‘ethnic enclave economy’, as though they were coterminous with those of national‐origin immigrant groups, this assumption is unreliable. Ethnic boundaries need not coincide with those of nationality origin when internal ethnicity exists. To test this hypothesis, we utilize survey data collected from a sample of Iranians in Los Angeles. Because this national‐origin immigrant group contains four ethno‐religious subgroups (Armenians, Bahais, Jews and Muslims), the Iranians in Los Angeles operated four distinctive ethnic economies, not one. Each ethno‐religious subgroup had its own ethnic economy, and these separate economies were only weakly tied to an encompassing Iranian ethnic economy.     

Description of the female and new data on the distribution of Annitella apfelbecki Klapálek, 1899 (Insecta: Trichoptera)

Annitella apfelbecki is one of three Annitella species with distribution ranges restricted to the Balkan Peninsula. In this paper, we describe the hitherto unknown female of A. apfelbecki and give the most important morphological features to enable its identification and separation from the other Annitella females. Additionally, we provide new data on distribution and discuss zoogeography, life cycle and ecology of this species.     

Association of Shiga toxin glycosphingolipid receptors with membrane microdomains of toxin-sensitive lymphoid and myeloid cells

Glycosphingolipids (GSLs) of the globo-series constitute specific receptors for Shiga toxins (Stxs) released by certain types of pathogenic Escherichia coli strains. Stx-loaded leukocytes may act as transporter cells in the blood and transfer the toxin to endothelial target cells. Therefore, we performed a thorough investigation on the expression of globo-series GSLs in serum-free cultivated Raji and Jurkat cells, representing B- and T-lymphocyte descendants, respectively, as well as THP-1 and HL-60 cells of the monocyte and granulocyte lineage, respectively. The presence of Stx-receptors in GSL preparations of Raji and THP-1 cells and the absence in Jurkat and HL-60 cells revealed high compliance of solid-phase immunodetection assays with the expression profiles of receptor-related glycosyltransferases, performed by qRT-PCR analysis, and Stx2-caused cellular damage. Canonical microdomain association of Stx GSL receptors, sphingomyelin, and cholesterol in membranes of Raji and THP-1 cells was assessed by comparative analysis of detergent-resistant membrane (DRM) and nonDRM fractions obtained by density gradient centrifugation and showed high correlation based on nonparametric statistical analysis. Our comprehensive study on the expression of Stx-receptors and their subcellular distribution provides the basis for exploring the functional role of lipid raft-associated Stx-receptors in cells of leukocyte origin.