NKCS, a Mutant of the NK-2 Peptide, Causes Severe Distortions and Perforations in Bacterial, But Not Human Model Lipid Membranes.

NKCS is an improved mutant of the bioactive peptide NK-2, which shows strong activity against Escherichia coli and low toxicity towards human cells. The different activity demonstrates the relevance of the physico-chemical nature of the target membrane for the biological effect of this peptide. We studied the effect of this potent antimicrobial peptide on model membranes by activity studies, differential scanning calorimetry, single molecule tracking and tracer efflux experiments. We found that NKCS severely distorted, penetrated and perforated model lipid membranes that resembled bacterial membranes, but not those that were similar to human cell membranes. The interactions of NKCS with phosphatidylethanolamine, which is abundant in bacterial membranes, were especially strong and are probably responsible for its antimicrobial activity.

Mesoporous Titania Powders: The Role of Precursors, Ligand Addition and Calcination Rate on Their Morphology, Crystalline Structure and Photocatalytic Activity.

We evaluate the influence of the use of different titania precursors, calcination rate, and ligand addition on the morphology, texture and phase content of synthesized mesoporous titania samples, parameters which, in turn, can play a key role in titania photocatalytic performances. The powders, obtained through the evaporation-induced self-assembly method, are characterized by means of ex situ X-Ray Powder Diffraction (XRPD) measurements, N2 physisorption isotherms and transmission electron microscopy. The precursors are selected basing on two different approaches: the acid-base pair, using TiCl4 and Ti(OBu)4, and a more classic route with Ti(OiPr)4 and HCl. For both precursors, different specimens were prepared by resorting to different calcination rates and with and without the addition of acetylacetone, that creates coordinated species with lower hydrolysis rates, and with different calcination rates. Each sample was employed as photoanode and tested in the water splitting reaction by recording I-V curves and comparing the results with commercial P25 powders. The complex data framework suggests that a narrow pore size distribution, due to the use of acetylacetone, plays a major role in the photoactivity, leading to a current density value higher than that of P25.

Antioxidant and other quality properties of reindeer muscle from two different Norwegian regions.

The effects of origin, gender, age, and muscle type on chemical composition, colour, antioxidant status and sensory profile of reindeer muscles Longissimus dorsi (LD) and Semimembranosus (SM) from two production regions were investigated. For some variables, the comparison between reindeer and beef muscles was also included. Muscles from North Norway (NN) were darker and contained more myoglobin and moisture, and less protein and fat than muscles from Mid Norway (MN). Oxygen radical absorbance capacity (ORAC) was significantly higher in these muscles while the levels of antioxidant enzymes were significantly lower in contrast to MN muscles. Relative to male reindeer, muscles from females contained significantly more total phenols and showed higher antiradical power (ARP). Carcass weight and the sensory attributes colour, sharp and bitter flavour had higher scores for older animals. Considerable differences between LD and SM were revealed in sensory assessment. In comparison to beef reindeer meat was darker, had more myoglobin, total phenols, antioxidant enzymes, and higher ARP and ORAC values.

Interaction of an antimicrobial peptide with membranes: experiments and simulations with NKCS.

We used Monte Carlo simulations and biophysical measurements to study the interaction of NKCS, a derivative of the antimicrobial peptide NK-2, with a 1-palmitoyl-2-oleoyl-sn-glycero-3-phosphoethanolamine (POPE) membrane. The simulations showed that NKCS adsorbed on the membrane surface and the dominant conformation featured two amphipathic helices connected by a hinge region. We designed two mutants in the hinge to investigate the interplay between helicity and membrane affinity. Simulations with a Leu-to-Pro substitution showed that the helicity and membrane affinity of the mutant (NKCS-[LP]) decreased. Two Ala residues were added to NKCS to produce a sequence that is compatible with a continuous amphipathic helix structure (NKCS-[AA]), and the simulations showed that the mutant adsorbed on the membrane surface with a particularly high affinity. The circular dichroism spectra of the three peptides also showed that NKCS-[LP] is the least helical and NKCS-[AA] is the most. However, the activity of the peptides, determined in terms of their antimicrobial potency and influence on the temperature of the transition of the lipid to hexagonal phase, displayed a complex behavior: NKCS-[LP] was the least potent and had the smallest influence on the transition temperature, and NKCS was the most potent and had the largest effect on the temperature.