Effect of amyloid beta peptides Aβ<Subscript>1–28</Subscript> and Aβ<Subscript>25–40</Subscript> on model lipid membranes

To investigate the molecular interaction of amyloid beta peptides Aβ_1–28 or Aβ_25–40 with model lipid membranes differential scanning calorimetry (DSC) and DPH and TMA DPH fluorescence anisotropy approaches were used. The main transition temperature (T _m) and enthalpy change (ΔH) of model lipid membranes composed of DMPC/DPPG on addition of Aβ_25–40 or Aβ_25–40 at 10:1 (w/w) phospholipid/peptide ratio either non-aggregated or previously aggregated were examined. The effect of Aβ_1–28 and Aβ_25–40 on the membrane fluidity of liposomes made of DMPC/DPPG (98:2 w/w) was determined by fluorescence anisotropy of incorporated DPH and TMA DPH. The results of this study provide information that Aβ_1–28 preferentially interacts with the hydrophilic part of the model membranes, while Aβ_25–40 rather locates itself in the hydrophobic core of the bilayer where it reduces the order of the phospholipids packing.     

Heterologous Expression and Engineering Studies of Labyrinthopeptins,Class III Lantibiotics from Actinomadura namibiensis

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Highlights? Heterologous expression of a class III lantibiotic gene cluster in S. lividans and S. albus ? Leader peptide adaptation for proteolytic processing in the S. lividans host ? Development of an efficient expression system for production of labyrinthopeptin variants ? Identification of variable regions in labyrinthopeptins and generation of analogs     

Microwave measurements of the critical fields and currents in HTS

The technique of magnetically modulated microwave absorption (MMMA) has been used for measuring the critical fields and critical currents of granular high-temperature superconductors (HTS) and for investigating the Josephson/intergrain critical state.     

Preconcentration and Fractionation of Cd, Co, Cu, Ni, Pb and Zn in Natural Water Samples Prior to Analysis by Inductively Coupled Plasma Atomic Emission Spectrometry

The strong cation exchanger Dowex 50W-x4 was used for the enrichment of traces of Cd, Co, Cu, Fe, Ni, Pb and Zn in mineral and mine waters as an alternative to the commonly applied procedures based on the application of chelating resins. The resin used was found suitable for complete retention of these metals both from the solutions of very low pH as well as those close to neutral, thus eliminating the need to buffer the samples. An analytical scheme based on filtration and solid phase extraction with Dowex 50W-x4 was proposed for partitioning Cd, Co, Cu, Fe, Ni and Pb in the examined waters. The fraction of metals associated with the suspended particles was determined after filtration through a 0.45 µm pore size filter and decomposition of the deposited matter. For the evaluation of fractions of the labile metal species and the total dissolved metals, the untreated filtrates and the solutions resulting from their digestion, respectively, were passed through Dowex 50W-x4 cation exchange columns. The retrieval of the metals was completed using a 4.0 mol L⁻¹ solution of HCl. The described metal preconcentration and fractionation protocol offered the enrichment factor of 25 with detection limits equal to 22, 30, 92, 41, 70, 36 and 340 ng L⁻¹, respectively for Cd, Co, Cu, Fe, Ni and Pb. Reasonably good precision and accuracy were attained.     

High-performance ion chromatography assessment of inorganic and organic nitrogen fractions in potatoes

A new high-performance ion chromatography assay for organic and inorganic nitrogen analysis has been proposed and examined. In the devised protocol, inorganic sample constituents were measured after ultrasonically assisted water extraction. The amine and amide nitrogen content was assessed after modified Kjeldahl digestion and determined as NH₄⁺, and the total nitrogen content was quantified as NO₃⁻ after microwave-facilitated digestion. Finally, the nitro, azo, azoxy nitrogen was calculated by comparison of the total nitrogen content and all measured nitrogen species. The detection limits of the measured ions were 2.0, 0.82 and 0.17 mg L⁻¹ for nitrate, nitrite and ammonium, respectively. For samples of potatoes, the average shares of the nitrogen species found in the total nitrogen content were: 0.83% of nitrate nitrogen, <0.03% of nitrite nitrogen, 2.1% of ammonium nitrogen, 71% of nitro, azo, azoxy nitrogen, and 26% of amine, amide nitrogen. We expect the method to be applicable to different vegetable samples. The quality of the results obtained was verified by analyzing certified reference material and comparing to another analytical method.     

Enthalpic pair interaction coefficient between zwitterions of L-alpha-amino acids and urea molecule as a hydrophobicity parameter of amino acid side chains

Dissolution enthalpies of L-alpha-proline, L-alpha-tyrosine, L-alpha-tryptophan, L-alpha-histidyne, L-alpha-arginine, L-alpha-lysine, L-aspartic acid, and L-alpha-glutamic acid in aqueous solutions of urea have been measured by calorimetry at a temperature of 298.15 K. The values of dissolution enthalpy were used to determine enthalpic heterogeneous pair interaction coefficients between the zwitterions of the natural amino acids and a molecule of urea in water solution. These coefficients were interpreted in terms of the hydrophobic or hydrophilic effects of the side chains of amino acids on their interactions with a polar molecule of urea in water.     

Interaction between PAMAM 4.5 dendrimer, cadmium and bovine serum albumin: a study using equilibrium dialysis, isothermal titration calorimetry, zeta-potential and fluorescence

Binding of Cd²⁺ by PAMAM 4.5 dendrimer was studied by equilibrium dialysis, isothermal titration calorimetry and zeta-potential measurement. The following binding parameters were obtained: n = 23.8 ± 9.5, K_b = 4.7 ± 0.9 × 10³ in water; and n = 41.3 ± 13.4, K_b = 2.1 ± 0.8 × 10³ in 0.15 mol/l phosphate-buffered saline. The location of the bound Cd²⁺ is discussed. The interactions between bovine serum albumin, PAMAM 4.5 dendrimer and cadmium were analyzed using fluorescence and equilibrium dialysis. The competition between Cd²⁺ binding to BSA and PAMAM 4.5 dendrimer was investigated. It is proposed that PAMAM 4.5 dendrimer could be successfully used for extracting Cd²⁺ from aqueous solutions (environmental protection).