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H Triebel

Publications and source records attributed to H Triebel.

At least 19 recordsLinked to original sources
PubMed1998

Binding of 2-azaanthraquinone derivatives to DNA and their interference with the activity of DNA topoisomerases in vitro.

We have investigated the binding ability to DNA of compounds belonging to the 2-azaanthraquinone-type structure and have examined the effect on the activity of DNA gyrase as well as on mammalian topoisomerases in vitro. Using different biophysical techniques it was found that one of these ligands, 9-((2-dimethylamino)ethyl)amino)-6-hydroxy-7-methoxy-5, 10-dihydroxybenzo[g]isoquinoline-5,10-dione (TPL-I), is an intercalating DNA binding agent, whereas the parent compound tolypocladin (TPL) and a derivative (TPL-II) showed almost no similar affinity to DNA. CD measurements demonstrated a significant and selective binding tendency of TPL-I to alternating purine/pyrimidine sequences with some preference for poly(dA-dT). poly(dA-dT). Tm values were increased of the ligand complex with the alternating AT-containing duplex polymer. The binding to various DNAs was characterized by CD and visible absorption spectral changes. From the latter, different binding constants of 6.2 x 10(5) and 1.5 x 10(5) M-1 were obtained for poly(dA-dT).poly(dA-dT) and poly(dA). poly(dT), respectively. Sedimentation measurements with supercoiled pBR322 plasmid DNA clearly indicated an intercalative binding mechanism associated with an unwinding angle of about 18 degrees. These results suggest that the intercalative binding of TPL-I is promoted by the 2-(dimethylamino)ethylamino group substituted on carbon 9 of the anthraquinone system. The cytotoxic compound TPL-I, but not TPL or TPL-II, effectively inhibited the DNA supercoiling reaction of DNA gyrase and the activity of mammalian topoisomerases I and II as measured by the relaxation assay. TPL-I affects the cleavage reaction of topoisomerases on a single site located in alternating purine-pyrimidine sequence regions. The inhibitory potency of TPL-I can be ascribed to a blocking of cleavage sites on the DNA substrate, which correlates with the sequence preference of the ligand.

Anthraquinones↗
PubMed1997

DNA binding studies and influence on the activity of DNA topoisomerases of bis-netropsins: different effects of analogs containing cis and trans ethylene linkers.

Binding to DNA and synthetic duplex polymers of two bifunctional netropsins and effects on supercoiled plasmid DNA as well as their inhibitory potency on DNA topoisomerases have been investigated. Characteristic differences were found in the DNA binding properties of the two bis-netropsins containing a cis and trans tether as reflected by CD, thermal melting and sedimentation measurements. CD results indicate, that the bis-netropsins interact with DNA by a two-step binding mode depending on the ligand concentration. The trans bis-netropsin may form stable complexes with different DNA's at high salt concentration, whereas for cis bis-netropsin DNA complexes the second binding step is completely abolished. The variations in the DNA binding ability of trans and cis bis-netropsin show a close relationship to the differences observed in their inhibitory effects on DNA topoisomerases. It appeared that trans bis-netropsin more strongly blocks topoisomerase activity than the cis isomer and represents the most potent inhibitor of DNA gyrase. Differences in the DNA. binding ability of the bis-netropsins and their inhibitory potency on topoisomerase activity are explained in terms of bidentate and monodentate binding mode of the trans and cis isomer, respectively.

Binding, Competitive↗
PubMed1994

Modulation of DNA supercoiling by interaction with netropsin and other minor groove binders.

The assay of DNA unwinding by ethidium, followed by sedimentation velocity techniques, was applied to complexes of supercoiled plasmid DNA with different non-intercalating drugs which strongly and sequence-specifically bind to DNA. Compared with the behaviour of naked DNA, most of the complexes exhibit an increase in the critical EB/nucleotide binding ratio associated with the principal minimum in the sedimentation profile. Using netropsin (Nt) as the paradigm of the minor groove binders investigated, the drug-induced alterations in various structural parameters of both the relaxed and supercoiled form of DNA are described. Whereas winding number, helical repeat (both being defined with reference to a surface normal), and linking number of the superhelical DNA remain constant in our experiments, its twist number, surface twist, number of superhelical turns as well as the absolute values of linking number difference, superhelix density, and writhing number increase on binding of Nt. Correspondingly, compared with the naked relaxed DNA a higher linking number (or twist number, or winding number), a higher average duplex winding angle and a lower helical repeat have to be assigned to the relaxed Nt-DNA complex. The various minor groove binders investigated were found to differ considerably in their efficiency to alter the structure of supercoiled DNA.

Base Sequence↗
PubMed1993

Physical and conformational properties of staphylokinase in solution.

The structure of staphylokinase has been analyzed by solution X-ray scattering, dynamic light scattering, ultracentrifugation and ultraviolet circular dichroism spectroscopy. Staphylokinase has a radius of gyration of 2.3 nm, a Stokes radius of 2.12 nm and a maximum dimension of 10 nm. The sedimentation coefficient is 1.71 S. These physical parameters indicate that the shape of staphylokinase is very elongated. The protein molecule consists of two folded domains of similar size. The mean distance of the centres of gravity of the domains is 3.7 nm. The mutual positions of the two domains are variable in solution. Thus, the molecule is shaped like a flexible dumbbell. About 18% of the amino acids of staphylokinase are organized in helical structures, 30% are incorporated in beta-sheets and 20% form turns.

Circular Dichroism↗
PubMed1989

Structural differences between histone H1 molecules from sea urchin (Strongylocentrotus intermedius) sperm and calf thymus: hydrodynamic and c.d. studies.

Comparative sedimentation, diffusion and circular dichroism (c.d.) measurements have been performed on two histones H1 from sperm of the sea urchin Strongylocentrotus intermedius (H1S) and from calf thymus (H1T), at a high salt concentration of M NaCl. Both the Stokes radius and the frictional ratio derived from the hydrodynamic parameters were found to be somewhat smaller for H1S than the corresponding values for H1T. In view of the considerably higher molar mass of H1S compared with that of H1T, this result indicates that H+S in 2 M NaCl has a more compact conformation than H1T, probably due to a higher degree of secondary structure in the flanking domains of H1S. The c.d. measurements likewise show that H1S has a higher content of ordered structures than H1T. Model considerations indicate that the C-terminal tail of H1S is the main candidate for accommodation of these additional secondary structure regions.

Animals↗
PubMed1989

DNA binding protein from Streptomyces hygroscopicus: detection of binding by gel retardation, sedimentation and effects on the transcriptional activity in vitro.

The binding to supercoiled plasmid DNA as well as to double-stranded short DNA fragments of the DNA binding protein. ASBIII, from S. hygroscopicus has been demonstrated by gel retardation asay. As further revealed by sedimentation analysis, the protein-DNA complex formation also involves condensation of DNA and an aggregation step at higher total protein-to-DNA ratio (w/w). In vitro studies of the transcriptional activity of DNA-protein complexes showed that the ASBIII protein inhibits the overall template activity in the RNA polymerase II system to nearly similar extents for various DNA's. Preincubation of ASBIII-DNA complexes of different GC content, however, suggested a selective inhibitory effect on GC-rich DNA due to the higher stability of this complex. The results also indicate that the initiation of transcription of the GC-rich DNA template is affected by the ASBIII protein. The present results on the DNA binding properties and inactivation of the transcription of the ASBIII protein suggest that this protein may be a potential candidate for the local compaction of chromosomal DNA in Streptomyces hygroscopicus.

Animals↗
PubMed1985

Interaction of histone H1 from sea urchin sperm with superhelical and relaxed DNA.

Complexes of histone H1 from sea urchin sperm (H1S) and calf thymus (H1T) with superhelical DNA I and relaxed circular DNA II have been analyzed by analytical sedimentation. Similar to H1T, the highly basic and relatively arginine-rich histone H1S preferentially interacts with DNA I compared to DNA II under competition conditions. However, H1S induces a stronger aggregation of both forms of DNA than H1T. Below 0.05 M NaCl, the soluble complexes formed by both histones have similar properties, but aggregation proceeds in a different manner: H1S induces a stronger aggregation of DNA II as compared to DNA I, whereas H1T fails to aggregate DNA I. The results are explained on the basis of differences in amino acid sequence and structure of the two histones and related to the special chromatin condensing ability of histone H1S.

Animals↗
PubMed1982

Studies on interaction of anthracycline antibiotics and deoxyribonucleic acid: geometry of intercalation of iremycin and daunomycin.

The structure of iremycin [10-(alpha-L-rhodosaminyl)-gamma-rhodomycinone] hydrochloride has been confirmed by 1H and 13C nuclear magnetic resonance (NMR) spectroscopy. We studied the interaction of iremycin and the related compound daunomycin with DNA by transient electric dichroism and by sedimentation analysis of supercoiled closed duplex DNA. The apparent length increase of sonicated calf thymus DNA (150 +/- 20 base pairs) in 2.5 mM sodium cacodylate buffer (pH 7) at 12 degrees C was determined to be 0.40 +/- 0.02 nm/bound drug). The Cu(II) complex of iremycin with a metal/drug ratio of 0.7 induces a length increase of DNA of 0.44 +/- 0.02 nm/added drug. The alignment of the iremycin chromophore with respect to the DNA helix axis was determined from the electric dichroism of the complex. The tilt (long axis) and twist (short axis) of the chromophore are both 28 +/- 4 degrees, whereas for daunomycin the long axis is perpendicular to the helix axis and the short axis is twisted by about 25 degrees. Intercalation of iremycin between DNA base pairs is supported by unwinding of the supercoiled closed duplex form of pBR 322 plasmid DNA from Escherichia coli. In 2.5 mM sodium cacodylate buffer at pH 7 and at 25 degrees C, the unwinding induced by iremycin is 15.0 +/- 1.5 degrees/bound drug. Under identical conditions daunomycin shows on unwinding angle of 15.4 +/- 1.5 degrees. The superhelical density of pBR 322 DNA (sigma 0) was determined to be -0.087 +/- 0.002 at standard conditions (0.2 M NaCl, 37 degrees C).

Anthracyclines↗
PubMed1979

Structural changes of ultraviolet-irradiated DNA derived from hydrodynamic measurements.

The paper reports on sedimentation and viscosity measurements performed on ultraviolet-irradiated DNA from T7 phage and calf thymus. From the hydrodynamic data the relative changes in the mean molecular weight, radius of gyration, and effective Kuhn statistical segment length were calculated. The results show that ultraviolet irradiation (254 nm) leads to a significant decrease of the effective statistical segment length of DNA which may be due to small local helix kinks (produced by the generation of photodimers) and a local increase of chain flexibility. Alterations in the overall DNA conformation may be observed even at low fluences where the mean molecular weight almost stays constant. The locally distorted helix regions possibly may serve as recognition sites in the first step of excision repair.

Animals↗
PubMed1979

Properties of Thermoactinomyces vulgaris phage Ta1 and its extracted DNA.

The virulent phage Ta1 was obtained in good yields from infected cultures of Thermoactinomyces vulgaris 1227. The purified phage was found to sediment with a single band, the sedimentation constant being (519 +/- 14)S, and to exhibit a typical nucleoprotein behaviour in UV-spectrophotometric and CD experiments. The Ta1 phage consists of a hexagonal head about 0.056 micrometers in diameter and a very short tail. It is morphologically similar to the temperate Salmonella phage P22. The nucleic acid extracted from the phage was found to be a double-stranded linear DNA with a G+C content of 42 mole-% as deduced both from its melting temperature and buoyant density in CsCl. Analytical sedimentation revealed a high degree of molecular homogeneity of Ta1 Dna. the sedimentation constant of this DNA amounts to (35.9 +/- 0.3)S, corresponding to a DNA molecular weight of about 29 millions daltons. The biological activity of Ta1 DNA was indicated by its ability to infect the mycelium of the components T. vulgaris strain 1227 and to give rise to mature phages.

Bacteriophages↗
PubMed1979

Molecular characterization of the genomes of actinophages SH3, SH10, SH11, and SH12 infecting Streptomyces hygroscopicus.

Some physico-chemical properties of the DNAs released from the actinophages SH3, SH10, SH11, and SH12 are described. The four phage DNAs have a linear double-stranded secondary structure and are unique with respect to their high G.C contents which, from melting studies and buoyant density experiments, were found to be in the range of 68-73 mol-%. The DNA molecular weights were determined by sedimentation velocity experiments and by electron microscopic length measurements, the mean values of the two corresponding data sets being 34.0 x 10(6) (SH3), 26.7 x 10(6) (SH10), 26.1 x 10(6) (SH11), and 28.7 x 10(6) (SH12) with a mean relative error of +/- 5%. From different observations it was concluded that SH10 DNA, and possibly also SH11 and SH12 DNA, have cohesive ends and can undergo intramolecular or intermolecular association to form ring-like monomers or linear and ring-like multimers. Cleavage of the DNAs of SH3, SH10, SH11, and SH12 by EcoRI restriction endonuclease delivered two, one, zero, and two cleavage sites, respectively, and by BamHI restriction endonuclease eight, zero, zero, and zero cleavage sites, respectively.

Bacteriophages↗
PubMed1974

Conformation dependent binding of netropsin and distamycin to DNA and DNA model polymers.

The binding of the antibiotics netropsin and distamycin A to DNA has been studied by thermal melting, CD and sedimentation analysis. Netropsin binds strongly at antibiotic/nucleotide ratios up to at least 0.05. CD spectra obtained using DNA model polymers reveal that netropsin binds tightly to poly (dA) . poly (dT), poly (dA-dT) . poly(dA-dT) and poly (dI-dC) . poly (dI-dC) but poorly, if at all, to poly (dG) . poly (dC). Binding curves obtained with calf thymus DNA reveal one netropsin-binding site per 6.0 nucleotides (K(a)=2.9 . 10(5) M(-1)); corresponding values for distamycin A are one site per 6.1 nucleotides with K(a)= 11.6 . 10(5) M(-1). Binding sites apparently involve predominantly A.T-rich sequences whose specific conformation determines their high affinity for the two antibiotics. It is suggested that the binding is stabilized primarily by hydrogen bonding and electrostatic interactions probably in the narrow groove of the DNA helix, but without intercalation. Any local structural deformation of the helix does not involve unwinding greater than approximately 3 degrees per bound antibiotic molecule.

Animals↗