Oxidation-induced Spin Probes in Low-density Lipoproteins

PBN trapping indicated the presence of at least two types of radicals induced in LDL upon slow oxidation, as observed with EPR spectroscopy. The EPR spectra are very similar to those of the spin probes or spin labels, which are routinely used in the studies of macromolecular systems and supramolecular assemblies. The parameters of the spectral line shapes, treated in two different theoretical models, did not provide conclusive evidence for the phase transition in the LDL particles, known to be present at about 25 °C. It is concluded that both types of trapped radicals, or at least one of them, are associated with the apolipoproteins, with the spin probe sticking into the lipid domain of phospholipids

Slabo izražene pojave u epr spektru paramagnetičnog centra sličnog šupljini u citozin hidrokloridu

The fine phenomena in the EPR spectra of the hole-like paramagnetic centre formed in cytosine(thiocytosine)-HCl crystals upon irradiation are studied with EPR spectroscopy. The spin Hamiltonian including the electronic Zeeman term, hyperfine coupling, quadrupole coupling and the nuclear Zeeman term has been used in the second-order perturbation treatment for the interpretation of the experimental observations. It is shown that the quadrupolar term causes a detectable shift of the EPR lines and also induces the "forbidden\u27\u27 transitions. From the shift of the "allowed\u27\u27 transitions and the positions of the ``forbidden\u27\u27 transitions, the chlorine quadrupolar coupling tensor [P], has been determined.Proučavane su slabo izražene, neredovite pojave u EPR spektrima paramagnetičnog centra sličnog šupljini u ozračenim kristalima citozin hidroklorida s primjesama tiocitozina. Za objašnjenje ponašanja upotrijebljen je spinski Hamiltonijan koji se sastoji od elektronskog Zeemanovog člana, nuklearnog Zeemanovog člana, člana hiperfine i člana kvadrupolne sprege jezgre s elektronom. Pokazano je da kvadrupolni član koji potječe od klora ne samo unosi pomak EPR spektralnih linija, nego uzrokuje i pojavu dodatnih, “zabranjenih” prijelaza. Iz mjerenja slabo izraženih pomaka linija i položaja “zabranjenih” linija izračunat je kvadrupolni tenzor

Slabo izražene pojave u epr spektru paramagnetičnog centra sličnog šupljini u citozin hidrokloridu

The fine phenomena in the EPR spectra of the hole-like paramagnetic centre formed in cytosine(thiocytosine)-HCl crystals upon irradiation are studied with EPR spectroscopy. The spin Hamiltonian including the electronic Zeeman term, hyperfine coupling, quadrupole coupling and the nuclear Zeeman term has been used in the second-order perturbation treatment for the interpretation of the experimental observations. It is shown that the quadrupolar term causes a detectable shift of the EPR lines and also induces the "forbidden\u27\u27 transitions. From the shift of the "allowed\u27\u27 transitions and the positions of the ``forbidden\u27\u27 transitions, the chlorine quadrupolar coupling tensor [P], has been determined.Proučavane su slabo izražene, neredovite pojave u EPR spektrima paramagnetičnog centra sličnog šupljini u ozračenim kristalima citozin hidroklorida s primjesama tiocitozina. Za objašnjenje ponašanja upotrijebljen je spinski Hamiltonijan koji se sastoji od elektronskog Zeemanovog člana, nuklearnog Zeemanovog člana, člana hiperfine i člana kvadrupolne sprege jezgre s elektronom. Pokazano je da kvadrupolni član koji potječe od klora ne samo unosi pomak EPR spektralnih linija, nego uzrokuje i pojavu dodatnih, “zabranjenih” prijelaza. Iz mjerenja slabo izraženih pomaka linija i položaja “zabranjenih” linija izračunat je kvadrupolni tenzor

Structural and Oxidation Properties of Plasma Lipoproteins from Different Phenotypes: FT-IR and ESR Study

Subclasses of lipoproteins VLDL, LDL and HDL were isolated from plasma of two different phenotypes, A and B. Phenotype B is present in people with diabetes, atherosclerosis and higher risk for cardiovascular disease. Lipoproteins were studied by FT-IR spectroscopy to investigate conformational and structural differences reflected in spectra. Differences were observed in spectra of LDL and VLDL. In protein domain differences were observed in amide I band profile and discussed in terms of conformation¬al change of apo B-100 in small LDL and large VLDL particles. The changes in lipid bands from pheno¬type B are associated with differences in core composition and lipids\u27 ordering in monolayer. The study of slow oxidation was done by measuring the oxygen consumption in lipoprotein solutions. Oxidation was faster in HDL and VLDL from phenotype B, while for LDL it was similar for A and B samples and signif¬icantly faster than in other two lipoproteins. (doi: 10.5562/cca2236

ERP spektroskopija suprahiperfinog međudjelovanja bakarnog paramagnetskog centra u kristalima citozin monohidrata

The planar complex of Cu(II) with two cytosine bases was formed by gamma irradiation of the cytosine monohydrate crystal, containing copper impurities. The paramagnetic complex was probably formed by trapping the radiation-induced migrating holes by Cu(I), that is originally present in the crystal lattice. The structure of the complex was analyzed from the superhyperfine pattern of its EPR spectra. The experimentally evaluated tensor elements of the three 14N couplings and the observation of an additional proton coupling unequivocally confirm the structure. The ab initio B3LYP density functional method calculations are in good agreement with the experiments. Both experiments and the calculations demonstrate large spin delocalization in the cytosine ring plane.Gama ozračivanjem kristala citozin monohidrata, koji je sadržavao bakarne nečistoće, pripremali smo planarni kompleks Cu(II) s dvije citozinske baze. Paramagnetski se kompleks vjerojatno stvarao vezanjem zračenjem proizvedenih šupljina i Cu(I) koji je prvotno bio u kristalnoj rešetci. Proučavali smo strukturu kompleksa analizirajući suprahiperfinu strukturu njegovog EPR spektra. Eksperimentalno određeni elementi tenzora triju vezanja 14N i opažanje dodatnog protonskog vezanja pouzdano potvrđuju strukturu. Ab initio B3LYP računi metodom funkcionala gustoće u dobrom su slaganju s mjerenjima. Eksperimenti i računi pokazuju jaku delokalizaciju spina u ravnini citozinskog prstena

Interaction of High Density Lipoprotein with Nicotine – an IR and Raman Study

The direct interaction of high density lipoprotein (HDL) with nicotine, one of the major components of cigarette particulate matter, has been studied here at molecular level. Nicotine affects the vibration modes of HDL due to its embedment within the lipid monolayer. The changes in the positions and intensities of vibration bands in protein and lipid domain of the particle were studied by IR and Raman spectroscopy. Three types of samples were prepared: native HDL sample and two HDL samples with added nicotine. The molecular ratio of nicotine /phospholipids in two samples was 1: 12 and 1: 6. The same types of samples were prepared from liposomes containing phosphatidylcholine, and sphingomyelin with addition of cholesterol. Spectra of liposome samples were used for distinguishing and attribution of lipid bands in spectra of HDL samples, where the majority of changes were observed. The incorporation of nicotine into lipid monolayer induces changes in the lipid bands from the vibrations in acyl chains and head groups of phospholipids. The changes in vibration bands from particular amino acids\u27 residues confirm that nicotine molecule is located within lipid monolayer but close to lipid-protein interface

ERP spektroskopija suprahiperfinog međudjelovanja bakarnog paramagnetskog centra u kristalima citozin monohidrata

The planar complex of Cu(II) with two cytosine bases was formed by gamma irradiation of the cytosine monohydrate crystal, containing copper impurities. The paramagnetic complex was probably formed by trapping the radiation-induced migrating holes by Cu(I), that is originally present in the crystal lattice. The structure of the complex was analyzed from the superhyperfine pattern of its EPR spectra. The experimentally evaluated tensor elements of the three 14N couplings and the observation of an additional proton coupling unequivocally confirm the structure. The ab initio B3LYP density functional method calculations are in good agreement with the experiments. Both experiments and the calculations demonstrate large spin delocalization in the cytosine ring plane.Gama ozračivanjem kristala citozin monohidrata, koji je sadržavao bakarne nečistoće, pripremali smo planarni kompleks Cu(II) s dvije citozinske baze. Paramagnetski se kompleks vjerojatno stvarao vezanjem zračenjem proizvedenih šupljina i Cu(I) koji je prvotno bio u kristalnoj rešetci. Proučavali smo strukturu kompleksa analizirajući suprahiperfinu strukturu njegovog EPR spektra. Eksperimentalno određeni elementi tenzora triju vezanja 14N i opažanje dodatnog protonskog vezanja pouzdano potvrđuju strukturu. Ab initio B3LYP računi metodom funkcionala gustoće u dobrom su slaganju s mjerenjima. Eksperimenti i računi pokazuju jaku delokalizaciju spina u ravnini citozinskog prstena

Interaction of High Density Lipoprotein with Nicotine – an IR and Raman Study

The direct interaction of high density lipoprotein (HDL) with nicotine, one of the major components of cigarette particulate matter, has been studied here at molecular level. Nicotine affects the vibration modes of HDL due to its embedment within the lipid monolayer. The changes in the positions and intensities of vibration bands in protein and lipid domain of the particle were studied by IR and Raman spectroscopy. Three types of samples were prepared: native HDL sample and two HDL samples with added nicotine. The molecular ratio of nicotine /phospholipids in two samples was 1: 12 and 1: 6. The same types of samples were prepared from liposomes containing phosphatidylcholine, and sphingomyelin with addition of cholesterol. Spectra of liposome samples were used for distinguishing and attribution of lipid bands in spectra of HDL samples, where the majority of changes were observed. The incorporation of nicotine into lipid monolayer induces changes in the lipid bands from the vibrations in acyl chains and head groups of phospholipids. The changes in vibration bands from particular amino acids\u27 residues confirm that nicotine molecule is located within lipid monolayer but close to lipid-protein interface

EPR study of lipid phase in renal cortical membrane organelles from intact and cadmium-intoxicated rats

Numerous studies have demonstrated various structure/function correlations at the level of transport proteins in the kidney cell membranes and various intracellular organelles. However, characterization of the lipid phase of these membranes is rare. Here, we report the differences in lipid organization and dynamics of the brush-border membranes (BBM), basolateral membranes (BLM) and endocytotic vesicles (EV), isolated from the kidney cortex of intact rats, studied with the EPR spectroscopy of the spin-labeled membrane lipids. The EPR spectra were analyzed by comparing experimentally observed line shapes with the line shapes calculated according to the theoretical model developed for liquid crystals. In the fitting procedure, three different lipid domains were assumed, which revealed clear differences in the lipid ordering and rotational correlation times, as well as in the lipid partition of these domains in each of the three types of membranes. A similar approach, used to compare the spectroscopic characteristics of BBM from control and cadmium-intoxicated rats, showed significantly changed ordering and increased molecular mobility in the lipid phase of BBM from Cd-treated animals. As tested by an established fluorescence assay, the Cd-induced changes in the lipid mobility co localized with approximately 5-fold higher conductance of BBM for potassium, with unchanged conductance for protons

Micro and Nano Structure of Electrochemically Etched Silicon Epitaxial Wafers

Silicon epitaxial wafers, consisting of 280 μm thick n-type substrate layer and 4–5 μm thick epitaxial layer, were electrochemically etched in hydrofluoric acid ethanol solution, to produce porous silicon samples. The resistivity of epitaxial layer was 1 Ω cm, while the substrate was much better conductor with resistivity 0.015 Ω cm. By varying the etching time, the micro- and nano-pores of different sizes were obtained within the epitaxial layer, and on the substrate surface. Due to the lateral etching the epitaxial layer was partially detached from the substrate and could be peeled off. The influence of etching time duration on the optical and structural properties of porous samples was investigated by Raman, infrared and photoluminescence spectroscopy. The samples were analysed immediately after the etching and six months later, while being stored in ambient air. The Raman spectra showed the shift in positions of transversal optical (TO) phonon bands, between freshly etched samples and the one stored in ambient air. Infrared spectra indicated the presence of SiHx species in the freshly etched samples, and appearance of oxidation after prolonged storage. Photoluminescence spectra were very weak in freshly etched samples, but their intensity has increased substantially in six month period. (doi: 10.5562/cca1971