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Biomedical subjects

V Nöthig-Laslo

Publications and source records attributed to V Nöthig-Laslo.

15 recordsLinked to original sources
PubMed1992

Aspartic acid as a trap for gamma-radiation energy in the amorphous Al5(OH)15(Asp)3.3H2O.

Paramagnetic molecular centers produced by gamma irradiation at 77 K and at room temperature in the novel compound Al5(OH)15(Asp)3.3H2O were studied by ESR spectroscopy. The g value of 2.0034 and the lack of such lines in pure aluminum hydroxide suggested that all the paramagnetic centers observed are related to the aspartic acid molecule. However, none of the paramagnetic centers gave an ESR spectrum characteristic for gamma-irradiated pure aspartic acid powder. The influence of the oxygen on the formation of the paramagnetic centers was noticed. The extreme stability of the paramagnetic molecular centers formed in Al5(OH)15(Asp)3.3H2O suggests that aspartic acid complexed in aluminum hydroxide is a good trap for gamma-radiation energy.

Aluminum Hydroxide↗
PubMed1986

NH2-terminal spin labeling of human hemoglobin--spin states and temperature dependence.

In order to explore fully how ligand- and temperature-induced alterations in the spin states of heme iron are related to protein readjustments, the spin label 4-isothiocyanate (I) was covalently attached at beta-93 cysteines and at NH2-terminal valines of various heme-iron ligand forms of human hemoglobin. It was found that the mobility of NH2-terminally bound spin labels depends on the magnetic moment of the heme iron. There is a an approximately linear relationship between the magnetic moment of the heme iron and the mobility of NH2-terminally bound spin labels. In accordance with our previous results, the temperature dependence of ESR spectra of spin-labeled hemoglobin suggests the temperature-induced protein conformational change in those heme-iron ligand forms that are characterized by the equilibrium of the spin states of the heme iron. The conformational change was sensed at both spin-label-binding sites: at beta-93 cysteines and at NH2-terminal valines.

Electron Spin Resonance Spectroscopy↗
PubMed1985

Comparative study of the lipid dynamics in the surface layer of porcine and human high density lipoprotein subclasses by spin labeling.

In order to obtain information on the determinants of the lipid dynamics in the high density lipoproteins (HDL), we have compared the structural properties of human HDL subclasses with porcine HDL artificially subdivided into density subfractions corresponding to those of human HDL. Four different positional isomers of spin labeled fatty acids and spin labeled androstanol experienced more restricted motion in porcine HDL than in the human HDL2 and HDL3 subclasses. The differences in the spin label motion could not be accounted for on the basis of the differences in the chemical composition of the lipoproteins examined. They are, however, most probably due to the specific properties of the interactions between lipids and proteins that differ among the lipoproteins.

Animals↗
PubMed1985

Structural changes of yeast tRNA(Tyr) caused by the binding of divalent ions in the presence of spermine.

The existence of specific sites in tRNA for the binding of divalent cations has been seriously questioned by electrostatic considerations [Leroy & Guéron (1979) Biopolymers, 16, 2429-2446]. However, our earlier studies of the binding of Mg2+ and Mn2+ to yeast tRNA(Tyr) have indicated that spermine creates new binding sites for divalent cations [Weygand-Durasević et al. (1977) Biochim. Biophys, Acta, 479, 332-344; Nöthig-Laslo et al. (1981) Eur. J. Biochem. 117, 263-267]. We have now used yeast tRNA(Tyr), spin labeled at the hypermodified purine (i6A-37) in the anticodon loop, to study the effect of spermine on the binding of manganese ions. The presence of eight spermine molecules per tRNA(Tyr) at high ionic strength (0.2 M NaCl, 0.05 M triethanolamine.HCl) and at low temperature (7 degrees C) enhances the binding of manganese to tRNA(Tyr). This effect could not be explained by electrostatic binding. The initial binding of manganese to tRNA(Tyr) affects the motional properties of the spin label indicating a change of the conformation of the anticodon loop. From the absence of the paramagnetic effect of manganese on the ESR spectra of the spin label one can conclude that the first binding site for manganese is at a distance from i6A-37, influencing the spin label motion through a long-range effect. The enhancement of the binding of manganese to tRNA(Tyr) by spermine is lost upon destruction of its specific macromolecular structure and it does not occur in single stranded or in double-stranded polynucleotides. The observed effect can be explained by the binding of Mn2+ to new sites, created by the binding of spermine, which are specific for the macromolecular structure of tRNA.

Anticodon↗
PubMed1984

Involvement of the 3' side of the anticodon loop of yeast tRNATyr in messenger-free binding to ribosomes. An electron-spin resonance study.

Electron-spin resonance (ESR) spectra of a nitroxide spin-label attached to residue i6A-37 of yeast tRNATyr were measured in complexes of deacylated tRNATyr with Escherichia coli ribosomes. A Scatchard plot, obtained in the absence of mRNA, indicated strong binding with an association constant of 1 X 10(7) l X mol-1, suggesting the P-site binding. The ESR spectrum of free tRNATyr, characteristic for a rapidly tumbling nitroxide, changes to a spectrum with extensively broadened lines in the ribosome-tRNA complex. The original spectrum can be restored upon long incubations of the complex with an excess of extraneous tRNA. ESR spectra suggest that the spin-label motion is drastically perturbed though not completely blocked in the ribosome-tRNATyr complex. Since ESR spectra of a spin-label attached to the opposite, i.e. 5', side of the anticodon loop are only slightly perturbed by the messenger-free binding to ribosomes [Rodriguez et al. (1980) J. Biol. Chem. 255, 8116-8120], it is concluded that the two sides of the anticodon loop face entirely different environments when bound to the P site, the 3' side being oriented towards the surface of the ribosome, and the other side towards its environment or a large cavity.

Anticodon↗
PubMed1984

Comparative study of Ca2+ binding to lipoprotein(a) and low density lipoprotein by spin labeling.

The effect of Ca2+ binding on the dynamic properties of various spin labeled fatty acids in lipoprotein(a) (Lp(a)) was studied in comparison with low density lipoprotein (LDL) isolated from human plasma. In contrast to LDL, binding of Ca2+ to Lp(a) induced broadening of the lines in the ESR spectra of the spin labeled stearic acids. In 1.6 M NaBr solutions the thermotropic change in the surface structure was observed in both lipoproteins at similar temperatures. Ten millimolar concentration of Ca2+ shifted the temperature of the thermotropic change in the surface structure of Lp(a) to considerably higher values. We conclude that Ca2+ binding to Lp(a) induces changes in the lipid structure of the particle surface.

Calcium↗
PubMed1982

Temperature-dependent conformation change in spin-labeled hemoglobin.

Hemoglobin was spin labeled at beta-93(F9)-cysteine with N-oxyl-2,2,6,6-tetramethylpiperidinylmaleimide. The inward shift of the high-field hyperfine line (delta Hx) position in the ESR spectra of the spin label was measured as a function of temperature. One can except that an abrupt change in the microenvironment around the tightly bound spin label will be reflected in the function delta Hx(T) as a discontinuity (break point). This was shown for aquo-, azido-, nitro- and oxyhemoglobin derivatives. The presented results suggest that the microenvironment around the tightly bound spin label in those methemoglobin derivatives that exhibit the mixed-spin state of the heme iron is prone to an abrupt change above a certain ligand-specific temperature. The change in microenvironment of the spin label is probably due to a temperature-dependent change in the teritary structure of the protein.

Hemoglobins↗
PubMed1981

Binding of spermine to tRNATyr stabilizes the conformation of the anticodon loop and creates strong binding sites for divalent cations.

Electron spin resonance (ESR) spectra of yeast tRNATyr. spin-labelled in the isopentenyladenosine residue adjacent to the anticodon, were measured as a function of temperature at various spermine/tRNA ratios. The critical temperature, at which a change in the activation energy for spin-label motion takes place, changes abruptly by almost 10 degrees C upon the addition of the fifth spermine molecule/tRNATyr molecule, indicating a marked stabilization of the anticodon region. Scatchard plots for Mn2+ binding to tRNATyr in the presence of spermine do not follow theoretically predicted curves for electrostatic type of interaction, assuming that four negative charges on tRNA are neutralized by each spermine molecule. It was estimated that two to three new binding sites for divalent cations are created upon the binding of spermine to tRNATyr.

Anticodon↗
PubMed1977

Conformational changes in yeast tRNATyr revealed by EPR spectra of spin-labelled N6-(delta2-isopentenyl)-adenosine residue.

Temperature-induced conformational changes in the anticodon region of yeast tRNATyr were studied by EPR spectroscopy. The spin label 4-amino-2,2,6,6-tetramethylpiperidine-1-oxyl was attached to the N6-(delta2-isopentenyl)-adenosine residue in tRNATyr, previously made reactive by iodination. The labelled tRNATyr gave an asymmetrical triplet spectrum typical of rapidly tumbling nitroxide, with a rotational correlation time (tauc) of 0.65 ns. Spin-labelled tRNATyr was exposed to heating and cooling in three different buffers each with or without MgCl2. In each case the Arrhenius plot of --log tauc vs. inverse absolute temperature gave two straight lines, intersecting at a critical temperature (tcr). Above tcr, the anisotropy of the spectrum was not reduced and the activation energy of motion increased, indicating that the transition is associated with a conformational change of the macromolecule. Transitions in 0.05 M potassium phosphate (pH 8.0) and 0.02 M Tris - HC1 (pH 7.0) were observed at potassium phosphate (pH 8.0) and 0.02 M Tris - Hc1 (pH 7.0) were observed at approx. 37 degrees C. When 0.01 M mgCl2 was present in these buffers, transitions were shifted to 46 degrees and 53 degrees C, respectively. Transitions in 0.01 M sodium cacodylate were observed at temperatures which are significantly lower. Since all these transitions occur at temperatures considerably below those required to melt the helical regions of tRNA, and at least approximately 10 degrees C below those reported to break tertiary interactions, it is supposed that they reflect some reorientation of the anticodon region, e.g. a change in tilt of the bases.

Anticodon↗
PubMed1977

Collective behaviour of hemoglobin in dense solutions.

The formation of radical pairs of spin-labelled hemoglobin molecules (beta-93 cysteine) in a mixture with unlabelled hemoglobin of concentrations higher than the critical one [(5.7 less than c less than 6.3) mM/sigma per heme] is due to some kind of long-range order characterizing these solutions. Labelled molecules induce pertubation in an unlabelled hemoglobin solution of concentration higher than the critical one. The collective behaviour of unlabelled molecules gives rise to the formation of radical pairs of spin-labelled hemoglobin molecules. Such behaviour is dependent on the ligand bound at the heme iron (carbonmonoxide, oxygen, or water.)

Electron Spin Resonance Spectroscopy↗
PubMed1976

Temperature dependence of ESR spectra of spin-labelled met-hemoglobin.

The maleimide spin-label, firmly fixed to the protein, was used to study conformation changes of various met-hemoglobin derivatives. The temperature dependence of the rotational correlation time shows a distinct conformation change in aquomet-hemoglobin at about 25 degrees C. The other met-hemoglobin derivatives studied (fluoro-, cyano-, aquomet-complexed with inositol hexaphosphate) and carbonmonoxy-hemoglobin exhibit no conformation changes in the temperature range from 0-50 degrees C.

Electron Spin Resonance Spectroscopy↗