Ausgehend von den Komponenten (I) und (II) werden die Pterin‐Derivate (VI), (VI I) [== Zf‐Oxidationsprodukt von (VI)] bzw. (IX) synthetisiert.

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The synthesis of 4,5-dihydro-4,5-dioxo-l/f-pyrrolo[2,3-/]quinoline-2-carboxylic acid (7,9-didecarboxymethoxatin, 70X) and its ester (60X) are described and their acid-base properties, electrochemistry, and chemical properties are compared to the cofactor Methoxatin, as well as to those of other o-quinones. The two-electron redox potentials of 60x and 70x are shown to be ca. 110 mV less than those of the penanthroline-5,6-quinones but to be comparable to those of methoxatin at all pH values. Replacement of the pyridine ring of 70X by a benzene ring reduces its oxidation potential by 100 mV. 70x forms a C-5 adduct with acetone and a cyclic bis(carbinolamine) adduct with urea. The rate constants for formation and dissociation of the urea adducts of methoxatin, 60X, and the most electrophilic phenanthrolinequinone (30x) are compared. The o-quinone

The influence of sulphated ligand and pH on thermal denaturation of basic fibroblast growth factor (bFGF) was investigated by differential scanning calorimetry (DSC), and verified by fluorescence spectrophotometry. Purity of bFGF before and after heat denaturation was assessed by SDS-PAGE analysis. In DSC studies the samples were heated to 95 degrees C. The midpoint of the temperature change in the thermogram was designated as Tm. Sulphated ligand experiments were undertaken in potassium phosphate (pH 6.5) and sodium acetate buffers. Control thermograms (with no ligand) showed a Tm at 59 degrees C in potassium phosphate buffer. Higher Tm values were noted as sulphated ligand concentration was increased. Similarly when heparin was added, the Tm moved to a higher temperature. A ratio as low as 0.3:1 of heparin to bFGF, increased the Tm to 90 degrees C, which is a 31 degrees C shift in Tm. The effect of pH on thermal denaturation of bFGF was studied in a citrate-phosphate-borate buffer system. A shift in Tm from 46 to 65 degrees C was observed as the pH is changed from 4 to 8. Changes in protein conformation as a function of pH were monitored by fluorescence spectroscopy. It was found that a pH range from 5 to 9 is optimal for the stability of bFGF formulations. In a stability study it was noted that heparin protected bFGF from thermal denaturation only at high temperature.

Although cholecystokinin-58 (CCK-58) is a major molecular form stored in the intestine, it has not yet been shown to be released into the circulation. This report describes in vitro degradation of CCK-58 in human blood and plasma and the molecular forms detected when this degradation is inhibited. After incubation of CCK-58 for 150 min between 20 and 24 degrees C, approximately 60% of immunoreactivity recovered was degraded to smaller immunoreactive forms. Storage of the 150-min incubate at -20 degrees C for 3 days greatly increased the observed degradation to 85%. When CCK-58 was added in vitro to blood, similar degradation occurred. Degradation of CCK-58 could be inhibited by addition of acid. Blood was obtained 1 h after a test meal designed to stimulate CCK release. The pH was lowered during collection and processing of blood and plasma to inhibit in vitro degradation of cholecystokinin. This method permitted the detection of significant amounts of CCK-58 in circulation.

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