The ﬂuorescence behavior of pyrene solubilized in the hexadecyltrimethylammonium bromide aqueous micellar solution in the presence of adenosine 5′ -monophosphate (AMP) and uridine 5′ -monophosphate (UMP) was investigated. AMP and UMP were found to inﬂuence oppositely the ﬂuorescence of micellized pyrene. UMP acts as quencher, while AMP acts as dequencher. Both effects saturate at high nucleotide concentration (about 40 mM). Dequenching of micellized pyrene ﬂuorescence is induced also by addition of disodium hydrogen orthophosphate (Na2HPO4), while loading with sodium bromide (NaBr) quenches the ﬂuorescence. Furthermore, in absence of micelles, pyrene ﬂuorescence depends on the UMP, according to the Stern-Volmer relation, but is unaffected by AMP. Dynamic light scattering experiments showed that the size and shape of aggregates is not affected by different types of nucleotide loaded into the solution; thus, we conclude that the opposite photophysical effect exploited by AMP and UMP are uncorrelated to any change in micellar microstructure. The whole ﬂuorescence data set was successfully accounted for by assuming that the anionic nucleotides compete with the surfactant counterion (bromide) for the surface of the micelle. Accordingly, substitution of bromide with the more effective quencher UMP results in a strong decrease of the pyrene ﬂuorescence, while the substitution of bromide with the nonquencher AMP results in an increase in the pyrene ﬂuorescence.
|Digital Object Identifier (DOI):||10.1021/jp8003344|
|Codice identificativo ISI:||000256731900027|
|Codice identificativo Scopus:||2-s2.0-49649099320|
|Titolo:||Quenching and dequenching of pyrene fluorescence by nucleotide-monophosphates in cationic micelles|
|Appare nelle tipologie:||1.1 Articolo in rivista|