Translational operator of mRNA on the ribosome: how repressor proteins exclude ribosome binding

The ribosome of Thermus thermophilus was cocrystallized with initiator transfer RNA (tRNA) and a structured messenger RNA (mRNA) carrying a translational operator. The path of the mRNA was defined at 5.5 angstroms resolution by comparing it with either the crystal structure of the same ribosomal complex lacking mRNA or with an unstructured mRNA. A precise ribosomal environment positions the operator stem-loop structure perpendicular to the surface of the ribosome on the platform of the 30S subunit. The binding of the operator and of the initiator tRNA occurs on the ribosome with an unoccupied tRNA exit site, which is expected for an initiation complex. The positioning of the regulatory domain of the operator relative to the ribosome elucidates the molecular mechanism by which the bound repressor switches off translation. Our data suggest a general way in which mRNA control elements must be placed on the ribosome to perform their regulatory task.     

The involvement of the orbitofrontal cortex in the experience of regret

Facing the consequence of a decision we made can trigger emotions like satisfaction, relief, or regret, which reflect our assessment of what was gained as compared to what would have been gained by making a different decision. These emotions are mediated by a cognitive process known as counterfactual thinking. By manipulating a simple gambling task, we characterized a subject's choices in terms of their anticipated and actual emotional impact. Normal subjects reported emotional responses consistent with counterfactual thinking; they chose to minimize future regret and learned from their emotional experience. Patients with orbitofrontal cortical lesions, however, did not report regret or anticipate negative consequences of their choices. The orbitofrontal cortex has a fundamental role in mediating the experience of regret.     

Selective one-step extraction of Arabidopsis thaliana seed oleosins using organic solvents

Oleosins are hydrophobic proteins from oleaginous seeds, surrounding and stabilizing oil bodies. They are known to display interesting interfacial properties. Specific sera were raised against four different A. thaliana oleosins and used in dot-blot assays for oleosin quantification. These assays were used to set up extraction of oleosins from A. thaliana seeds. One mixture of chloroform/methanol gave optimal oleosin extraction. Extracted proteins represented 9% of seed proteins and were identified by immunoblot and proteomic analyses. Oleosins accounted for 79% of the extracted proteins. This simple one-step procedure allows selective extraction and concentration of oleosins from seeds without tedious oil body purification. Oleosin extract was indeed used to demonstrate the presence of the rare oleosin S5 in mature seeds. Moreover, this method will be useful to investigate the potential use of oleosins as emulsifier and to question their possible allergenicity.     

Model studies on the release of aroma compounds from structured and nonstructured oil systems using proton-transfer reaction mass spectrometry

Relative retention, volatility, and temporal release of volatile compounds taken from aldehyde, ester, and alcohol chemical classes were studied at 70 degrees C in model systems using equilibrium static headspace analysis and real time dynamic headspace analysis. These systems were medium-chain triglycerides (MCT), sunflower oil, and two structured systems, i.e., water-in-oil emulsion and L2 phase (water-in-oil microemulsion). Hydrophilic domains of the emulsion type media retained specifically the hydrophilic compounds and alcohols. Four kinetic parameters characterizing the concentration- and time-dependent releases were extracted from the aroma release curves. Most of the kinetic parameter values were higher in structured systems than in oils particularly when using MCT. The oil nature was found to better control the dynamic release profiles than the system structures. The release parameters were well-related (i) to the volatile hydrophobicity as a function of the oil used and (ii) to the retention data in the specific case of the L2 phase due to a specific release behavior of alcohols.     

Fortification of pork loins with docosahexaenoic acid(DHA) and its effect on flavour

Pork is traditionally low in docosahexanoic acid(DHA, C22:6n-3) and deficient in omega-3 fats for a balanced human diet. DHA as triglycerides was commercially prepared from the microalgae Schizochytrium and injected into fresh pork loins. Treatments of a mixed brine control(CON), 3.1% sunflower oil in mixed brine(SF) and a 3.1% DHA oil in mixed brine(DHA) were injected into pork loins at 10 mL/100 g and grilled at 205°C. After cooking, the CON and SF pork loins contained 0.03 to 0.05 mg DHA/g of pork and the DHA injected loins contained approximately1.46 mg DHA/g. This also changed the fatty acid profile of omega-6: omega-3 from, 5 to 1 in the CON pork, to a ratio of 1.7 to 1 in DHA pork. The appearance, odor, oxidation rates and sensory taste, as judged by a trained panel,determined the DHA injected meat to be, ‘slightly desirable' and gave lower ‘off flavour' scores, relative to the CON and SF injected pork. Pork can be fortified with DHA oil to 146 mg/100 g serving, which would meet half the recommended daily omega 3 fatty acid requirements for adult humans and would be desirable in taste.     

Effect of coffee husk and cocoa pods biochar on phosphorus fixation and release processes in acid soils from West Cameroon

Acid soil in West Cameroon has limited phosphorus (P) availability which limits plant growth. This is mainly because of low pH, high levels of exchangeable aluminium (Al) and iron (Fe) and fixation of P. In this study, acid soils, sampled in Bafang, were amended with biochar produced from coffee husks (CH) and cocoa pod husks (CP) at two different temperatures (350 and 550 °C) in other to evaluate the effect on the physicochemical properties of the acid soil and the effect on P sorption and desorption. The soil was amended with biochar at a rate of 0, 20, 40 and 80 g/kg and incubated for 7 and 60 days. Physicochemical properties of all soil–biochar samples were determined followed by sorption experiments and data fitted in the Langmuir and Freundlich isotherm models in other to evaluate soil P sorption capacity and its affinity to soil amended with biochar. Moreover, desorption studies were done to evaluate the availability of P in soil amended with biochar after sorption. The outcomes of this study reveal an increase in soil pH, electrical conductivity (EC), available P, soil organic carbon and a drastic decrease in exchangeable Al and Fe. The point of zero charge of biochar-amended soil was higher than the control and increased with amendment rate. The experimental data of the sorption of P on soils and soil–biochar samples fits into Langmuir and Freundlich models (R² > 0.9) suggesting that the P adsorption is controlled by both model mechanisms. Soil–biochar mixture results in a decrease in the sorption capacity as compared with the control and the decrease was predominant with increasing amendment rate. At amendment rates of 20, 40 and 80 g/kg after 7 days of incubation, $Q_{\max }$ for SCH350 were 2267, 2048 and 1823 mg/kg which increased to 2407, 2112 and 1990 mg/kg after 60 days of incubation. This tendency was observed for all biochar inputs with respect to the increase in incubation days. Furthermore, desorption of P from soil–biochar mixtures was enhanced with biochar added at greater rate and produced at higher temperature. The desorption percentage was increased by more than around 10% for all biochar types from 20 mg/kg to 80 mg/kg amendment. Thus, biochar addition to acid soils reduces P fixation to acid soil and improves P desorption to soil solution, thereby providing more available P in the soil solution and better conditions for plant growth.