Efficient electroformation of supergiant unilamellar vesicles containing cationic lipids on ITO-coated electrodes

Giant unilamellar vesicles (GUVs) represent a versatile in vitro system widely used to study properties of lipid membranes and their interaction with biomacromolecules and colloids. Electroformation with indium tin oxide (ITO) coated coverslips as electrodes is a standard approach to GUV production. In the case of cationic GUVs, however, application of this approach leads to notorious difficulties. We discover that this is related to aging of ITO-coated coverslips during their repeated use, which is reflected in their surface topography on the nanoscale. We find that mild annealing of the ITO-coated surface in air reverts the effects of aging and ensures efficient reproducible electroformation of supergiant (diameter > 100 μm) unilamellar vesicles containing cationic lipids.     

A Study of the Activity of Recombinant Mn-Superoxide Dismutase in the Presence of Gold and Silver Nanoparticles

Applied Biochemistry and Biotechnology - Superoxide dismutase (SOD) is one of the best characterized enzyme maintaining the redox state in the cell. A bacterial expression system was used to...     

Loss of isocyanic acid from the internal oxadiazole ring of protonated molecules of some 2,5-diaryl-1,3,4-oxadiazoles

The fragmentation pattern of some protonated 2,5-diaryl-1,3,4-oxadiazoles is discussed. An unusual decomposition consisting of elimination of the isocyanic acid molecule from the internal oxadiazole ring was found. This fragmentation pathway was deduced on the basis of B/E linked scan mass spectra of metastable ions with liquid secondary ion mass spectrometry as the ionization method and also of low-energy CID mass spectra where electrospray was used as the ionization technique. High resolution measurements were also performed.     

Preparation of Sec-Alkyl Isouronium Salts

Eight examples of sec-alkyl isouronium salts were readily prepared from sec-alcohols, cynamide, and methanesulfonic acid (or CF₃SO₃H or HBF₄).     

Spectroscopic and PM5 semiempirical studies of new hydrazone of gossypol with 3,6-dioxaheptylhydrazine

A new hydrazone of gossypol with 3,6-dioxaheptylhydrazine (GHDO) has been synthesised and its structure has been studied by FT-IR, ¹H NMR, ¹³C NMR as well as PM5 semiempirical methods. All the studies have provided clear evidence of the existence of GHDO in the solution in the N-imine–N-imine tautomeric form. The structure and the spectroscopic behaviour of this tautomer are discussed in details. It is shown the structure of GHDO is strongly stabilised by different types of intramolecular hydrogen bonds. In two of them the oxygen atoms of the oxaalkyl chains are also engaged. The strongest intramolecular hydrogen bond is formed between the O₇H proton and N₁₆ atom from the hydrazone group.     

Electrodeposition of ferrocenoyl peptide disulfides

Using electrodeposition of cyclic and acyclic Fc-peptide disulfides tightly-packed Fc-peptide monolayers were conveniently formed, which exhibit significant differences in their electron transfer kinetics.     

Indirect Measurement of Biologically Important Compounds by Means of X-Ray Microanalysis

 The main objective of our work was to investigate the possibility and usefulness of indirect methods in X-ray microanalysis for the quantification of biologically important compounds. Metallothionein-like proteins (MT-like proteins) from kidney and liver, rich in sulfur were chosen as an indicator of heavy metal presence in cells and their environment. Tissues from goldfish (Carassius auratus gibelio) were sampled after short and prolonged periods of exposure to Co⁺², CrO₄ ⁻², Pb⁺², Cu⁺² and control treatment and prepared for histochemical staining for peroxidated thiolate groups. Commonly used –S–S– bonds dye (Nitro Red) was replaced with iodine atoms and they were quantified at L line by means of X-ray microanalysis combined with SEM. After fish treatments with heavy metal solutions changes in MT-like proteins and in I atom contents were expected. There was statistically significant decrease in MT-like proteins level in kidney after lead treatment (Pb/C = 0.62). In liver a statistically significant increase in MT-like proteins concentration was observed after chromium, cobalt and lead ions treatment in comparison to control animals. The following ratios were noted: 3.04 for Cr/C, 2.18 for Co/C and 2.10 for Pb/C. Our finding indicates that the method of indirect measurement of MT-like proteins in fish and other animal tissues is possible. The concentration of iodine atoms is above their detection level by EDS and their changes are possible to identify. During histochemical procedures it is worth taking into account sample preparation methods which might disturb the quality and quantity of the analysed material.     

Synthesis of Bis‐Heterocyclic 1H‐Imidazole 3‐Oxides from 3‐Oxido‐1H‐imidazole‐4‐carbohydrazides

The reaction of 1H‐imidazole‐4‐carbohydrazides 1 , which are conveniently accessible by treatment of the corresponding esters with NH₂NH₂?H₂O, with isothiocyanates in refluxing EtOH led to thiosemicarbazides (=hydrazinecarbothioamides) 4 in high yields (Scheme 2). Whereas 4 in boiling aqueous NaOH yielded 2,4‐dihydro‐3H‐1,2,4‐triazole‐3‐thiones 5 , the reaction in concentrated H₂SO₄ at room temperature gave 1,3,4‐thiadiazol‐2‐amines 6 . Similarly, the reaction of 1 with butyl isocyanate led to semicarbazides 7 , which, under basic conditions, undergo cyclization to give 2,4‐dihydro‐3H‐1,2,4‐triazol‐3‐ones 8 (Scheme 3). Treatment of 1 with Ac₂O yielded the diacylhydrazine derivatives 9 exclusively, and the alternative isomerization of 1 to imidazol‐2‐ones was not observed (Scheme 4). It is important to note that, in all these transformations, the imidazole N‐oxide residue is retained. Furthermore, it was shown that imidazole N‐oxides bearing a 1,2,4‐triazole‐3‐thione or 1,3,4‐thiadiazol‐2‐amine moiety undergo the S‐transfer reaction to give bis‐heterocyclic 1H‐imidazole‐2‐thiones 11 by treatment with 2,2,4,4‐tetramethylcyclobutane‐1,3‐dithione (Scheme 5).     

Unexpected Course of the Reaction of 2‐Unsubstituted 1H‐Imidazole 3‐Oxides with Ethyl Acrylate

The attempted ethenylation at C(2) of 2‐unsubstituted 1H‐imidazole N‐oxides with ethyl acrylate (=prop‐2‐enoate) in the presence of Pd(OAc)₂ does not occur. In contrast to the other aromatic N‐oxides, the [2+3] cycloaddition of imidazole N‐oxides predominates, and 3‐hydroxyacrylates, isomeric with the cycloadducts, are key products for the subsequent reaction. The final products were identified as dehydrated 2+1 adducts of 1H‐imidazole N‐oxide and ethyl acrylate. The role of the catalyst is limited to the dehydration of the intermediate 3‐hydroxypropanoates to give 1H‐imidazol‐2‐yl‐substituted acrylates.