Improved method to determine succinylacetone in dried blood spots for diagnosis of tyrosinemia type 1 using UPLC-MS/MS

We describe an improved diagnostic method for tyrosinemia type 1 based on quantifying succinylacetone in dried blood spots by ultra-performance liquid chromatography tandem mass spectrometry. Succinylacetone extracted from a single 3/16 inch disk of specimen collection paper containing a dried blood spot was derivatized with dansylhydrazine, separated on an Acquity UPLC BEH C(18) column (2.1 x 50 mm, 1.7 microm) and detected by electrospray ionization tandem mass spectrometry. Succinylacetone derivative eluted at 0.6 min with a complete run time of 1 min. Using a 13C4 labeled succinylacetone as an internal standard, the calibration plot was linear up to 100 micromol/L with a detection limit (S/N = 3) of 0.2 micromol/L. Intra-day (n = 13) and inter-day (n = 10) variations were better than 10%. The cutoff level of succinylacetone in dried blood spots from healthy infants obtained by the current method was 0.63 micromol/L (n = 151). In dried blood spots from patients with established tyrosinemia type 1 (n = 11), concentration of succinylacetone was 6.4-30.8 micromol/L.     

Merging Iron Catalysis and Biocatalysis—Iron Carbonyl Complexes as Efficient Hydrogen Autotransfer Catalysts in Dynamic Kinetic Resolutions

A dual catalytic iron/lipase system has been developed and applied in the dynamic kinetic resolution of benzylic and aliphatic secondary alcohols. A detailed study of the Knölker‐type iron complexes demonstrated the hydrogen autotransfer of alcohols to proceed under mild reaction conditions and allowed the combination with the enzymatic resolution. Different racemic alcohols were efficiently converted to chiral acetates in good yields and with excellent enantioselectivities.     

Investigating 2,2'-bipyridine-3,3'-diol as a microenvironment-sensitive probe: its binding to cyclodextrins and human serum albumin

The 2,2'-bipyridine-3,3'-diol molecule (BP(OH)2) was investigated as a potential photophysical probe in inclusion and biological studies. Binding of BP(OH)2 to cyclodextrins (CDs) and human serum albumin (HSA) was studied by following the changes in its absorption and fluorescence spectra. The stoichiometric ratios and binding constants of the complexes were deduced by fitting the changes in the spectral intensity to binding isotherms. The stoichiometric ratio in the BP(OH)2/(alpha-CD) complex is dominated by 1:2, whereas in all other CDs and in HSA this ratio is 1:1. The structure of the BP(OH)2:(alpha-CD)2 complex, calculated using ab initio methods, indicates that the inclusion of the BP(OH)2 molecule is axial and centered between the two cavities of alpha-CD with van der Waals and electrostatic interactions dominating the binding. Analysis of these results along with the inclusion results of BP(OH)2 in beta-CD, methyl-beta-CD, 2,6-di-O-methyl-beta-CD, and gamma-CD shows that absorption and fluorescence of BP(OH)2 are very sensitive to the change in the cavity size of CD and its hydrophobicity. This change is reflected in the form of a decrease in the intensity of the absorption peaks of the BP(OH)2/water complex in the region 400-450 nm and a red shift in the fluorescence peak as the cavity size decreases and its hydrophobicity increases. Binding of BP(OH)2 as a probe ligand to HSA, a prototype protein, reflects the hydrophobic interior of HSA in a similar manner. The spectral changes indicate that BP(OH)2 binds in the hydrophobic cavity of HSA's subdomain IIA. The results presented here show that BP(OH)2 can be used in binding sites and biological systems as a microenvironment-sensitive probe.     

Solubility of pyrene in simple and mixed solvent systems

The solubility of pyrene was experimentally determined in simple and complex solvent systems (single, binary, ternary, quaternary and pentinary solvent systems) composed of benzene, ethylbenzene, hexane, hexanol and methylcyclohexane over a temperature range from 293 to 318 K. In addition, six models were used in this study to represent pyrene solubility in the different solvent systems. The interaction parameters for modified Wilson, NIBS/Redlich-Kister, UNIQUAC and NRTL models were estimated using the solubility data generated for pyrene in single, binary and ternary solvent systems. By re-adjusting the interaction parameters reported for Dortmund UNIFAC and ASOG models, a better representation of the solubility of pyrene was obtained compared to using reported values. Furthermore, a correction term is introduced for the ASOG model in this study to better improve pyrene solubility prediction in simple and mixed solvent systems. These estimated or re-adjusted interaction parameters for the different models, along with the reported parameters for Dortmund UNIFAC and ASOG models, were tested on complex solvent systems (quaternary and pentinary solvent mixtures), in order to check their validity and accuracy for such predictions.     

Growth Mechanism of Metal–Organic Frameworks: Insights into the Nucleation by Employing a Step‐by‐Step Route

One step at a time : The in situ monitoring of the step‐by‐step formation of metal–organic frameworks (MOFs) by using surface plasmon resonance (SPR), allows the nucleation process and the formation of the secondary building units to be investigated. Growth rates on functionalized organic surfaces with different crystallographic orientations can also be studied.

     

Development of a gradient elution preparative high performance liquid chromatography method for the recovery of the antibiotic ertapenem from crystallization process streams

A gradient elution preparative chromatography method was developed for the recovery of the antibiotic ertapenem from crystallization mother-liquor streams. The preparative HPLC method that was developed on the lab-scale employs an analytical size column of conventional dimensions (25 cm x 0.46 cm) packed with Kromasil C8 stationary phase. Gradient elution was used with aqueous acetic acid and acetonitrile as mobile phases. A target of processing approximately 30 mg of ertapenem per half an hour at a flow rate of 1.5 mL/min with high yield and adequate rejection of all major impurities was achieved. This corresponds to a productivity of approximately 0.6 kg ertapenem as free acid per kilogram of stationary phase per day (kkd). The scalability of the method was demonstrated by using a 5 cm i.d. column configuration to generate 10 g of purified ertapenem. This work complements a previous study improving on the productivity and throughput of the method by employing gradient elution and the use of crystallization to remove some key impurities that are chromatographically difficult to resolve [A. Vailaya, P. Sajonz, O. Sudah, V. Capodanno, R. Helmy, F.D. Antia, J. Chromatogr. A 1079 (2005) 80].     

Improvement of sintering,nonlinear electrical,and dielectric properties of ZnO-based varistors doped with TiO_2

The effects of TiO_2 on sintering and nonlinear electrical properties of(98.5-x)ZnO–0.5MnO_2–0.5Co_2O_3-0.5Bi_2O_(3–x)TiO_2(x = 0.3,0.5,0.7,0.9 mol%) ceramic varistors prepared by the ceramic technique are investigated in this work.The optimum sintering temperature of the prepared samples is deduced by determining the firing shrinkage and water absorption percentages.The optimum sintering temperature is found to be 1200℃,at which each of the samples shows a maximum firing shrinkage and minimum water absorption.Also minimum water absorption appears in a sample of x = 0.9 mol%.Higher sintering temperature and longer sintering time give rise to a reduction in bulk density due to the increased amount of porosity between the large grains of ZnO resulting from the rapid grain growth induced by the liquid phase sintering.The crystal size of ZnO decreases with increasing TiO_2 doping.The addition of TiO_2 improves the nonlinear coefficient and attains its maximum value at x = 0.7 mol% of TiO_2,further addition negatively affects it.A decrease in capacitance consequently in the dielectric constant is recorded with increasing the frequency in a range of 30 kHz–200 kHz.The temperature and composition dependences of the dielectric constant and AC conductivity are also studied.The increase of temperature raises the dielectric constant because it increases ionic response to the field at any particular frequency.     

1H-1,2,3-triazole,a promising precursor for chemical vapor deposition of hydrogenated carbon nitride

Well-crystallized hydrogenated carbon nitride thin films have been prepared by microwave plasma enhanced chemical vapor deposition (MWPECVD). 1H-1,2,3-triazole+N₂ and Si (1 0 0) were used as precursor and substrate, respectively. Substrate temperature during the deposition was recorded to be 850 °C. The synthesized samples were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), and X-ray photo-electron spectroscopy (XPS) analyses. The plasma compositions were checked by optical emission spectroscopy (OES). XRD observation strongly suggests that the films contain polycrystalline carbon nitride with graphitic structure of (1 0 0), (0 0 2), (2 0 0) and (0 0 4). XPS peak quantification reveals that the atomic ratio of the materials C:N:O:Si is 32:41:18:9. X-ray photo-electron peak deconvolution shows that the most dominant peak of C (1s) and N (1s) narrow scans correspond to sp² hybrid structure of C₃N₄. These observations indicate that 1H-1,2,3-triazole favors the formation of hydrogenated carbon nitride with graphitic phase by CVD method and thus is in good agreement with XRD results. SEM of surface and OES of plasma also support the formation of polycrystalline carbon nitride films from 1H-1,2,3-triazole+N₂ by CVD.     

Performance evaluation of a WDM/OCDM based hybrid optical switch utilizing efficient resource allocation

A hybrid optical switch （HOS） with physical layer of wavelength division multiplexing and optical code division multiplexing （WDM/OCDM） scheme is proposed. An additional feature to the HOS than optical cross connect （OXC） is that the controller can process requests for both circuit establishment and burst scheduling. In our study, the measurement criteria of HOS are the blocking probability, probability of error, and probability of outage. To simplify the analysis, no distinction is made between a circuit in progress and a burst in progress. Moreover, a minimum fit （MinF） resource allocation strategy is applied in order to increase the bandwidth efficiency and control the multiplexing interference of the OCDM. A 2D Markov model for the HOS is presented using the MinF strategy. Numerical results reveal that the code parameters and the resource allocation strategy greatly affect the performance. Certain periority can be achieved by assigning shorter codes to high periority users and longer codes to low periority users. Also, the probability of error and outage are reduced bv aonling the MinF strategy.     

Stress field characteristics of eccentrically loaded aircraft spliced joints

The paper details the stress characteristics in eccentrically loaded aircraft spliced joints. It is shown that the hoop stress (σ_θθ) around each rivet is characterized by two peak values located at θ = (0°, 90°). The magnitude of (σ_θθ) is then reduced to a minimum value between these two peaks. A sharp increase in the axial stress component (σ_xx) along the vertical splice lines occurs in the vicinity of the rivet centerlines followed by a rapid decrease in the areas between the rivets. It is shown that stresses along the first interior rivet row is the most critical. The axial stress (σ_xx) profile along horizontal rivet lines has a “sinusoidal” pattern. It is observed that the transverse stress profile (σ_yy), along the horizontal lines, has different peak and minimum values between the rivets. The magnitude of the peak/minimum values depends upon the line location within the splice region. It is also shown the bending stress component varies significantly and must be accounted for the analysis of the eccentric aircraft joints. Experimental comparisons are made along several lines in the splice region. The numerical model is utilized for analysis of a full frame-bay/splice of aircraft fuselage. The paper provides valuable information that can be utilized by practicing engineers for analysis and design of joints with large number of rivets.