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At least 1,207 records · Page 67Linked to original sources
PubMed1979

The ternary 5-S RNA complex of proteins L 18 and L 25. A small-angle X-ray scattering titration study.

The 5-S RNA (A) and the proteins L 18 (B) and L25 (C) from Escherichia coli ribosomes form a ternary complex of the type ABC with a stepwise stability constant, log K111 approximately equal to 6.5. This is indicated from X-ray scattering titrations recorded at 21 degrees C in ribosomal reconstitutional buffer. When the ternary ABC complex forms there is only a limited change in the scattering curve compared to that of 5-S RNA, indicating that 5-S RNA does not undergo a major conformational change during the complex formation. The increase in the radius of gyration from 3.61 nm (5-S RNA) to 3.95 nm (ABC complex) as well as the experimental scattering curve can be explained by models where it is assumed that the elongated L 18 and L25 models are quite far from the electron density centre and where the protein molecules interact mainly with the minor arms of the supposed Y-shaped 5-S RNA molecule.

Escherichia coli↗
PubMed1980

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↗
PubMed1975

[The supramolecular organization of oxyhemoglobin in erythrocytes. A small-angle x-ray scattering study].

From X-ray scattering diagrams of concentrated solutions of hemoglobin the pair-correlation function of the molecules is calculated. At a concentration of 324 g/l the distance between neighbouring molecules amounts to 65 A. The number of direct neighbours of one molecule is 9. The pair-correlation function cannot be described by the assumption of a lattice-cell-model; therefore, a lattice-vacancy-model with fluid order is proposed.

Erythrocytes↗
PubMedDate not supplied

[Mechanism of action of biogenic chloramines and hypochlorite on initial aggregation of blood platelets].

The antiaggregant action of two reactive oxidants N,N-dichlorotaurine (chloramine of biogenic type) and sodium hypochlorite on the initial ADP-induced aggregation of rabbit blood platelets has been studied. Platelet aggregation in the reconstructed platelet-rich plasma (PRP) was measured by the nephelometric method, and the aggregation index was an increase in the intensity of small-angle light scattering. The introduction of chloramine at comparatively small concentrations (no greater than 1 mM active chlorine) directly into the reconstructed platelet-rich plasma induces the suppression of the initial aggregation (formation of small aggregates) several times stronger than in the case of its preliminary incubation with plasma alone. This suggests that N,N-dichlorotaurine exerts its antiaggeregant action on the platelet-rich plasma by direct interaction with cells. The effects of the inhibition of platelet aggregation in two variants of introduction of high concentrations of N,N-dichlorotaurine do not significantly differ. In this case a great amount of residual chloramine remains in the plasma, which just induces the suppression of platelet aggregation during subsequent reconstruction of the platelet-rich plasma. Similar data have been obtained in the study of the antiaggregant action of hypochlorite. N,N-Dichlorotaurine and hypochlorite at final concentrations of 0.2-0.3 and 0.15 mM, respectively, inhibit strongly the initial aggregation of isolated platelets (approximately 2 x 10(8) cells in 1 ml) preliminarily activated for 1.5 min by the addition of 100-500 nM ADP. However, the antiaggregants show a more profound suppression of aggregation of unstimulated platelets. The antiaggregant effects of N,N-dichlorotaurine and hypochlorite are probably due to the oxidative modification of sulfur-containing groups in platelet plasmatic membrane.

Adenosine Diphosphate↗
PubMedDate not supplied

[Analysis of fractal properties of globular protein surfaces by means of small-angle x-ray scattering].

The "cube method" [M. Yu. Pavlov, B. A. Fedorov, Biopolymers, 22, 1507, 1983] has been used to calculate the intensity of the large-angle X-ray scattering from the volumes of several globular proteins. In the logarithmic plots of the scattered intensity curves from three of these proteins, there is a linear region at scattering angles corresponding to Bragg distances of from about 6.3 A to 21 A. This linear region possibly may be due to the fractal properties of the surfaces of these proteins on length scoles from 6.3 A to 21 A, and the fractal dimensions corresponding to the power-law scattering at these scattering angles have been evaluated.

Chymotrypsin↗
PubMed1986

Shape and quaternary structure of alpha-globulin from sesame (Sesamum indicum L.) seed as revealed by small angle x-ray scattering and quasi-elastic light scattering.

The alpha-globulin from sesame seed has a molar mass of 2.7 X 10(5) g mol-1, determined by x-ray scattering, and (2.8 +/- 0.3) 10(5) g mol-1, determined by quasi-elastic light scattering. The radius of gyration RG amounts to (4.1 +/- 0.1) nm and (3.9 +/- 0.2) nm as determined by Guinier approximation and from the distribution function D(x), respectively. The molecule has a Stokes radius Rs of (5.4 +/- 0.15) nm and a maximum dimension L of (11 less than L less than 15) nm. The translational diffusion coefficient D0(20),w and the ratio of fractional coefficients f/fmin amount to (3.95 +/- 0.12) X 10(-7) cm2 s-1 and 1.25, respectively. The quaternary structure of the protein molecule is approximated by a model consisting of six spherical subunits situated at the vertices of an octahedron having the symmetry 32.

Alpha-Globulins↗