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On the basis of the results obtained in a previous paper it is shown that in the thermodynamic limit the analogues of the Massieu-Plandc functions are linked with each other by means of the Legendre transformation. The existence of the limiting function φk(∞) implies the existence of the limiting function φl(∞) (l<k) under the same assumptions. Passage to the limit and derivation with respect to all independent variables commute. A statistical derivation of the thermodynamic stability condition in its most general form is given which leads naturally to a statistical interpretation of the concept of thermodynamic stability.
It is shown that, for all conceivable ensembles of statistical thermodynamics, at the thermodynamic limit, the frequency function of the fluctuations of macroscopic extensive parameters equals a Gaussian. The proof is based on a generalisation of Khinchin's method using the concept of "smoothed frequency functions."
Fluorescense spectra of lactate dehydrogenase * (E.C. 1.1.1.27) were investigated in the presence of the coenzyme fragments dihydronicotinamide mononucleotide and dihydronicotinamide-ribose-5'-pyrophospho- (P2) -5“-ribose. The reduced mononucleotide is enzymatically less active as a hydrogen donor. However, formation of a complex with the enzyme was not observed under the conditions used. All the other substances: dihydronicotinamide-ribose-5'-pyrophospho- (P2) -5“-ribose, dihydronicotinamide- benzimidazole-dinucleotide, dihydronicotinamide-3-desazapurine-dinucleotide and dihydronicotinamide-6-mercaptopurine-dinucleotide form more or less stable complexes with lactate dehydrogenase. The complexes do not markedly differ from the complex formed with the natural cofactor. In all cases spectra indicate change in conformation of the coenzyme by forming the coenzyme-enzyme-complex which has been proposed by VELICK 1 too. The cysteine residues of the lactate dehydrogenase are not essential for binding the coenzyme to the active center; this was shown with mercury blocked enzyme.
The autoxidation of NaSH and Cysteine in the presence of heavy metal ions is accompanied by chemiluminescence due to the formation of O2⊖ or adequate compounds as intermediates. The observation of the luminescence intensity and its time dependence has been used as analytical indication of the occurrence of electron transfer reactions from - SH to O2.
This enabled the study of the influence of different catalytic promoters. The efficiency of different metal ions could easily be demonstrated by their enhancement of light production during the reaction of NaSH with molecular oxygen. Cu (II) as one of the most efficient catalysts was also applied in the form of different complexes. Because it would catalyse the oxidation of cysteine, glutathione and other electron donors of biological interest, the influence of the nature of the ligands of the complexes was investigated. In the case of cysteine only complexes with stability constants of medium strength and planar configuration acted as effective catalysts. Therefore it has to be assumed that for an effective electron transport to the loosely bound oxygen the cysteine molecule has to enter the inner sphere of the complex. The much longer time of luminescence of this reaction (4 -10 min) compared to the short time luminescence caused by free O2H. OH and H2O2 indicates that these intermediates are stabilized by binding to the Cu (II) -complex as in compounds (I), (II) and (III) of oxidizing enzymes.
Um den Mechanismus der Reaktion des Cysteins mit molekularem Sauerstoff in Gegenwart von Komplexen des zweiwertigen Kupfers als Katalysatoren zu ermitteln, wurden Messungen der Chemilumineszenz, der Sauerstoff- und der Cysteinkonzentration in Abhängigkeit von der Zeit vorgenommen. Variation der Konzentration der Reaktionsteilnehmer führte zu Meßergebnissen, die die Aufstellung eines Reaktionsschemas gestattete. Das hieraus abzuleitende System nichtlinearer Differentialgleichungen für die Reaktionsgeschwindigkeiten wurde in einem Analogrechner gelöst, wobei Übereinstimmung zwischen Rechnung und Meßergebnissen sowohl für die Zeitabhängigkeit als auch für die Konzentrationsabhängigkeit gefunden wurde.
Über Natriumhexaoxometallate
(1969)