Synthesis of Ester-Linked Ursolic Acid-Based Hybrid Compounds: Potential Antibacterial and Anticancer Agents

The molecular hybridization of two or more drugs into a single molecule is an effective drug design approach to reduce pill burden and improve patient treatment adherence. Ursolic acid-based hybrid compounds were synthesized and characterized followed by molecular docking studies. In vitro studies against various bacterial strains and human cancer cells (MDA-MB-231, HeLa, and MCF-7) were performed. Compounds 14 – 19 , 21 , 34 , 31 , and 30 demonstrated significant antibacterial activities with MIC values of 15.625 μg/ml. Compounds 29 and 34 were more cytotoxic than ursolic acid, with IC₅₀ values of 46.99 and 48.18 μg/ml. Compounds 29 and 34 in the docking studies presented favourable binding interactions and better docking energy against the Epidermal Growth Factor Receptor (EGFR) than the parent compound, ursolic acid. The findings revealed that the ursolic acid scaffold is a promising precursor for the development of molecules with promising anticancer and antimicrobial activities. However, more studies are needed to fully understand their mode of action.     

Vertical distributions and relations of euphausiid populations off Elephant Island,March 1984

Summary Distributional relationships are described for post-larval and larval Euphausia superba and Thysanoessa sp. (probably macrura) and post-larval Euphausia frigida collected in 0–70/80 m and 0–175/200 m depth ranges with a MOCNESS sampler north of Elephant Island (61°S, 55°W) during 17–23 March 1984. Larval E. superba (predominantly calyptopes stage 2 and 3) were rare shallower than 80 m at night. Day catches of post-larval E. suberba were small and night catches were primarily near the top of the thermocline above 50 m depth. Thysanoessa sp. occurred throughout the 0–200 m depth range and was abundant in the upper 80 m both night and day. E. frigida migrated to the upper 80 m at night from deeper day depths. Larval stages of E. superba and bost-larval stages of all three species demonstrated independent and variable vertical distribution patterns both night and day. Changes in E. superba abundance and distributional patterns could to a certain extent be associated with observed environmental changes. An increase in larval and decrease in post-larval E. superba abundances between 0–80 m was associated with an intrusion of cold water at depth. At night, vertically restricted concentrations of post-larval E. superba were associated with shallow mixed layer depths, and a significant vertical separation of developmental stages and size categories was observed only during periods of stratification in the upper 80 m. Fluctuations in the distribution and abundance of Thysanoessa sp. and distribution of E. frigida did not appear to be influenced by physical parameters within the upper 80 m. Within the 0–80 m depth range, the distributions of these two species differed from each other and from E. superba and showed large tow to tow variability that could not be related to physical parameters in the upper water column.     

Human anticentromere antibodies: Distribution,characterization of antigens,and effect on microtubule organization

Properties of human anticentromere autoantibodies were analyzed. In intact cells or isolated cell fractions, these sera stain the centromeres of mitotic chromosomes and discrete speckles (prekinetochores) in nuclei. Staining is also retained in matrix preparations from nuclei or chromosomes. Immunoprecipitation or immunoblotting demonstrates protein antigens of 14, 20, 23, and 34 kd in HeLa nuclei and chromosomes; immunoprecipitates of nuclei also contain a protein of 15.5 kd. Matrix preparations contain only the 20, 23, and 34 kd species. Absorption of the anticentromere serum with any one of the four nuclear antigens immobilized on nitrocellulose is sufficient to eliminate centromere staining. Using a lysed cell model for microtubule nucleation, anticentromere sera are shown to inhibit specifically the organization of microtubules at the kinetochore.     

Explicit water near the catalytic I helix Thr in the predicted solution structure of CYP2A4

The solution structure of mouse cytochrome P450 2A4 (CYP2A4), a monooxygenase of deoxysteroids, was obtained using homology modeling and molecular dynamics. The solvent-equilibrated CYP2A4 preserves the essential features of CYP450s. A comparison of the models CYP2A4 and CYP2A4 with testosterone bound CYP2A4/T illustrates the changes induced by the binding of the substrate. Experimental evidence links four amino acid residues to the catalytic activity, substrate specificity, and regioselectivity of this enzyme. Three of the four amino acids are found within contact distance of the testosterone substrate, and therefore may control the binding of the substrate through direct interaction. Remarkably, a water complex previously observed in x-ray crystal structure forms near the bulge in the central I helix that contains a conserved Thr. The properties of the I helix are computed in the context of the presence or absence of ligand.     

A point mutation in ribosomal protein L7/L12 reduces its ability to form a compact dimer structure and to assemble into the GTPase center

An Escherichia coli mutant, LL103, harboring a mutation (Ser15 to Phe) in ribosomal protein L7/L12 was isolated among revertants of a streptomycin-dependent strain. In the crystal structure of the L7/L12 dimer, residue 15 within the N-terminal domain contacts the C-terminal domain of the partner monomer. We tested effects of the mutation on molecular assembly by biochemical approaches. Gel electrophoretic analysis showed that the Phe15-L7/L12 variant had reduced ability in binding to L10, an effect enhanced in the presence of 0.05% of nonionic detergent. Mobility of Phe15-L7/L12 on gel containing the detergent was very low compared to the wild-type proteins, presumably because of an extended structural state of the mutant L7/L12. Ribosomes isolated from LL103 cells contained a reduced amount of L7/L12 and showed low levels (15-30% of wild-type ribosomes) of activities dependent on elongation factors and in translation of natural mRNA. The ribosomal activity was completely recovered by addition of an excess amount of Phe15-L7/L12 to the ribosomes, suggesting that the mutant L7/L12 exerts normal functions when bound on the ribosome. The interaction of Ser15 with the C-terminal domain of the partner molecule seems to contribute to formation of the compact dimer structure and its efficient assembly into the ribosomal GTPase center. We propose a model relating compact and elongated forms of L7/L12 dimers. Phe15-L7/L12 provides a new tool for studying the functional structure of the homodimer.     

Simultaneous transfer, introgression, and genomic localization of genes for resistance to stem rust race TTKSK (Ug99) from Aegilops tauschii to wheat

Wheat production is currently threatened by widely virulent races of the wheat stem rust fungus, Puccinia graminis f. sp. tritici, that are part of the TTKSK (also known as ‘Ug99’) race group. The diploid D genome donor species Aegilops tauschii (2n = 2x = 14, DD) is a readily accessible source of resistance to TTKSK and its derivatives that can be transferred to hexaploid wheat, Triticum aestivum (2n = 6x = 42, AABBDD). To expedite transfer of TTKSK resistance from Ae. tauschii, a direct hybridization approach was undertaken that integrates gene transfer, mapping, and introgression into one process. Direct crossing of Ae. tauschii accessions with an elite wheat breeding line combines the steps of gene transfer and introgression while development of mapping populations during gene transfer enables the identification of closely linked markers. Direct crosses were made using TTKSK-resistant Ae. tauschii accessions TA1662 and PI 603225 as males and a stem rust-susceptible T. aestivum breeding line, KS05HW14, as a female. Embryo rescue enabled recovery of F₁ (ABDD) plants that were backcrossed as females to the hexaploid recurrent parent. Stem rust-resistant BC₁F₁ plants from each Ae. tauschii donor source were used as males to generate BC₂F₁ mapping populations. Bulked segregant analysis of BC₂F₁ genotypes was performed using 70 SSR loci distributed across the D genome. Using this approach, stem rust resistance genes from both accessions were located on chromosome arm 1DS and mapped using SSR and EST-STS markers. An allelism test indicated the stem rust resistance gene transferred from PI 603225 is Sr33. Race specificity suggests the stem rust resistance gene transferred from TA1662 is unique and this gene has been temporarily designated SrTA1662. Stem rust resistance genes derived from TA1662 and PI 603225 have been made available with selectable molecular markers in genetic backgrounds suitable for stem rust resistance breeding.     

Dung beetles ignore landmarks for straight-line orientation

Upon locating a suitable dung pile, ball-rolling dung beetles shape a piece of dung into a ball and roll it away in a straight line. This guarantees that they will not return to the dung pile, where they risk having their ball stolen by other beetles. Dung beetles are known to use celestial compass cues such as the sun, the moon and the pattern of polarised light formed around these light sources to roll their balls of dung along straight paths. Here, we investigate whether terrestrial landmarks have any influence on straight-line orientation in dung beetles. We find that the removal or re-arrangement of landmarks has no effect on the beetle’s orientation precision. Celestial compass cues dominate straight-line orientation in dung beetles so strongly that, under heavily overcast conditions or when prevented from seeing the sky, the beetles can no longer orient along straight paths. To our knowledge, this is the only animal with a visual compass system that ignores the extra orientation precision that landmarks can offer.