[Absence of small-angle maximums on the x-ray images of ocular lens tissue]. / Otsutstvie malouglovykh maksimumov na rentgenogrammakh tkani khrustalika glaza.

X-ray small-angle scattering study of bovine lens tissue was carried out. It was shown that X-ray patterns of lens cortical and nuclear native tissues did not contain the small-angle maxima. The maximum in the range of 15-20 nm Bragg distance appeared as a result of the lens tissue partial dehydration. Earlier such maximum was considered by some authors as the evidence of crystallin proteins short-range order in the native lens. Now it is confirmed to be a preparative artefact of dehydration. It was shown also that similar maximum in 15-20 range existed in the case of concentrated crystallin solutions. This indicates that supramolecular organization of crystallins in the native lens is not similar to that in the concentrated solution.

[Quaternary structure of histidine decarboxylase according to small-angle x-ray diffraction and electron microscopic findings]. / Chetvertichnaia struktura gistidindekarboksilazy po dannym rentgenovskogo malouglovogo rasseianiia i élektronnoi mikroskopii.

The data on small angle X-ray scattering with histidine decarboxilase (HDC) from Micrococcus sp. n. were analysed and a line of succesively improving approximations of the molecule shape was found: by oblate ellipsoid a:b:c = 1:10.63, by continuous cylinder and hollow cylinder with H = 50 A, 2R = 76 A, 2r = 8A. Biochemical data and electron micrographs of HDC obtained made possible to distinguish subunits and thus to increase resolution of the model. The model of the enzyme molecule consisting of three subunits is suggested, whose X-ray small angle scattering curve well agrees with the experimental one up to value S = 0.21 A-1.

[X-ray structural study of the effect of light on isolated bovine photoreceptor membranes]. / Rentgenostrukturnoe issledovanie vozdeistviia sveta na izolirovannykh fotoretseptornye membrany byka.

The structure of multilamellar films prepared by air-drying of bovine retinal rod photoreceptor membrane suspension has been studied by means of small-angle X-ray diffraction methods. No reliable photoreceptor membrane structure modifications were observed with 100 s temporal resolution after the illumination of the film consisting of dark-adopted membranes. The comparative study of air-dried films prepared from dark-adopted and bleached photoreceptor membranes revealed no difference in their structures too. The structure alterations of photoreceptor membranes were recorded in the case of high (damaging) doses of visible light acting on photoreceptor membranes in suspension.

[Comparative study of crystallins from the nucleus and cortex of the bovine ocular lens by the gel filtration and x-ray diffraction methods]. / Sravnitel'noe issledovanie kristallinov iadra i korteksa glaza byka metodami gel'-filtratsii i difraktsii rentgenovskikh luchei.

Water--soluble proteins (alpha-, beta H-, beta L- and gamma-crystallins) from the bovine lens nucleus and cortex were fractionated and compared by gel filtration on Sephadex G-200. X-ray diffraction patterns from concentrated gels of these proteins were obtained. It allowed to compare qualitatively the structures of different crystallins and also to identify the maxima on X-ray diffraction patterns of the lens intact tissue.

[Comparative study of bovine ocular lens proteins in native tissue and an extract using the x-ray diffraction method]. / Sravnitel'noe issledovanie belkov khrustalika glaza byka v nativnoi tkani i v ékstrakte metodom difraktsii rentgenovskikh luchei.

It has been shown that the maxima (Bragg-spacings 4,5-19 A) on the X-ray diffraction patterns of the bovine lens native tissues from nuclear and cortical parts are predominantly due to the water-soluble crystallin intramolecular structure. The structures of water-soluble and water-insoluble fractions from bovine lens nucleus and cortex were qualitatively compared. Reversible dependence of the lens water-soluble protein structure on water content in the system was demonstrated.

[X-ray diffraction in the intact isolated frog ocular lens]. / Difraktsiia rentgenovskikh luchei na tselom izolirovannom khrustalike glaza liagushki.

X-ray diffraction method has been applied for investigating ocular lens native tissue of the frog. X-ray diffraction patterns of intact lenses, their nuclei and cortices are similar and contain a set of concentric diffuse diffraction maxima. The most intensive of these maxima corresponding to the Bragg-spacings of 14.6, 9.1 and 4.6 A are presumably associated with intramolecular structure of lens proteins--crystallins. Intensive small-angle X-ray scattering and diffraction patterns isotropy indicates unavailability of crystallin molecule ordering or orientation in the lens. The shift of 14.6 A maximum up to 12.8 A being the result of nuclei drying shows the necessity of aqueous surrounding for these protein native structure maintenance.

[Acute angle x-ray scattering by phospholipid membranes after treatment with valinomycin]. / Rasseianie pod malymi uglami rentgenovskikh luchei fosfolipidnymi membranami pri vvedenii valinomitsina.

It has been found by means of small-angle X-ray analysis of oriented bilayers of synthetic dimyristoyl phosphatidyl choline that the introduction of valinomycin modifies their structure and these modifications depend on the phase state of lipid.

[Determination of the molecular weight and form of the molecule histidine decarboxylase by the method of small-angle x-ray scattering]. / Opredelenie molekuliarnogo vesa i formy molekuly gistidin-dekarboksilazy metodom rentgenovskogo malouglovogo rasseianiia.

Shape and molecular weight of histidine-decarboxylase from Micrococus sp. n. were studied by the method of X-ray small-angle scattering. The inertion radius of the molecule: Rg-2,93 nm. The shape of the molecule is adequately approximated by rotation ellipsoids of two possible variants: the elongated and flattened ones. The eccentricity in both cases is 1.6. The volume of the enzyme molecule V=190 nm3. The molecular weight of histidine-dexarboxilase obtained from the X-ray experiment M=102 000 c.u.

[Comparative x-ray diffraction study of the crystalline lens in a number of vertebrates including man]. / Sravnitel'noe rentgenovskoe difraktsionnoe issledovanie khrustalikov glaza v riadu pozvonochnykh vkliuchaia cheloveka.

X-ray diffraction method has been applied for comparative investigation of native structure of eye lens proteins (crystallins). X-ray diffraction patterns of the whole lenses and/or their nuclear parts were obtained for man and vertebrate animals. Crystalline lenses of the fishes Acerina cernua and Pelmatochromis kribensis, frog Rana temporaria, bull and man contain crystallins with a very similar secondary and tertiary structure, whereas lenses of chicks and the tortoise Testudo horsfieldi contain mainly crystallins with other structure. The results obtained reveal evolutionary conservatism of crystallin structure in fishes, amphibians and mammals. It was also concluded that there is no correlation between crystallin structure of the lens, elasticity of the latter and accommodation mechanism.

Small-angle X-ray solution-scattering studies on ligand-induced subunit interactions of the thiamine diphosphate dependent enzyme pyruvate decarboxylase from different organisms.

The quaternary structures of the thiamine diphosphate dependent enzyme pyruvate decarboxylase (EC 4.1.1.1) from the recombinant wild type of Saccharomycescerevisiae and Zymomonas mobilis and from germinating Pisum sativum seeds were examined by X-ray solution scattering. The dependence of the subunit association equilibrium on the pH and the presence of the cofactors thiamine diphosphate and magnesium ions were compared, and the differences between the catalytic properties of the different enzymes are discussed. The influence of amino acid substitutions at the cofactor binding site of the enzyme from Saccharomyces cerevisiae (E51 is substituted by Q or A and G413 by W) on the subunit association was examined. Low-resolution models of the P. sativum, Z.mobilis, and S. cerevisiae enzymes were evaluated ab initio from the scattering data. The enzyme from the bacterium and yeast appear as a dimer of dimers, whereas the plant enzyme is an octamer formed by two tetramers arranged side-by-side. The shape of the S. cerevisiae enzyme agrees well with the atomic structure in the crystal but suggests that the dimers in the latter should be tilted by approximately 10 degrees. The resulting modification of the atomic structure also yields a significantly better fit to the experimental solution scattering data than that calculated form the original crystallographic model.

Temperature dependent structural changes of intraphage T7 DNA.

The phenomena connected with the first phase transition step of the native T7 phage at 40 degrees-65 degrees C have been studied using various methods. In this temperature range a) the optical melting curve shows an absorption decrease, b) the maximum of the small-angle X-ray scattering characteristic for DNA packing disappears, c) there is a drop of biological activity and d) there are changes in the structure of the difference absorption spectra of native phages versus isolated DNA. All data are interpreted assuming a structural change of the DNA due to the release of its protein coat towards the end of the first phase transition step (at 60 degrees-65 degrees C in the case of M9 buffer). Above this temperature the intraphage DNA packing appears to be destroyed and the DNA structure seems to be similar to that in DNA solution.

Structure of bacteriophage T7. Small-angle X-ray and neutron scattering study.

Small-angle x-ray and neutron scattering techniques were applied to bacteriophage T7 solutions at different scattering densities. Scattering curves determined under a variety of experimental conditions were used to derive a set of parameters characterizing the shape, size, and weight of the whole phage particle and of its DNA and protein components. The T7 head has an icosahedral shape with an edge of 37.7 +/- 0.5 nm, a volume of (12.0 +/- 1.0) x 10(4) nm3, and a small tail amounting to 6--7% of the head volume. The intraphage DNA region is most probably a hollow sphere. The best fit to the data was obtained with a model in which the hollow sphere filled with a protein core with a diameter of 24 nm. The average degree of swelling (i.e., the ratio of the hydrated to the dry volume) of the particle is 2.3; the degree of swelling of the DNA component is higher, 3.2, and that of the protein part is lower, 1.2.

Structural conversions of crystallins under senile cataract, dehydration and UV-irradiation studied by X-ray diffraction.

By means of X-ray diffraction analysis, structural conversions of crystallins in human lens were detected in senile cataract and upon artificial dehydration of lens tissue. In senile cataract certain characteristics of the native three-dimensional structure of gamma- and beta-crystallins are completely lost, whereas during dehydration of lens tissue a small but significant contraction of these protein molecules takes place. Upon artificial UV-irradiation of bovine crystallins destructive changes are observed, which are very similar to those in cataract.

[A structural study of crystallins in the normal and cataractous crystalline lens by x-ray diffraction]. / Strukturnoe issledovanie kristallinov v normal'nom i kataraktal'nom khrustalike metodom difraktsii rentgenovskikh luchei.

Nucleus of the normal and cataractous human lenses were studied by means of the X-ray diffraction method. The conformational changes, as it is shown, take place during cataract formation. The similar as in senile cataract, conformational changes of bovine lens crystallins were induced by UV irradiation.

Loosening of the phage structure in a low ionic strength environment.

Structural parameters of phage T7 were compared in two frequently used Tris buffers of high and low ionic strength, in order to explain the different biological activity and drug-binding characteristics. Characteristics of the whole phage geometry were obtained by viscosimetry, static and quasi-elastic light-scattering and small-angle X-ray scattering. The latter method revealed dissimilarities in the intraphage DNA compactness, consistent with the findings of the optical absorption melting studies. Alterations in the particle dimensions determined in the same sample by different methods are discussed, and a model is constructed to explain the structural modifications that occur on lowering the ionic strength.