Spektrochemische bestimmung von sulfat bzw. Chlorid mit roentgenfluoreszenz nach anreicherung durch mitfällung an BaCrO4 BZW. AgSCN aus verdünnten lösungen

Sulphate and chloride are quantitatively co-precipitated from dilute solutions (10^?5- 10^?4M) with BaCrO₄ and AgSCN respectively, and determined in the precipitate by X-ray fluorescence spectroscopy. Ratios of count-rates I_S/I_Cr and I_Cl/I_Sfor the appropriate K_α-lines are used for quantitative evaluation by comparison with reference standards prepared the same way. The method enables both sulphate and chloride to be determined in 50–100 ml of tap-water with a reproducibility of about 3%.     

Stopped-flow- und fluorescenzspektrometrische Untersuchungen des Bindungsverhaltens von Dansylsarkosin an Albumin in Nativserum

Zusammenfassung Mit Humanserumalbumin (HSA) von 12 gesunden mÄnnlichen Spendern, mit Aktivkohle behandelten Seren und mit aus Citratplasma isoliertem Albumin wurden Stopped-flow- und fluorescenzspektrometrische Untersuchungen der Bindung von Dansylsarkosin (DS) an HSA durchgeführt. Die AffinitÄtskonstanten sind für alle untersuchten Seren vergleichbar (K _A=5,93 · 10⁵M^–1). Die AffinitÄtskonstante des Anlagerungskomplexes ist für die 12 Spenderseren (K _A=4,31 · 10⁴M^–1) etwas höher als für mit Aktivkohle behandelte Seren und isoliertes Albumin (K _A=2,9 · 10⁴M^–1). Dagegen ist die Geschwindigkeit der Umlagerung in den stabilen DS-HSA-Komplex (t _1/2=2,4 ms für isoliertes Albumin) erniedrigt (t _1/2=3,4 ms). Die Bindungskonstanten für die DS-HSA-Komplexierung sind für die 12 Spenderseren fast identisch (Standardabweichung 15%), die Dissoziationshalbwertszeit ist für alle untersuchten Seren etwa 46 ms. Aus den Ergebnissen kann gefolgert werden, da\ sich DS im Serum ausschlie\lich an HSA bindet. In nicht mit Aktivkohle behandeltem Serum vorhandene endogene Substanzen beeinflussen allosterisch den DS-HSA-Komplex.

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Stopped-flow and fluorescence spectrometric investigations of the binding behaviour of dansylsarcosine to albumin in native serum

Summary In serum of 12 healthy men, in charcoal treated serum and with isolated albumin the binding of dansylsarcosine (DS) to human serum albumin (HSA) has been investigated by fluorescence and stopped-flow measurements. The affinity constants for all sera (K _A=5.93×10⁵M^–1)were comparable. The constant of the low affinity DS-HSA complex is in the 12 seras (K _A=4.31×10⁴M^–1) somewhat higher than in charcoal treated sera and isolated albumin (K _A=2.9×10⁴M^–1), conversion into the high affinity complex (t _1/2=3.4 ms) is faster (t _1/2=2.4 ms) for isolated albumin. Dissociation half-life of the DS-HSA complex was for all investigated sera 46 ms. HSA is probably the only acceptor for DS in serum. Endogenous substances in untreated serum are affecting DS-HSA complexation allosterically.

     

Observation of pure quadrupole resonance in zinc metal

We report the first observation of nuclear quadrupole resonance (NQR) in Zn metal. A resonance line, which under the assumption of axial symmetry (η=0) corresponds to the $\text{|M| =}\text{3}\text{2}\text{?}\text{5}\text{2}$ transition in the $\text{I =}\text{5}\text{2}$ ground state of ⁶⁷Zn, has been found at v = 4.086(2) MHz at 4.2K. This yields (for η=0) a quadrupole coupling constant of $\text{e}{}^2\text{qQ}\text{h}\text{= 13.620(8)}$MHz, which is the most accurate value currently available.     

Toward cocaine esterase therapeutics

Cocaine is among the most reinforcing of all drugs of abuse, yet no effective pharmacotherapy is available. Herein, we report the development and characterization of phage-displayed cocaine esterases with pharmacologically relevant kinetic parameters (kcat/Km approximately 104 M-1 s-1).     

ENDOR investigation of Ni3+ in GaP

With ENDOR measurements the ligand hyperfine and quadrupole interactions of Ni³⁺ in GaP with 3 shells of P neighbours and 3 shells of Ga neighbours could be resolved. It was established that the effective spin is $\text{3}\text{2}$, thus the defect is in the 3d⁷ state, which confirms the earlier assignment of the centre as an Ni³⁺ from ESR measurements. From the quadrupole interaction of the nearest Ga neighbours it can be concluded that Ni³⁺ is substitutional for Ga. From ENDOR-induced ESR experiments an upper limit for the u-parameter of the B·S³ term in the Spin Hamiltonian was determined. The unpaired spin density distribution shows a pronounced tetrahedral symmetry along the [111]-directions.     

A high-sensitivity laser microprobe mass analyzer

A laser microprobe mass analyzer has been developed. It is intended for application in biomedical and physiological research. A frequency-doubled ruby laser is focussed through an incident light microscope to a spot of minimally 0.5 μm in diameter on a thin section specimen of 0.1–1.5 μm thickness. The microplasma generated from the irradiated volume is analyzed in a time-of-flight mass spectrometer recording the complete spectrum for each shot. From lithium doped epoxy resin (5 ppm by weight), used as an organic standard, 1.4×10⁻¹⁹g or 1.4×10⁴ atoms of the⁶Li isotope have been detected. This sensitivity corresponds to that of ion microprobes but is at least an order of magnitude higher than obtained with electron probe X-ray microanalyzers.     

Order transition at the threshold for self-excited laser pulses

The laser-light field is shown to undergo a discontinuous order transition at the threshold for mode-locked pulses, accompanied by critical fluctuations below the transition point. These observations confirm theoretical predictions from the laser equations for a simplified model when incoherent interaction is included.     

Two body correlations between negative pions in pp interactions at 69 GeV/c

Correlations between two π^? in pp interactions at 69 GeV/c are presented in terms of longitudinal and transversal variables. The dominant feature is the existence of a strong shortrange positive correlation between the two π^? in the central region.