Studies on Succinate Dehydrogenase Walker, Wolfram H.; Singer, Thomas P.; Ghisla, Sandro ...
European journal of biochemistry,
March 1972, Letnik:
26, Številka:
2
Journal Article
Recenzirano
1
Succinate dehydrogenase flavocoenzyme (“SD‐flavin”), previously shown to be an 8α‐substituted riboflavin derivative containing a tertiary nitrogen homoconjugated to the flavin nucleus, was ...subjected to further hydrolysis and to reduction under acid conditions. Both conditions resulted in the liberation of 1 mole of histidine per mole of flavin. This proves histidine to be the covalent link between flavin and peptide backbone in succinate dehydrogenase and imidazole to be the tertiary nitrogen function homoconjugated to the flavin.
2
8α‐Histidyl‐riboflavin has been synthesized starting from riboflavin chemically and shown to be completely identical with the natural product in optical, ESR and NMR spectra, pH‐fluorescence curve and behavior on thin‐layer and paper chromatography, as well as paper electrophoresis.
3
Both the natural compound isolated by acid hydrolysis of flavin peptide and the synthetic one contain two isomers, which may be separated by high voltage electrophoresis. The isomers appear to be the N(1)‐and N(3)‐imidazole substituted compounds. Digestion of the flavin peptide with aminopeptidase M yields only one isomer but on treatment with 6‐N HCl this is gradually converted to a mixture of the two isomers. The absolute assignment of the natural isomer is suggested as 8α‐N(3)‐histidyl‐riboflavin on the basis of imidazole quaternization with CH3I, reductive cleavage of the flavin‐imidazole bond and identification of the methyl‐histidine liberated as 1‐methyl‐histidine.
The design of the preparative gas chromatographic (GC) hydrogen isotope separation system at JET, the process of displacement chromatography and the results of the commissioning phase with inactive ...gas mixtures of protium and deuterium are presented. The GC system meets fully the specifications for isotope separation. Protium and deuterium concentrations in the Pd filled column can be calculated by means of a simple program which simulates the gas chromatographic process.
Studies on Succinate Dehydrogenase Salach, Jim; Walker, Wolfram H.; Singer, Thomas P. ...
European journal of biochemistry,
March 1972, Letnik:
26, Številka:
2
Journal Article
Recenzirano
Improved methods have been devised for the isolation in μmole quantities of a pure flavin pentapeptide and its acid‐hydrolysis product (SD‐flavin) from inner‐membrane preparations of heart ...mitochondria and from soluble, purified succinate dehydrogenase. SD‐flavin differs from riboflavin in still having an amino acid covalently linked to the isoalloxazine ring system. SD‐flavin may be compared with riboflavin and with various 8α‐substituted synthetic flavins by optical spectrophotometry in the neutral and cationic states and by ESR and ENDOR spectrometry in the cationic radical state. On the basis of these experiments is was concluded that the FAD prosthetic group of mitochondrial succinate dehydrogenase is covalently linked through the 8α‐position to the peptide backbone of the protein. This conclusion is in accord with the acid stability of the natural product and its tendency to yield riboflavin under reductive conditions. The unusual pH‐fluorescence spectrum of the flavin strongly suggests that the 8α‐methylene group is linked to an amino acid through a tertiary nitrogen group.
The installation of all AGHS subsystems in compliance with a strict Quality Assurance Programme was completed in 1993. Installation was followed by end-to-end commissioning of signal and control loop ...connections to the Distributed Control System. Plant layout and function are described and results of process tests with hydrogen, deuterium and other test gases are presented. These tests have revealed some minor deficiencies on the subsystems for Cryogenic Distillation, Exhaust Detritiation and Impurity Processing which have been or are in the process of being resolved prior to commissioning with tritium, initially 3g of T/sub 2/, due to start in 1994.
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