Bestimmung der Geschwindigkeitskonstante der Bromierungsreaktion von Acetanilid mittels Titrationsmethode in diffuser Schicht an der rotierenden Ring-Scheiben-Elektrode

The kinetics of the bromination of acetanilide has been studied with the diffusion layer titration method. The results have been obtained using the apparatus which consists of the ring-disc electrode and an amperostat-potentiostat system. Dependence of the ring current on the disc current has been determined as a function of rotation speeds of the electrode, of the solution concentration and temperature. It has been shown the bromination reaction of acetanilide exhibits by first order kinetics. In that case Br₂ and Br₃ ^? are the brominating species. The rate of bromination changes with the concentration of the Br^? ions. This reaction rate depends on reactions of molecular bromine with acetanilide. For 0.033<[Br^?]<0.173M the rate constant changes in the following range: $$17530M^{ - 1} s^{ - 1}< k< 6400M^{ - 1} s^{ - 1} ([H + ] = 1,34;T = 298K)$$      

Stepwise O2-Induced Rearrangement and Disassembly of the [NiFe4(OH)(μ3-S)4] Active Site Cluster of CO Dehydrogenase

Ni,Fe-containing carbon monoxide dehydrogenases (CODHs) catalyze the reversible reduction of carbon dioxide to carbon monoxide. CODHs are found in anaerobic microorganisms and can rapidly lose their activity when exposed to air. What causes the loss of activity is unclear. In this study, we analyzed the time-dependent structural changes induced by the presence of air on the metal centers of CODH-II. We show that inactivation is a multistep process. In a reversible step, the open coordination site on the Ni ion is blocked by a Ni,Fe-bridging μ-sulfido or chlorido ligand. Blocking this open coordination site with a cyanide ligand stabilizes the cluster against O₂-induced decomposition, indicating that O₂ attacks at the Ni ion. In the subsequent irreversible phase, nickel is lost, the Fe ions rearrange and the sulfido ligands disappear. Our data are consistent with a reversible reductive reactivation mechanism to protect CODHs from transient over-oxidation.     

Analytical method development for exploring pharmacokinetic profile of ursolic acid in rat tissues by high-performance thin-layer chromatography

JPC – Journal of Planar Chromatography – Modern TLC - A simple and rapid high-performance thin-layer chromatographic (HPTLC) determination of ursolic acid (UA) in tissue is necessary...     

Interlocked multiplets in anisotropically scattering medium with exponential Planck function

The equation of transfer for interlocked multiplets in anisotropically scattering atmosphere with planetary phase function has been considered. The Planck function is considered as exponential function of optical depth. The diffusely reflected intensity and emergent intensity in nth approximation has been obtained. Attempt has been made to get exact diffusely reflected intensity and emergent intensity.     

Characterization of buffers for electrokinetic separations

Buffers used in electrophoresis and electrochromatography must have a relatively low ionic strength in order to minimize ohmic heating in the presence of an applied potential. Calculation of pH, ionic strength, and the van Slyke buffer capacity, β, is therefore important. This paper describes thea priori calculation of these parameters for tris buffer made up with either glycine (a zwitterion) or HCl. A quadratic expression for pH, valid over wide ranges, is obtained for both buffer systems. The calculated values of pH, ionic strength, and buffer capacity are shown to agree with experimental results as a function of tris, HCl, and glycine concentrations ranging from 1 to 50 mM. A new parameter, the electrokinetic buffer effectiveness factor, is introduced to characterize buffers being considered for use in electrokinetic systems such as electrochromatography, and is used to determine the appropriate composition ranges for the buffer components.     

IBX/Sc(OTf)3-promoted one-pot oxidative conjugate addition of allyltrimethylsilane to Baylis-Hillman adducts

Baylis-Hillman adducts undergo smooth one-pot oxidative Michael addition with allyltrimethylsilane in the presence of 2-iodoxybenzoic acid (IBX)/Sc(OTf)₃ under mild conditions to afford homoallyl β-ketoesters in good yields with high 1,4-selectivity.     

Synthetically Tuning the 2‐Position of Halogenated Quinolines: Optimizing Antibacterial and Biofilm Eradication Activities via Alkylation and Reductive Amination Pathways

Agents capable of eradicating bacterial biofilms are of great importance to human health as biofilm‐associated infections are tolerant to our current antibiotic therapies. We have recently discovered that halogenated quinoline (HQ) small molecules are: 1) capable of eradicating methicillin‐resistant Staphylococcus aureus (MRSA), methicillin‐resistant Staphylococcus epidermidis (MRSE) and vancomycin‐resistant Enterococcus faecium (VRE) biofilms, and 2) synthetic tuning of the 2‐position of the HQ scaffold has a significant impact on antibacterial and antibiofilm activities. Here, we report the chemical synthesis and biological evaluation of 39 HQ analogues that have a high degree of structural diversity at the 2‐position. We identified diverse analogues that are alkylated and aminated at the 2‐position of the HQ scaffold and demonstrate potent antibacterial (MIC≤0.39 μm ) and biofilm eradication (MBEC 1.0–93.8 μm ) activities against drug‐resistant Staphylococcus aureus, Staphylococcus epidermidis and Enterococcus faecium strains while demonstrating <5 % haemolysis activity against human red blood cells (RBCs) at 200 μm . In addition, these HQs demonstrated low cytotoxicity against HeLa cells. Halogenated quinolines are a promising class of antibiofilm agents against Gram‐positive pathogens that could lead to useful treatments against persistent bacterial infections.