The effect of a Taylor vortex flow on the agglomeration of Ni-rich hydroxide (Ni0.90Co0.05Mn0.05)(OH)2 was investigated in a Couette–Taylor (CT) crystallizer. The agglomeration process was found to be significantly affected by the rotation speed of the inner cylinder (hydrodynamic intensity) and gap size between the inner and outer cylinders of the CT crystallizer (vortex dimension), as these parameters affected the fluid shear and stability of the Taylor vortex flow. Thus, the agglomerate size was reduced when increasing the rotation speed and decreasing the gap size due to the increased fluid shear. A high rotation speed also improved the agglomerate size distribution and tap density. However, the agglomerate size distribution became broader and the tap density lower when decreasing the gap size, despite the increased fluid shear. This was due to an increase in the axial dispersion effect in the CT crystallizer when decreasing the gap size. As a result, the effective fluid motion of the Taylor vortex produced narrowly distributed and spherical agglomerates with a coefficient of variation of 0.22 and tap density of 2.15 g/cm3 when using a high rotation speed (1500 rpm), wide gap size (0.89 of radius ratio), and only 1-h mean residence time in the continuous CT crystallizer. This confirmed that a Taylor vortex would be highly applicable for the practical production process of agglomerates of Ni-rich hydroxide.
Antimicrobial peptides (AMPs) kill bacteria by targeting their membranes through various mechanisms involving peptide assembly, often coupled with disorder‐to‐order structural transition. However, for several AMPs, similar conformational changes in cases in which small organic compounds of both endogenous and exogenous origin have induced folded peptide conformations have recently been reported. Thus, the function of AMPs and of natural host defence peptides can be significantly affected by the local complex molecular environment in vivo; nonetheless, this area is hardly explored. To address the relevance of such interactions with regard to structure and function, we have tested the effects of the therapeutic drug suramin on the membrane activity and antibacterial efficiency of CM15, a potent hybrid AMP. The results provided insight into a dynamic system in which peptide interaction with lipid bilayers is interfered with by the competitive binding of CM15 to suramin, resulting in an equilibrium dependent on peptide‐to‐drug ratio and vesicle surface charge. In vitro bacterial tests showed that when CM15⋅suramin complex formation dominates over membrane binding, antimicrobial activity is abolished. On the basis of this case study, it is proposed that small‐molecule secondary structure regulators can modify AMP function and that this should be considered and could potentially be exploited in future development of AMP‐based antimicrobial agents.
Anticancer peptides (ACPs) could potentially offer many advantages over other cancer therapies. ACPs often target cell membranes, where their surface mechanism is coupled to a conformational change into helical structures. However, details on their binding are still unclear, which would be crucial to reach progress in connecting structural aspects to ACP action and to therapeutic developments. Here we investigated natural helical ACPs, Lasioglossin LL-III, Macropin 1, Temporin-La, FK-16, and LL-37, on model liposomes, and also on extracellular vesicles (EVs), with an outer leaflet composition similar to cancer cells. The combined simulations and experiments identified three distinct binding modes to the membranes. Firstly, a highly helical structure, lying mainly on the membrane surface; secondly, a similar, yet only partially helical structure with disordered regions; and thirdly, a helical monomeric form with a non-inserted perpendicular orientation relative to the membrane surface. The latter allows large swings of the helix while the N-terminal is anchored to the headgroup region. These results indicate that subtle differences in sequence and charge can result in altered binding modes. The first two modes could be part of the well-known carpet model mechanism, whereas the newly identified third mode could be an intermediate state, existing prior to membrane insertion.
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