Fatty acid profiles in the gonads of the sea urchin Strongylocentrotus droebachiensis on natural algal diets

We examined fatty acid (FA) compositions of gonads of the green sea urchin Strongylocentrotus droebachiensis collected from a grazing aggregation (front) at the edge of a kelp bed and from barrens dominated by coralline algae, and those of urchins fed single algal diets in the laboratory. We compared these gonad FAs with those of the algal diets, which represented known urchin food sources in rocky subtidal habitats. Gonads of urchins collected from both wild habitats, and of urchins fed kelp Saccharina longicruris in the laboratory, contained more lipid than did urchins fed single diets of barrens macroalgae (Agarum clathratum, coralline red algae or Desmarestia viridis). Substantial biosynthesis of non-methylene interrupted dienes and other FAs by urchins markedly affected their overall FA signatures. Although the FA compositions of gonads of laboratory-fed urchins did not clearly correspond with those of their diets, 3 clusters of urchins were distinguished in multivariate space using multidimensional scaling (PADS): (1) urchins fed single diets of barrens macroalgae in the laboratory; (2) urchins fed S. longicruris in the laboratory or collected from the grazing front; and (3) urchins from the barrens. Characteristics of FA signatures found in urchins from the barrens suggested the occurrence of benthic diatoms in their diet. Our results indicate that, while the FA signatures of urchin gonads are affected by diet and can be used to differentiate feeding groups of urchins in the laboratory and field, significant de novo biosynthesis and/or modification of FAs precludes correspondence of urchin FAs to those of their algal diets

The application of the Quasi-steady Theory to full scale measurements on the Texas Tech Building

Full scale wind velocity and pressure measurements at the Texas Tech Field Research Laboratory have been used to evaluate the performance of the Quasi-steady Theory. As expected the pressure fluctuations deviate away from the theory's predictions in regions of flow separation, although the incorporation of non-linear terms improves the match. Significantly, the area-averaged loads over substantial parts of the building have high correlation with the approach flow and the probability density functions, as well as the rms and peak pressure coefficients, are well predicted by the Quasi-steady Theory. © 1993

Synthesis, antibacterial action, and ribosome inhibition of deoxyspectinomycins

Spectinomycin, an aminocyclitol antibiotic, is subject to inactivation by aminoglycoside modifying enzymes (AMEs) through adenylylation or phosphorylation of the 6-hydroxy group position. In this study, the effects of deoxygenation of the 2- and 6-hydroxy group positions on the spectinomycin actinamine ring are probed to evaluate their relationship to ribosomal binding and the antimicrobial activities of spectinomycin, semisynthetic aminomethyl spectinomycins (amSPCs), and spectinamides. To generate these analogs, an improved synthesis of 6-deoxyspectinomycin was developed using the Barton deoxygenation reaction. 6-Dehydrospectinamide was also synthesized from spectinamide 4 to evaluate the H-bond acceptor character on the C-6 position. All the synthesized analogs were tested for antibacterial activity against a panel of Gram (+) and Gram (-) pathogens, plus Mycobacterium tuberculosis. The molecular contribution of the 2- and 6-hydroxy group and the aryl functionalities of all analogs were examined by measuring inhibition of ribosomal translation and molecular dynamics experiments with MM/GBSA analysis. The results of this work indicate that the 6-hydroxy group, which is the primary target of AMEs, is a required motif for antimicrobial activity in current analogs. Removal of the 6-hydroxy group could be partially rescued by offsetting ribosomal binding contributions made by the aryl side chains found in the spectinamide and amSPCs. This study builds on the knowledge of the structure-activity relationships of spectinomycin analogs and is being used to aid the design of next-generation spectinomycins