Interaction between Delta *b-carboline-3-carboxylic acid N-methylamide, Delta *bCMAM, and nucleobases, nucleosides and nucleotides is studied in the ground state with UV-visible, 1H NMR and 31P NMR ...spectroscopies and in the first excited state, with steady-state and time-resolved fluorescence spectroscopy. Job plots show a predominant 1:1 interaction in both electronic states. Association constants are estimated from changes in the absorption spectra, and show that the strongest interaction is produced with the nucleosides: 2'-deoxyadenosine (dAdo) and thymidine (Thd), and with the mononucleotides: 2'-deoxycytidine 5'- monophosphate (5'-dCMP) and uridine 5'- monophosphate (5'-UMP). These results are corroborated by the upfield shifts of two 1H NMR resonances of the Delta *bCMAM indole group. The 31P NMR resonance of nucleotides is shifted downfield, suggesting the presence of electrostatic or hydrogen bond interaction with Delta *bCMAM. In the first electronic singlet excited state, static and dynamic quenching of Delta *bCMAM emission is achieved upon addition of nucleobases, nucleosides and nucleotides. This has been analysed using Stern--Volmer kinetics.
CHOICE, EXPERIENCE, AND THE GENERALIZED MATCHING LAW Todorov, João Claudio; Castro, Jorge Mendes de Oliveira; Hanna, Elenice Seixas ...
Journal of the experimental analysis of behavior,
September 1983, Letnik:
40, Številka:
2
Journal Article
Recenzirano
Odprti dostop
Five pigeons were exposed to different pairs of concurrent variable‐interval, variable‐interval schedules on nine experimental conditions of 30 sessions each. For every session, the parameters of the ...generalized matching equation were computed for the first five, six, seven, eight, and nine experimental conditions. The exponent a, both for response and time distribution, tended to decrease with increases in number of experimental conditions and to increase with number of sessions per condition, but values of k (bias) varied unsystematically. When the subjects were exposed to five new pairs of schedules, with 55 sessions per condition, the findings were confirmed. Data from the literature on the generalized matching law suggest that the variability of exponent values may be explained in part by the use of naive or experienced subjects in different investigations and by the variability in number of experimental conditions and in number of sessions per condition.
Two pigeons, with previous exposure to concurrent schedules, were submitted to 29 sessions of 8 hours each with concurrent variable‐interval variable‐interval schedules in which reinforcement ...parameters changed from session to session. In the first nine sessions reinforcement durations were equal in both schedules while reinforcement frequencies varied; in Sessions 10 through 18, both frequency and duration of reinforcement were varied; in Sessions 19 through 29, only reinforcement duration was varied. Results with this different procedure confirm previous findings that behavior is more sensitive to changes in reinforcement frequency than to reinforcement magnitude.
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