The peptides of α-aminosuberic acid I New intermediates for synthetic studies

Summary. The paper describes the synthesis of α-aminosuberic acid derivatives suitable for the synthesis of peptides. These include Z-, Boc- and Fmoc-protection on the α-amino group, benzyl ester, Boc-hydrazide and Z-hydrazide as well as the free carboxylic function in the side chain, and methyl ester, benzyl ester or free α-carboxylic group. Their use is demonstrated on the synthesis of the respective derivatives of Asu-Val-Leu. The enzyme catalyzed reaction was succesfully used both as a route to L-Asu from the D,L-compound as well as for the direct synthesis of the optically active tripeptide derivative from the Z-D,L-Asu-OH. Received February 5, 1999     

Predicting distributions of Wolbachia strains through host ecological contact—Who's manipulating whom?

Reproductive isolation in response to divergent selection is often mediated via third‐party interactions. Under these conditions, speciation is inextricably linked to ecological context. We present a novel framework for understanding arthropod speciation as mediated by Wolbachia, a microbial endosymbiont capable of causing host cytoplasmic incompatibility (CI). We predict that sympatric host sister‐species harbor paraphyletic Wolbachia strains that provide CI, while well‐defined congeners in ecological contact and recently diverged noninteracting congeners are uninfected due to Wolbachia redundancy. We argue that Wolbachia provides an adaptive advantage when coupled with reduced hybrid fitness, facilitating assortative mating between co‐occurring divergent phenotypes—the contact contingency hypothesis. To test this, we applied a predictive algorithm to empirical pollinating fig wasp data, achieving up to 91.60% accuracy. We further postulate that observed temporal decay of Wolbachia incidence results from adaptive host purging—adaptive decay hypothesis—but implementation failed to predict systematic patterns. We then account for post‐zygotic offspring mortality during CI mating, modeling fitness clines across developmental resources—the fecundity trade‐off hypothesis. This model regularly favored CI despite fecundity losses. We demonstrate that a rules‐based algorithm accurately predicts Wolbachia infection status. This has implications among other systems where closely related sympatric species encounter adaptive disadvantage through hybridization.     

Azetidinone-isothiazolidinones: Stereoselective synthesis and antibacterial evaluation of new monocyclic beta-lactams

A simple and efficient procedure for the stereoselective synthesis of new azetidinone-isothiazolidinones has been developed. New compounds were tested in vitro on a panel of Gram-positive and Gram-negative bacterial pathogens, some of them showing weak antibacterial activity.     

Phenological differences among selected residents and long-distance migrant bird species in central Europe

The phenological responses to climate of residents and migrants (short- and long-distance) differ. Although few previous studies have focussed on this topic, the agree that changes in phenology are more apparent for residents than for long-distance migrants. We analysed the breeding times of two selected residents (Sitta europaea, Parus major) and one long-distance migrant (Ficedula albicollis) from 1961 to 2007 in central Europe. The timing of the phenophases of all three bird species showed a significant advance to earlier times. Nevertheless, the most marked shift was observed for the long-distance migrant (1.9 days per decade on average in mean laying date with linearity at the 99.9 % confidence level). In contrast, the shifts shown by the residents were smaller (1.6 days for S. europaea and 1.5 days for P. major also on average in mean laying date for both, with linearity at the 95 % confidence level). Spearman rank correlation coefficients calculated for pairs of phenophases of given bird species in 20-year subsamples (e.g. 1961–1980, 1962–1981) showed higher phenological separation between the residents and the migrant. This separation is most apparent after the 1980s. Thus, our results indicate that the interconnections between the studied phenological stages of the three bird species are becoming weaker.     

Novel insight into the process of nutrients removal using an algal biofilm: The evaluation of mechanism and efficiency

Eutrophication of water by nutrient pollution remains an important environmental issue. The aim of this study was to evaluate the nutrient uptake capacity of an algal biofilm as a means to treat polluted water. In addition, the study investigated the nutrient removal process. The algal biofilm was able to remove 99% of phosphorus within 24 hours of P addition, with the PO₄-P concentration in inflowing water ranging from 3 to 10 mg L^?1. Different patterns of phosphorus and nitrogen removal were observed. Daily quantity of removed NO₃-N ranged from 2 to 25% and was highly dependent on solar irradiance. Precipitation of phosphorus during the removal process was studied using X-ray diffraction analyses and was not confirmed in the biofilm. The biofilm system we constructed has a high efficiency for phosphorus removal and, therefore, has great potential for integration into wastewater treatment processes.     

1H, 13C, and 15N resonance assignment of the N-terminal domain of Mason-Pfizer monkey virus capsid protein, CA 1-140

Mason-Pfizer monkey virus (M-PMV) belongs to the family of betaretroviruses characterized by the assembly of immature particles within cytoplasm of infected cells in contrast to other retroviruses (e.g. HIV, RSV) that assemble their immature particles at a plasma membrane. Simultaneously with or shortly after budding a virus-encoded protease is activated and the Gag polyprotein is cleaved into three major structural proteins: matrix (MA), capsid (CA), and nucleocapsid (NC) protein. Mature retroviral CA proteins consist of two independently folded structural domains: N-terminal domain (NTD) and C-terminal dimerization domain (CTD), separated by a flexible linker. As a first step toward the solution structure elucidation, we present nearly complete backbone and side-chain ¹H, ¹⁵N and ¹³C resonance assignment of the M-PMV NTD CA.     

Arabidopsis Exocyst Subcomplex Containing Subunit EXO70B1 Is Involved in Autophagy‐Related Transport to the Vacuole

Autophagic transport to the vacuole represents an endomembrane trafficking route, which is widely used in plants, not only during stress situations, but also for vacuole biogenesis and during developmental processes. Here we report a role in autophagic membrane transport for EXO70B1—one of 23 paralogs of Arabidopsis EXO70 exocyst subunits. EXO70B1 positive compartments are internalized into the central vacuole and co‐localize with autophagosomal marker ATG8f. This internalization is boosted by induction of autophagy. Loss of function (LOF) mutations in exo70B1 cause reduction of internalized autopagic bodies in the vacuole. Mutant plants also show ectopic hypersensitive response (HR) mediated by salicylic acid (SA) accumulation, increased nitrogen starvation susceptibility and anthocyanin accumulation defects. Anthocyanin accumulation defect persists in npr1x exo70B1 double mutants with SA signaling compromised, while ectopic HR is suppressed. EXO70B1 interacts with SEC5 and EXO84 and forms an exocyst subcomplex involved in autophagy‐related, Golgi‐independent membrane traffic to the vacuole. We show that EXO70B1 is functionally completely different from EXO70A1 exocyst subunit and adopted a specific role in autophagic transport .     

Modulation of the antagonistic properties of an insulin mimetic peptide by disulfide bridge modifications

Insulin is a peptide responsible for regulating the metabolic homeostasis of the organism; it elicits its effects through binding to the transmembrane insulin receptor (IR). Insulin mimetics with agonistic or antagonistic effects toward the receptor are an exciting field of research and could find applications in treating diabetes or malignant diseases. We prepared five variants of a previously reported 20-amino acid insulin-mimicking peptide. These peptides differ from each other by the structure of the covalent bridge connecting positions 11 and 18. In addition to the peptide with a disulfide bridge, a derivative with a dicarba bridge and three derivatives with a 1,2,3-triazole differing from each other by the presence of sulfur or oxygen in their staples were prepared. The strongest binding to IR was exhibited by the peptide with a disulfide bridge. All other derivatives only weakly bound to IR, and a relationship between increasing bridge length and lower binding affinity can be inferred. Despite their nanomolar affinities, none of the prepared peptide mimetics was able to activate the insulin receptor even at high concentrations, but all mimetics were able to inhibit insulin-induced receptor activation. However, the receptor remained approximately 30% active even at the highest concentration of the agents; thus, the agents behave as partial antagonists. An interesting observation is that these mimetic peptides do not antagonize insulin action in proportion to their binding affinities. The compounds characterized in this study show that it is possible to modulate the functional properties of insulin receptor peptide ligands using disulfide mimetics.