179 research outputs found
On the validity of continuous spectrophotometric assays for adenosine deaminase activity: A critical reappraisal
No full textKinetic investigations on adenosine deaminase from calf intestinal mucosa by spectrophotometric monitoring of the reaction at 264, 270, or 228 nm show that this method does not produce artifactual inhibition by substrate excess up to 0.7 mm concentration, when either adenosine or 2â2-deoxyadenosine are employed with calf adenosine deaminase. The evaluation of kinetic parameters for this system was carried out both by initial rate measurements and by numerical differentiation of time progress curves according to a recently published method (S. C. Koerber and A. L. Fink, 1987, Anal. Biochem. 165, 75-87). The following results were obtained by the latter method at pH 7.0 and 30°C: for the conversion of adenosine to inosine, kcat= 251 ± 15 s-1, KMs= 29.7 ± 2.8 Î1⁄4m, KMp= 613 ± 62 Î1⁄4m; for the conversion of 2â2-deoxyadenosine to 2â2-deoxyinosine, kcat= 283 ± 17 s-1, KMs= 22.4 ± 2.2 Î1⁄4m, KMp= 331 ± 35 Î1⁄4m. At 285 nm, a slight negative deviation from Beer's law was observed for adenosine at concentrations higher than 0.9 mm. No deviation was found for inosine up to 2.0 mm at the same wavelenth. © 1991
Comparing the photoresponses in different strains of Halobacterium salinarum: the puzzle is growing wilder
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Photoresponses in two strains of Halobacterium salinarum and current models for phototransduction
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Prefazione}, al volume "Ludwig Boltzmann e la meccanica statistica" di C. Cercignani, Collana ``I percorsi della Fisica'', p. I--X, La Goliardica Pavese, Pavia, 1997, ISBN 88-7830-263-5.} \cr
No full textLa Goliardica Pavese, Pavia
Photoresponses of Halobacterium salinarum to repetitive pulse stimuli
No full textAbstractHalobacterium salinarum cells from 3-day-old cultures have been stimulated with different patterns of repetitive pulse stimuli. A short train of 0.6-s orange light pulses with a 4-s period resulted in reversal peaks of increasing intensity. The reverse occurred when blue light pulses were delivered as a finite train: with a 3-s period, the response declined in sequence from the first to the last pulse. To evaluate the response of the system under steady-state conditions of stimulation, continuous trains of pulses were also applied; whereas blue light always produced a sharply peaked response immediately after each pulse, orange pulses resulted in a declining peak of reversals that lasted until the subsequent pulse. An attempt to account for these results in terms of current excitation/adaptation models shows that additional mechanisms appear to be at work in this transduction chain
The photosensory transduction in Halobacterium salinarium: An overview of behavioural and biophysical data
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