Surface dynamics on submonolayer Pb/Cu(001) surfaces.

The interplay of the atomic structure and phonon spectra in a variety of two dimensional phases forming during submonolayer Pb adsorption on a Cu(001) surface has been investigated using embedded atom method interatomic interaction potentials. Complementary calculations of the equilibrium atomic structure of these phases were performed using density functional theory. It has been shown that the dynamic stability of the Pb/Cu(001) structures increases with increasing the coverage from 0.375 ML to ultimately 0.6 ML, when a dense Pb layer is formed. The increase of the coverage also results in progressive shift of the Rayleigh mode of the copper surface to higher energy and the appearance of new mixed adsorbate-substrate vibration modes.

Magnetic and vibrational properties of small chromium clusters on the Cu(111) surface.

The structure and magnetic properties of small Cr clusters, Cr3 and Cr4, adsorbed on the Cu(111) surface have been investigated using density functional theory (DFT) calculations and their vibrational properties have been studied within calculations based on tight-binding second moment approximation interatomic interaction potentials (TBSMA). It has been shown that the magnetic ordering in the Cr clusters significantly affects their crystal structure and symmetry, which influences the vibrational modes of the clusters and nearest neighbor copper atoms. In turn, these modes select potentially possible structures of Cr3 and Cr4, prohibiting the lowest total energy cluster structure as dynamically unstable.

[Diagnostic search for causes for urinary holding in a uniform kidney girl].

Ectopic of the ureter into the cervix is a rare case in the clinical practice of pediatric urologists around the world. This paper presents an observation of congenital urinary incontinence in a 13-year-old girl who underwent an annual examination in a hospital at the place of residence.

Rapid diagnostics of urinary iodine using a portable EDXRF spectrometer.

A method for urinary iodine diagnostics using a portable energy-dispersion X-ray fluorescent (EDXRF) spectrometer is proposed. The principle of the method consists in excitation of the sample atoms fluorescence by the energy spectrum intentionally formed from the spectrum of an X-ray tube using an optimized X-ray scheme. The optimization by the criterion of the minimum detection limit for L-series iodine fluorescence lines included the calculation of optimal atomic numbers for materials of a re-radiator and a filter, and their thicknesses, the collimation system parameters, and an X-ray tube voltage. Experimentally achieved detection limits were 45 and 75 µg/L by I-Lα and I-Lß lines, respectively, at the theoretically extreme value 30 µg/L. This sensitivity is found to be sufficient for urinary iodine diagnostics in the range from 50 to 200 µg/L. The results obtained from different patients have shown the satisfactory convergence for the iodine concentration determination by Lα and I-Lß fluorescence lines. The simple sample preparation procedure and comparably small sizes of the apparatus allows rapid researches directly in clinical settings.

Preliminary joint neutron time-of-flight and X-ray crystallographic study of human ABO(H) blood group A glycosyltransferase.

The biosyntheses of oligosaccharides and glycoconjugates are conducted by glycosyltransferases. These extraordinarily diverse and widespread enzymes catalyze the formation of glycosidic bonds through the transfer of a monosaccharide from a donor molecule to an acceptor molecule, with the stereochemistry about the anomeric carbon being either inverted or retained. Human ABO(H) blood group A α-1,3-N-acetylgalactosaminyltransferase (GTA) generates the corresponding antigen by the transfer of N-acetylgalactosamine from UDP-GalNAc to the blood group H antigen. To understand better how specific active-site-residue protons and hydrogen-bonding patterns affect substrate recognition and catalysis, neutron diffraction studies were initiated at the Protein Crystallography Station (PCS) at Los Alamos Neutron Science Center (LANSCE). A large single crystal was subjected to H/D exchange prior to data collection and time-of-flight neutron diffraction data were collected to 2.5 Šresolution at the PCS to ∼85% overall completeness, with complementary X-ray diffraction data collected from a crystal from the same drop and extending to 1.85 Šresolution. Here, the first successful neutron data collection from a glycosyltransferase is reported.

Phonons on Cu(001) surface covered by submonolayer alkali metals.

We present a theoretical investigation of the structural and vibrational properties of ordered 2D phases formed by the Li, Na and K atoms on the Cu[Formula: see text] surface. The lattice relaxation, phonon dispersions and polarization of vibrational modes as well as the local density of states are calculated using the embedded-atom method. The obtained structural parameters and vibrational frequencies are in close agreement with available experimental results.

Determination of coal ash content by the combined x-ray fluorescence and scattering spectrum.

An alternative method is proposed for the determination of the inorganic constituent mass fraction (ash) in solid fuel by the ratio of Compton and Rayleigh X-ray scattering peaks IC/IR subject to the iron fluorescence intensity. An original X-ray optical scheme with a Ti/Mo (or Sc/Cu) double-layer secondary radiator allows registration of the combined fluorescence-and-scattering spectrum at the specified scattering angle. An algorithm for linear calibration of the Compton-to-Rayleigh IC/IR ratio is proposed which uses standard samples with two certified characteristics: mass fractions of ash (Ad) and iron oxide (WFe2O3 ). Ash mass fractions have been determined for coals of different deposits in the wide range of Ad from 9.4% to 52.7% mass and WFe2O3 from 0.3% to 4.95% mass. Due to the high penetrability of the probing radiation with energy E > 17 keV, the sample preparation procedure is rather simplified in comparison with the traditional method of Ad determination by the sum of fluorescence intensities of all constituent elements.

Phonons in the ordered c(2 × 2) phases of Na and Li on Al(001).

The vibrational properties of the Al(001)-c(2 × 2)-Na (Li) ordered phases formed by alkali atoms (Na and Li) on the Al(001) surface at low and room temperatures are presented. The equilibrium structural characteristics, phonon dispersions and polarization of vibrational modes as well as the local density of phonon states are calculated using the embedded-atom method. The obtained structural parameters are in close agreement with experimental data.

In vitro Research Concerning Effect of Clopidogrel Alone and on Combination with Aspirin and Dypiridamoleon Sedimentation of Erythrocytes.

Based on extended theory of Derjaguin, Landau and Overbeeck (xDLVO) concerning aggregation of colloids and biological cells it was hypothesized that platelet antiaggregant agents have to reduce the aggregation of erythrocytes also. Applying Einstein-Stokes theory of sedimentation of spheres in viscous media it was concluded that sedimentation of erythrocytes is in fact sedimentation of aggregates of the approximately same size. Consequently, an expected outcome was that addition of antiaggregants in vitro to blood samples from patients with rheumatic or cardiovascular diseases will be the decrease of erythrocytes sedimentation. Starting from usual practice of dual antiaggregant therapy (aspirin and clopidogrel) effects of clopidogrel were compared with effects of clopidogrel plus small concentrations of aspirine and dipyridamole (smaller that their concentrations in plasma after in vivo administration) in order to put in evidence a possible synergic effect at platelet membrane level. Whole blood (0.8ml) was collected on 0.1ml 1% EDTA and then was added 25 or 50µl normal saline solution of clopidogrel or of the combination acetylosalycilic acid, clopidogrel and dypyridamole. The final concentrations were 1, 2 and µg/ml, of the same order as cumulated concentration of clopidogrel and its metabolites in clinical pharmacokinetics. Experiments were performed on a number of 40 human blood samples obtained from 2 groups of 20 patients. Sedimentation of erythrocytes was recorded using a camera and captured data were stored on a computer. Global analysis evidenced that in presence of antiaggregants the clusters of the sedimentation curves shifted down and into right, indicating a decrease and delay of sedimentation. Initial slopes and extent of sedimentation decreased linearly on clopidogrel concentration within the 1-3µg/ml range. For comparison of mean curves corresponding to different clopidogrel concentrations it was applied a metric from biopharmacy: areas under plasma concentrations curves (AUC) of drugs. The areas under average sedimentation curves decreased linearly at clopidogrel concentration within the 1-3µg/ml range. The same experiments were performed and similar results were obtained with the triple antiaggregant combination (clopidogrel, acetylosalycilic acid and dipyridamole). Apparently, a synergism between the tested antiaggregants appeared at studied concentration but the number of data was not sufficient to prove the statistical significance of the difference between clopidogrel alone and in triple combination.

In vitro Research of the Concentration Dependence of Effect of Adrenaline on Platelets Aggregation.

PURPOSE: Paper intended to present experimental evidences that adrenaline has a direct effect of inducing platelets aggregation in the concentration range 1-8µM. MATERIAL/METHODS: Platelet rich plasma from patients of Colentina Clinical Hospital, following an informed consent. The platelet rich plasma (PRP) was prepared by centrifuging the anticoagulated sample at 200 G for 10 minutes. Aggregation was evaluated by optical aggregometry, classical method of Born, using Helena PACKS-4 Aggregometer. RESULTS: The curves transmission light-time followed the structure: a lag-time, a first phase aggregation, more or less linear, defined by a "Slope 1", a second wave of aggregation defined by "slope 2" and a "saturation" phase. Slope 1 increases with the concentration of adrenaline. The second slopes of the aggregation curves, maximum aggregation and areas under curves depended linear on adrenaline concentration. CONCLUSIONS: Adrenaline, in concentrations in the 1-8µM, induce aggregation of human platelets from platelet rich plasma. Linear regression models for slope and area were practically identical suggesting a rather unique than biphasic mechanism of action of adrenaline during the time course of aggregation.

Application of Biopharmaceutical and Clinical Metrics in Analyzing Modification of Platelets Aggregation Curves by Calcium Ion.

In context of Evidence Based Medicine concept, Good Clinical Practice rules specify that "data generated should be reliable and robust".Reliability and robustness are further translated in requirements concerning statistical and clinical significance of results. Paper presents main aspectsconnected with comparison of evolutions of endpoints as function of different parameters like time, administered dose, proportion of active components etc., leading to problems of comparison of curves, with direct application to comparison of platelets aggregation curves in presence of different concentrations of ionic calcium. Theoretical part presents comparison of curves in biopharmacyusing f2 metric and area under curve metric, and comparison of survival curves in clinical studies.Platelet aggregation test was performed using Bornturbidimetric light transmission method using Helena PACKS-4 Aggregometer. Blood samples were collected from patients in internal medicine ward of Colentina Clinical Hospital. Platelet rich plasma (PRP) was obtained by centrifugation at 200G. Washed platelets where extracted by centrifugation of PRP at 2700G. The supernatant was replaced with sodium chloride 0.9%. Platelets aggregation was induced by adding different concentrations of calcium gluconate into cuvettes which contained washed platelets. After digitalization, curves were compared using similarity factor f2and areas under curves. Paper puts in evidence that both type of comparison, after mathematical and statistical evaluation, have to define a clinical threshold for clinical significance. In case of f2, in dissolution studies the threshold is 10%, in case of bioequivalence based on area under curves threshold is 20%. Establishment of the threshold for significant clinical difference in comparison of aggregation curves is not only a problem of statistics.Graphical representation of data suggested significant differences between curves obtained with different concentrations of calcium ion. Application of both f2 method and log-rank test let to conclusion that differences were statistical significant. Representation of aria under curves as function of calcium concentration put in evidence an approximate linear dependence. In spite of apparently objective character of mathematical approach, the problem of comparison of aggregation curves remains practically unsolved since we do not know the threshold between clinical significant and non-significant results.

[Effects of nootropic agents on visual functions and lacrimal antioxidative activity in patients with primary open-angle glaucoma].

The paper presents the results of an investigation of the effect of the nootropic agents pantogam and nooclerine on visual functions in patients with primary open-angle glaucoma. These agents have been found to have a beneficial effect on the functional activity of the retina and optic nerve, light sensitivity, hemo- and hydrodynamics of the eye.

Spectral properties of phosphopyridoxyl-Lys-7(-41)-ribonuclease A.

We have studied the spectral properties of RNAase A containing a phosphopyridoxyl residue at the epsilon-NH2 group of Lys-7 or Lys-14. The overall conformations of the native and modified enzymes were shown to be rather similar. All three proteins have similar circular dichroism spectra within the 220-300-nm region, and similar thermal transition temperatures. All the changes in the RNAase A molecule modified are located in close proximity to the alkylated lysine residue. The phosphopyridoxyl group of (P-Pxy)-epsilon-Lys-41-RNAase A is situated directly at the enzyme active site and is 25% butied in the protein globule. The P-pyridoxyl group of (P-Pxy)-epsilon-Lys-7-RNAase A was shown to be located in the vicinity of the active site and to be more exposed to the solvent. In the pyridoxyl phosphate absorption band, optical activity is induced in both proteins. Study of the pH dependence of the changes occurring in the circular dichroism and absorption spectra has shown that in the modified proteins, the pyridoxyl phosphate chromophore is rather sensitive to the ionic state of the surrounding medium and serves as a "reporter" group when the relationship between structure and function of the RNAase A active site is being investigated.

Crystallization and preliminary X-ray diffraction studies of the lepidopteran-specific insecticidal crystal protein CrylA(a).

A trypsin-activated CrylA(a) protein from Bacillus thuringiensis has been purified and crystallized. Crystals belong to orthorhombic space group P2(1)2(1)2(1), with cell dimensions a = 53.3, b = 111.3 and c = 154.7 A. The crystals diffract to at least 2.2 angstrum resolution and are suitable for X-ray structural analysis. They contain a single molecule in the asymmetric unit.

Bacillus thuringiensis CryIA(a) insecticidal toxin: crystal structure and channel formation.

The activated 65 kDa lepidopteran-specific CryIA(a) toxin from the commercially most important strain Bacillus thuringiensis var. kurstaki HD-1 has been investigated by X-ray diffraction and for its ability to form channels in planar lipid bilayers. Its three-dimensional structure has been determined by a multiple isomorphous replacement method and refined at 2.25 A resolution to an R-factor of 0.168 for data with I > 2 delta (I). The toxin is made of three distinct domains. The N-terminal domain is a bundle of eight alpha-helices with the central, relatively hydrophobic helix surrounded by amphipathic helices. The middle and C-terminal domains contain mostly beta-sheets. Comparison with the structure of CryIIIA, a coleopteran-specific toxin, shows that although the fold of these two proteins is similar, there are significant structural differences within domain II. This finding supports the conclusions from genetic studies that domain II is involved in recognition and binding to cell surface receptors. The distribution of electrostatic potential on the surface of the molecule is non-uniform and identifies one side of the alpha-helical domain as negatively charged. The predominance of arginine residues as basic residues ensures that the observed positive charge distribution is also maintained in the highly alkaline environment found in the lepidopteran midgut. Structurally important salt bridges that are conserved across Cry sequences were identified and their possible role in toxin action was postulated. In planar lipid bilayers, CryIA(a) forms cation-selective channels, whose conductance is significantly smaller than that reported for CryIIIA but similar to those of other Cry toxins.

Antibody recognition of a conformational epitope in a peptide antigen: Fv-peptide complex of an antibody fragment specific for the mutant EGF receptor, EGFRvIII.

Epitope mapping studies and the determination of the structure to 1.8 A resolution have been carried out for the antigen-binding fragment MR1 in complex with peptide antigen. MR1 is specific for the novel fusion junction of the mutant epidermal growth factor receptor EGFRvIII and has been reported to have a high degree of specificity for the mutant EGFRvIII over the wild-type EGF receptor. The structure of the complex shows that the peptide antigen residue side-chains found by epitope mapping studies to be critical for recognition are accommodated in pockets on the surface of the Fv. However, the most distinctive portion of the peptide antigen, the novel fusion glycine residue, makes no contact to the Fv and does not contribute directly to the epitope. The specificity of MR1 lies in the ability of this glycine residue to assume the restricted conformation needed to form a type II' beta-hairpin turn more easily, and demonstrates that a peptide antigen can be used to generate a conformational epitope.

Biosynthesis of desosamine: construction of a new macrolide carrying a genetically designed sugar moiety.

[formula: see text] The appended sugars in macrolide antibiotics are indispensable to the biological activities of these important drugs. In an effort to generate a set of novel macrolide derivatives, we have created a new analogue of methymycin and neomethymycin, antibiotics produced by Streptomyces venezuelae. This analogue 15 carrying a different sugar, D-quinovose, instead of D-desosamine, was constructed by taking advantage of targeted gene deletion combined with a specific pathway-independent C-3 reduction capability of the wild type S. venezuelae.

Self-irradiation effect on yeast cells.

The effect of self irradiation on yeast cells has been investigated by counting the young gemmae formation in 104 self irradiated samples, as compared with an equal set of control samples. The results show that the rate of gemmae formation is higher in self irradiated samples; the statistical significance of the results is discussed.

Identification of N epsilon-[(R)-1-carboxyethyl]-L-lysine in, and the complete structure of, the repeating unit of the O-specific polysaccharide of Providencia alcalifaciens O23.

N epsilon-[(R)-1-Carboxyethyl]-L-lysine was released by acid hydrolysis from the O-specific polysaccharide of Providencia alcalifaciens O23 and identified by 1H and 13C NMR spectroscopy, GLC-MS after conversion to a di-N-acetylated dimethyl ester, and by comparison with the authentic sample. Solvolysis of the polysaccharide with anhydrous HF resulted in an amide of D-glucuronic acid with N epsilon-[(R)-1-carboxyethyl]-L-lysine. These and published data allowed the determination of the full structure of the repeating unit of the O-specific polysaccharide.

Structure of the O-specific polysaccharide of Citrobacter freundii O3a,3b,1c.

The following structure of the O-specific polysaccharide of Citrobacter freundii O3a,3b,1c containing D-mannose and D-rhamnose was established using sugar analysis and NMR spectroscopy, including computer-assisted analysis of the 13C NMR spectrum, 2D COSY, H,H-relayed COSY, heteronuclear 13C, 1H correlation (HETCOR), and rotating-frame NOE spectroscopy (ROESY):-->4)-alpha-D-Manp-(1-->3)-beta-D-Rhap-(1-->4) -beta-D-Rhap-(1-->.