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PubMed2004

Security infrastructure services for electronic archives and electronic health records.

Communication and co-operation in the domain of healthcare and welfare require a well-defined set of security services based on a Public Key Infrastructure and provided by a Trusted Third Party (TTP). These services describe both status and relation of communicating principals, corresponding keys and attributes, and the access rights to applications and data. Additional services are needed to provide trustworthy information about dynamic issues of communication and co-operation such as time and location of processes, workflow relations, and system behaviour. Legal, social, behavioural and ethical requirements demand securely stored patient information and well-established access tools and tokens. Electronic (and more specifically digital) signatures--as important means for securing the integrity of a message or file--along with certified time stamps or time signatures are especially important for purposes of data storage in electronic archives and electronic health records (EHR). While just mentioning technical storage problems (e.g. lifetime of the storage devices, interoperability of retrieval and presentation software), this paper identifies mechanisms of securing data items, files, messages, sets of archived items or documents, electronic archive structures, and life-long electronic health records. Other workshop contributions will demonstrate related aspects of policies, patient privacy, and privilege management.

Access to Information↗
PubMedDate not supplied

Distribution and movement of membrane-associated platelet glycoproteins: use of colloidal gold with correlative video-enhanced light microscopy, low-voltage high-resolution scanning electron microscopy, and high-voltage transmission electron microscopy.

Scanning electron microscopy (SEM), especially low-voltage (1 KeV) high-resolution SEM, can be used in conjunction with stereo pair high-voltage (1 MeV) transmission electron microscopy (HVEM) of whole spread cells or thick sections effectively to correlate surface structure with internal structure. Surface features such as microvilli, pits, pseudopodia, ruffles, attached virus, and other surface-related morphologic characteristics can be identified using SEM, while underlying cytoskeletal structure and organelle organization can be viewed by HVEM of the same preparation. However, the need to "prepare" cells for electron microscopy precludes observation in the living state. The use of several types of video-enhanced light microscopy (VLM) permits observation of living cells such that certain surface and internal features can be observed at a relatively high level of resolution or detection. Thus, changes in living cells can be followed, and at appropriate times the cells may be chemically fixed or rapidly frozen and prepared for ultrastructural examination by electron microscopy. We have utilized VLM in conjunction with SEM and HVEM to correlate changes in shape and surface structure with changes in the internal structure of platelets. In addition, we have found it advantageous to use colloidal gold-labeling procedures, because these markers are detectable by all three forms of microscopy. Using this approach we have labeled platelet membrane GPIIb/IIIa, a receptor for RGD-containing adhesive proteins, with gold-fibrinogen or gold-anti-IIb/IIIa. The initial binding and subsequent movement of gold-fibrinogen-IIb/IIIa complexes in living platelets was followed by VLM. The movement of individual labels could be mapped. Subsequent observation by low-voltage (1 KeV) high-resolution SEM and HVEM permits visualization of the same individual receptors tracked by LM. The final position on the membrane or the position-in-transit when fixative was added was determined relative to surface ultrastructure (SEM) and internal, particularly cytoskeletal, ultrastructure (HVEM).

Biological Transport↗
PubMed2004

Effect of conformational changes on a one-electron reduction process: evidence of a one-electron P-P bond formation in a bis(phosphinine).

EPR spectra show that one-electron reduction of bis(3-phenyl-6,6-(trimethylsilyl)phosphinine-2-yl)dimethylsilane (1) on an alkali mirror leads to a radical anion that is localized on a single phosphinine ring, whereas the radical anion formed from the same reaction in the presence of cryptand or from an electron transfer with sodium naphthalenide is delocalized on the two phosphinine rings. Density functional theory (DFT) calculations show that in the last species the unpaired electron is mainly confined in a loose P-P bond (3.479 A), which results from the overlap of two phosphorus p orbitals. In contrast, as attested by X-ray spectroscopy, the P-P distance in neutral 1 is large (5.8 A). As shown by crystal structure analysis, addition of a second electron leads to the formation of a classical P-P single bond (P-P 2.389 A). Spectral modifications induced by the presence of cryptand or by a change in the reaction temperature are consistent with the formation of a tight ion pair that stabilizes the radical structure localized on a single phosphinine ring. It is suggested that the structure of this pair hinders internal rotation around the C-Si bonds and prevents 1 from adopting a conformation that shortens the intramolecular P-P distance. The ability of the phosphinine radical anion to reversibly form weak P-P bonds with neutral phosphinines in the absence of steric hindrance is confirmed by EPR spectra obtained for 2,6-bis(trimethylsilyl)-3-phenylphosphinine (2). Moreover, as shown by NMR spectroscopy, in this system, which contains only one phosphinine ring, further reduction leads to an intermolecular reaction with the formation of a classical P-P bond.

Crystallization↗
PubMed2004

Ultrafast proton-coupled electron-transfer dynamics in pyrene-modified pyrimidine nucleosides: model studies towards an understanding of reductive electron transport in DNA.

5-(Pyren-1-yl)-2'-deoxyuridine (PydU) and 5-(Pyren-1-yl)-2'-deoxycytidine (PydC) were used as model nucleosides for DNA-mediated reductive electron transport (ET) in steady-state fluorescence and femtosecond time-resolved transient absorption spectroscopy studies. Excitation of the pyrene moiety in PydU and PydC leads to an intramolecular electron transfer that yields the pyrenyl radical cation and the corresponding pyrimidine radical anion (dU.- and dC.-. By comparing the excited state dynamics of PydC and PydU, we derived information about the energy difference between the two pyrimidine radical anion states. To determine the influence of protonation on the rates of photoinduced intramolecular ET, the spectroscopic investigations were performed in acetonitrile, MeCN, and in water at different pH values. The results show a significant difference in the basicity of the generated pyrimidine radical anions and imply an involvement of proton transfer during electron hopping in DNA. Our studies revealed that the radical anion dC.- is being protonated even in basic aqueous solution on a picosecond time scale (or faster). These results suggest that protonation of dC.- may also occur in DNA. In contrast, efficient ET in PydU could only be observed at low pH values (< 5). In conclusion, we propose--based on the free energy differences and the different basicities--that only dT.- but not dC.- can participate as an intermediate charge carrier for excess electron migration in DNA.

Anions↗
PubMed1992

Characterization of the annealed (0001) surface of sapphire (alpha-Al2O3) and interaction with silver by reflection electron microscopy and scanning reflection electron microscopy.

Annealed (0001) surfaces of single-crystal sapphire (alpha-Al2O3) rod have been studied in the electron microscope using reflection electron microscopy (REM), scanning reflection electron microscopy (SREM), and reflection high energy electron diffraction (RHEED). Annealed surfaces of (0001) sapphire are vicinal and characterized by close-packed (0001)-oriented terraces separated by faceted multiple-height steps, with edges parallel to energetically preferred low-index directions (less than 1010 greater than and less than 1120 greater than). These structural features are not seen on cleaved surfaces or polished surfaces treated at temperatures less than 1,250 degrees C. Oxygen-annealing produces clean surfaces which prove useful for investigating the interaction of deposited metals with the (0001) sapphire. Both REM and SREM (with microdiffraction spots) techniques have been used to observe fine structure of flat Ag islands on the scale of 1-100 nm on the (0001)-oriented terraces as well as aggregations at the steps. A preliminary result on interaction with Cu is also included.

Aluminum Oxide↗
PubMedDate not supplied

Characterization of an oil-degrading Microcoleus consortium by means of confocal scanning microscopy, scanning electron microscopy and transmission electron microscopy.

A consortium of microorganisms with the capacity to degrade crude oil has been characterized by means of confocal laser scanning microscopy (CLSM), transmission electron microscopy (TEM), and scanning electron microscopy (SEM). The analysis using CLSM shows that Microcoleus chthonoplastes is the dominant organism in the consortium. This cyanobacterium forms long filaments that group together in bundles inside a mucopolysaccharide sheath. Scanning electron microscopy and transmission electron microscopy have allowed us to demonstrate that this cyanobacterium forms a consortium primarily with three morphotypes of the heterotrophic microorganisms found in the Microcoleus chthonoplastes sheath. The optimal growth of Microcoleus consortium was obtained in presence of light and crude oil, and under anaerobic conditions. When grown in agar plate, only one type of colony (green and filamentous) was observed.

Cyanobacteria↗
PubMed1983

Crystalloids in salivary duct cysts of the human parotid gland. Scanning electron microscopical study with electron probe X-ray microanalysis.

Crystalloids found in salivary duct cysts of the human parotid gland were examined by scanning electron microscopical observations with electron probe X-ray microanalysis. The cystic spaces were filled with numerous crystalloids which had a variety of forms with slight eosinophilic and glassy appearance. Scanning electron microscopically, crystalloids were hexagonal and rhombohedral in shape, and cutting the surface showed a polycyclic structure or regular parallel lamination. By electron probe X-ray microanalysis, sulphur was the only detected element. The present study suggests that crystalloids resulted from deposition from supersaturated saliva containing sulphur containing compounds into the cystic lumen or into epithelial cytoplasm.

Crystalloid Solutions↗
PubMed1975

Demineralization of bone matrix: observations from electron microscope and electron-probe analysis.

Displacement or removal of mineral during the processing of calcified tissues for electron microscopy is a recognized phenomenon. An electron microscope analysis has been made of artefactual mineral loss during ultramicrotomy of osteogenic tissue. It is concluded from morphological investigation and the use of electron diffraction that this loss of crystalline mineral during sectioning can considerably change the morphology of calcified tissues and may lead to inaccurate interpretation of cell and matrix morphology. Electron probe X-ray microanalysis has been used to demonstrate in a semi-quantitative manner, the artefactual loss of calcium and phosphorus. Problems of specimen preparation for such analytical work are discussed.

Animals↗
PubMed1978

The relative electron affinities of the alpha and beta chains of oxyhaemoglobin as a function of pH and added inositol hexaphosphate. An electron spin resonance study.

Exposure of aqueous glasses of oxyhaemoglobin to 60Co gamma-rays at 77K results in electron addition to the FeO2 unit, the ESR spectrum for the alpha-chain electron adduct being well separated from that for the beta-chain. The relative yields of these two centres has been measured in the pH range 4.5 to 8.5, with or without added inositol hexaphosphate. We find that, in the absence of inositol hexaphosphate, the yield of beta-chain adduct is almost equal to that of the alpha-chains in the pH 4--5 region, but these rapidly diverge with increasing pH, the beta-yield increasing and the alpha-yield decreasing. After a plateau in the pH 6--8 region, the yield of beta-chain adduct decreases, but that of the alpha-chain adduct remains constant. In the presence of an excess of inositol hexaphosphate the pH change for the beta-adduct remains, but at low pH values the yield of the alpha-adduct is much greater than that of the beta-adduct. This constraint is removed with a pK of approx. 7.7 and at high pH values the yield of the beta-adduct is once again greater than that of the alpha-adduct. These results are significant in that they suggest that the electron affinities of the alpha and beta chains in oxyhaemoglobin are a function of pH, with that of the beta-chains being greater than that of the alpha-chains in the neutral region. Also inositol hexaphosphate clearly binds to one or both chains, and this has the effect of reversing the relative electron affinities of the two chains.

Electron Spin Resonance Spectroscopy↗
PubMed1988

Silver accumulations in periapical granulomas: report of five cases using the scanning electron microscope, the electron microprobe, and other complementary methods.

A series of cytologic imprints obtained from periapical granulomas were studied with the conventional light microscope, the scanning electron microscope, and the electron microprobe to analyze the chemical composition of several black deposits that were randomly observed near or in the cytoplasm of macrophages and multinucleated giant cells. These granulomas had been removed from endodontically treated human teeth in which the root canals had been obturated with silver cones and Grossman's sealer 3 to 5 years previously. To investigate whether corrosion had occurred on the silver cones, the cones were also examined with the scanning electron microscope and the electron microprobe. Our observations revealed that all the examined silver cones showed different degrees of corrosion on their surfaces, whereas different concentrations of silver, sulfur, and chlorine were detected at the same sites in the cytologic imprints. However, it is impossible to determine from this study whether the presence of corrosive by-products in the periapical tissues is responsible for the development of a pathologic reaction at these sites.

Adolescent↗
PubMedDate not supplied

Contribution of electron energy loss spectroscopy to the development of analytical electron microscopy.

The combined use of an electron energy loss spectrometer and an electron microscope provides some chemical information at the nanometer scale. The physics of the interaction processes between the incident electron beam and the thin sample foil is reviewed in terms of energy and momentum transfer. This analysis of the content of an electron energy loss spectrum allows us to establish rules for a satisfactory use of the information and to discuss the detection limits of this newly developed microanalytical technique.

Electron Probe Microanalysis↗
PubMed2006

Bidirectional electron transfer in photosystem I: replacement of the symmetry-breaking tryptophan close to the PsaB-bound phylloquinone A1B with a glycine residue alters the redox properties of A1B and blocks forward electron transfer at cryogenic temperatures.

A conserved tryptophan residue located between the A(1B) and F(X) redox centres on the PsaB side of the Photosystem I reaction centre has been mutated to a glycine in Chlamydomonas reinhardtii, thereby matching the conserved residue found in the equivalent position on the PsaA side. This mutant (PsaB:W669G) was studied using EPR spectroscopy with a view to understanding the molecular basis of the reported kinetic differences in forward electron transfer from the A(1A) and the A(1B) phyllo(semi)quinones. The kinetics of A(1)(-) reoxidation due to forward electron transfer or charge recombination were measured by electron spin echo spectroscopy at 265 K and 100 K, respectively. At 265 K, the reoxidation kinetics are considerably lengthened in the mutant in comparison to the wild-type. Under conditions in which F(X) is initially oxidised the kinetics of charge recombination at 100 K are found to be biphasic in the mutant while they are substantially monophasic in the wild-type. Pre-reduction of F(X) leads to biphasic kinetics in the wild-type, but does not alter the already biphasic kinetic properties of the PsaB:W669G mutant. Reduction of the [4Fe-4S] clusters F(A) and F(B) by illumination at 15 K is suppressed in the mutant. The results provide further support for the bi-directional model of electron transfer in Photosystem I of C. reinhardtii, and indicate that the replacement of the tryptophan residue with glycine mainly affects the redox properties of the PsaB bound phylloquinone A(1B).

Algal Proteins↗
PubMed1998

Electron microscopy: use of transmission and scanning electron microscopy to study cells in culture.

Standard techniques for electron microscopy were developed for tissues dissected from animals. Optimal methods for electron microscopy of cells in culture are different. This chapter describes methods for processing cells grown on plastic or in suspension. Both transmission and scanning electron microscopy are discussed. The focus is on the procedures for fixation, dehydration, embedding, and staining, which will help the reader to obtain superior electron micrographs of cultured cells.

Animals↗
PubMed1994

An ultrastructural study of the smear layer: comparative aspects using secondary electron image and backscattered electron image.

The aim of this investigation was to study the influence of three irrigation procedures on the composition, structure, and aspect of the smear layer within root canals. Three homogeneous groups were prepared without irrigation, with physiological serum, or with Dakin (dilute, neutral solution of sodium hypochlorite). Root canals were instrumented with Rispi Reamers mounted on a counterangle Giromatic. The irrigating solution was delivered with an endodontic irrigation needle. Modifications were observed by scanning electron microscope using secondary electron imaging and backscattered electron imaging. Instrumentation without irrigation produced a very thick smear layer that appeared in backscattered electron imaging as a compact assembly or organic and inorganic components. Instrumentation using Dakin produced canal walls that were less smeared, and the pockets of debris remaining were smaller in size than when using physiological serum. When the root canals were irrigated, the smear layer appeared as a double layer, one superficial and the other deep. The layers were predominantly inorganic with Dakin.

Blood↗
PubMed1978

Applications of electronically controlled illumination in the conventional transmission electron microscope.

A device used to produce electronic cone illumination in an analog fashion in the conventional transmission electron microscope has been applied to a number of materials problems which require special diffraction conditions not readily achieved in the microscope's normal operating mode. The device manipulates the primary beam tilt to produce a variety of virtual condenser aperture conditions, and hence electron diffraction patterns can be recorded which reflect the manner in which the direct beam is tilted during the exposure of a micrograph. For single crystalline material, the device provides an improvement over convergent-beam electron diffraction for systematic row reflections and allows direct observation of dynamical beam interactions. It has also been applied to imaging defects in thin crystalline films which would often be obscured under normal microscope conditions. The device allows the imaging of polycrystalline material and the selection of given diffraction orders to determine the orientation of crystallites in a large field of view. It can also modify amorphous patterns to extend the information contained in dark-field images beyond normal tilted-beam dark-field imaging. Control of the incident beam can be accomplished digitally for more varied beam manipulation requirements. A few cases of manipulation of diffraction patterns will be considered.

Crystallography↗
PubMed1985

Reaction of electron-transfer flavoprotein with electron-transfer flavoprotein-ubiquinone oxidoreductase.

The oxidative half-reaction of electron-transfer flavoprotein (ETF), electron transfer from ETF to electron-transfer flavoprotein-ubiquinone oxidoreductase (ETF-QO), is dependent on complementary surface charges on the two proteins. ETF is the positively charged member of the redox pair. The evidence is based on the pH and ionic strength dependencies of the comproportionation of oxidized ETF and ETF hydroquinone catalyzed by ETF-QO and on the effects of chemical modification of ETF on the comproportionation reaction. Acetylation of one and five epsilon-amino groups of lysyl residues results in 3- and 13-fold increases, respectively, in the Km of ETF-QO for ETF but no change in Vmax. Amidination, which maintains positive charge at modified loci, has no effect on steady-state kinetic constants. These chemical modifications have no effect on the equilibrium constant for equilibration of ETF redox states. The Km of ETF-QO for ETF is pH dependent above pH 8.5, suggesting titration of lysyl residues as previously observed in studies of the reductive half-reaction of ETF [Beckmann, J. D., & Frerman, F. E. (1983) J. Biol. Chem. 258, 7563-7569]. The ionic strength dependence of TN/KmETF for the reaction follows the limiting Brønsted equation ln (TN/Km) = ln k0 + 2 alpha Z1Z2I1/2, and Z1Z2, the product of charges on the reacting proteins, is similar to the value of Z1Z2 for the reductive half-reaction of ETF by the general acyl-CoA dehydrogenase. The ETF-QO-catalyzed comproportionation reaction exhibits a primary deuterium isotope effect in D2O, perhaps indicating the participation of solvent water in the electron-transfer reaction.

Acyl-CoA Dehydrogenases↗
PubMed1991

Klebsiella pneumoniae nitrogenase. The pre-steady-state kinetics of MoFe-protein reduction and hydrogen evolution under conditions of limiting electron flux show that the rates of association with the Fe-protein and electron transfer are independent of the oxidation level of the MoFe-protein.

The pre-steady-state kinetics of H2 evolution from Klebsiella pneumoniae nitrogenase functioning at 23 degrees C, pH 7.4, under conditions of extremely low electron flux through the MoFe-protein exhibited a lag phase of several minutes duration. The approach to a steady-state rate of H2 evolution was accompanied by a 50% decrease in the amplitude of the MoFe-protein e.p.r. signal. These kinetics have been simulated using our published kinetic model for nitrogenase [Lowe & Thorneley (1984) Biochem. J. 224, 877-886], which was developed using data obtained with nitrogenase functioning at high electron fluxes. The e.p.r. data showed that the rate of complex-formation between reduced Fe-protein and the MoFe-protein (k+1 = 5 x 10(7) M-1.s-1) is the same for the resting (E0) and one-electron-reduced (E1H) states of the MoFe-protein. Stopped-flow spectrophotometry also showed that electron transfer from the Fe-protein to the MoFe-protein in states E0 and E1H occurs at the same rate (kobs. = 140 s-1). These data support our previous assumption that the rate constants that define the 'Fe-protein cycle' are independent of the level of reduction of the MoFe-protein.

Computer Simulation↗
PubMed1985

Deficiency of electron transfer flavoprotein or electron transfer flavoprotein:ubiquinone oxidoreductase in glutaric acidemia type II fibroblasts.

Glutaric acidemia type II (GA II) is a human genetic disorder. It has been suggested that the primary defect in this disorder is a deficiency of a protein involved in electron transport between the acyl-CoA dehydrogenases and the bc1 complex of the mitochondrial respiratory chain. Antisera were raised to purified porcine electron transfer flavoprotein (ETF) and electron transfer flavoprotein:ubiquinone oxidoreductase (ETF:QO). The antisera were used to detect the two electron transferases in control and GA II fibroblasts by immunoblotting. Fibroblasts from three unrelated GA II patients were deficient in immunologically detectable ETF:QO and extracts from these three fibroblast lines contained no detectable ETF:QO catalytic activity. Fibroblasts from parents of two of these patients had ETF:QO activity intermediate between activities in control fibroblasts and fibroblasts from the patients. These data indicate that the primary defect in these patients is a deficiency of ETF:QO and that the mode of transmission of the gene is autosomal recessive. Fibroblasts from two other patients with severe GA II had normal levels of ETF-QO activity and antigen but were deficient in immunoreactive ETF. These findings show that GA II results from a deficiency of ETF in some patients and ETF:QO in others. In addition, these investigations provide strong evidence for the specificity and physiological function of the iron-sulfur flavoprotein ETF:QO.

Animals↗