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T Kurucsev

Publications and source records attributed to T Kurucsev.

12 recordsLinked to original sources
PubMed1994

Analysing DNA complexes by circular and linear dichroism.

The application of linear and circular dichroism (LD and CD) in nucleic acid research is illustrated by recent results aimed at answering specific structural problems in the interaction of DNA with molecules of biological importance. We first consider the circumstances under which ligands, such as DAPI (4',6-diamidino-2-phenylindole), change their preferred binding mode in the minor groove to major groove binding or intercalation. As an extension of this problem we refer to the switch between groove binding and intercalation of structurally similar ligands such as ellipticines and trigonal ruthenium complexes. We also explore the use of LD and CD in the determination of the structure of the complex formed between the polynucleotide poly(dA) and the novel 'peptide nucleic acid', consisting of nucleic acid bases joined by a polyamide homomorphous with the deoxyribose-phosphate backbone of DNA. Finally, the structure and interaction of the recombination enzyme RecA with DNA is discussed, in particular the influence of the presence of intercalators, groove binders or covalent DNA adducts.

Base Sequence↗
PubMed1991

Effect of 2.45 GHz microwave radiation on permeability of unilamellar liposomes to 5(6)-carboxyfluorescein. Evidence of non-thermal leakage.

The influence of 2.45 GHz microwave radiation on the membrane permeability of unilamellar liposomes was studied using the marker 5(6)-carboxyfluorescein trapped in phosphatidylcholine liposomes. The release of the fluorescent marker was followed by spectrofluorimetry after an exposure of 10 minutes to either microwave radiation or to heat alone of the liposome solutions. A significant increase of the permeability of carboxyfluorescein through the membrane was observed for the microwave-exposed samples compared to those exposed to normal heating only. Exposure to 2.45 GHz microwave radiation of liposomes has been previously found to produce increased membrane permeability as compared with heating. However, in contrast to previous studies, the observations reported here were made above the phase transition temperature of the lipid membrane. The experimental setup included monitoring of the temperature during microwave exposure simultaneously at several points in the solution volume using a fiberoptic thermometer. Possible mechanisms to explain the observations are discussed.

Fiber Optic Technology↗
PubMed1987

Direct spectrophotometric determination of the two site binding of aluminum to transferrin.

Difference UV spectrophotometry is used to determine the conditional binding constants for aluminum to human transferrin in the presence of HCO3- of initial concentration 18 mM according to a two site model. The values obtained at 37 degrees C and pH 7.4 are: K1 = 3.0 (+/- 0.8) X 10(15) M-2, K2 = 2.9 (+/- 0.7) X 10(15) M-2 for the reactions: Tr + Al3+ + HCO3- = Tr-Al-HCO3 and Tr-Al-HCO3 + Al3+ + HCO3- = Tr-Al2-(HCO3)2 respectively. Possible consequences arising for the transport of aluminum in human serum are discussed.

Aluminum↗
PubMed1985

The binding of 9-aminoacridine to calf thymus DNA in aqueous solution. Electronic spectral studies.

Absorption, circular dichroism and steady-state fluorescence spectra were determined of 9-aminoacridine solutions in the presence of DNA at an ionic strength of 0.001 mol dm-3. Up to a dye/DNA phosphorus ratio of about 0.2 the results are fully consistent with the requirements and predictions of a binding model already shown to apply to the binding of other aminoacridines to DNA. The apparently anomalous spectroscopic behaviour of the 9-aminoacridine/DNA system compared with proflavine/DNA, for example, can be satisfactorily explained from a consideration of the magnitudes of exciton interactions between dyes bound to DNA.

Aminacrine↗
PubMed1984

Vibronic exciton interactions. Resolution and interpretation of the temperature-dependent circular dichroism and absorption spectra of ApA and of dApdA.

The circular dichroism and absorption spectra of the stacked and unstacked forms of ApA and dApdA were derived. The unstacked spectra are not identical with the corresponding free nucleoside spectrum. The stacked spectra can be satisfactorily described in terms of the vibronic degenerate exciton theory which suggests that the non-degenerate interactions have a less important influence on the observed circular dichroic spectra than hitherto assumed. From the experimental spectra the magnitudes of the exciton coupling were found to correspond to very fast transfer rates of energy between the adenine moieties. The absorption spectra of the stacked species are consistent with average angles of near 60 degrees and 20 degrees in ApA and dApdA, respectively, between the degenerate transition moments of the adenine moieties.

Adenosine Monophosphate↗