Laboratory multiple-crystal X-ray topography and reciprocal-space mapping of protein crystals: influence of impurities on crystal perfection.

Double-axis multiple-crystal X-ray topography, rocking-curve measurements and triple-axis reciprocal-space mapping have been combined to characterize protein crystals using a laboratory source. Crystals of lysozyme and lysozyme crystals doped with acetylated lysozyme impurities were examined. It was shown that the incorporation of acetylated lysozyme into crystals of lysozyme induces mosaic domains that are responsible for the broadening and/or splitting of rocking curves and diffraction-space maps along the direction normal to the reciprocal-lattice vector, while the overall elastic lattice strain of the impurity-doped crystals does not appear to be appreciable in high angular resolution reciprocal-space maps.

[Duodenogastric reflux in humans].

Human duodenogastric reflux (DGR) was comprehensively studied via measurement of gastric juice bile acid levels, manometric, endoscopic and X-ray study in health and benign gastrointestinal diseases and during exercise. DRG is shown to fall in the physiological events that have a biologically determined circadian rhythm. There was an association of DGR with gastric secretion.

Isolation and characterization of Rous sarcoma virus recombinant reverse transcriptase dimers.

Reverse transcriptase (RT) preparations containing various molecular forms of the enzyme consisting of alpha- and/or beta-subunits have been isolated from E. coli cells transformed with plasmid pMF14 containing the Rous sarcoma virus (RSV) pol gene. The three possible dimeric forms of the enzyme demonstrated DNA polymerase activity, the relative activities of the alphaalpha, betabeta, and alphabeta forms being about 1:3:4.

Macromolecular impurities and disorder in protein crystals.

The mechanisms by which macromolecular impurities degrade the diffraction properties of protein crystals have been investigated using X-ray topography, high-resolution diffraction line shape measurements, crystallographic data collection, chemical analysis, and two-photon excitation fluorescence microscopy. Hen egg-white lysozyme crystals grown from solutions containing a structurally unrelated protein (ovotransferrin) and a related protein (turkey egg-white lysozyme) can exhibit significantly broadened mosaicity due to formation of cracks and dislocations but have overall B factors and diffraction resolutions comparable to those of crystals grown from uncontaminated lysozyme. Direct fluorescence imaging of the three-dimensional impurity distribution shows that impurities incorporate with different densities in sectors formed by growth on different crystal faces, and that impurity densities in the crystal core and along boundaries between growth sectors can be much larger than in other parts of the crystal.

Refined structure of orthorhombic lysozyme crystallized at high temperature: correlation between morphology and intermolecular contacts.

The structure of orthorhombic hen egg-white lysozyme (HEWL) crystallized at 310 K has been refined at 1.7 A resolution. Large displacements of the side-chain atoms with respect to the tetragonal structure were observed in many places, in contrast to small displacements of the main-chain atoms.

[Molecular mechanisms of the biological effects of weak magnetic fields. V. Inactivation in vitro of recombinant Rous sarcoma virus reverse transcriptase under the combined action of weak direct and low-frequency alternating magnetic fields, adjusted to the cyclotron resonance of polar amino acid ions].

The effect of weak direct and alternative magnetic fields adjusted to cyclotron frequencies of ions of polar amino acids leads to a functional inactivation of the recombinant reverse transcriptase of Rous sarcoma virus, which is coupled with the proteolysis of this enzyme.

Crystal growth and crystallography.

Selected topics that may be of interest for both crystal-structure and crystal-growth communities are overviewed. The growth of protein crystals, along with that of some other compounds, is one of the topics, and recent insights into related phenomena are considered as examples of applications of general principles. The relationship between crystal growth shape and structure is reviewed and an attempt to introduce semiquantitative characterization of binding for proteins is made.

Masc2, a C5-DNA-methyltransferase from Ascobolus immersus with similarity to methyltransferases of higher organisms.

The filamentous fungus Ascobolus immersus represents an eukaryotic model organism to study genetic phenomena linked to DNA methylation. Following our previous characterization of a gene, masc1 from A. immersus, encoding the 'de novo' C5-DNA-methyltransferase (MTase), we report here the identification of a second MTase gene, masc2.

[Two site-specific endonucleases from the thermophilic OV Bacillus species strain].

Two site-specific endonucleases, BspOVI and BspOVII, were isolated from a thermophilic strain Bacillus species OV. The activities of both enzymes are maximal at 48 degrees C and do not depend on ATP and S-adenosyl-L-methionine. BspOVI recognizes the sequence [sequence: see text] and cleaves it as indicated by arrows.

[Site-specific endonuclease BspKT8 from the thermophilic strain KT8 of Bacillus species].

A site-specific endonuclease capable of recognizing the sequence 5'-AAGCTT-3' was detected and purified to homogeneity from the thermophilic strain of Bacillus species KT8. The endonuclease has a molecular mass of 34 kDa and is found in solution in a monomeric form. The activity of BspKT8 does not depend on ATP and is not stimulated by S-adenosyl-L-methionine.

Calcium phosphate crystallization under terrestrial and microgravity conditions.

Calcium phosphate crystalline powders grown under terrestrial and space (EURECA 1992-1993 flight) conditions in the Solution Growth Facility are analyzed and compared by optical and electron microscopy (scanning and transmission), electron and X-ray microdiffraction and microanalyses. On earth, only small, micrometer size scale, spherolites of hydroxyapatite (HAP) grow. In space, the HAP spherolites reach hundreds of micrometer.

[Recombinant reverse transcriptase from Rous sarcoma virus. Kinetics and inhibition of DNA polymerase activity].

Preparations of Rous sarcoma virus reverse transcriptase isolated from a culture of E. coli HB101 (pMF14) and purified to homogeneity were used to study the steady state kinetics of DNA polymerization and inhibition of DNA-polymerase activity. DNA synthesis was examined using a system of poly(rA) as template, oligo(dT) as primer and dTTP as nucleotide substrate.

BspLUII III, a bifunctional restriction and modification enzyme from a thermophilic strain Bacillus species LUII.

BspLUII III, an isomer of FinI (1) and BsmFI (2), was found to cleave DNA at two points 10, 11 and 14, 15 bp in the different strands away from the recognition site, and in the presence of SAM it exhibits the adenine specific methyltransferase activity.Images

[The outer membranes of Vibrio cholerae as a potential component in a chemical vaccine].

The results of the study of the preparation of V. cholerae eltor membrane, obtained by the lysis and inactivation of microbial cells with urea and the subsequent differential centrifugation and nuclease treatment. As revealed in this study, the outer membrane preparation, when introduced parenterally and orally to mice, induced pronounced immunity to experimental cholera infection and the production of vibriocidal antibodies in high titers.

Crystallization of calcium phosphate in microgravity.

Dilute solutions of CaCl2 and KH2PO4 + K2HPO4 were diffusing from either side into a mixing chamber with KCl solution. The microgravity experiment yielded aggregates of large crystals of OCP (Ca8H2(PO4)3,5H2O) and spherolites of smaller, but still visible crystals of HAP (Ca5OH(PO4)3), the stable final phase. Ground-based experiments yielded submicroscopic HAP crystals.

[A new site specific endonuclease-methylase from a thermophilic strain of Bacillus species LU11].

A new site-specific endonuclease BspLU11III was purified to homogeneity from a thermophilic strain Bacillus species LU11. BspLU11III recognizes the 5'-GGGAC-3' sequence on the double-stranded DNA and cleaves the 10/14 and 11/15 nucleotides in different strands away from the recognition site. The enzyme exists in solution as a monomer with a molecular mass of about 93 kDa.

[Results of the treatment of open heart injuries at a central regional hospital].

In a period of 10 years seven patients with open injury to the heart were treated. Their ages ranged from 17 to 39 years. One patient had a gunshot injury, in six the injury was inflicted with a knife.

[Characteristics of regional hemodynamics in the lower extremities of patients with flaccid paralysis].

On the basis of treatment and examination of 2675 patients with residual effects of poliomyelitis and consequences of the nervous system traumata are considered the functioning peculiarities of vascular system of the lower extremities in case of absence or abrupt decrease of pumping function of the skeletal muscles. There have been detected discrepancies between the reovasographic regional blood circulation pattern and the microcirculation state indexes in the tissues of the damaged extremity. They have studied the dynamics of the hemodynamics indexes in the process of preoperative preparation, during early and late postoperative periods as well as during remote postoperative periods.