Temperature-Dependent Re-alignment of the Short Multifunctional Peptide BP100 in Membranes Revealed by Solid-State NMR Spectroscopy and Molecular Dynamics Simulations

BP100 is a cationic undecamer peptide with antimicrobial and cell-penetrating activities. The orientation of this amphiphilic α-helix in lipid bilayers was examined under numerous conditions using solid-state ¹⁹F, ¹⁵N and ²H NMR. At high temperatures in saturated phosphatidylcholine lipids, BP100 lies flat on the membrane surface, as expected. Upon lowering the temperature towards the lipid phase transition, the helix is found to flip into an upright transmembrane orientation. In thin bilayers, this inserted state was stable at low peptide concentration, but thicker membranes required higher peptide concentrations. In the presence of lysolipids, the inserted state prevailed even at high temperature. Molecular dynamics simulations suggest that BP100 monomer insertion can be stabilized by snorkeling lysine side chains. These results demonstrate that even a very short helix like BP100 can span (and thereby penetrate through) a cellular membrane under suitable conditions.     

Activity of plant extracts for preserving functional food containing<Emphasis Type="Italic"> n</Emphasis>-3-PUFA

The ability of antioxidants obtained from natural sources to stabilise foodstuffs containing long n-3 fatty acids of marine origin has been determined. Food systems enriched in polyunsaturated fatty acids (PUFA) were: emulsified horse mackerel (Trauchurus trauchurus) muscle, fish oil-in-water emulsions (4% of n-3 PUFA) and fish oils (40% of n-3 PUFA). Rosemary leaves and extra virgin olive oil (EVO) were employed as sources of natural phenolic antioxidants. Both vegetable extracts were able to retard lipid oxidation in the different lipid systems. Rosemary extracts with a high content of carnosoic acid showed a significant synergism with fish proteins, by reinforcing their antioxidative effectiveness. Fish proteins and EVO-phenolics showed minor cooperative effects for inhibiting oxidation. The antioxidative partition into the different phases in the emulsified systems showed minor amounts of phenolics in the aqueous phases, except hydroxytyrosol and tyrosol, and a high adsorption on fish muscle.An erratum to this article can be found at     

Wood chips size distribution in relation to blade wear and screen use

The study investigated the effect of wearing chipper knives on machine productivity, fuel consumption and particles size distribution. The test included two different tree species (poplar and pine), two tree parts (branches and logs) and two screen types (large and medium). Chip quality was defined by CEN international technical standards. Knife wear causes a significant reduction of chipping productivity and a remarkable increase of fuel consumption. The replacement of the standard wide mesh screen with a narrower screen has a similar effect, further decreasing productivity and increasing fuel consumption. For the same screen type and knife wear level, productivity and fuel consumption are the same for poplar and pine. Knife, tree species and tree part also have a significant impact on chip size distribution. Chips produced from logs always contain a smaller proportion of oversize particles and a higher proportion of accepts. For the same large mesh screen, poplar chips tend to be larger than pine chips and to contain a higher proportion of oversize particles. On the contrary, pine chips tend to be smaller and to contain a higher proportion of fines. The use of a narrower mesh screen on pine material does not seem to offer any significant reduction of oversize particles, whose presence is already very limited. Therefore, a standard large mesh screen should be used when chipping pine material.     

Free and total malondialdehyde assessment in biological matrices by gas chromatography-mass spectrometry: what is needed for an accurate detection

A method to determine free and total (free and bound) malondialdehyde (MDA) in fresh human plasma, or in rat liver microsomes, using selected ion monitoring (SIM) gas chromatography-mass spectrometry in the electron impact mode was set up. The dideuterated internal standard, 3-hydroxy[1, 3-2H2]-2-propenal (dMDA), was added to the biological samples before their analytical manipulation. To detect free MDA the samples were reacted under mild conditions (25 degreesC, pH 4.0, 30 min) with phenylhydrazine (PH), affording 1-phenyl-1H-pyrazole and its 3, 5-dideuterated isotopomer. For the evaluation of total MDA level the plasma or microsomes were subjected, before the derivatization step, to hydrolysis in the presence of 1 M NaOH under preestablished conditions. This method offers several advantages such specificity, precision (within-day CV 2.0%, between-day CV 2.1%), linearity (0. 01-15 microM) and high sensitivity (5 pmol injected). The recovery of known added MDA amounts from plasma and microsomes, hydrolyzed or not, accounted for 98 +/- 0.6%. The free MDA levels found in the plasma and microsomes were 0.14 +/- 0.03 microM and 0.048 +/- 0.006 nmol/mg protein, respectively. The total MDA levels were 1.3 +/- 0. 07 microM in plasma and 0.36 +/- 0.04 nmol/mg protein in the microsomes.     

Inhibition of in vitro lipid peroxidation by stable steroidic nitroxyl radicals

4',4'-dimethylspiro (5 alpha-cholestane-3,2'-oxazolidin)-3'-yloxy (IK-1) and 7 alpha,12 alpha-dihydroxy-4',-4'-dimethylspiro (5 beta-cholan-24-oic-3,2'-oxazolidin)-3'-yloxy acid (IK-2), two stable steroidic nitroxyl radicals, were newly synthesized and tested as possible inhibitors of lipid peroxidation, induced by Fenton's reagent in both rat liver microsomes and egg phosphatidylcholine liposomes. The inhibitory activity, evaluated through the formation of thiobarbituric acid reactive substances (TBARS) and the conjugated diene, was compared with that of alpha-tocopherol and 2,2,6,6-tetramethylpiperidine-1-yloxy (TEMPO). In each model system IK-1 and IK-2 exhibited an IC50 of 8 microM and reduced the formation of TBARS and conjugated diene, showing IK-1 a potency comparable to alpha-tocopherol and higher than TEMPO. Moreover IK-1 and, to a lesser extent IK-2, reduced the lipid peroxidation induced in the microsomes by the water-soluble azo-initiator 2,2'-Azobis (2-methylpropionamidine) dihydrochloride (AMPH), indicating the IK-1 and IK-2 ability as chain-breaking antioxidants. The hydroxylamine 4',4'-dimethylspiro (5 alpha-cholestane-3,2'-oxazolidin)-3'-hydroxide (IK-3), obtained by chemical reduction of IK-1, was completely inactive as an inhibitor of lipid peroxidation in heat pre-treated microsomes and in liposomes. However in microsomes it was active since it was oxidized to the corresponding nitroxyl radical IK-1.     

The Association of Il28b Genotype with the Histological Features of Chronic Hepatitis C Is HCV Genotype Dependent

The interleukin 28B (IL28B) rs12979860 polymorphism is associated with treatment outcome in hepatitis C virus (HCV) genotype 1 and 4 patients. Its association with the histological features of chronic hepatitis C and disease severity needs further clarifications. To assess the correlation between IL28B genotype, HCV genotype and liver biopsy findings in untreated patients.

Materials and Methods

Pre-treatment liver biopsies from 335 HCV Caucasian patients (59% males, age 50 years) enrolled in the MIST study were staged for fibrosis and inflammation according to the METAVIR and the Ishak scoring systems; steatosis was dichotomized as <5% or ≥5%. IL28B was typed by Taqman Single Nucleotide Polymorphism (SNP) genotyping assay. HCV genotype was 1 in 151 (45%), 2 in 99 (30%), 3 in 50 (15%) and 4 in 35 (10%) patients. IL28B genotype was CC in 117 (34%), CT in 166 (49%) and TT in 52 (15%). At univariate analysis, the IL28B CC genotype was associated with severe portal inflammation in HCV-1 patients (CC vs. CT/TT: 86% vs. 63%, p = 0.005), severe lobular inflammation in HCV-2 patients (CC vs. CT/TT: 44% vs. 23%, p = 0.03), and less fatty infiltration in HCV-1 patients (CC vs. CT/TT: 72% vs. 51%, p = 0.02). Despite the lack of any association between IL28B and fibrosis stage, in HCV-3 patients IL28B CC correlated with METAVIR F3–F4 (CC vs. CT/TT: 74% vs. 26%, p = 0.05). At multivariate analysis, the genotype CC remained associated with severe portal inflammation in HCV-1, only (Odds Ratio (OR): 95% Confidence Interval (CI): 3.24 (1.23–8.51)). IL28B genotype is associated with the histological features of chronic hepatitis C in a HCV genotype dependent manner, with CC genotype being independently associated with severe portal inflammation.     

Tuning light emission of PbS nanocrystals from infrared to visible range by cation exchange

Colloidal semiconductor nanocrystals, with intense and sharp-line emission between red and near-infrared spectral regions, are of great interest for optoelectronic and bio-imaging applications. The growth of an inorganic passivation layer on nanocrystal surfaces is a common strategy to improve their chemical and optical stability and their photoluminescence quantum yield. In particular, cation exchange is a suitable approach for shell growth at the expense of the nanocrystal core size. Here, the cation exchange process is used to promote the formation of a CdS passivation layer on the surface of very small PbS nanocrystals (2.3 nm in diameter), blue shifting their optical spectra and yielding luminescent and stable nanostructures emitting in the range of 700–850 nm. Structural, morphological and compositional investigation confirms the nanocrystal size contraction after the cation-exchange process, while the PbS rock-salt crystalline phase is retained. Absorption and photoluminescence spectroscopy demonstrate the growth of a passivation layer with a decrease of the PbS core size, as inferred by the blue-shift of the excitonic peaks. The surface passivation strongly increases the photoluminescence intensity and the excited state lifetime. In addition, the nanocrystals reveal increased stability against oxidation over time. Thanks to their absorption and emission spectral range and the slow recombination dynamics, such highly luminescent nano-objects can find interesting applications in sensitized photovoltaic cells and light-emitting devices.     

Twin mirrors for laser interferometric gravitational-wave detectors

Gravitational-wave detectors such as Virgo and the laser interferometric gravitational-wave observatory (LIGO) use a long-baseline Michelson interferometer with Fabry-Perot cavities in the arms to search for gravitational waves. The symmetry between the two Fabry-Perot cavities is crucial to reduce the interferometer's sensitivity to the laser amplitude and frequency noise. To this purpose, the transmittance of the mirrors in both cavities should be as close as possible. This paper describes the realization and the characterization of the first twin large low-loss mirrors with transmissions differing by less than 0.01%.