A proposed molecular basis for the selective resveratrol inhibition of the PGHS-1 peroxidase activity

Docking results have enabled us to propose how resveratrol could act as a selective PGHS-1 peroxidase site inhibitor. The docking model has predicted a slightly less favorable DeltaG(bind) (-17.9 kcal/mol) of the resveratrol to the PGHS-2 peroxidase site in comparison with its corresponding binding to the PGHS-1 (-20.4 kcal/mol). The formation of hydrogen bonds among the hydroxyl groups of the resveratrol phenyl rings, the backbone of Fe-heme and the carbonyl group of Leu294 inside the PGHS-1 peroxidase site, associated with the absence of His214 in the backbone of PGHS-1, are essential features that are required to maintain the aromatic rings of the natural product parallel to the Fe-heme group and transverse to the peroxidase access channel promoting a large steric hindrance at this site and its consequent selective inhibition.     

A molecular dynamics study of an L-type calcium channel model

In this work, we propose a molecular model of the L-type calcium channel pore from the human cardiac alpha1 subunit. Four glutamic acid residues, the EEEE locus, located at highly conserved P loops (also called SS1-SS2 segments) of the alpha1 subunit, molecularly express the calcium channel selectivity. The proposed alpha-helix structure for the SS1 segment, analyzed through molecular dynamics simulations in aqueous-phase, was validated by the plotting of Ramachandran diagrams for the averaged structures and by the analysis of i and i + 4 helical hydrogen bonding between the amino acid residues. The results of the simulation of the calcium channel model with one and two Ca2+ ions at the binding site are in accordance with mutation studies which suggest that the EEEE locus in the L-type calcium channel must form a single high-affinity binding site. These results suggest that the Ca2+ permeation through the channel would be derived from competition between two ions for the only high-affinity binding site. Furthermore, the experimentally observed blocking of the Na+ flux at micromolar Ca2+ concentrations, probably due to the occupancy of the single high-affinity binding site for one Ca2+, was also reproduced by our model.     

Oxygen transfer and scale-up in lysine production by Ustilago maydis mutant

The oxygen transfer coefficient estimated by both sulfite and dynamic methods and some of the rheological properties of fermentation broths derived from the batch cultivation of a mutant of U. maydis in a sugar cane juice substrate, are used in a scaling-up procedure on the basis of the power consumption per volume unit concept. The fluid was of the Binham plastic type; the Np-N_RE correlations showed that the modified Reynolds numbers of the flat-blade turbine impellers were low, near to or in the laminar region; the Na-Pg/P relations were established and then used in the calculation regardless of the geometrical dissimilarities of the vessels. A change of scale from 5 to 50 liters was calculated and operated keeping the power per volume value constant. Reproduction of lysine yields, 2.5–3.2 g/liter, was repeatedly reached in 8 successive runs.     

Effect of temperature,pH and ionic strength on hydroxyapatite stabilised Pickering emulsions produced in batch and continuous mode

Oil-in-water (O/W) Pickering emulsions are attracting attention as carriers of lipophilic active compounds with clear advantages over traditional systems. Having in view their effective use it is important to study their stability against environmental stresses impacting manufacture, storage, and application conditions. In this work, hydroxyapatite nanoparticles (n-HAp) Pickering emulsions produced in continuous mode using a mesostructured reactor (average size?~?7, 11 and 18 µm) and in batch mode using a rotor–stator device (average size?~?18 µm) were studied concerning their behaviour at different temperatures (5–90 ºC), pH (2–10) and ionic strength (0–500 mM), conditions with relevance for food applications. Droplet size, morphology, and zeta-potential were analysed after 1 and 7 days under storage. In general, and despite the droplet size, the n-HAp Pickering emulsions were stable within the tested ionic strength range, at relatively high pH environments (6–10), and at temperatures up to 70 ºC. Pickering emulsions undergo complete phase separation at very low pH (2) due to n-HAp particle's disruption. A clear tendency to aggregation and coalescence was observed for high temperatures (70–90 ºC). Results indicate no significant differences related to the used production method. From an industrial perspective, this work also corroborates that the scale-up to a continuous process using a mesostructured reactor, NETmix, from a batch laboratorial process is feasible without impacting stability.

Graphical abstract