Characterization of photoinduced normal state through charge density wave in superconducting YBa2Cu3O6.67

The normal state of high-T_c cuprates has been considered one of the essential topics in high-temperature superconductivity research. However, compared to the high magnetic field study of it, understanding a photoinduced normal state remains elusive. Here, we explore a photoinduced normal state of YBa₂Cu₃O_6.67 through a charge density wave (CDW) with time-resolved resonant soft x-ray scattering, as well as a high magnetic field x-ray scattering. In the nonequilibrium state where people predict a quenched superconducting state based on the previous optical spectroscopies, we experimentally observed a similar analogy to the competition between superconductivity and CDW shown in the equilibrium state. We further observe that the broken pairing states in the superconducting CuO₂ plane via the optical pump lead to nucleation of three-dimensional CDW precursor correlation. Ultimately, these findings provide a critical clue that the characteristics of the photoinduced normal state show a solid resemblance to those under magnetic fields in equilibrium conditions.

Femtosecond electronic structure response to high intensity XFEL pulses probed by iron X-ray emission spectroscopy

We report the time-resolved femtosecond evolution of the K-shell X-ray emission spectra of iron during high intensity illumination of X-rays in a micron-sized focused hard X-ray free electron laser (XFEL) beam. Detailed pulse length dependent measurements revealed that rapid spectral energy shift and broadening started within the first 10 fs of the X-ray illumination at intensity levels between 10¹⁷ and 10¹⁸ W cm^-2. We attribute these spectral changes to the rapid evolution of high-density photoelectron mediated secondary collisional ionization processes upon the absorption of the incident XFEL radiation. These fast electronic processes, occurring at timescales well within the typical XFEL pulse durations (i.e., tens of fs), set the boundary conditions of the pulse intensity and sample parameters where the widely-accepted ‘probe-before-destroy’ measurement strategy can be adopted for electronic-structure related XFEL experiments.

Detection of the Chiral Spin Structure in Ferromagnetic SrRuO3 Thin Film

SrRuO₃ (SRO) thin films and their heterostructure have attracted much attention because of the recently demonstrated fascinating properties, such as topological Hall effect and skyrmions. Critical to the understanding of those SRO properties is the study of the spin configuration. Here, we conduct resonant soft X-ray scattering (RSXS) at the oxygen K edge to investigate the spin configuration of a four-unit-cell SRO film that was grown epitaxially on a single-crystal SrTiO₃. The RSXS signal under a magnetic field (∼0.4 tesla) clearly shows a magnetic dichroism pattern around the specular reflection. Model calculations on the RSXS signal demonstrate that the magnetic dichroism pattern originates from a Néel-type chiral spin structure in this SRO thin film. We believe that the observed spin structure of the SRO system is a critical piece of information for understanding its intriguing magnetic and transport properties.

Pectoralis muscle area is associated with bone mineral density and lung function in lung transplant candidates

Loss of bone mineral density and skeletal muscle area are linked in lung transplant patients. This loss is greater in patients with restrictive compared with obstructive lung diseases.

INTRODUCTION

Sarcopenia and osteoporosis are associated with aging and chronic illnesses and may be linked in patients with advanced lung disease. Pectoralis muscle index (PMI) quantitated on computed tomography (CT) of the chest can be used to measure skeletal muscle mass. This study aimed to determine the relationship of PMI to clinical parameters including bone mineral density (BMD) in candidates for lung transplantation.

METHODS

A retrospective review of transplant candidates at a single center was performed. Demographic, anthropomorphic, and clinical data were recorded. Pectoralis muscle area (PMA) was determined on an axial slice from a chest CT. PMI was calculated as the PMA divided by height squared. BMD was obtained from routine dual-energy X-ray absorptiometry (DXA) scan.

RESULTS

In 226 included patients, mean PMI was 8.2 ± 3.0 cm²/m² in males and 6.1 ± 2.1 cm²/m² in females. Osteopenia was present in 44.4%, and 23.2% of patients had osteoporosis. Patients with obstructive lung disease had lower body mass index (22.0 ± 4.9 versus 27.9 ± 4.9 kg/m², p < 0.001), PMI (6.0 ± 2.3 versus 8.2 ± 2.8 cm²/m², p < 0.001), and BMD (- 2.3 ± 1.1 versus - 1.3 ± 1.1, p < 0.001) compared with patients with restrictive lung disease. PMI was a significant predictor of BMD (β = 0.16, p < 0.001).

CONCLUSION

The association between muscle area and BMD in lung transplant candidates suggests that similar mechanisms may underlie the development of both. Differences in PMI and BMD in patients with obstructive versus restrictive lung disease may result from differences in respiratory physiology or disease processes.

The juxtamembrane sequence of the Hepatitis C virus polymerase can affect RNA synthesis and inhibition by allosteric polymerase inhibitors

The Hepatitis C virus (HCV) RNA-dependent RNA polymerase (RdRp), nonstructural protein 5B (NS5B), is anchored in the membrane through a C-terminal helix. A sequence of ca. 12 residues that connects the catalytically competent portion of the RdRp and the C-terminal helix, the juxtamembrane sequence (JMS), has a poorly defined role in RdRp function in a large part since it is translated from a cis-acting RNA element (CRE) that is essential for HCV replication. Using a HCV replicon that transposed a second copy of CRE to the 3' UTR of the HCV replicon, we demonstrate that amino acid substitutions in the JMS were detrimental for HCV replicon replication. Substitutions in the JMS also resulted in a defect in de novo-initiated RNAs synthesis in vitro and in a cell-based reporter assay. A nonnucleoside inhibitor of the NS5B that binds to the catalytic pocket was less potent in inhibiting NS5B in the presence of JMS mutations. The JMS mutants exhibit reduced stability in thermodenaturation assays, suggesting that the JMS helps confer a more stable conformation to NS5B that could impact RNA synthesis.

Pressure-induced metathesis reaction to sequester Cs

We report here a pressure-driven metathesis reaction where Ag-exchanged natrolite (Ag16Al16Si24O80·16H2O, Ag-NAT) is pressurized in an aqueous CsI solution, resulting in the exchange of Ag(+) by Cs(+) in the natrolite framework forming Cs16Al16Si24O80·16H2O (Cs-NAT-I) and, above 0.5 GPa, its high-pressure polymorph (Cs-NAT-II). During the initial cation exchange, the precipitation of AgI occurs. Additional pressure and heat at 2 GPa and 160 °C transforms Cs-NAT-II to a pollucite-related, highly dense, and water-free triclinic phase with nominal composition CsAlSi2O6. At ambient temperature after pressure release, the Cs remains sequestered in a now monoclinic pollucite phase at close to 40 wt % and a favorably low Cs leaching rate under back-exchange conditions. This process thus efficiently combines the pressure-driven separation of Cs and I at ambient temperature with the subsequent sequestration of Cs under moderate pressures and temperatures in its preferred waste form suitable for long-term storage at ambient conditions. The zeolite pollucite CsAlSi2O6·H2O has been identified as a potential host material for nuclear waste remediation of anthropogenic (137)Cs due to its chemical and thermal stability, low leaching rate, and the large amount of Cs it can contain. The new water-free pollucite phase we characterize during our process will not display radiolysis of water during longterm storage while maintaining the Cs content and low leaching rate.

Atomically engineered metal-insulator transition at the TiO2/LaAlO3 heterointerface

We demonstrate that the atomic boundary conditions of simple binary oxides can be used to impart dramatic changes of state. By changing the substrate surface termination of LaAlO3 (001) from AlO2 to LaO, the room-temperature sheet conductance of anatase TiO2 films are increased by over 3 orders of magnitude, transforming the intrinsic insulating state to a high mobility metallic state, while maintaining excellent optical transparency.

Resolving material-specific structures within Fe₃O₄|γ-Mn₂O₃ core|shell nanoparticles using anomalous small-angle X-ray scattering

Here it is demonstrated that multiple-energy, anomalous small-angle X-ray scattering (ASAXS) provides significant enhancement in sensitivity to internal material boundaries of layered nanoparticles compared with the traditional modeling of a single scattering energy, even for cases in which high scattering contrast naturally exists. Specifically, the material-specific structure of monodispersed Fe₃O₄|γ-Mn₂O₃ core|shell nanoparticles is determined, and the contribution of each component to the total scattering profile is identified with unprecedented clarity. We show that Fe₃O₄|γ-Mn₂O₃ core|shell nanoparticles with a diameter of 8.2 ± 0.2 nm consist of a core with a composition near Fe₃O₄ surrounded by a (Mn(x)Fe(1-x))₃O₄ shell with a graded composition, ranging from x ≈ 0.40 at the inner shell toward x ≈ 0.46 at the surface. Evaluation of the scattering contribution arising from the interference between material-specific layers additionally reveals the presence of Fe₃O₄ cores without a coating shell. Finally, it is found that the material-specific scattering profile shapes and chemical compositions extracted by this method are independent of the original input chemical compositions used in the analysis, revealing multiple-energy ASAXS as a powerful tool for determining internal nanostructured morphology even if the exact composition of the individual layers is not known a priori.

Chemical reactivity of brome mosaic virus capsid protein

Viral particles are biological machines that have evolved to package, protect, and deliver the viral genome into the host via regulated conformational changes of virions. We have developed a procedure to modify lysine residues with S-methylthioacetimidate across the pH range from 5.5 to 8.5. Lysine residues that are not completely modified are involved in tertiary or quaternary structural interactions, and their extent of modification can be quantified as a function of pH. This procedure was applied to the pH-dependent structural transitions of brome mosaic virus (BMV). As the reaction pH increases from 5.5 to 8.5, the average number of modified lysine residues in the BMV capsid protein increases from 6 to 12, correlating well with the known pH-dependent swelling behavior of BMV virions. The extent of reaction of each of the capsid protein's lysine residues has been quantified at eight pH values using coupled liquid chromatography-tandem mass spectrometry. Each lysine can be assigned to one of three structural classes identified by inspection of the BMV virion crystal structure. Several lysine residues display reactivity that indicates their involvement in dynamic interactions that are not obvious in the crystal structure. The influence of several capsid protein mutants on the pH-dependent structural transition of BMV has also been investigated. Mutant H75Q exhibits an altered swelling transition accompanying solution pH increases. The H75Q capsids show increased reactivity at lysine residues 64 and 130, residues distal from the dimer interface occupied by H75, across the entire pH range.

High pressure investigation of alpha-form and CH4-loaded beta-form of hydroquinone compounds

The high pressure compression behaviors of two hydroquinone compounds have been investigated using a combination of in situ synchrotron x-ray powder diffraction and Raman spectroscopy up to ca. 7 GPa. The structural integrity of the alpha-form hydroquinone clathrate is maintained throughout the pressure range, whereas the CH(4)-loaded beta-form hydroquinone clathrate decomposes and transforms to a new high pressure phase near 5 GPa. The bulk modulus (K) and its pressure derivative (K(')) of the alpha-form and the CH(4)-loaded beta-form hydroquinones are measured to be 8.2(3) GPa and 8.4(4), and 10(1) GPa and 9(2), respectively, representing one of the most compressible classes of crystalline solids reported in the literature. The corresponding axial compression behaviors, however, show greater contrast between the two hydroquinone compounds; the elastic anisotropy of the alpha-form is only marginal, being K(a):K(c) = 1.08:1, whereas that of the CH(4)-loaded beta-form is rather drastic, being K(a):K(c) = 11.8:1. This is attributed to the different dimensionality of the hydrogen bonding networks between the two structures and might in turn explain the observed structural instability of the beta-form, compared to the alpha-form.

Intrashell electron-interaction-mediated photoformation of hollow atoms near threshold

Double photoionization (DPI) of an atom by a single photon is a direct consequence of electron-electron interactions within the atom. We have measured the evolution of the K-shell DPI from threshold up in transition metals by high-resolution x-ray emission spectroscopy of the Kh alpha hypersatellites, photoexcited by monochromatized synchrotron radiation. The measured evolution of the single-to-double photoionization cross-section ratio with excitation energy was found to be universal. Theoretical fits suggest that near threshold DPI is predominantly a semiclassical knockout effect, rather than the purely quantum-mechanical shake-off observed at the infinite photon energy limit.

Low-energy charge-density excitations in MgB2: Striking interplay between single-particle and collective behavior for large momenta

A sharp feature in the charge-density excitation spectra of single-crystal MgB2, displaying a remarkable cosinelike, periodic energy dispersion with momentum transfer (q) along the c* axis, has been observed for the first time by high-resolution nonresonant inelastic x-ray scattering (NIXS). Time-dependent density-functional theory calculations show that the physics underlying the NIXS data is strong coupling between single-particle and collective degrees of freedom, mediated by large crystal local-field effects. As a result, the small-q collective mode residing in the single-particle excitation gap of the B pi bands reappears periodically in higher Brillouin zones. The NIXS data thus embody a novel signature of the layered electronic structure of MgB2.

Valence band x-ray emission spectra of compressed germanium

We report measurements of the valence band width in compressed Ge determined from x-ray emission spectra below the Ge K edge. The width of the valence band does not show any pressure dependence in the semiconducting diamond-type structure of Ge below 10 GPa. On the other hand, in the metallic beta-Sn phase above 10 GPa the valence band width increases under compression. Density-functional calculations show an increasing valence band width under compression both in the semiconducting phase (contrary to experiment) and in the metallic beta-Sn phase of Ge (in agreement with observed pressure-induced broadening). The pressure-independent valence band width in the semiconducting phase of Ge appears to require theoretical advances beyond the density-functional theory or the GW approximation.

Recombinant viral RdRps can initiate RNA synthesis from circular templates

The crystal structure of the recombinant hepatitis C virus (HCV) RNA-dependent RNA polymerase (RdRp) revealed extensive interactions between the fingers and the thumb subdomains, resulting in a closed conformation with an established template channel that should specifically accept single-stranded templates. We made circularized RNA templates and found that they were efficiently used by the HCV RdRp to synthesize product RNAs that are significantly longer than the template, suggesting that RdRp could exist in an open conformation prior to template binding. RNA synthesis using circular RNA templates had properties similar to those previously documented for linear RNA, including a need for higher GTP concentration for initiation, usage of GTP analogs, sensitivity to salt, and involvement of active-site residues for product formation. Some products were resistant to challenge with the template competitor heparin, indicating that the elongation complexes remain bound to template and are competent for RNA synthesis. Other products were not elongated in the presence of heparin, indicating that the elongation complex was terminated. Lastly, recombinant RdRps from two other flaviviruses and from the Pseudomonas phage phi6 also could use circular RNA templates for RNA-dependent RNA synthesis, although the phi6 RdRp could only use circular RNAs made from the 3'-terminal sequence of the phi6 genome.

Observation of structural anisotropy and the onset of liquidlike motion during the nonthermal melting of InSb

The melting dynamics of laser excited InSb have been studied with femtosecond x-ray diffraction. These measurements observe the delayed onset of diffusive atomic motion, signaling the appearance of liquidlike dynamics. They also demonstrate that the root-mean-squared displacement in the [111] direction increases faster than in the [110] direction after the first 500 fs. This structural anisotropy indicates that the initially generated fluid differs significantly from the equilibrium liquid.

Atomic-Scale Visualization of Inertial Dynamics

The motion of atoms on interatomic potential energy surfaces is fundamental to the dynamics of liquids and solids. An accelerator-based source of femtosecond x-ray pulses allowed us to follow directly atomic displacements on an optically modified energy landscape, leading eventually to the transition from crystalline solid to disordered liquid. We show that, to first order in time, the dynamics are inertial, and we place constraints on the shape and curvature of the transition-state potential energy surface. Our measurements point toward analogies between this nonequilibrium phase transition and the short-time dynamics intrinsic to equilibrium liquids.

Clocking femtosecond X rays

Linear-accelerator-based sources will revolutionize ultrafast x-ray science due to their unprecedented brightness and short pulse duration. However, time-resolved studies at the resolution of the x-ray pulse duration are hampered by the inability to precisely synchronize an external laser to the accelerator. At the Sub-Picosecond Pulse Source at the Stanford Linear-Accelerator Center we solved this problem by measuring the arrival time of each high energy electron bunch with electro-optic sampling. This measurement indirectly determined the arrival time of each x-ray pulse relative to an external pump laser pulse with a time resolution of better than 60 fs rms.

Ordering of hydrogen bonds in high-pressure low-temperature H2O

The near K-edge structure of oxygen in liquid water and ices III, II, and IX at 0.25 GPa and several low temperatures down to 4 K has been studied using inelastic x-ray scattering at 9884.7 eV with a total energy resolution of 305 and 175 meV. A marked decrease of the preedge intensity from the liquid phase and ice III to ices II and IX is attributed to ordering of the hydrogen bonds in the proton-ordered lattice of the latter phases. Density functional theory calculations including the influence of the Madelung potential of the ice IX crystal correctly account for the remaining preedge feature. Furthermore, we obtain spectroscopic evidence suggesting a possible new phase of ice at temperatures between 4 and 50 K.

De novo initiation pocket mutations have multiple effects on hepatitis C virus RNA-dependent RNA polymerase activities

The hepatitis C virus (HCV) RNA-dependent RNA polymerase (RdRp) has several distinct biochemical activities, including initiation of RNA synthesis by a de novo mechanism, extension from a primed template, nontemplated nucleotide addition, and synthesis of a recombinant RNA product from two or more noncovalently linked templates (template switch). All of these activities require specific interaction with nucleoside triphosphates (NTPs). Based on the structure of the HCV RdRp bound to NTP (S. Bressanelli, L. Tomei, F. A. Rey, and R. DeFrancesco, J. Virol. 76:3482-3492, 2002), we mutated the amino acid residues that contact the putative initiation GTP and examined the effects on the various activities. Although all mutations retained the ability for primer extension, alanine substitution at R48, R158, R386, R394, or D225 decreased de novo initiation, and two or more mutations abolished de novo initiation. While the prototype enzyme had a K(m) for GTP of 3.5 microM, all of the mutations except one had K(m)s that were three- to sevenfold higher. These results demonstrate that the affected residues are functionally required to interact with the initiation nucleotide. Unexpectedly, many of the mutations also affected the addition of nontemplated nucleotide, indicating that residues in the initiating NTP (NTPi)-binding pocket are required for nontemplated nucleotide additions. Interestingly, mutations in D225 are dramatically affected in template switch, indicating that this residue of the NTPi pocket also interacts with components in the elongation complex. We also examined the interaction of ribavirin triphosphate with the NTPi-binding site.

Small-gap insertion-device development at the National Synchrotron Light Source--performance of the new X13 mini-gap undulator

The National Synchrotron Light Source (NSLS) 2.8 GeV electron storage ring continues to set high standards in insertion-device research and development. The Chasman-Green NSLS lattice design provides for dispersion-free long straight sections in addition to a very small vertical beta function. As the electron beam size is proportional to the square root of this function, a program to exploit this feature was undertaken more than a decade ago by implementing short-period small-gap insertion devices in the NSLS storage ring. The possibility of utilizing existing moderate-energy synchrotron radiation electron storage rings to produce high-brightness photon beams into the harder X-ray region have been realised using in-vacuum undulators. In this article the operation of a 1.25 cm-period mini-gap undulator, operating down to a gap of 3.3 mm within the NSLS X13 straight section, is reported. It is the brightest source of hard X-rays in the energy range approximately 3.7-16 keV at the NSLS, and replaces an in-vacuum undulator which had a more limited tunability.

Diagram X-ray emission spectra of a hollow atom: the Kh alpha1,2 and Kh beta1,3 hypersatellites of Fe

High-resolution Fe K(h) beta(1,3) and K(h) alpha(1,2) hypersatellite spectra were measured, using monochromatized synchrotron radiation photoexcitation. The lines' energies, splitting, excitation thresholds, and the K(h) alpha(1)/K(h) alpha(2) intensity ratio were derived with high accuracy. Having both spectra, not hitherto available for any atom with high resolution, allows separating out the energy shifts of the outer levels caused by a K shell spectator vacancy. Comparison with ab initio relativistic multiconfigurational Dirac-Fock calculations reveals that while the influence of relativity and QED effects is mostly accounted for, discrepancies remain in the lines' intensity ratio, which sensitively measures the intermediacy of the coupling. Similar discrepancies, of unknown origin, are found in the energy shifts of the outer levels due to the final-state K shell spectator vacancy.

Single-element elliptical hard x-ray micro-optics

Using micro-fabrication techniques, we have manufactured a single element kinoform lens in single-crystal silicon with an elliptical profile for 12.398 keV (1A) x-rays. By fabricating a lens that is optimized at fixed wavelengths, absorption in the lens material can be significantly reduced by removing 2_ phase-shifting regions. This permits short focal length devices to be fabricated with small radii of curvatures at the lens apex. This feature allows one to obtain a high demagnification of a finite synchrotron electron source size. The reduced absorption loss also enables optics with a larger aperture, and hence improved resolution for focusing and imaging applications. Our first trial of these lenses has resulted in a one micron line focus (fwhm) at the National Synchrotron Light Source X13B beamline.

A lamellar model for the X-ray rocking curves of sagittally bent Laue crystals

The use of sagittally bent asymmetric Laue crystals in horizontally focusing monochromators for high-energy synchrotron X-rays necessitates simulation of the X-ray reflectivity by such crystals. Based on the theory of the lattice distortion in the diffraction plane of sagittally bent Laue crystals, a lamellar model was developed to predict their rocking curves. The model was experimentally verified by rocking-curve measurements from various reflections on silicon crystals of four representative orientations, sagittally bent to various radii, using X-rays of 67 keV energy.

Rocking-curve width of sagittally bent Laue crystals

The use of bent asymmetric Laue crystals to sagittally focus high-energy synchrotron X-rays calls for an understanding of the mechanisms affecting X-ray diffraction by such crystals. The rocking-curve width, a measurable quantity directly related to the distortion of the lattice planes, is the necessary first step towards such an understanding. A model is formulated for assessing the rocking-curve widths of sagittally bent Laue crystals, considering the elastic anisotropy. A method for depth-resolved measurement of the rocking curves was also developed to verify the model. The model successfully explains the wide range of rocking-curve widths of a large number of reflections from silicon crystals with two different orientations.

Reconstruction of magnetization density in two-dimensional samples from soft X-ray speckle patterns using the multiple-wavelength anomalous diffraction method

A non-destructive technique for imaging magnetic domains in thin films and two-dimensional magnetic structures using coherent soft X-ray scattering and the multiple-wavelength anomalous diffraction method (MAD) is proposed. The method exploits the strong energy dependence in the magnetic scattering amplitude for 3d transition metals near the L(2,3) absorption edges and 4f elements near the M(4,5) absorption edges. The phase information required in the reconstruction algorithm is derived from the interference between the charge and magnetic scattering amplitudes. Magnetic speckle patterns from the magnetic domain distribution in an artificially defined Fe thin film are used to demonstrate this reconstruction algorithm. Circularly and linearly polarized incident light are examined separately to investigate the effect of polarization on the capability of the method.

Association between serum inflammatory cytokines and disease activity in juvenile idiopathic arthritis

Circulating interleukin-1beta (IL-1beta), IL-6, tumour necrosis factor-alpha (TNF-alpha), osteocalcin, and conventional parameters of inflammation were examined serially in 14 children with juvenile idiopathic arthritis (JIA) to determine any correlation with the disease activity. Serum IL-1beta was undetectable in all JIA patients. Serum IL-6, white blood cell counts, platelet counts, erythrocyte sedimentation rate and C-reactive protein levels were significantly elevated in the active phase of JIA, whereas hemoglobin levels were significantly lower. Osteocalcin levels were decreased and TNF-alpha increased in active JIA status, but these differences showed no statistical significance. We concluded that inflammatory cytokines play an important role in JIA. Monitoring IL-6 in children with JIA is useful in determining disease activity and response to therapy. These findings confirm earlier reports.

Core promoter for initiation of Cucumber mosaic virus subgenomic RNA4A

summary The core subgenomic promoter for the initiation of Cucumber mosaic virus (CMV) RNA4A was characterized in vitro using a template-dependent RNA synthesis assay and variants of the core promoter RNAs. The minimal sequence required for specific initiation from the cytidylate (T1) used in vivo consists of 31-nucleotides (nt) 3' of T1 and a 13 nt template sequence. This 44 nt RNA was found to provide three elements that contribute to efficient initiation of RNA4A synthesis by the CMV replicase: a stem-loop secondary structure 3' of T1, a template sequence that is rich in adenylates and uridylates, and T1 in an unbase-paired sequence.

Development of a high-performance liquid chromatographic method for bioanalytical applications with sulpiride

An improved HPLC method using a silica gel column with fluorescence detection (excitation at 300 nm and emission at 365 nm) was developed for the determination of sulpiride concentrations in plasma. Analysis of sulpiride in plasma samples was simplified by a one-step liquid-liquid extraction after alkaline treatment of only 1 ml of plasma. The low limit of quantitation was 20 ng/ml with a coefficient of variation of less than 20%. A linear range was found from 20 to 1500 ng/ml. This HPLC method was validated with the precision for inter-day and intra-day runs being 0.36-8.01% and 0.29-5.25%, respectively, and the accuracy (standard deviation of mean, SD) for inter-day and intra-day runs being -1.58 to 5.02% and -2.14 to 5.21%, respectively. Bioequivalence of the two products was evaluated in 12 normal healthy male volunteers in a single-dose, two-period, two-sequence, two-treatment cross-over study. Sulpiride plasma concentrations were analyzed with this validated HPLC method. Results demonstrated that the two tablet formulations of sulpiride appear to be bioequivalent.

A mutant viral RNA promoter with an altered conformation retains efficient recognition by a viral RNA replicase through a solution-exposed adenine

Brome mosaic virus (BMV) genomic minus-strand RNA synthesis requires an RNA motif named stem-loop C (SLC). An NMR-derived solution structure of SLC was reported by Kim et al. (Nature Struc Biol, 2000, 7:415-423) to contain three replicase-recognition elements, the most important of which is a stable stem with a terminal trinucleotide loop, 5'AUA3'. The 5'-most adenine of the triloop is rigidly fixed to the stem helix by interactions that require the 3'-most adenine, which is called a clamped adenine motif. However, a change of the 3' adenine to guanine (5'AUG3') unexpectedly directed RNA synthesis at 130% of wild type (Kim et al., Nature Struc Biol, 2000, 7:415-423). To understand how RNA with the AUG mutation maintains interaction with the BMV replicase, we used NMR and other biophysical techniques to elucidate the solution conformation of a 13-nt RNA containing the AUG triloop, called S-AUG. We found that S-AUG has a drastically different loop conformation in comparison to the wild type, as evidenced by an unusual C x G loop-closing base pair. Despite the conformational change, S-AUG maintains a solution-exposed adenine similar to the clamped adenine motif found in the wild type. Biochemical studies of the 5'AUG3' loop with various substitutions in the context of the whole SLC construct confirm that the clamped adenine motif exists in S-AUG remains a primary structural feature required for RNA synthesis by the BMV replicase.

Terminal nucleotidyl transferase activity of recombinant Flaviviridae RNA-dependent RNA polymerases: implication for viral RNA synthesis

Recombinant hepatitis C virus (HCV) RNA-dependent RNA polymerase (RdRp) was reported to possess terminal transferase (TNTase) activity, the ability to add nontemplated nucleotides to the 3' end of viral RNAs. However, this TNTase was later purported to be a cellular enzyme copurifying with the HCV RdRp. In this report, we present evidence that TNTase activity is an inherent function of HCV and bovine viral diarrhea virus RdRps highly purified from both prokaryotic and eukaryotic cells. A change of the highly conserved GDD catalytic motif in the HCV RdRp to GAA abolished both RNA synthesis and TNTase activity. Furthermore, the nucleotides added via this TNTase activity are strongly influenced by the sequence near the 3' terminus of the viral template RNA, perhaps accounting for the previous discrepant observations between RdRp preparations. Last, the RdRp TNTase activity was shown to restore the ability to direct initiation of RNA synthesis in vitro on an initiation-defective RNA substrate, thereby implicating this activity in maintaining the integrity of the viral genome termini.

Completion of RNA synthesis by viral RNA replicases

How the 5'-terminus of the template affects RNA synthesis by viral RNA replicases is poorly understood. Using short DNA, RNA and RNA-DNA chimeric templates that can direct synthesis of replicase products, we found that DNA templates tend to direct the synthesis of RNA products that are shorter by 1 nt in comparison to RNA templates. Template-length RNA synthesis was also affected by the concentration of nucleoside triphosphates, the identity of the bases at specific positions close to the 5'-terminus and the C2'-hydroxyl of a ribose at the third nucleotide from the 5'-terminal nucleotide. Similar requirements are observed with two bromoviral replicases, but not with a recombinant RNA-dependent RNA polymerase. These results begin to define the interactions needed for the viral replicase to complete synthesis of viral RNA.

De novo initiation of viral RNA-dependent RNA synthesis

RNA viruses use several initiation strategies to ensure that their RNAs are synthesized in appropriate amounts, have correct termini, and can be translated efficiently. Many viruses with genomes of single-stranded positive-, negative-, and double-stranded RNA initiate RNA synthesis by a de novo (primer-independent) mechanism. This review summarizes biochemical features and variations of de novo initiation in viral RNA replication.

Time trends and seasonal variations in hospital admissions for childhood asthma in Taiwan from 1990 to 1998

The aim of the study was to determine the trends and seasonal variations in hospital admissions for childhood asthma in a tertiary medical center since 1990. Data were collected according to the age and sex of patients and obtained from hospital registries between 1990 and 1998. Children between 2 and 14 years of age admitted with the diagnosis of asthma, or asthmatic bronchitis (ICD-9 code 493) were included. Age-specific and sex-specific hospital admission rates for asthma were calculated for each calendar year. The asthma admission rates were defined as the number of asthma admissions divided by the total number of all pediatric admissions in a year. Seasonal admission rates were calculated in a similar fashion. In addition, the number of readmissions was also calculated during the study period with comparisons of sex and age differences. The asthma admission rates showed a significant upward trend throughout the period studied, particularly among the 2-4 years of age group (relative risk = 2.08; p = 0.0001). Seasonal admission rates revealed a statistically significant increase during the October-December period, peaking in November or December of each calendar year (relative risk = 1.84; p = 0.0001). There was a male predominance in both age categories during the 9-year period. Comparisons of readmissions for asthma (at least three admissions) disclosed that girls were far more likely to be readmitted than boys among the 5-14 years of age group (p = 0.01). Our results indicate 1) an increased prevalence and severity of childhood asthma in Taiwan; 2) boys and younger children aged 2-4 years with asthma had increased risks of admission for asthma (relative risks were 1.22 and 1.96, respectively) and 3) girls among the older children with asthma tend to present with greater severity than boys owing to higher relative risks of readmission for asthma.

Spin-resolved NEXAFS from resonant X-ray scattering (RXS)

Resonantly excited metal K core line spectra of NiO, MnO, CoO and other compounds have been investigated at the beamlines X21 (NSLS/BNL), BW1 and W1.1 (HASYLAB/DESY). From analysis of spectral data we have drawn the following conclusions: -spin conservation is valid in the scattering process, for excitations below the absorption threshold as well as above it, -the absorption thresholds are different for spin-up and spin-down components of resonantly scattered spectra, -quadrupole transitions are very important or even crucial in the excitation process. Provided that these conclusions are true, a novel technique for quantitative resolution of NEXAFS spectra into spin-up and spin-down components has been developed. Since the method employs spin conservation and local spin references, it needs no circularly polarized radiation and no sample magnetization for taking both the RXS and NEXAFS spectra. Hence antiferromagnetic and paramagnetic materials can be investigated as well. Utilizing linear dichroism by angular-dependent measurements on single-crystal samples additional resolution of NEXAFS spectra is possible with respect to the orbital symmetry. Application of the method to paramagnetic MnO, for the first time, provides new and unambiguous experimental results confirming modern (LSDA+U) calculations: The metal K pre-edge XAS of MnO has predominantly 3d(t2g and eg) spin-down character. On the other hand, the delocalized p-like states, arising from the p-d band effect hybridization have spin-up character.

Tumor lysis syndrome in an infant with Langerhans cell histiocytosis successfully treated using continuous arteriovenous hemofiltration

Langerhans cell histiocytosis (LCH) is an enigmatic disease usually occurring in children. Tumor lysis syndrome (TLS) is a clinical syndrome associated with severe metabolic derangement and oliguric acute renal failure. In this report, we present the clinical course of an infant with advanced LCH who had TLS develop after chemotherapy. Treatment with continuous arteriovenous hemofiltration resulted in effective control of serum uric acid, potassium, creatinine, phosphorus, and blood urea nitrogen levels in the blood.

Template requirements for RNA synthesis by a recombinant hepatitis C virus RNA-dependent RNA polymerase

The RNA-dependent RNA polymerase (RdRp) from hepatitis C virus (HCV), nonstructural protein 5B (NS5B), has recently been shown to direct de novo initiation using a number of complex RNA templates. In this study, we analyzed the features in simple RNA templates that are required to direct de novo initiation of RNA synthesis by HCV NS5B. NS5B was found to protect RNA fragments of 8 to 10 nucleotides (nt) from RNase digestion. However, NS5B could not direct RNA synthesis unless the template contained a stable secondary structure and a single-stranded sequence that contained at least one 3' cytidylate. The structure of a 25-nt template, named SLD3, was determined by nuclear magnetic resonance spectroscopy to contain an 8-bp stem and a 6-nt single-stranded sequence. Systematic analysis of changes in SLD3 revealed which features in the stem, loop, and 3' single-stranded sequence were required for efficient RNA synthesis. Also, chimeric molecules composed of DNA and RNA demonstrated that a DNA molecule containing a 3'-terminal ribocytidylate was able to direct RNA synthesis as efficiently as a sequence composed entirely of RNA. These results define the template sequence and structure sufficient to direct the de novo initiation of RNA synthesis by HCV RdRp.

Efficient and specific initiation of subgenomic RNA synthesis by cucumber mosaic virus replicase in vitro requires an upstream RNA stem-loop

We defined the minimal core promoter sequences responsible for efficient and accurate initiation of cucumber mosaic virus (CMV) subgenomic RNA4. The necessary sequence maps to positions -28 to +15 relative to the initiation cytidylate used to initiate RNA synthesis in vivo. Positions -28 to -5 contain a 9-bp stem and a 6-nucleotide purine-rich loop. Considerable changes in the stem and the loop are tolerated for RNA synthesis, including replacement with a different stem-loop. In a template competition assay, the stem-loop and the initiation cytidylate are sufficient to interact with the CMV replicase. Thus, the mechanism of core promoter recognition by the CMV replicase appears to be less specific in comparison to the minimal subgenomic core promoter of the closely related brome mosaic virus.

Genomic plus-strand RNA synthesis by the brome mosaic virus (BMV) RNA replicase requires a sequence that is complementary to the binding site of the BMV helicase-like protein

Summary Initiation of genomic plus-strand RNA synthesis by the brome mosaic virus (BMV) replicase in vitro requires a 26-nucleotide (nt) RNA sequence at the 3' end of the minus-strand RNA and a nontemplated nucleotide 3' of the initiation cytidylate [Sivakumaran, K. and Kao, C.C. (1999)J. Virol.64, 6415-6423]. At the 5' end of this RNA is a 9-nt sequence called the cB box, the complement of the previously defined B box. The cB box can not be functionally replaced by the B box and has specific positional and sequence requirements. The portion of the cB box that is required for RNA synthesis in vitro is well-conserved in species in the Bromoviridae family. An equivalent RNA from Cucumber mosaic virus was unable to direct efficient RNA synthesis by the BMV replicase until the cB box was positioned at the same site relative to the BMV RNA and guanylates were present at positions +6 and +7 from the initiation cytidylate. These results further define the elements required for the recognition and initiation of viral genomic plus-strand RNA synthesis and suggest that a sequence important for minus-strand RNA synthesis is also required for plus-strand RNA synthesis.

Template nucleotide moieties required for de novo initiation of RNA synthesis by a recombinant viral RNA-dependent RNA polymerase

The recombinant RNA-dependent RNA polymerase of the bovine viral diarrhea virus specifically requires a cytidylate at the 3' end for the de novo initiation of RNA synthesis (C. C. Kao, A. M. Del Vecchio, and W. Zhong, Virology 253:1-7, 1999). Using RNAs containing nucleotide analogs, we found that the N3 and C4-amino group at the initiation cytidine were required for RNA synthesis. However, the ribose C2'-hydroxyl of the initiating cytidylate can accept several modifications and retain the ability to direct synthesis. The only unacceptable modification is a protonated C2'-amino group. Quite strikingly, the recognition of the functional groups for the initiation cytidylate and other template nucleotides are different. For example, a C5-methyl group in cytidine can direct RNA synthesis at all template positions except at the initiation cytidylate and C2'-amino modifications are tolerated better after the +11 position. When a 4-thiouracil (4sU) base analog that allows only imperfect base pairing with the nascent RNA is placed at different positions in the template, the efficiency of synthesis is correlated with the calculated stability of the template-nascent RNA duplex adjacent to the position of the 4sU. These results define the requirements for the specific interactions required for the initiation of RNA synthesis and will be compared to the mechanisms of initiation by other RNA-dependent and DNA-dependent RNA polymerases.