Pteridines. Part CVI. Isolation and characterization of limipterin (1-O-(L-erythro-biopterin-2′-yl)-β-N-acetylglucosamine) and its 5,6,7,8-tetrahydro derivative from green sulfur bacterium Chlorobium limicola f. thiosulfatophilum NCIB 8327

A new pteridine compound was isolated from green sulfur photosynthetic bacteria, Chlorobium limicola f. thiosulfatophilum NCIB 8327. The structure of this pterin derivative was established to be 1-O-(L -erythro-5,6,7,8- tetrahydropterin-2′-yl)-β-N-acetylglucosamine ( 1 ) from ¹H-NMR and CD spectra as well as from various mass spectrometric techniques and chemical-cleavage techniques. Upon acid hydrolysis of 1 , equimolar amounts of biopterin ( 2 ) and N-acetylglucosamine were produced. The structure of the hydrolysis product 2 was confirmed by comparing its NMR, UV, CD, and MS and its chromatographical behavior with those of an authentic specimen. N-Acetylglucosamine was identified by an enzymatic hydrolysis experiment as well as by NMR and thin layer chromatography. Electrospray (ES), fast-atom-bombardment (FAB), and thermospray (TS) mass spectrometry of 1 yielded an MH⁺ at m/z 441. Periodate-oxidation experiments of the intact molecule 1 and of its hydrolysis product 2 are consistent with the proposed structure. Differential I₂ oxidation experiments with the native compound showed that the in vivo oxidation state of this pterin is its tetrahydro form. We propose the trivial name ‘limipterin’ for this new compound.     

Cathodic deposition of uranium

Cathodic depositions of uranium were carried out at controlled pH from a number of solutions containing the metal salt, and a complexing agent. A reducing agent was also present to prevent oxidation of the element. The current density ranged from 50 to 200 mA cm^?2. The purity of the deposited uranium was better than 99.7%. The mechanism of formation of uranium is proposed and discussed.     

A sensitive radiochemical assay for Coenzyme A

Summary A simple and sensitive assay for Coenzyme A (CoA) is described. The method is based on coupling the enzymatic reactions of acetyl-CoA synthetase and acetyl-CoA carboxylase. CoA is converted into acetyl-CoA with acetyl-CoA synthetase in the presence of excess ATP and acetate. Acetyl-CoA is subsequently converted into malonyl-CoA with acetyl-CoA carboxylase in the presence of excess ATP and KH¹⁴CO₃. The formation of labelled acid-stable material (i.e. malonyl-CoA) is determined. Under conditions of the assay CoA is quantitatively converted into malonyl-CoA. This procedure permits the detection of as little as 15 pmoles of CoA in biological samples. Elimination of acetyl-CoA synthetase from the reaction mixture allows for the determination of acetyl-CoA.

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Empfindlicher radiochemischer Assay für Coenzym A

Zusammenfassung Ein einfacher und empfindlicher Assay für Coenzym A (CoA) wird beschrieben, der auf einer Kopplung der enzymatischen Reaktionen von Acetyl-CoA-synthetase und Acetyl-CoA-carboxylase beruht. CoA wird mit Hilfe von Acetyl-CoA-synthetase in Gegenwart von überschüssigem ATP und Acetat zu Acetyl-CoA umgesetzt. Dieses wird anschließend mit Acetyl-CoA-carboxylase in Gegenwart von überschüssigem ATP und KH¹⁴CO₃ zu Malonyl-CoA umgewandelt. Die Bildung von markierter säurestabiler Substanz (d.h. Malonyl-CoA) wird bestimmt. Unter den Versuchsbedingungen ist die Umsetzung von CoA zu Malonyl-CoA quantitativ. Noch 15 pMol CoA können in biologischem Material erfaßt werden. Durch Entfernung von Acetyl-CoA-synthetase aus dem Reaktionsgemisch kann auch Acetyl-CoA bestimmt werden.

     

Synthesis of monodisperse chromium nanoparticles from the thermolysis of a Fischer carbene complex

We successfully synthesized monodisperse chromium nanoparticles from the thermolysis of a Fischer carbene complex.     

All but Finitely Many Non-Trivial Zeros of the Approximations of the Epstein Zeta Function are Simple and on the Critical Line

The Chowla–Selberg formula is applied in approximatinga given Epstein zeta function. Partial sums of the series derivefrom the Chowla–Selberg formula, and although these partialsums satisfy a functional equation, as does an Epstein zetafunction, they do not possess an Euler product. What we callpartial sums throughout this paper may be considered as specialcases concerning a more general function satisfying a functionalequation only. In this article we study the distribution ofzeros of the function. We show that in any strip containingthe critical line, all but finitely many zeros of the functionare simple and on the critical line. For many Epstein zeta functionswe show that all but finitely many non-trivial zeros of partialsums in the Chowla–Selberg formula are simple and on thecritical line. 2000 Mathematics Subject Classification 11M26.     

Juche versus Sadae: Game-theoretic approach

We argue that to some degree Juche is represented by the concept of Nash equilibrium, and Sadae by Thompson and Faith's truly perfect information equilibrium. We characterize the latter, and show that for a Pareto optimal Nash equilibrium, Juche is as good as, or better than Sadae. This includes the game of brinkmanship.     

Generalized fuzzy matrices

We give a systematic development of fuzzy matrix theory. Many of our results generalize to matrices over the two element Boolean algebra, over the nonnegative real numbers, over the nonnegative integers, and over the semirings, and we present these generalizations. Our first main result is that while spaces of fuzzy vectors do not have a unique basis in general they have a unique standard basis, and the cardinality of any two bases are equal. Thus concepts of row and column basis, row and column rank can be defined for fuzzy matrices. Then we study Green's equivalence classes of fuzzy matrices. New we give criteria for a fuzzy matrix to be regular and prove that the row and column rank of any regular fuzzy matrix are equal. Various inverses are also studied. In the next section, we obtain bounds for the index and period of a fuzzy matrix.