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Biomedical subjects

A Rupprecht

Publications and source records attributed to A Rupprecht.

At least 55 records · Page 3Linked to original sources
PubMed1989

Interaction of water with oriented DNA in the A- and B-form conformations.

High resolution 2H nuclear magnetic resonance (NMR) was used to investigate the interaction of D2O with solid samples of uniaxially oriented Li-DNA (B-form DNA) and Na-DNA (A- and B-form DNA). At low levels of hydration, 0 approximately 4 D2O/nucleotide, the 2H spectra shows a very weak (due to short T2) broad single resonance, suggestive of unrestricted rotational diffusion of the water. At approximately 5 or more D2O/nucleotide, the Li-DNA (B-form) spectra suddenly exhibit a large doublet splitting, characteristic of partially ordered water. With increasing hydration, the general trend is a decrease of this splitting. From our analysis we show that the DNA water structure reorganizes as the DNA is progressively hydrated. The D2O interaction with Na-DNA is rather different than with Li-DNA. Below 10 D2O/nucleotide Na-DNA is normally expected to be in the A-form, and a small, or negligible splitting is observed. In the range 9-19 D2O/nucleotide, the splitting increases with increasing hydration. Above approximately 20 D2O/nucleotide Na-DNA converts entirely to the B-form and the D2O splittings are then similar to those found in Li-DNA. We show that the complex Na-DNA results obtained in the range 0-20 D2O/nucleotide are caused by a mixture of A- and B-DNA in those samples.

DNA↗
PubMed1989

[The axillary brachial plexus block. A study of 178 patients].

Success rates and complications were studied in 178 patients scheduled for brachial block. METHODS. Patients of both sexes aged 9 to 79 years received axillary blocks in order to permit typical surgical procedures of the hand an forearm. The block was performed using the transarterial method described be Dejong. Half of the local anesthetic was administered anterior to and half posterior to the axillary artery. The incidence of successful blocks, latency time, and systemic complications were investigated; 14 days after the blocks, motor function and sensation were examined in order to evaluate the local neurological status. RESULTS. The rate of successful blocks averaged 79% using 40 ml 1% mepivacaine after 12 min latency; this rate was increased to 89% by administering a further 20 ml 1% mepivacaine. Disagreeable sensations from the operative field occurred in 5% and mild symptoms of cerebral toxicity in 2.8% of cases; 1.6% of patients had cardiovascular disturbances such as hypotension or arrhythmias. Local complications such as hematomas were found in 17.5% local pain in the axillary region in 15%, and long-lasting paresthesias in 12% of cases. DISCUSSION AND CONCLUSIONS. The 90% rate of successful blocks is comparable to the range of 86-98% presented in the literature. The success rate depends on the definition of successful block, the experience of the anesthetist, and the volume and concentration of the anesthetic solution administered. The incidence of systemic cardiovascular complications was similar to that in the literature, but we observed fewer symptoms of cerebral toxicity.(ABSTRACT TRUNCATED AT 250 WORDS)

Adolescent↗
PubMed1988

Static disorder and librational motions of the purine bases in films of oriented Li-DNA.

Solid-state 2H nuclear magnetic resonance line shapes have been obtained from folded films of oriented Li-DNA molecules with the purine bases selectively labeled with deuterium at the 8-position. From line shape simulations, the static base tilts as well as the anisotropic motional amplitudes were determined as a function of hydration level and temperature. It was found that the average tilt angle of the bases is close to 0 degrees and at a hydration of ten water molecules per nucleotide the distribution width of tilt angles about this average cannot be larger than 9 degrees (standard deviation). A slightly increased distribution width is observed at low hydration levels. The motional amplitudes are hydration dependent, with the tilting motion ranging from 4 degrees for the driest, up to 15 degrees for the wettest sample, and slightly larger amplitudes are observed for the twisting motion. The amplitude of the twisting motion is unaffected by a temperature decrease down to -60 degrees C, in contrast to the tilting motion that is suppressed at low temperatures.

Animals↗
PubMed1988

Phosphorescence of adenosine and poly(riboadenylic acid). Evidence for dual emissions and n pi states.

Phosphorescence from the 9-adenylyl group in the form of microcrystalline powders of adenosine films of poly(riboadenylic acid) (poly(rA)) in hyaluronic acid has been studied at 77 K. For adenosine, clearly resolved vibronic structure consists of two progressions, A and B, with delta vA = 1363 cm-1 and delta vB = 1575 cm-1, correlated with in-plane C5-N7 and in-plane C4-C5 stretch, respectively. The relative strength of the progressions varies with excitation wavelength and this, together with the absence of a common origin, indicates the existence of two independent emitting states with 0-0' levels separated by either 300 or 1000 cm-1. Two different excitation spectra are observed lying below the normal (pi pi*) adsorption and one is assigned as a previously undetected 1(n pi*) transition. For poly(rA) films the emission band envelope is identical with that of adenosine but the vibronic structure is lost. Only one excitation peak is observed at 32.9 X 10(3) cm-1, identical with one of the adenosine spectra. The second adenosine excitation spectrum probably represents an intermolecular charge transfer transition. Comparison is made with the predictions of six semi-empirical MO calculations.

Adenosine↗
PubMed1988

Hydration of NaDNA by neutron quasi-elastic scattering.

Preliminary results of neutron quasi-elastic scattering experiments are reported for hydrated paracrystals of sodium deoxyribonucleic acid (NaDNA). The samples were investigated at two water contents: 3.5 +/- 1.0 and 9.5 +/- 1.5 mol H2O per mole nucleotide. The results of the scattering experiments were almost independent of whether the NaDNA fibers were oriented parallel or perpendicular to the momentum transfer. The data indicate that at the lower hydration the water molecules do not diffuse appreciably on the time scale of the neutron measurements (approximately 3 X 10(-10) s). At the higher hydration the water molecules diffuse isotropically in a sphere of 9 A in diameter with a diffusion coefficient of (5 +/- 2) X 10(-6) cm2 s-1.

DNA↗
PubMed1986

Hydration of sodium hyaluronate, NMR study of an oriented sample.

A sample of highly oriented Na-hyaluronate was prepared with a wet--spinning method and equilibrated to 75% relative humidity. Its proton NMR spectrum was recorded as a function of the angle theta between the hyaluronate helix axis and the external magnetic field. It appeared as a singlet with an angle-dependent line width expressed by delta v o + A(1-3cos2 theta)2. This reveals a residual intramolecular dipolar interaction of anisotropically rotating water molecules. The merging of the expected doublet into a single line is assumed to be caused by proton exchange between water molecules. The result indicates a hydration similar to that of many other fibrous biopolymers at comparable relative humidities.

Extracellular Matrix↗