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Biomedical subjects

R Müller

Publications and source records attributed to R Müller.

At least 739 records · Page 41Linked to original sources
PubMed1981

Multiplicity of 3-hexulosephosphate synthase from bacterium MB 58. 1. Product-induced transition in velocity.

Purified 3-hexulosephosphate synthase (HPS) from the facultative methylotrophic Bacterium MB 58 exhibits a burst-like progress curve. The transition appears in an abrupt manner at physiological substrate concentrations. The following phase of lower activity again shows linear progress in the observation period. Effects of substrates, temperature or dilution on the enzyme can be ruled out as causes of this transition. However, it is obvious that it takes place after the same amount of product has accumulated. That the reaction product causes this diminution in velocity can be demonstrated by varying the enzyme concentration or the possibility for accumulating product or the product concentration itself. The substrates of HPS counteract this product-induced transition in that an increased amount of the former makes necessary an increased amount of the latter to trigger the transition. The shape of the progress curve and experiments with different amounts of in situ-generated or synthesized product show that no simple product inhibition is involved. For the explanation of all phenomena observed three enzyme forms showing different affinities for substrates and product are postulated. These forms may be interconverted into each other by substrates and product of HPS in a specific manner.

Aldehyde-Lyases↗
PubMed1981

Multiplicity of 3-hexulosephosphate synthase from bacterium MB 58. 2. Generation of complex kinetic characteristics.

3-hexulosephosphate synthase (HPS) from the facultative methanol-utilizing Bacterium MB 58 exhibits a complex kinetic behaviour characterized by intermediary plateau regions. This feature could be related to the existence of multiple enzyme forms. With the aid of gel chromatography or isoelectric focusing purified HPS has partially been separated into at least four fractions. The individual enzyme forms are characterized by different kinetic properties exhibiting either hyperbolic or sigmoidal response to substrate saturation. In the sum of their action these forms generate the complex shape of the kinetic characteristics. Furthermore, these forms were found to be interconvertible. After partial separation a new equilibrium between the conformers is established in each case. The multiplicity of HPS can be demonstrated in qualitatively the same manner with the purified enzyme and with freshly prepared crude extracts. Proteolytic modifications on the enzyme as a cause for the multiplicity could be ruled out. The multiple character of the enzyme is also evident at different pH-values showing two optima. At different temperatures, anomalies in the Arrhenius plot depending on the substrate concentration were observed. From the present data a qualitative model of regulating HPS in the methylotrophic metabolism is proposed. Accordingly, several stable states of the metabolism should be realized.

Aldehyde-Lyases↗
PubMed1980

The conformation of a large RNA fragment from the E.coli ribosomal 16S-RNA. An X-ray and neutron small-angle scattering study.

A large 12S RNA fragment which constitutes the 5' two-thirds of 16S-RNA from the E. coli 30S subunit has been investigated by small-angle X-ray and neutron scattering. The results indicate that in reconstitution buffer the 12S-RNA fragment has a molecular weight of 270,000 +/- 20,000 and a radius of gyration of 7.1 nm. The scattering data are compatible with the RNA being folded into two major domains with the shapes of two adjacent, quite similar cylinders.

Escherichia coli↗
PubMed1980

[Influence of (+)-cyanidanol-3 on the course of acute viral hepatitis (author's transl)].

A double-blind study was conducted in four hospitals to test the effect of (+)-cyanidanol-3 (Catergen) on the course of acute viral hepatitis. Activities of a number of enzymes, bilirubin levels and gamma-globulin concentrations, as well as elimination of HBs antigen in blood were measured serially in 73 patients with viral hepatitis, 37 being treated with the drug, 36 patients receiving a placebo. In addition, liver biopsies before and after treatment were compared (19 patients treated, 23 patients on placebo). There was no significant difference between the treatment and placebo groups with regards to morphological and biochemical changes.

Adolescent↗
PubMed1980

A critical analysis of kinetic data of 3-hexulosephosphate synthases. Michaelis-Menten or complex characteristics.

Investigations of the 3-hexulosephosphate synthase (HPS) from different methylotrophic bacteria have revealed apparent discrepancies in kinetic behaviour. In all methanol-utilizing species investigated by us the kinetic characteristics showed intermediary plateau regions. Therefore, this behaviour is assumed to be a general feature of the HPS from all non-methane-utilizing methylotrophic bacteria. However, this assumption is in contrast to the results of other authors. Both for Methylomonas M15 (SAHM et al. 1976) and Methylomonas aminofaciens 77a (KATO et al. 1977, 1978) MICHAELIS-MENTEN kinetics of the HPS were stated. To check the validity of our assumption we have analyzed the kinetic data given by others. Indications of the existence of intermediary plateau regions could be found with the enzyme from Arthrobacter globiformis (BYKOVSKAYA and VORONKOV 1977) and Methylomonas aminofaciens 77a (KATO et al. 1978). Furthermore, biphasic ARRHENIUS plots indicate a multiple character of the HPS from these species as could already be demonstrated with the enzyme from Bacterium MB 58 and Pseudomonas oleovorans. In addition, causes which may obscure the detection of intermediary plateau regions are demonstrated.

Aldehyde-Lyases↗
PubMed1980

[Does aircraft noise affect health?].

A field study of the Institute of Behavioral Sciences at the Federal Institute of Technology, Zürich, has verified that aircraft noise effects severe annoyance and inconvenience of airport area residents. This causes irritation, which manifests itself in numerous negative intentions, attitudes and opinions, in actions and meaures and even in psychosomatic disorders. Moreover noise exerts influence on vegetative reactions of persons performing different activities, mostly if they have to concentrate on a task.

Aircraft↗
PubMed1980

Calculation of average antibody affinity in anti-hapten sera from data obtained by competitive radioimmunoassay.

A method is described for rapid and precise determination of average antibody affinity in anti-hapten sera from the following data obtained by competitive radioimmunoassay (RIA): the molar hapten (inhibitor) concentration giving 50% inhibition of tracer-antibody binding under equilibrium conditions, the molar tracer concentration in the assay and the amount of tracer bound by the antibodies in the absence of inhibitor. Thus, no additional experiments are required once a competitive RIA has been established. As an example, the average antibody affinity constants for 2'-deoxyguanosine, O6-ethyl-guanosine, and O6-ethyl-2'-deoxyguanosine were determined in antisera raised against the respective nucleoside-protein conjugates.

Antibody Affinity↗
PubMed1980

Action of chronic peracetic acid (Wofasteril) administration on the rabbit oral mucosa.

Peracetic acid Wofasteril) is increasingly made use of as a disinfecting fluid. Because of its high effectiveness it has found widespread use in medical practice. The action of Wofasteril on the oral mucosa during long-term action is studied by aid of an "oral tank". After a test period of 11 months peracetic acid only caused a slight ballooning of the superficial layers and enhanced vascularization of the submucous tissue. The results of the experiment suggest the intraoral administration of peracetic acid in oral surgery and stomatology.

Acetates↗