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Biomedical subjects

M Hahn

Publications and source records attributed to M Hahn.

At least 289 records · Page 16Linked to original sources
PubMed1976

Radiation damage in tripalmitin layers studied by means of infrared spectroscopy and electron microscopy.

Structural deteriorations in biomembranes, as inevitably induced while structural information is gathered by electron optical methods, were evaluated by infrared spectroscopy. Tripalmitin model membranes were irradiated with 100 keV-electrons in an electron microscope. The intensity decay of group vibrations over the dose reveals the sequence of damage in the polar and nonpolar part of the molecule. The C-C backbone, being the most important structural feature, shows a significant latency effect up to 0.6 e-/A2 and is completely disordered by 3 e-/A2, corresponding to about three inelastic processes per molecule.

Electrons↗
PubMed1976

Inactivation of catalase monolayers by irradiation with 100 keV electrons.

A catalase monolayer adsorbed on a layer of arachidic acid deposited on a solid support was irradiated with 100 keV electrons simulating the conditions of electron microscopic imaging. Effective doses were calculated taking into account the angular and energy distribution of backscattered electrons. Enzymatic inactivation was chosen as the criterion for damage and was monitored by a rapid and quantifiable but nevertheless sensitive assay. Dose-response curves revealed that inactivation is a one-hit-multiple-target phenomenon, which is consistent with biochemical evidence for a cooperative function of subunits. The experimentally determined target size coincides fairly well with both calculated cross sections for inelastic interactions based on the atomic composition of catalase and with calculated cross sections for ionizing events based on the chemical bonds involved. This legitimates both types of calculations even for complex biomolecules.

Binding Sites↗
PubMed1975

Relevance of three-dimensional reconstructions of stain distributions for structural analysis of biomolecules.

The relevance of a three-dimensional model of a protein molecule is discussed in the context of artefacts which inevitably occur during the preparation and imaging process. It is emphasized that even under optimistic assumptions, there-construction of a structure complementary to a given spatial stain distribution cannot, at resolutions below 10-15 A, be regarded as being identical with the real protein structure.

Glutaral↗
PubMed1975

Evaluation of the asymmetry of renal sodium excretion in patients with renal artery stenosis.

Despite the fact that excretion and reabsorption fractions of sodium and water should express complementary aspects of the same renal process, calculation of ratios of excretion and reabsorption fractions in both kidneys can lead to differences in results. A theoretical analysis demonstrates that from the physiological point of view it is more correct to evaluate asymmetry on the basis of the ratios of reabsorption fractions. In 13 patients with renal artery stenosis, changes in reabsorption and excretion fractions of sodium, all osmotically active substances and water investigated before and after furosemide administration. The ratios of reabsorption fractions of sodium increased in 9 cases and syymmetry in function on the two sides was accentuated. It is suggested that separate investigation of tubular reabsorption of sodium and water in patients with renal artery stenosis should be combined with administration of furosemide and that the evaluation should be carried out on the basis of calculation of reabsorption fractions.

Adult↗