Ueber die Beziehungen von Neutralsalz zu Säureeiweiß

Ohne Zusammenfassung     

Sensitive determination of cystathionine and assays for cystathionine beta- and gamma-lyase, as well as cystathionine beta-synthase, using high-performance liquid chromatography.

Cystathionine was cleaved into 2-ketobutyric acid, cysteine and ammonia by cystathionase. 2-Ketobutyric acid was converted into 3-ethyl-2-hydroxy-6,7-dimethoxyquinoxaline (EHDQ) by reaction with 1,2-diamino-4,5-dimethoxybenzene. When EHDQ was measured in a mobile phase of pH 2.1 using high-performance liquid chromatography with ultraviolet detection, 250 pmol of L-cystathionine in 250 microliters of the reaction mixture could be determined. Because EHDQ has a strong fluorescence in a mobile phase of pH 6.5 at 447 nm, on excitation at 365 nm, as little as 2.5 pmol of cystathionine in 250 microliters of the reaction mixture could be determined by high-performance liquid chromatography with fluorimetric detection. Cystathionase activity was assayed on the basis of the same principle by determining cystathionine in as little as 63 ng of rat liver by fluorimetric detection. Cystathionine beta-synthase activity was measured by the same method by determining cystathionine formed in only 113 ng of wet weight of rat liver. Using these methods, both cystathionine beta- and gamma-lyase activities in Saccharomyces cerevisiae were determined, because quinoxaline derivatives from pyruvate and 2-ketobutyrate could be measured simultaneously by high-performance liquid chromatography.     

Significance of anti-HBc IgM in acute hepatitis and hepatitis B associated chronic liver disease

To determine the diagnostic value of anti-HBc IgM in acute viral hepatitis or chronic liver disease B, Anti-HBc IgM was measured by a RIA and an ELISA in 32 patients with acute hepatitis (4 with type A, 15 with type B and 13 with type non A non B), 18 patients with chronic hepatitis and 19 patients with liver cirrhosis. In acute hepatitis B, anti-HBc IgM (both RIA and ELISA) was positive in 14(93%) of 15 patients and its cut-off index value was very high. However, anti-HBc IgM was always negative in one patient with typical course of type B. In 1 of 4 patients with acute hepatitis A and 2 of 13 with non A non B, anti-HBc IgM (RIA and/or ELISA) was positive. These 3 patients were positive for anti-HBs at the onset of disease, so we could not made the diagnosis of acute hepatitis B. Anti-HBc IgM was positive in 21(51%) of 37 patients with HBsAg-positive chronic liver disease by RIA and in 11 (30%) by ELISA, and its cut-off index value was relatively low. These results suggest that when adequate cut-off index value is established, anti-HBc analysis is useful for differentiating recent and current infections from remote infections.     

Protonation susceptibility of functional groups: A new parameter for interpreting chemical ionization mass spectra of bifunctional organic compounds

A new parameter, the protonation susceptibility (PS), of functional groups in the chemical ionization mass spectrometry of bifunctional organic compounds is presented. In terms of quasi-equilibrium theory of unimolecular decomposition of the molecular protonated ion of [MH]⁺, the relative PS corresponds to the relative area under P(E) curves of [MH]⁺ ions that have a proton at different functional groups. Numerical evaluation of the PS values of pertinent functional groups was made by using particularly selected compounds. The results clearly indicate that PS is independent of proton affinity (PA).     

Synthesis and properties of segmented aromatic poly(ether sulfone)-amide and poly(ether sulfone)-imide copolymers

New segmented aromatic poly(ether sulfone)-amide and poly(ether sulfone)-imide copolymers were synthesized by the chain extension of α,w-diamine-terminated poly(ether sulfone) oligomer with both aromatic dicarboxylic acid chlorides and tetracarboxylic dianhydrides, respectively. Crystallization of the poly(ether sulfone)unit was suppressed by the introduction of amide or imide linkage along the polymer backbone, giving amorphous copolymers that were +eadily soluble in various organic solvents. The copolymers had somewhat higher glass transition temperatures than the parent poly(ether sulfone). They afforded transparent and tough films by solution casting. © 1992 John Wiley & Sons, Inc.     

Jellium-model calculation for monomer and dimer decays of some potassium clusters

We have studied several decay processes of potassium clusters and found that a dimer-decay mechanism can explain the observed lowest abundance of K₁₀ in the K _n mass spectra. Total-energy curves for decay processes are calculated using a jellium-background model for positive-ion cores and the local-spin-density-functional approximation for valence electrons. The energy-barrier height for a dimer decay of K₁₀ from the energy-minimum point is found to be 0.18 eV, which is a reasonable magnitude for the decay to take place thermally in the experiment. The monomer decay of K₉ and the dimer decay of K₁₁, which are expected to be the most favorable decays of K₉ and K₁₁, are found to have high barriers. Monomer and dimer decays of K₈ are also studied and the monomer decay is found to be more favorable, in accord with the high-nozzle-temperature mass spectrum.