Conformations of proline-containing cyclic peptides. 1H and 13C n.m.r. evidence for a solvent stabilized All-Cis X-Pro conformer of Cyclo-(Pro-Gly-Gly-Pro)2

As inferred from 13C, 1H n.m.r. data, CD measurements and ion-binding experiments, the title molecule can assume two major C2 symmetric conformations. One of these has an all-trans X-Pro peptide backbone and two 1 comes from 4 intramolecular H-bonds and represents the predominant (greater than or equal to 95%) form in D2O and nonpolar (CD3CN) solvents. Stabilized by specific solvent-solute interactions, the other conformer becomes competitive (45%) in DMSO solution. It is shown to possess a four-cis X-Pro skeleton and no intramolecular H-bonds. The Mg++ complex of the cyclic peptide in CD3CN is again C2 symmetric and its formation proceeds via a slow trans leads to cis isomerization of two X-Pro peptide bonds.     

Pseudomonas aeruginosa Inhibits the Growth of Scedosporium and Lomentospora In Vitro

Mycopathologia - In vitro bacterial–fungal interaction studies in cystic fibrosis (CF) have mainly focused on interactions between bacteria and Candida. Here we investigated the effect of...     

Expanded hammerhead ribozymes containing addressable three-way junctions

Recently, hammerhead ribozyme (HHR) motifs have been utilized as powerful tools for gene regulation. Here we present a novel design of expanded full-length HHRs that allows attaching additional functionalities to the ribozyme. These features allowed us to construct a very efficient artificial riboswitch in bacteria. Following the design of naturally occurring three-way junctions we attached an additional helix (IV) to stem I of the HHR while maintaining very fast cleavage rates. We found that the cleavage activity strongly depends on the exact design of the junction site. Incorporation of the novel ribozyme scaffold into a bacterial mRNA allowed the control of gene expression mediated by autocatalytic cleavage of the ribozyme. Appending an aptamer to the newly introduced stem enabled the identification of very powerful theophylline-inducible RNA switches by in vivo screening. Further investigations revealed a cascading system operating beyond the ribozyme-dependent mechanism. In conclusion, we extended the hammerhead toolbox for synthetic biology applications by providing an additional position for the attachment of regulatory modules for in vivo control of gene expression.     

Recruitment to Golgi membranes of ADP-ribosylation factor 1 is mediated by the cytoplasmic domain of p23.

Binding to Golgi membranes of ADP ribosylation factor 1 (ARF1) is the first event in the initiation of COPI coat assembly. Based on binding studies, a proteinaceous receptor has been proposed to be critical for this process. We now report that p23, a member of the p24 family of Golgi-resident transmembrane proteins, is involved in ARF1 binding to membranes. Using a cross-link approach based on a photolabile peptide corresponding to the cytoplasmic domain of p23, the GDP form of ARF1 (ARF1-GDP) is shown to interact with p23 whereas ARF1-GTP has no detectable affinity to p23. The p23 binding is shown to localize specifically to a 22 amino acid C-terminal fragment of ARF1. While a monomeric form of a non-photolabile p23 peptide does not significantly inhibit formation of the cross-link product, the corresponding dimeric form does compete efficiently for this interaction. Consistently, the dimeric p23 peptide strongly inhibits ARF1 binding to native Golgi membranes suggesting that an oligomeric form of p23 acts as a receptor for ARF1 before nucleotide exchange takes place.     

Spatial Analysis and Modeling Tool (SAMT): 2. Applications

The Spatial Analysis and Modeling Tool (SAMT) is a GIS-based analytical software for land use study. This paper demonstrates the capabilities of SAMT as applied in studies of land use and landscape change in the catchment area of the River Quillow, North-East Germany. Neural network and fuzzy models are important features that were incorporated in SAMT. The region of study for this application is a catchment area of about 170 km² and is subdivided into 54,000 grid cells for spatial simulations.Three different applications of SAMT are discussed in this article. The first application involves assessment of the potential soil erosion risk on arable land. This user-defined application combines an economic model (LP model), a temperature-driven crop coverage model and a soil erosion risk model (Universal Soil Loss Equation) using data from tables and map information. The second and third applications are winter wheat yield estimates using, respectively, the fuzzy toolbox SAMT_FUZZY in conjunction with expert knowledge, and using the neural network toolbox SAMT_NN based on observations.     

Stock differences in the susceptibility of rats to learned helplessness training

Learned helplessness (LH) consists of shock escape deficits evidenced by animals previously exposed to inescapable shock. This phenomenon has shown promise as a behavioral screen for new antidepressant drugs. Unfortunately, some stocks of rats evidence low susceptibility to LH training. Accordingly, male rats from 8 different stocks were tested for susceptibility to LH training. The outbred stocks consisted of Harlan SD, Sasco Holtzman, and Charles River Holtzman. The inbred stocks (i.e. strains) tested were Lewis, Wistar Kyoto, Brown Norway, Fischer F-344, and Buffalo. The Lewis, Brown Norway, Fischer and Sasco Holtzman rats were found to be virtually non-susceptible to LH training. Harlan SD and Buffalo rats evidenced intermediate susceptibilities of 28% and 33%, respectively. Kyoto and Charles River Holtzman rats were the most susceptible at 53% and 55%, respectively. No stock differences between control animals were observed. These results indicate that wide differences in susceptibility to LH training exist in rats from different stocks or suppliers and researchers should be careful to choose subjects from a susceptible stock. Charles River Holtzman and Wistar Kyoto rats appear to be very susceptible to LH training.