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H Fritzsche

Publications and source records attributed to H Fritzsche.

At least 37 records · Page 2Linked to original sources
PubMed1997

Hairpin-dimer equilibrium of a parallel-stranded DNA hairpin: formation of a four-stranded complex.

The 24mer deoxyoligonucleotide 3'-d(T)10-5'-5'-d(C)4- d(A)10-3'(psC4) with an uncommon 5'-p-5'phosphodiester linkage was designed to enable the formation of a hairpin structure with unusual parallel-stranded stem. As reference hairpin structure with an antiparallel-stranded stem, the 24mer 5'-d(T)10-d(C)4-d(A)10-3'(apsC4) was chosen. The behaviour of these oligonucleotides at different temperatures, DNA and salt concentrations was characterised by a combination of UV melting, CD, CD melting, infrared and Raman spectroscopy, infrared melting and analytical ultracentrifugation. The parallel-stranded hairpin structure was found to be formed by psC4 only under conditions of low DNA concentration and low salt concentration. Increase of the NaCl concentration beyond the physiological level or high DNA concentration supports the formation of intermolecular multi-stranded structures. The experimental data are in agreement with a four-stranded complex formed by two molecules of psC4. The base pairing model of this asymmetric four-stranded complex is based on the pyrimidine motif of a triple helix with two bifurcated hydrogen bonds at the O4 of the thymine each directed towards one of the amino protons of both adenines. In contrast, the reference oligonucleotide apsC4 forms only an antiparallel-stranded hairpin under all experimental conditions.

Base Composition↗
PubMed1996

A correlation between thermal stability and structural features of staphylokinase and selected mutants: a Fourier-transform infrared study.

Variants of recombinant staphylokinase (Sak) were investigated by Fourier-transform infrared spectroscopy: Sak (wild type), Sak-M26A, Sak-M26L, and Sak-G34S/R36G/R43H (Sak-B). Estimation of the secondary structure and hydrogen-deuterium exchange experiments revealed the existence of fast-exchanging and strongly solvent-exposed fractions of the helical structures in the two samples Sak and Sak-M26L. These two samples are also thermally less stable with unfolding transition temperatures of 43.7 degrees C (Sak) and 43.5 degrees C (Sak-M26L), respectively. On contrast, Sak-M26A and Sak-G34S/R36G/R43H have a slower hydrogen-deuterium exchange, have a smaller solvent-exposed portion of the helical part, and are more resistant against thermal unfolding; the transition temperatures are 51.7 degrees C and 59.3 degrees C, respectively. The secondary structure analysis was performed by two different approaches, by curve-fitting after band narrowing and by pattern recognition (factor analysis) based upon reference spectra of proteins with known crystal structure. Within the limits of the used methods, we are unable to detect significant differences in the secondary structure of the four variants of Sak. According to the results of the factor analysis, the portions of secondary structure elements were obtained to 16-20% alpha-helix, 28-30% beta-sheet, 23-27% turns, 28-30% irregular (random) and other structure. The sharp differences in the specific plasminogen-activating capacity (Sak, Sak-G34S/R36G/R43H and Sak-M26L are fully active, but Sak-M26A does not form a stable complex with plasminogen) are not reflected in the structural features revealed by the infrared spectra of this study.

Deuterium↗
PubMed1996

Parallel-stranded duplex DNA containing dA.dU base pairs.

DNA oligonucleotides with dA and dU residues can form duplexes with trans d(A.U) base pairing and the sugar-phosphate backbone in a parallel-stranded orientation, as previously established for oligonucleotides with d(A.T) base pairs. The properties of such parallel-stranded DNA (ps-DNA) 25-mer duplexes have been characterized by absorption (uv), CD, ir, and fluorescence spectroscopy, as well as by nuclease sensitivity. Comparisons were made with duplex molecules containing (a) dT in both strands, (b) dU in one strand and dT in the second, and (c) the same base combinations in reference antiparallel-stranded (aps) structures. Thermodynamic analysis revealed that total replacement of deoxythymine by deoxyuridine was accompanied by destabilization of the ps-helix (reduction in Tm by -13 degrees C in 2 mM MgCl2, 10 mM Na-cacodylate). The U-containing ps-helix (U1.U2) also melted 14 degrees C lower than the corresponding aps-helix under the same ionic conditions; this difference was very close to that observed between ps and aps duplexes with d(A.T) base pairs. Force field minimized structures of the various ps and aps duplexes with either d(A.T) or d(A.U) base pairs ps/aps and dT/dU combinations are presented. The energy-minimized helical parameters did not differ significantly between the DNAs containing dT and dU.

Base Composition↗
PubMed1996

The detection of B-form/A-form junction in a deoxyribonucleotide duplex.

The transition of the 14-meric deoxyoligonucleotide duplex d-(ACCCCCTTTTTTTG).d-(CAAAAAAAGGGGGT) from the B- to the A-conformation in water/trifluorethanol (TFE) solution was studied with the use of circular dichroism. An increase in the fraction of TFE induces a two-step B-A transition. In the first step, up to 73% TFE, the A-form is generated from the GC-rich part; in the second step, 73-82% TFE, the AT-rich part shifts to the A-form. By this we suggest the existence of a B/A junction near 73% TFE. Emergence of the B/A junction has been directly confirmed with the use of distamycin A and netropsin, ligands known to selectively bind to AT stretches of B-DNA. It can be shown that both ligands suppress formation of the A-form in the B-philic part. The free energy value for the B/A junction was estimated to be 2.1 kcal/mol, which agrees well with known data for polymeric DNAs. The obtained results may have biological relevance in connection with recently published x-ray data about the occurrence of the B/A junction in the complex of DNA with reverse transcriptase of HIV.

Base Composition↗
PubMed1996

Selective cytokine release induced by serum and separated plasma from septic patients.

OBJECTIVE: To investigate the activating properties of serum from septic patients on monocytes and the potential effect of plasmapheresis. DESIGN: Prospective controlled study. SETTING: Teaching hospital, Germany. SUBJECTS: 7 Patients with life-threatening systemic inflammatory response syndrome (SIRS) and 4 control patients with serious but not life-threatening conditions. INTERVENTIONS: We measured the amount of mediators released by healthy donor monocytes incubated in serum and separated plasma from septic patients. MAIN OUTCOME MEASURES: Release of interleukin 6 (IL-6), prostaglandin E2 (PGE2), interleukin 1 (IL-1), and tumour necrosis factor (TNF). RESULTS: The serum and separated plasma from infected patients selectively induced the release of IL-6 and PGE2. The mean PGE2 production in serum was 10,895 pg/ml/10(5) cells, and in plasma was 14,023 pg/ml/10(5) cells compared with a control of 0 (p < 0.05). The mean IL-6 production in serum was 4925 pg/ml/10(5) cells and in plasma 4262 pg/ml/10(5) cells compared with a control of 0 (p < 0.05). In contrast, IL-1 and TNF did not seem to be associated with sepsis and were present in small amounts if at all. Additional stimulation with lipopolysaccharide (LPS) increased the serum and plasma induced release of PGE2 and IL-6 (p < 0.05). Serum and plasma from septic patients did, however, selectively reduce the maximum LPS-stimulated release of PGE2 and TNF (p < 0.05) compared with healthy donor monocytes. CONCLUSION: Serum and separated plasma from septic patients contained agents which induced monocytes to release mediators without additional stimulation, and modified their response to LPS. Removing plasma from septic patients may therefore reduce the deleterious effect of the inflammatory response.

Catecholamines↗
PubMed1995

NMR studies and restrained-molecular-dynamics calculations of a long A+T-rich stretch in DNA. Effects of phosphate charge and solvent approximations.

The nonamer duplex d(GCAAAAACG).d(CGTTTTTGC) was studied by 1H-NMR at 500 MHz. With the exception of the H5' and H5" sugar protons, all protons were assigned by two-dimensional NMR experiments [NOE spectroscopy (NOESY), double-quantum-filtered J-correlated spectroscopy (DQF-COSY) and total correlation spectroscopy (TOCSY)]. The exchange kinetics of the imino protons of the Watson-Crick base pairing were studied at 15 degrees C by measuring inversion-recovery rates under conditions of extensive ammonia base catalysis. Extrapolation to infinite base concentration gave anomalous long lifetimes for the A-tract in accordance with previous results [Leroy, J.-L., Charettier, E., Kochoyan, M. & Guéron, M. (1988) Biochemistry 27, 8894-8898]. On average, 11 NOESY distance constraints/nucleotide were evaluated using the complete relaxation matrix approach. Deoxyribose coupling constants were obtained from simulations of the DQF-COSY cross-peaks, assuming a rapid two-state equilibrium between a C2'-endo and C3'-endo conformer. The sugars were found to be predominantly in the C2'-endo conformation. The NMR-derived distance and torsion constraints were implemented into three different restrained-molecular-dynamics (rMD) protocols, two in vacuo, with different charges on the phosphate group and the third with the solvent explicitly included. All protocols displayed good convergence from different starting structures. The structures derived from the three protocols satisfied experimental restraints equally well and had similar final energies. Although the overall pattern of sequence dependence of helical parameters shows some resemblance in all structures, we find that the absolute amplitudes of the parameters are largely dependent on the rMD protocols, particularly the twist parameters. The minor groove distance P(n + 2)-P(m + 2) varies from 0.7 nm to 1.2 nm in the three protocols. Still the NOESY-derived anomalously short distances AH2(n)-H1'(m + 1) and AH2(n)-H1'(n + 1), n and m denote complementary residues, which are assumed to be indicative of a compressed minor groove, are kept in all calculated structures.

Base Composition↗
PubMed1995

Mechanochemical study of NaDNA and NaDNA-netropsin fibers in ethanol-water and trifluoroethanol-water solutions.

Highly oriented calf-thymus NaDNA fibers, prepared by a wet-spinning method, were complexed with netropsin in ethanol-water and trifluoroethanol (TFE)-water solutions. The relative fiber length, L/L0, was measured at room temperature as a function of ethanol or TFE concentration to obtain information on the B-A conformational transition. The B-A transition point and transition cooperativity of the fibers were calculated. The binding of netropsin to NaDNA fibers was found to stabilize B form and to displace the B-A transition to higher ethanol concentration, as indicated by its elongational effect on the fiber bundles. An increased salt concentration was found to reduce netropsin binding. In netropsin-free ethanol solution, the dissociation of bound netropsin from the DNA fibers was observable. Pure B-NaDNA fibers were found to be more stable in TFE solution than in ethanol solution. This was interpreted as being due to a different steric factor and a larger polarity of TFE compared with ethanol, resulting in its smaller capacity to reduce the water activity and dielectric constant of the medium in the immediate vicinity of DNA fibers. Therefore, the effect of netropsin binding on the B-A transition of NaDNA fibers became less obvious in TFE solution. In another series of experiments, L/L0 was measured as a function of temperature to obtain information on the helix-coil transition, or melting, as well as the B-A transition of NaDNA and NaDNA-netropsin fibers. The melting temperature and helix-coil transition width were calculated from the melting curves. A phenomenological approach was used to describe the melting behavior of the fibers in and around the B-A transition region. The effect of netropsin on the melting of DNA fibers was attributed mainly to the stabilization of B-DNA and to a higher melting cooperativity in the B-DNA region.

Animals↗
PubMed1995

Changes of carbohydrate-deficient transferrin in chronic alcoholism.

Compared with other well established liver enzyme parameters, carbohydrate-deficient transferrin (CDT) offers a new method for the identification of chronic alcoholism. The dependence of CDT and alcoholism/abstinence was studied in 29 controls and 64 alcoholics (both groups comprising men and women). In contrast to the currently used parameters GOT, GPT, gammaGT, LDH and MCV, CDT measures chronic alcoholism exclusively. CDT is dependent on sex but not age. In chronic alcoholism its rate increases significantly, but drops quickly after a short time of abstinence. CDT variations may be a specific and sensitive indicator of alcoholism or abstinence and possibly the duration.

Adult↗
PubMed1995

[Thallium scintigraphy of the myocardium. Uniform research protocols of the Austrian Society for Nuclear Medicine].

A uniform protocol for thallium scintigraphy of the myocardium has been issued in Austria to avoid difficulties in interpreting results and to avoid repeated examinations to save expenses and radiation burden. From the beginning of 1995 this protocol will be used in the Austrian departments of Nuclear Medicine, differences from this protocol have to be mentioned separately. In this protocol the procedure of examination, bicycle and pharmacological stress testing and vasodilatation, acquisition techniques for planar and SPECT imaging, data processing and quality control of devices are defined.

Adenosine↗
PubMed1994

Infrared linear dichroism studies of DNA-drug complexes: quantitative determination of the drug-induced restriction of the B-A transition.

The B-A transition of films or fibers of NaDNA occurs at a relative humidity of 75-85%. The fraction of DNA that changed the conformation from B to A form can be determined quantitatively by infrared linear dichroism. DNA-binding drugs can 'freeze' a fraction of DNA in the B form. This fraction of DNA is in the B form and cannot be converted to A-DNA even at a reduced relative humidity of 54%. The 'freezing' potentiality of various drugs can be described by the 'freezing' index, FI, expressed in base pairs per added drug. Drugs with a high value of FI (more than eight base pairs per drug) were observed among both intercalating and groove-binding drugs. High values of FI imply restriction of the conformational flexibility of DNA significantly going beyond the binding site of the drug. This long-range effect of drugs on the conformational flexibility of DNA may be connected with the molecular mechanism of drug action. The freezing index FI is a new quantitative parameter of drug-DNA interaction that should be considered as a valuable tool for drug design.

Antibiotics, Antineoplastic↗
PubMed1993

Structure and drug interactions of parallel-stranded DNA studied by infrared spectroscopy and fluorescence.

The infrared spectra of three different 25-mer parallel-stranded DNAs (ps-DNA) have been studied. We have used ps-DNAs containing either exclusively dA x dT base pairs or substitution with four dG x dC base pairs and have them compared with their antiparallel-stranded (aps) reference duplexes in a conventional B-DNA conformation. Significant differences have been found in the region of the thymine C = O stretching vibrations. The parallel-stranded duplexes showed characteristic marker bands for the C2 = O2 and C4 = O4 carbonyl stretching vibrations of thymine at 1685 cm-1 and 1668 cm-1, respectively, as compared to values of 1696 cm-1 and 1663 cm-1 for the antiparallel-stranded reference duplexes. The results confirm previous studies indicating that the secondary structure in parallel-stranded DNA is established by reversed Watson--Crick base pairing of dA x dT with hydrogen bonds between N6H...O2 and N1...HN3. The duplex structure of the ps-DNA is much more sensitive to dehydration than that of the aps-DNA. Interaction with three drugs known to bind in the minor groove of aps-DNA--netropsin, distamycin A and Hoechst 33258--induces shifts of the C = O stretching vibrations of ps-DNA even at low ratio of drug per DNA base pair. These results suggest a conformational change of the ps-DNA to optimize the DNA-drug interaction. As demonstrated by excimer fluorescence of strands labeled with pyrene at the 5'-end, the drugs induce dissociation of the ps-DNA duplex with subsequent formation of imperfectly matched aps-DNA to allow the more favorable drug binding to aps-DNA. Similarly, attempts to form a triple helix of the type d(T)n.d(A)n.d(T)n with ps-DNA failed and resulted in the dissociation of the ps-DNA duplex and reformation of a triple helix based upon an aps-DNA duplex core d(T)10.d(A)10.

Base Composition↗
PubMed1993

[Prognosis and epidemiology of malignant hemangioendotheliomas of the thyroid gland].

Five new cases of malignant hemangioendothelioma of the thyroid are reported. This rare malignant tumor is described predominantly in regions with endemic goiter such as the Alpine zone. The estimated incidence of the disease is between 0.15 and 0.25 per 100,000 inhabitants per year for Western Austria. Two of the five patients were heavily exposed to vinyl chloride occupationally for 9 and 30 years respectively. Surgically, a R-0 resection was performed in two patients, R-1 in two, and R-2 in one patient. Postoperative radiotherapy was given in four cases. The tumor doses were between 58 and 65 Gy. Three patients received the sensitizer razoxane in addition. Local tumor control was achieved in 4 of 5 patients. The survival times of the 5 patients were 78, 68+, 38+, 7.5 and 3 months. Two patients are still alive after 68 and 38 months. This small series may indicate that the outcome of the disease may not be uniformly deleterious and the resistance to radiotherapy reported in the literature [3, 10] is debatable.

Aged↗
PubMed1993

Sonographic observation of pulmonary infarction and early infarctions by pulmonary embolism.

Fifty-eight consecutive patients with clinical symptoms of pulmonary embolism/infarction were examined by ultrasound as the first imaging modality. The diagnosis was confirmed in 35 patients by ventilation-perfusion scintigraphy; 13 underwent pulmonary angiography for verification of clinical diagnosis. Seven patients died, necropsy was performed and the diagnosis of pulmonary embolism was confirmed in six cases; three patients were submitted to transthoracic lung biopsy. Intercostal space and an additional small pleural effusion in 48% of the examined patients served as a sonic window for the 5 MHz sector scanner. In 42 of the 54 cases with a final diagnosis of pulmonary embolism/infarction a total of 69, hypoechoic, lesions with a pleural basis were detected. These were conspicuous, predominantly triangular, of a mean size 4.6 x 3.7 cm (range 9 x 8 to 2 x 1.5). A hyperechoic structure with reverberation artefacts suggestive of air was frequently visible in the centre: a sign of segmental involvement. The ultrasound examination yielded a true positive result in 41 cases. The overall sensitivity was 98% and the specificity 66%. The prevalence of pulmonary embolism was 83% and the diagnostic accuracy 90%. This suggests that chest sonography can be an efficient technique in the detection of pulmonary infarction.

Adult↗