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Biomedical subjects

J Frank

Publications and source records attributed to J Frank.

At least 379 records · Page 21Linked to original sources
PubMed1982

Covalent addition of H2O, enzyme substrates and activators to pyrrolo-quinoline quinone, the coenzyme of quinoproteins.

The fluorescence excitation and the adsorption spectrum of 2,7,9-tricarboxy-1H-pyrrolo [2,3-f]quinoline-4,5-dione (pyrrolo-quinoline quinone, PQQ), measured in the pH range 7.0-10.0, are quite different. However, when the temperature of the solution is lowered, the shape and maxima of these spectra become more similar. 1H-NMR in 2H2O revealed a temperature-dependent equilibrium between PQQ and a hydrated form. Evidence is presented that low temperature favours the formation of the fluorescing species which is PQQ, hydrated at the C-5 position. Even further hydration is possible since absorption, fluorescence and NMR spectroscopy of PQQ in borate buffer pH 10.0 reveal additional hydration at the C-4 position, pointing to a dihydrate. PQQ also reacts with quinoprotein enzyme substrates and activators. Spectroscopic measurements showed the existence of 5-alkoxy-5-hydroxy-PQQ and 5-amino-5-hydroxy-PQQ in the presence of alcohols and 2 M NH4Cl, pH 9.0, respectively. In the latter case, the existence of 5-imino-PQQ could also be demonstrated. Addition compounds with amines appear to be unstable. The amines become probably oxidized because pyrrolo-quinoline quinol (PQQH2) was found as the reaction product. On the other hand, an addition compound containing an imino bond could be isolated after addition of urea to a PQQ solution. Spectral characteristics of PQQ and its addition compounds are presented since these data are necessary for the spectral analysis of quinoproteins and the quantitative estimation of coenzyme.

Chemical Phenomena↗
PubMed1982

[Thyroid other endocrine and disorders in a general internal medicine group practice].

Retrospective analysis of 3397 patients of a general group practice revealed thyroid disease in 5.8% and other endocrine disease (including diabetes) in 2%. Of the total of 6629 diagnoses, one out of 25 was an endocrinopathy. Every 35th practice patient had an endocrine disease which required treatment. Endocrine laboratory tests were ordered in every 7th patient. Diabetes mellitus (1.7%), hyperthyroidism (0.38%), hypothyroidism (0.53%) and euthyroidism after goiter operation (1.4%) were the most frequent endocrine problems recorded. Euthyroid goiter was relatively rare (4%), probably because it was often considered an irrelevant finding and not coded for. The thyroid gland was therefore the most frequently affected endocrine organ and diabetes mellitus the most prevalent endocrine dysfunction. Compared with other diseases, endocrine problems were of intermediate prevalence. The analyzed group practice had relatively young patient population, which may account for the surprisingly low prevalence of diabetes mellitus. On the whole, however, the prevalence of various diseases in this group practice compared well with statistics in representative samples of Swiss medical practices.

Adolescent↗
PubMed1982

Dimeric arrangement and structure of the membrane-bound acetylcholine receptor studied by electron microscopy.

The acetylcholine receptor protein (AChR) from the electric organ of Torpedo marmorata is studied in its membrane-bound form by electron microscopy and single-particle image averaging. About half the molecule protrudes from the membrane surface by approximately 5 nm. The low-resolution 3-D structure of this hydrated portion, including its handedness, can be deduced from averaged axial and lateral projections and from freeze-etched membrane surfaces. In native membrane fragments, a dimeric form of the AChR is observed and the relative orientation of the AChR monomers within the dimer is established. The dimers disappear upon disulfide reduction of the membrane preparations, whereas the average axial projections of the AChR monomer remain unaffected. Since the existence of disulfide bonds linking AChR monomers between their respective delta-subunits is well documented, the approximate position of the delta-subunit within the low-resolution structure of the AChR molecule can be deduced from the structure of the dimers.

Animals↗
PubMed1982

A refined quaternary structure of Androctonus australis Hemocyanin.

The quaternary structure of the (4 X 6)-mer hemocyanin from the Scorpion Androctonus australis previously published [Lamy, J., Bijlholt, M. M. C., Sizaret, P.-Y., Lamy, J., and van Bruggen, E. F. J. (1981) Biochemistry, 20, 1849-1856] has been refined. The relative positions in the half molecule of subunits Aa 3A and Aa 3B compared to those of Aa 3C and Aa 5B have been established by double labeling of the (2 X 6)-mer with binary mixtures of subunit-specific Fab fragments. The results show that subunits Aa 3B and Aa 5B are located in the same hexamer while Aa 3A and Aa 3C are in the other half of the (2 X 6)-mer. The choice of the enantiomer was deduced from a careful examination of electron micrographs of the native molecule. Finally a position was assigned to each of the 24 subunits on the flip and flop faces as defined by Van Heel and Frank [Ultramicroscopy, 6, 187-194 (1981)].

Animals↗
PubMed1981

Computer averaging of electron micrographs of 40S ribosomal subunits.

An enhanced lateral view of the 40S ribosomal subunit of HeLa cells has been obtained by computer averaging of single particles visualized in the electron microscope. Application of crystallographic criteria to independent averages shows that the reproducibility of the result is comparable to that obtained for thin, stained protein crystals by conventional Fourier filtration methods.

Computers↗
PubMed1981

Rapid automated determination of D-penicillamine in plasma and urine by ion-exchange high-performance liquid chromatography with electrochemical detection using a gold electrode.

A high-performance liquid chromatographic method for the determination of D-penicillamine in plasma and urine has been developed, based on separation on a cation-exchange resin followed by an amperometric detection of the SH group of D-penicillamine oxidized on a gold electrode. The method has been automated and separations from plasma and urine take 7 and 9 min, respectively. The detection limits are 0.05 micrograms/ml in plasma and 0.2 micrograms/ml in urine, with a coefficient of variation of 2.9% (n = 10).

Chromatography, High Pressure Liquid↗
PubMed1981

Use of multivariate statistics in analysing the images of biological macromolecules.

We have developed a new technique of analysis that allows automatic classification of molecule images according to subtle differences. Computer alignment and multivariate statistical methods were used to analyze electron micrographic images of horseshoe crab hemocyanin half-molecules. The molecule projections fell into four distinct classes related to four different positions of the molecule on the grid. Averages obtained for each images subset are interpreted in terms of a three-dimensional model arrangement for the four subunits forming the half-molecule.

Animals↗
PubMed1981

The radiological assessment of arm muscle and fat stores in normal and malnourished patients.

Radiological assessment of arm fat and muscle stores was performed in 46 controls and 10 malnourished patients. Values for arm fat and muscle thickness were obtained. In malnourished patients there was no significant correlation between fat estimation from the radiograph and measurement with skinfold calipers. Significant correlation between arm muscle circumference measurement and radiological muscle thickness however was found (P less than 0.05). Radiological assessment of arm muscle is a simple and useful test of muscle protein depletion in malnourished patients.

Adipose Tissue↗
PubMed1981

Quinoprotein alcohol dehydrogenase from a non-methylotroph, Acinetobacter calcoaceticus.

Acinetobacter calcoaceticus grown on ethanol contains an NAD(P)+-independent alcohol dehydrogenase which resembles methanol dehydrogenase from methylotrophic bacteria in many respects. Likewise, the prosthetic group of this enzyme appears to be identical to that of methanol dehydrogenase, namely, pyrrolo quinoline quinone. The organism is unable to grow on methanol, which means that quinoprotein alcohol dehydrogenases are not restricted to methylotrophs. Arguments are presented for the idea that quinoprotein alcohol dehydrogenases exist in other alkane- or alcohol-grown bacteria. Although the enzyme from A. calcoaceticus can be best compared with that from Rhodopseudomonas acidophila in that both have very low affinities for methanol and are activated by aliphatic amines, the two enzymes are immunologically and electrophoretically unrelated. Furthermore, the A. calcoaceticus enzyme shows the broadest substrate specificity hitherto known for this type of enzyme in that it also oxidizes higher aldehydes. The extent of hydration of aldehydes cannot account for the aldehyde substrate specificity of these enzymes but the concept of a dual substrate specificity for alcohols and aldehydes can explain this very well. The different properties of the two enzymes compared with those of methanol dehydrogenases cannot be ascribed to the presence of iron as both enzymes contained a negligible amount of this metal.

Acinetobacter↗
PubMed1981

Characterization of the second prosthetic group in methanol dehydrogenase from hyphomicrobium X.

Procedures are described for preparing 2,7,9-tricarboxy-1H-pyrrolo [2, 3-f]quinoline-4,5-diol (pyrrolo-quinoline quinol) from 2.7,9-tricarboxy-1 H-pyrrolo[2,3-f]quinoline-4,5-dione (pyrrolo-quinoline quinone). When methanol dehydrogenase is denatured, two compounds are liberated which have the same properties as the quinone and quinol mentioned above. On analysing the extract by high-performance liquid chromatography, one molecule of the quinone and one molecule of the quinol per enzyme molecule are found. Mixtures of pyrrolo-quinoline quinone and pyrrolo-quinoline quinol at high pH produce the semiquinone form and, under certain conditions, a diamagnetic complex. Since electron spin resonance (ESR) shows that methanol dehydrogenase contains the semiquinone and the absorption spectrum suggests the presence of a diamagnetic dimer, it is tentatively concluded that the two prosthetic group molecules in the enzyme interact with each other. NMR experiments of pyrrolo-quinoline quinone in 2H2O demonstrate that it is partly hydrated, most probably at the C-5 position. Although methanol adds in the same way, it is still questionable whether the product of this addition plays a role in the mechanism of the enzymic reaction. Potentiometric titrations show a midpoint potential of the quinone/quinol couple of + 90 mV at pH 7.0 and the formation of the semiquinone as an intermediate in the titration at pH 13.0.

Alcohol Oxidoreductases↗
PubMed1980

The prosthetic group of methylamine dehydrogenase from Pseudomonas AM1: evidence for a quinone structure.

The g-value and linewidth of ESR spectra of methylamine dehydrogenase (primary-amine:(acceptor) oxidoreductase (deaminating) EC 1.4.99.-) and methanol dehydrogenase (alcohol:(acceptor) oxidoreductase, EC 1.1.99.8) are very similar. This similarity is also reflected in electron-nuclear double resonance (ENDOR) results, the coupling constants of two protons in one enzyme equalling those in the other. The presence of a third proton in the ENDOR spectrum of methylamine dehydrogenase suggests a different structure or a different kind of interaction which can be related to the finding that the resolved ROSTHETIC GROUP IS PROTEIN-BOUND. The bound prosthetic group has a high redox-potential, supporting the conclusion from the ESR and ENDOR results that it is a quinone derivative.

Electron Spin Resonance Spectroscopy↗
PubMed1980

Studies on methanol dehydrogenase from Hyphomicrobium X. Isolation of an oxidized form of the enzyme.

1. Double-reciprocal plots of initial reaction rates of methanol dehydrogenase [alcohol--(acceptor) oxidoreductase, EC 1.1.99.8] in vitro show patterns of parallel lines. The results with various methanol, ammonia and phenazine methosulphate concentrations can be described by an equation valid for a Ping Pong kinetic mechanism with three reactants. 2. The overall maximum velocity was the same for several primary alcohols, C(2)-deuterated ethanols and different electron acceptors, but it was significantly lower for C(1)-deuterated substrates. 3. Oxidation of the isolated enzyme with electron acceptors required the presence of ammonia and a high pH. The inclusion of cyanide or hydroxylamine during the incubation was essential to prevent enzyme inactivation. The absorbance spectrum of an oxidized form of the enzyme was clearly different from that of the isolated enzyme and the free radical was no longer present. On addition of substrate, the original absorption spectrum and electron-spin-resonance signal reappeared and a concomitant substrate oxidation was found. This reaction could be carried out at pH 7 and ammonia was not required. 4. Based on the activity of the enzyme with one-electron acceptors, the presence of a free radical and the kinetic behaviour, an oxidation of the enzyme via one-electron steps is proposed.

Alcohol Oxidoreductases↗
PubMed1980

The prosthetic group of methanol dehydrogenase. Purification and some of its properties.

Methanol dehydrogenases isolated from bacteria belonging to different classes of methylotrophs contain the same prosthetic group. A procedure for its purification from whole cells is given. The reduced and oxidized form of the enzyme from Hyphomicrobium X and those of the isolated group are compared and it is concluded that the latter indeed functions in the enzyme. Further evidence is presented that the prosthetic group is not a pterine or lumazine derivative, but a water-soluble nitrogen-containing quinone.

Alcohol Oxidoreductases↗