Small-angle x-ray study of DNA-dependent RNA polymerase subunit alpha 2 from Escherichia coli.
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DNA-Directed RNA Polymerases↗
Biomedical subjects
I Pilz
Publications and source records attributed to I Pilz.
Small-angle X-ray studies of the quaternary structure of the lac repressor from Escherichia coli.
The quarternary structures of the lac repressor molecule from Escherichia coli and its tetrametic core, which can be derived from it by proteolytic cleavage, were studied in dilute solutions by small-angle X-ray scattering. The dimensions and general shape of the lac repressor and of the tetrameric core are reported. The core itself appears to be an elongated structure, and in the intact repressor the headpieces are located at its ends. The results ar derived from model calculations and from the following molecular parameters determined from the scattering curve and the pair distance distribution function: for lac repressor, radius of gyration 5.30 +/- 0.02 nm, radius of gyration of the cross section 2.20 +/- 0.03 nm, maximum diameter 18.0 +/- 0.5 nm, hydrated volume 329 +/- 20 nm3, relative molecular mass 149 000 +/- 15 000, for tetrameric core, radius of gyration 4.92 +/- 0.02 nm, radius of gyration of the cross section 2.24 +/- 0.03 nm, maximum diameter 16.0 +/- 0.5 nm, hydrated volume 278 +/- 15 nm3, relative molecular mass 120 000 +/- 10 000.
Escherichia coli↗
Small-angle X-ray study of DNA-dependent RNA polymerase subunit sigma from Escherichia coli.
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Chemical Phenomena↗
[Serum levels of 25-hydroxycholecalciferol (25-OH-D3) in children of different age groups (author's transl)].
Serum 25-OH-D3 levels were determined in 78 children aged 6 weeks to 15 years, in March 1977 and March 1978 in Vienna. The total number of probands was divided into age groups, each comprising a range of 3 years. The average value with 1 SD. found over the whole age range was 48.3 +/- 25.75 nmol/l (i.e. 19.4 +/- 10.34 ng/ml). Somewhat higher levels were found in the age groups 3 to 6 and 6 to 9 years, with a slight decrease in the later age groups, but no significant differences were detected. The obtained values seem to represent the "normal" 25-OH-D3 serum levels of our population in the above-mentioned age range.
Adolescent↗
[Problems of distinction of normal, arteficial and pathological structures in mature human placental villi. III. Morphometric studies in rhesus incompatibility (author's transl)].
Sections of human placental villi which were up to 80 micrometer in diameter were examined light microscopically and morphometrically. The villi were obtained by taking an aspiration biopsy of the attached placenta from 20 normal patients at term and from eight patients delivered at or before 37 weeks because of varying degrees of rhesus incompatibility. The distribution of three histological types of villi was determined. The intermediate villi from patients with erythroblastosis showed an increase in number and volume matching the severity of the disease. The intermediate villi also showed an increase in the amount of cytotrophoblasts, in the amount of materno-fetal diffusion surface area, in the thickness of syncytium, and in the number of Hofbauer cells. The terminal villi were not affected by erythroblastosis and the mature end villi showed a relative decrease in number. To obtain these results an optimal fixation technique was required.
Biopsy, Needle↗
Effect of cleaving interchain disulfide bridges on the radius of gyration and maximum length of anti-poly(D-alanyl) antibodies before and after reaction with tetraalanine hapten.
The small-angle x-ray scattering of solutions of rabbits IgG antibodies and their derivatives has been investigated. The reduction and alkylation of the native antibody cause a small increase of the molecular parameters, indicating a limited expansion of the molecule. Binding of native antipoly(D-alanyl) antibodies with hapten (80% saturation) causes a significant change of the quaternary structure, expressed by a decrease in the maximum diameter of about 2 nm, of the radius of gyration by 5.5%, and of the volume. The same antibodies, in which the single inter-heavy-chain disulfide bridge was opened by reduction and carboxamidomethylation, do not show any significant decrease in the overall molecular parameters upon reaction with hapten, except for a local structural change in a part of the molecule. These data lend further support to the notion that binding of hapten induces a conformational transition in its specific antibodies and suggest that the opening of the interchain disulfide bridges affects that transition. The dimensions of the intact antibodies calculated from measurements of small-angle x-ray scattering at low concentrations agree closely with those obtained from crystallographic studies.
Alanine↗
Studies by small-angle X-ray scattering of the quaternary structure of the 24-S component of the haemocyanin of Astacus leptodactylus in solution.
The haemocyanin of Astacus leptodactylus was studied in several buffers at three pH values. The best stability and lowest mean deviation on repeating the measurements were found at pH 7.2 in a Tris-HCl buffer. The following molecular parameters were determined: radius of gyration 6.90 nm, radius of gyration of the cross-section 3.87 nm, maximum dimension 21.5 nm, relative molecular mass 854000, volume 1440 nm3, hydration 0.27 g H2O/g protein. The theoretical scattering curves of a large number of models were calculated to find one fitting these data and the experimental scattering curve. The model with the best agreement was compared with an electron micrograph.
Animals↗
[Rickets prophylaxis by daily administration of vitamin D tablets (author's transl)].
The efficiency of a daily vitamin D prophylaxis with tablets ("Laevovit D3"), containing 1000 I.U. cholecalciferol was studied in newborn babies (most of them "prematures") over a period of about 5 weeks. The blood-values of 25-hydroxycholecalciferol were taken as parameter and determined 1 week and 5 weeks after the start of vitamin D prophylaxis. The data obtained were--with very few exceptions-- in a range considered to be protective against development of vitamin D deficiency. No significant difference could be found comparing vitamin D prophylaxis with these "microtablets" vs. liquid vitamin D preparations.
Female↗
[Plasma 25-hydroxycholecalciferol after daily vitamin D administration in comparison with massive single-dose prophylaxis (author's transl)].
The effect of daily administration of 1200 IU vitamin D3 was compared with the response to a single oral dose of 200,000 IU in 21 young infants by determination of the plasma 25-OHCC levels. After about one week the mean value recorded in group 1 was 27 +/- 13 ng/ml; the corresponding value in group 2 was 127 +/- 78.4 ng/ml. At the second control examination about one month subsequently, the mean values were 61 +/- 26.2 ng/ml and 104 +/- 69.0 ng/ml respectively. The wide range of values found in the single-dose group clearly demonstrates the advantage of daily vitamin D administration for routine prophylaxis against rickets in infancy.
Administration, Oral↗
Small-angle X-ray studies of a human immunoglobulin M.
The conformation of a Waldenström immunoglobulin M (IgM) with antibody-like activity for X-ray contrast media, based on 3-amino-2,4,6-triiodobenzoic acid, was studied by small-angle X-ray scattering. The radius of gyration was determined as 12.1 nm, the maximum distance 35 nm, the volume 1900 nm3. A flat star-shaped model was found to be equivalent in scattering. Aggregation of IgM molecules seems to take place as side-by-side combinations of single molecules, manifesting itself as a relatively large increase of the radius of gyration and unchanged thickness of the flat aggregates.
Humans↗
A comparison of X-ray small-angle scattering results to crystal structure analysis and other physical techniques in the field of biological macromolecules.
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Apoferritins↗
[Small-angle X-ray-scattering investigation and structural-model study of the fatty-acid synthetase from pig liver (author's transl)].
The structure of the fatty acid synthetase from pig liver was studied on models based upon structural and functional properties selected from pertinent results available from numerous investigations carried out with fatty acid synthetases from this and other sources. When comparing small-angle X-ray-scattering curves calculated with these models and curves obtained from small-angle X-ray-scattering experiments carried out with the pig-liver enzyme, we tried to select a model which would lead to an acceptable correlation between the calculated and the experimental curves and at the same time fulfil the known structural and functional requirements. The comparison of the curves was started with a model of low complexity. The observed discrepancy, together with arguments from the structural and the functional properties, helped decide which is the next most reasonable model to be considered. This procedure was repeated for five models of increasing complexity. In the model which led to the best fit the multienzyme complex is composed of two halves in an assymetric conformation including hollow spaces. This highly anisotropic model would imply that the two halves change their conformation each time a synthetic cycle is completed and that the growing fatty acid is handed over from one half to the other.
Animals↗
Studies by small-angle X-ray scattering of the quaternary structure of the beta-haemocyanin of Helix pomatia.
Helix pomatia beta-haemocyanin was studied in solution by small-angle X-ray scattering. The following molecular parameters were determined: molecular weight = 9.02 X 10(6), volume = 14000 nm3, radius of gyration = 18.4 nm, radius of the spherical subunits = 2.5 +/- 0.2 nm. With these data, and with information of dissociation products described in a former paper, a model of the molecule was built whose theoretical scattering curve showed good agreement with the experimental one. The model consists of 160 spherical subunits of a radius of 2.5 nm; 12 rings each built up of 10 spheres form the outer wall of a hollow cylinder; 20 subunits are situated at the inner side of each end.
Animals↗
On the conformation of serine-specific transfer RNA. Studies by small-angle X-ray scattering and ultraviolet absorption of the molecule in solution.
The scattered X-ray intensities from dilute solutions of tRNASer (yeast) in 0.1 M Soerensen buffer at pH 7.0 were measured at 25 degrees C. The radius of gyration, molecular weight and volume were determined. A model equivalent in scattering is given. The change of the conformation of tRNASer by heating was followed by small-angle X-ray measurements and ultraviolet absorption in a temperature range 20-70 degrees C. The molecule begins to unfold at about 40 degrees C and 70 degrees C has a random coil conformation. Addition of magnesium stabilizes the tRNASer molecule. The reversibility of the melting process was also studied by both methods. An interesting effect was found by ultraviolet absorption: by heating the tRNASer solutions to 55 degrees C and 60 degrees C and subsequently slowly cooling, the melting curves lie at higher absorption values than the corresponding cooling curves. The small-angle data and optical properties of tRNASer are compared with those of tRNAPhe which has already been thoroughly investigated.
Binding Sites↗
Small-angle X-ray studies of the human immunoglobulin molecule Kol.
The conformation of the human immunoglobulin molecul Kol [IgG I, kappa2 gamma2, Gm(f)+] was studied by small-angle X-ray scattering in 0.15 M NaCl solution. The radius of gyration was found to be 5.84 +/- 0.04 nm, the volume 329 +/- 15 nm3 and the molecular weight 150 000 +/- 10 000. Information on the overall shape was obtained by comparing the experimental scattering curve with the calculated curves for various models. The models were obtained by arranging the models found for the Fab and Fc fragments of the same immunoglobulin molecule in a different manner. A model which fits all the date and the form of the experimental scattering curve is presented.
Female↗
Studies by small-angle x-ray scattering of the quaternary structure of dissociation products of the beta-haemocyanin of Helix pomatia.
Helix pomatia beta-haemocyanin was split into dissociation products by varying the pH and the ionic strength. The purity of the solution was checked in an ultracentrifuge. Two defined dissociation products were studied in solution by small-angle X-ray scattering. In Tris-HC1 buffer, pH 8.0 and ionic strength 1 M, the following parameters of the dissociation product (tenths) could be determined: molecular weight = 7 x 10(5), volume = 1350 nm3, radius of gyration = 9.0 nm, maximal distance = 28.3 nm, radius of the spherical subunits about 2.6 nm, number of the subunits approximately 19. Tris-HC1 buffer, pH 8.7 and ionic strength 0.01 M, yielded dissociation products (twentieths) with the following parameters: molecular weight = 3.5 x 10(5), volume = 635 nm3, radius of gyration = 7.5 nm, maximal distance = 21.9 nm, radius of the spherical subunits about 2.5 nm. With this information, the assumption that the larger fragment was double the smaller one and the latest biochemical and morphological results, theoretical scattering curves of models were calculated and compared with the experimental curves. Two models are suggested which argee well with the dissociation products in radius of gyration and scattering.
Animals↗
Small-angle X-ray studies of the Fab and Fc fragments from the human immunoglobulin molecule Kol.
The conformation of the Fab and Fc fragments from the human immunoglobulin molecule Kol [IgI I, chi2gamma2, Gm(f)+] was studied by small-angle x-ray scattering in solution. The fragments were studied in 0.02 M Tris-HCl buffer. For the Fab fragment the radius of gyration was found to be 3.15 +/- 0.15 nm, the volume to be 75 +/- 8 nm3. For the Fc fragment the respective values were 3.15 +/- 0.15 nm for the radius of gyration and 91 +/- 8 nm3 for the volume. A large number of models were calculated for both fragments to find models which fit these data and have the same scattering curve. The models with the best agreement were compared with the models found for the crystalline state by crystal x-ray studies.
Humans↗