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H Sprinz

Publications and source records attributed to H Sprinz.

At least 19 recordsLinked to original sources
PubMed2001

Efficiency and mechanism of the antioxidant action of trans-resveratrol and its analogues in the radical liposome oxidation.

trans-Resveratrol (trans-3,5,4'-trihydroxystilbene) is a nonflavonoid polyphenol reported to exert different biological activities, among them inhibition of the lipid peroxidation, scavenging of the free radicals, inhibition of the platelet aggregation, and anticancer activity as the most important. In order to enlighten the radical-scavenging mechanism of trans-resveratrol, stationary gamma-radiolytic experiments in liposomes and pulse radiolytic experiments in aqueous solutions were performed. Applying the stationary gamma-radiolysis together with the subsequent product analysis, reactions of lipid peroxyl radicals, LOO*, with trans-resveratrol and other natural antioxidants were investigated. It was found that trans-resveratrol was a better radical scavenger than vitamins E and C but similar to the flavonoids epicatechin and quercetin. The comparison of the radical-scavenging effects of trans-resveratrol and its analogues trans-4-hydroxystilbene and trans-3,5-dihydroxystilbene revealed that trans-resveratrol and trans-4-hydroxystilbene showed almost the same effect and were more efficient than trans-3,5-dihydroxystilbene. These findings indicate greater radical-scavenging activity of trans-resveratrols para-hydroxyl group than its meta-hydroxyl groups. Using the pulse radiolysis, reactions of trans-resveratrol and its analogues with trichloromethylperoxyl radicals, CCl(3)OO*, were studied. Spectral and kinetic properties of the observed transients showed great similarity between trans-resveratrol and trans-4-hydroxystilbene which seems to confirm that para-hydroxyl group of trans-resveratrol scavenges free radicals more effectively than its meta-hydroxyl groups.

2-Propanol↗
PubMed2001

Transformation of phospholipid membranes by thiyl radicals via cis-trans isomerization of fatty acid residues.

Thiyl radical-mediated transformation of unsaturated fatty acid residues are reported. Beside the initiation of lipid peroxidation, thiyl radicals can efficiently cause isomerization of fatty acid residues in a catalytic manner. The latter process is observed in homogeneous solutions as well as in organized assemblies, leading to a denaturation of the natural all-cis-isomers of fatty acid residues of lipid bilayers. The degree of denaturation goes parallel with an increase in the number of double bonds and in the hydrophobicity of thiols. For arachidonic acid methyl ester, a decay of the all-cis-isomer to approximately 30% after a gamma irradiation dose of 1.8 kGy in micelles is observed. The reversibility of the isomerization reaction is demonstrated in liposomes by the fact that the cis/trans-equilibrium is independent of configuration of the starting compound.

Arachidonic Acid↗
PubMed2000

Electrochemical and NMR spectroscopic investigations of the influence of the probe molecule Eu(fod)3 on the permeability of lipid membranes to ions.

Investigating the action of the fluorinated europium complex Eu(fod)3 on lipid membranes we found that the complex facilitates the ion transfer through the membrane. Electric measurements on planar lipid membranes showed that the membrane conductivity increases considerably by insertion of the complex into the membrane. The increase in the conductivity was only obtained if both layers of the membrane were modified with the complex. 1H NMR spectroscopic studies using DOPC liposomes gave information about the location of the modifier complex in the lipid membrane. From chemical shift effects we concluded that the complex resides in the choline head group region of the membrane and also in the membrane interior near the -C =C- lipid double bond, but not in the center of the bilayer. For understanding of the mentioned conductivity effect we assume that the europium complex induces defects of yet unknown structure in the lipid matrix which provide paths for the ion transfer through the membrane. As appropriate measurements revealed, these paths seem to conduct cations predominantly. Investigating the current voltage behavior of the modified lipid membranes in dependence on the ion concentration we obtained different shaped current-voltage curves. Calculation showed that a model with only one energy barrier inside the membrane is unable to describe these curves kinetically. However, by assuming two energy barriers--one barrier in each membrane lipid layer--the observed curve can be described satisfactorily.

Electrochemistry↗
PubMed2000

Mechanism of thiyl radical-catalyzed isomerization of unsaturated fatty acid residues in homogeneous solution and in liposomes.

NMR spectroscopy and gas chromatography were used on methanolic solutions of fatty acid methyl esters and on small bilayer liposomes to study the radical-induced denaturation of the fatty acid residues from the natural cis-configuration into trans-isomers. To analyze the mechanism of the thiyl radical-catalyzed lipid isomerization, we compared the effects of thiols on oleic and linoleic fatty acid residues using pulse radiolysis, gamma-radiolysis and chemolysis (AAPH) to generate thiyl radicals. The isomerization step takes place within the adduct of the thiyl radical to an olefinic group of unsaturated fatty acids, but not within the pentadienyl radical. The stability of the adduct can be described by an equilibrium constant of (12+/-5) mol(-1) dm(3). The isomerization rate depends on the structure of the thiol. However, the resulting isomeric equilibrium (trans-fraction: 81%) does not depend on the structure of the thiyl radical or the organization of the lipids. Quantum chemical calculations were performed to estimate the barriers for rotation, the geometry and the enthalpy difference between cis- and trans-thiyl radical adducts.

Chromatography, Gas↗
PubMed2000

Report on the third annual meeting of the Society for Biological Radiation Research, GBS '99.

During the past few decades radiation research has developed into specialized sub-disciplines, ranging from basic physics and chemistry to tumor biology and experimental radiotherapy. Scientific issues as well as the techniques and methodologies applied are subject to diverging discussion. The annual scientific meetings of the German "Gesellschaft für Biologische Strahlenforschung (GBS)" were established with the primary aim of allowing up-to-date transfer of current knowledge in any of the topics in radiation research and of promoting interaction between different research groups. This report provides a summary of the presentations at the third annual meeting which took place in 1999 in Dresden, Germany. The meeting particularly focussed on frontline research in radiation chemistry, modeling of radiation effects, dosimetry of non-ionizing radiation and unconventional radiation qualities, e.g., heavy ions or soft x-rays, stochastic radiation effects, DNA repair, and various aspects of radiobiological research of cells, normal tissues and tumors.

Animals↗
PubMed1999

Differences in the reactivity of phthalic hydrazide and luminol with hydroxyl radicals.

The reactivity of 5-amino-2,3-dihydro-phthalazine-1,4-dione (luminol) and phthalic hydrazide with hydroxyl radicals was studied. HO*-radicals were generated by the Fenton reaction as well as by water radiolysis. Both luminol and phthalic hydrazide react with hydroxyl radicals under intense chemiluminescence (CL) emission. However, exclusively the CL arising from phthalic hydrazide oxidation can be quenched by competition (e.g. by the addition of carbohydrates), whereas luminol CL is enhanced. The reactivities of both compounds with HO*-radicals were further studied by time-resolved spectroscopy (pulse radiolysis), competition methods, NMR spectroscopy and mass spectrometry. Whereas only slight differences were detectable by pulse radiolysis, the analysis of competition kinetics in the presence of p-nitroso-dimethylaniline (NDMA) gave a two-fold-enhanced reactivity for luminol (4.8 x 10(9) l mol(-1) s(-1)) in comparison to phthalic hydrazide (2.0 x 10(9) l mol(-1) s(-1)). NMR and mass spectrometric analyses revealed significant differences in the reactivity of HO*-radicals: whereas in luminol solutions hydroxylation of the aromatic ring system predominated, hydroxylated products were not detectable upon irradiation of phthalic hydrazide. A hypothetical mechanism is proposed which may explain the observed differences.

Binding, Competitive↗
PubMed1998

Thiyl radical-induced cis/trans-isomerization of methyl linoleate in methanol and of linoleic acid residues in liposomes.

PURPOSE: To investigate the role of a thiol-containing biologically active compound in lipid peroxidation of membranes. MATERIALS AND METHODS: Thiyl radicals were generated from 3-(2-mercaptoethyl)quinazoline-2,4(1H,3H)-dione (MECH) using pulse radiolysis and gamma-radiolysis in aqueous and alcoholic solutions saturated with N2O. The products were analysed by 1H NMR and by HPLC. RESULTS: THE thiyl radicals abstract bisallylic hydrogens from [cis-9, cis-12]-methyl linoleate, yielding a pentadienyl radical. In the absence of oxygen, a thiyl radical-induced cis/trans-isomerization leads to linoleic-type isomers. These chain-type isomerization reactions can occur with the long living pentadienyl radical, followed by a 'repair' reaction of the attached thiol, and with the thiyl radical adduct with a double bond of the fatty acid residue. CONCLUSIONS: The results show that the mechanism of cis/trans-isomerization is an integral part of the thiyl radical attack on polyunsaturated fatty acids in homogeneous solutions and in bilayers.

Chromatography, High Pressure Liquid↗
PubMed1998

Reactivity of cartilage and selected carbohydrates with hydroxyl radicals: an NMR study to detect degradation products.

It was investigated to what extent isolated, monomeric and polymeric carbohydrates as well as cartilage specimens are affected by hydroxyl radicals generated by gamma-irradiation or Fenton reaction and what products can be detected by means of NMR spectroscopy. Resonances of all protons in glucose and other monosaccharides as well as carbon resonances in 13C-enriched glucose were continuously diminished upon gamma-irradiation. Formate and malondialdehyde were found as NMR detectable products in irradiated glucose solutions under physiologically relevant (aerated) conditions. In polysaccharide solutions (e.g. hyaluronic acid) gamma-irradiation and also treatment with the Fenton reagent caused first an enhancement of resonances according to mobile N-acetyl groups at 2.02 ppm. This indicates a breakdown of glycosidic bonds in polysaccharides. Using higher radiation doses or higher concentrations of the Fenton reagent formate was also detected. The same sequence of events was observed upon treatment of bovine nasal cartilage with the Fenton reagent. First, glycosidic linkages in cartilage polysaccharides were cleaved and subsequently formate was formed. In contrast, collagen of cartilage was affected only to a very low extent. Thus, HO-radicals caused the same action on cartilage as on isolated polymer solutions, inducing a fragmentation of polysaccharides and the formation of formate.

Animals↗
PubMed1996

Binding and relaxation behaviour of prodan and patman in phospholipid vesicles: a fluorescence and 1H NMR study.

The relative location, binding behaviour and the solvent relaxation behaviour of the polarity sensitive membrane probes 6-propionyl-2-(dimethylamino)naphthalene and 6-palmitoyl-2-[[trimethylammoniumethyl]methylamino]naphthalene chloride in vesicles composed of 1,2-dimyristoyl-sn-glycero-3-phosphatidylcholine or egg yolk lecithin have been compared using steady-state and time-resolved fluorescence as well as high resolution NMR measurements. The reconstructed time-resolved emission spectra show unambiguously that the observed spectral shifts in vesicle systems have to be assigned to time-dependent solvent relaxation processes rather than to a probe relocation mechanism. All fluorescence as well as the NMR relaxation data suggest a deeper localization of Patman in the membrane, sensing a less polar and/or more restricted probe environment.

2-Naphthylamine↗
PubMed1989

[NMR research on blood plasma for tumor detection--a method for mass screening?].

Recently, a simple NMR test was proposed to distinguish patients with and without malignant diseases by line-width analysis of methyl and methylene lipoprotein resonances in human plasma (4). We have reevaluated this proposed cancer detection technique at 250 MHz (magnet field strength 5.9T). The mean line width for 11 controls was 31.2 Hz (SD 4.1 Hz). For 8 patients with untreated malignant tumors, the line width was 27.5 Hz (SD 3.9 Hz). The data confirm the reported lower line widths of human plasma NMR resonances for patients with malignant tumors compared with controls (4). However, the statistical significance (P greater than 0.07) does not justify to use this technique for individual differential diagnostic purposes without further improvements of the method.

Biomarkers, Tumor↗
PubMed1980

On the interaction of caffeine with nucleic acids. IV. Studies of the caffeine-DNA interaction by infrared and ultraviolet linear dichroism, proton and deuteron nuclear magnetic resonance.

The DNA-caffeine interaction at high concentration of caffeine (Cf) leads to an arrangement of Cf molecules outside of the DNA double helix with an orientation parallel to the bases both in the A and B form as demonstrated by infrared linear dichroism. Addition of DNA broadens the 1H NMR lines of Cf in aqueous solution indicating a specific binding. Intercalation is not the predominant mechanism, the deuterium relaxation time T1 = (38 +/- 7) ms and the estimated reorientation correlation time tau cb = 0.17 ns of caffeine-8[2H] in the Cf-DNA complex suggest an outside stacking of the ligand. According to the results a model on the DNA-Cf complex at high Cf concentration (binding process II) is suggested including the caffeine-induced reorientation of the hydration shell of DNA.

Caffeine↗
PubMed1979

Hydrophobic binding of phenoxyacetic and phenylacetic acids to horseradish peroxidase and human serum albumin: structure-activity relationships.

Studies of protein binding in homologous series of drugs are of great interest for drug research. Apparent binding constants of phenoxyacetic and phenylacetic acids to horseradish peroxidase and to human serum albumin are evaluated by NMR studies and an optical method. These constants are good parameters to describe hydrophobic interactions, and the results are in a good agreement with our protein binding model described previously.

Chemical Phenomena↗
PubMed1977

Carrageenan in formula and infant baboon development.

Male and female infant baboons were reared from birth to 112 days of age on infant formulas containing concentrations of carrageenan varying from none to 5 times the concentration in commercially available formulas for human infants. Carrageenan content of the formula did not affect weight, characteristics of urine and feces, findinds on physical examination, hematological variables, blood chemical analyses, organ system weights, or the macroscopic and microscopic appearance of the gastrointestinal tract.

Animals↗