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Hans W. Gottinger 《Biological cybernetics》1974,15(2):111-116
This paper discusses some measures of information which naturally arise in the context of statistical games (games against nature). Some useful inequalities are proven relating the entropy to the value of information provided by experiments. Two other measures, based on the notion of a metric as informational distance and that of a diameter value are also discussed. 相似文献
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1. A search was made for mechanisms which may exert a ;fine' control of the glucose 6-phosphate dehydrogenase reaction in rat liver, the rate-limiting step of the oxidative pentose phosphate cycle. 2. The glucose 6-phosphate dehydrogenase reaction is expected to go virtually to completion because the primary product (6-phosphogluconate lactone) is rapidly hydrolysed and the equilibrium of the joint dehydrogenase and lactonase reactions is in favour of virtually complete formation of phosphogluconate. However, the reaction does not go to completion, because glucose 6-phosphate dehydrogenase is inhibited by NADPH (Neglein & Haas, 1935). 3. Measurements of the inhibition (which is competitive with NADP(+)) show that at physiological concentrations of free NADP(+) and free NADPH the enzyme is almost completely inhibited. This indicates that the regulation of the enzyme activity is a matter of de-inhibition. 4. Among over 100 cell constituents tested only GSSG and AMP counteracted the inhibition by NADPH; only GSSG was highly effective at concentrations that may be taken to occur physiologically. 5. The effect of GSSG was not due to the GSSG reductase activity of liver extracts, because under the test conditions the activity of this enzyme was very weak, and complete inhibition of the reductase by Zn(2+) did not abolish the GSSG effect. 6. Preincubation of the enzyme preparation with GSSG in the presence of Mg(2+) and NADP(+) before the addition of glucose 6-phosphate and NADPH much increased the GSSG effect. 7. Dialysis of liver extracts and purification of glucose 6-phosphate dehydrogenase abolished the GSSG effect, indicating the participation of a cofactor in the action of GSSG. 8. The cofactor removed by dialysis or purification is very unstable. The cofactor could be separated from glucose 6-phosphate dehydrogenase by ultrafiltration of liver homogenates. Some properties of the cofactor are described. 9. The hypothesis that GSSG exerts a fine control of the pentose phosphate cycle by counteracting the NADPH inhibition of glucose 6-phosphate dehydrogenase is discussed. 相似文献
147.
Mathias Sprinzl Karl-Heinz Scheit Hans Sternbach Friedrich von der Haar Friedrich Cramer 《Biochemical and biophysical research communications》1973,51(4):881-887
2′-Deoxyadenosine and 3′-deoxyadenosine (cordycepin) can be incorporated into the 3′-terminal position of tRNAPhe by tRNA nucleotidyl transferase. tRNAPhe-C-C-2′dA and tRNAPhe-C-C-3′dA, missing the cis-diol group at the 3′-terminal end are resistant to periodate oxidation and are not able to form borate complexes. In aminoacylation experiments only the tRNAPhe-C-C-3′dA proved to be chargeable. 相似文献
148.
Ingemar Björkhem Hans Jörnvall Eila Zeppezauer 《Biochemical and biophysical research communications》1973,52(2):413-420
Recrystallized alcohol dehydrogenase from horse liver was found to oxidize 17-hydroxystearic acid into 17-oxostearic acid, the 17-L-enantiomer faster than the 17-D-enantiomer. Alone at high pH or in combination with aldehyde dehydrogenase, the alcohol dehydrogenase also catalyzed conversion of 18-hydroxystearic acid into 1, 18-octadecadioic acid and 5β-cholestane-3α,7α,12α,26-tetrol into 3α,7α,12α-trihydroxy-5β-cholestanoic acid. All the activities as well as the ethanol dehydrogenase activity disappeared after specific carboxymethylation of a single cystein residue at the active site of alcohol dehydrogenase. These results conclusively show that alcohol dehydrogenase itself has ω-hydroxyfatty acid dehydrogenase activity and ω-hydroxysteroid dehydrogenase activity. 相似文献
149.
Hans Löhrl und Gerhard Thielcke 《Journal of Ornithology》1973,114(2):250-252
Zusammenfassung Die Alarmlaute europäischer und nordafrikanischer Tannenmeisen gegen Nesträuber sind sehr verschieden (Abb. a, c). Europäische Tannenmeisen verwenden den nordafrikanischen Typ nur bei größter Erregung (eine Beobachtung an wildlebenden). Europäische Tannenmeisen und Schwarzschopfmeisen, die zusammen mit marokkanischen Tannenmeisen in einer Voliere gehalten wurden, brachten in Alarmsituationen zuerst die ihnen gemäßen Rufe und dann die der nordafrikanischen (Abb. d). Wahrscheinlich ist der afrikanische Alarmruftyp der ursprüngliche. Der stammesgeschichtlich junge Alarmruftyp der UntergattungPeriparus ging den nordafrikanischen Populationen verloren.
Alarm calls of European and North African Coal Tits(Parus ater ater, P. ater atlas, P. ater ledouci) and Vigor's Black Crested Tit(P. melanolophus)
Summary The alarm call against nestpredators of European and North African Coal Tits are quite different (fig. a, c). European Coal Tits call like African Coal Tits only in situations of drastic excitement (one observation in the field). European Coal Tits and Vigor's Black Crested Tits, kept together with Coal Tits from Morocco in an aviary, used in alarm situations first their usual calls and then the calls of the North African subspecies (Abb. d). Apparently the African form of the alarm call is the older. The North African populations have lost the evolutionarity young form of the alarm call of the subgenusPeriparus.相似文献
150.