Lipid thermotropic transitions in Triatoma infestans lipophorin

The structure and lipid thermotropic transitions of highly purified lipophorin of Triatoma infestam were examined by several techniques: steady-state fluorescence polarization of 1,6-diphenyl-1,3,5-hexatrien(eD PH), cis-parinaric acid (cis-PnA) and tram-parinaric acid (tram-PnA), light scattering fluorescence energy transfer between the lipophorin tryptophan residues and the bound chromophores, DPH, tram-parinaric acid cis-parinaric acid, gel electrophoresis, and gel filtration. Fluorescence polarization of PnAs and DPH revealed a reversible lipid thermotropic transition in intact lipophorin at about 2OoC and 18OC, respectively. In lipophorin, lipid dispersion fluorescence polarization of DPH detected a lipid transition approximately at 2OoC, while tram-PnA showed a gel phase formation at a temperature below 3OOC. Similar experiments in which tram-PnA was incorporated into diacylglycerols and phospholipids extracted from the lipophorin revealed gel phase formation below 3OoC and 24OC, respectively. Light scattering measurements showed that lipophorin particles aggregate irreversibly at 45OC, increasing the molecular weight, as determined by gel filtration on Sephacryl S-300, from 740,000 to values larger than 1,500,000. The particle aggregation did not change the physical properties of the lipophorin studied by fluorescence polarization, indicating that the aggregation is apparently a non-denaturing process. Energy transfer between the lipophorin tryptophans and the bound chromophores cis-PnA, tram-PnA, and DPA revealed a different locationo f the fluorescent probes within thleip ophorin. Temperature-dependence on the energy transfer efficiency for all probes confirmed a change in the ordering of the lipophorin lipids at 24'C-Instituto de Investigaciones Bioquímicas de La Plat

Lipid thermotropic transitions in Triatoma infestans lipophorin

The structure and lipid thermotropic transitions of highly purified lipophorin of Triatoma infestam were examined by several techniques: steady-state fluorescence polarization of 1,6-diphenyl-1,3,5-hexatrien(eD PH), cis-parinaric acid (cis-PnA) and tram-parinaric acid (tram-PnA), light scattering fluorescence energy transfer between the lipophorin tryptophan residues and the bound chromophores, DPH, tram-parinaric acid cis-parinaric acid, gel electrophoresis, and gel filtration. Fluorescence polarization of PnAs and DPH revealed a reversible lipid thermotropic transition in intact lipophorin at about 2OoC and 18OC, respectively. In lipophorin, lipid dispersion fluorescence polarization of DPH detected a lipid transition approximately at 2OoC, while tram-PnA showed a gel phase formation at a temperature below 3OOC. Similar experiments in which tram-PnA was incorporated into diacylglycerols and phospholipids extracted from the lipophorin revealed gel phase formation below 3OoC and 24OC, respectively. Light scattering measurements showed that lipophorin particles aggregate irreversibly at 45OC, increasing the molecular weight, as determined by gel filtration on Sephacryl S-300, from 740,000 to values larger than 1,500,000. The particle aggregation did not change the physical properties of the lipophorin studied by fluorescence polarization, indicating that the aggregation is apparently a non-denaturing process. Energy transfer between the lipophorin tryptophans and the bound chromophores cis-PnA, tram-PnA, and DPA revealed a different locationo f the fluorescent probes within thleip ophorin. Temperature-dependence on the energy transfer efficiency for all probes confirmed a change in the ordering of the lipophorin lipids at 24'C-Instituto de Investigaciones Bioquímicas de La Plat

Deep sequencing of small RNA libraries reveals dynamic regulation of conserved and novel microRNAs and microRNA-stars during silkworm development

<p>Abstract</p> <p>Background</p> <p>In eukaryotes, microRNAs (miRNAs) have emerged as critical regulators of gene expression. The Silkworm (<it>Bombyx mori </it>L.) is one of the most suitable lepidopteran insects for studying the molecular aspects of metamorphosis because of its large size, availability of mutants and genome sequence. Besides, this insect also has been amply studied from a physiological and biochemical perspective. Deep sequencing of small RNAs isolated from different stages of silkworm is a powerful tool not only for measuring the changes in miRNA profile but also for discovering novel miRNAs.</p> <p>Results</p> <p>We generated small RNA libraries from feeding larvae, spinning larvae, pupae and adults of <it>B. mori </it>and obtained ~2.5 million reads of 18-30 nt. Sequence analysis identified 14 novel and 101 conserved miRNAs. Most novel miRNAs are preferentially expressed in pupae, whereas more than 95% of the conserved miRNAs are dynamically regulated during different developmental stages. Remarkably, the miRNA-star (miR*) of four miRNAs are expressed at much higher levels than their corresponding miRNAs, and their expression profiles are distinct from their corresponding miRNA profiles during different developmental stages. Additionally, we detected two antisense miRNA loci (miR-263-S and miR-263-AS; miR-306-S and miR-306-AS) that are expressed in sense and antisense directions. Interestingly, miR-263 and miR-306 are preferentially and abundantly expressed in pupae and adults, respectively.</p> <p>Conclusions</p> <p>We identified 101 homologs of conserved miRNAs, 14 species-specific and two antisense miRNAs in the silkworm. Our results provided deeper insights into changes in conserved and novel miRNA and miRNA* accumulation during development.</p

Hydration and Localization of Diacylglycerol in the Insect Lipoprotein Lipophorin. A \u3csup\u3e13\u3c/sup\u3eC-NMR Study

In order to probe the organization of diacylglycerol (DG) in lipophorin, 13C-enriched lipophorin was prepared for NMR investigations. We obtained 13C-enriched lipophorin labeled exclusively in DG by feeding insects tobacco leaves coated with [1-13C]palmitic acid or [l-13C]oleic acid. Lipophorins enriched up to 5% with a [13C] fatty acid were obtained by this procedure. NMR studies of the isolated lipophorin DG showed that palmitic acid accumulates almost entirely (\u3e90%) in the sn-1 position. Oleic acid was found equally distributed between the sn-1 and sn-2 positions, yielding a DG enriched equally at both positions. The 13C-NMR spectra of both [13C]palmitate- and [13C]oleate-enriched lipophorins showed that DG had one narrow carbonyl resonance indicative of rapid motion. A comparative analysis of the 13C carbonyl chemical shift data for DG in organic solvents, aqueous solutions, and dispersions with the DG carbonyl chemical shift of native lipophorin enriched in [13C]palmitate or [13C]oleate shows a high degree of water exclusion from the DG carbonyls in lipophorin. This result is consistent with the existence of a lipophorin lipid core containing most of the lipophorin DG. This study represents the First attempt to elucidate the organization of DG in lipophorin. The possibility of obtaining [13C]DG-enriched lipophorins, selectively enriched in one or both acyl chains of DG, should provide a powerful tool for further analysis of the organization and the dynamic properties of DG in native lipoproteins. © 1994, American Chemical Society. All rights reserved