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The newly synthesized trans -4-( p - N , N -dimethylaminostyryl)- N -vinylbenzylpyridinium chloride ( 1 ) displays strong solvatochromic behavior resulting from a large increase of ∼18 D in its dipole moment upon excitation. This indicates that its excited state has considerable charge transfer character, suggesting that it may be subject to solute-induced fluorescence changes. The fluorescence quantum yield of 1 is enhanced dramatically (12-fold) in the presence of a buffered aqueous solution of cAMP, a purine nucleotide. In contrast, the pyrimidine nucleotides, CMP and UMP, have virtually no effect on the fluorescence of 1 . cGMP induced an increase in the quantum yield of 1 similar to that induced by cAMP, whereas other purine nucleotides (AMP, ADP and ATP) and adenosine induced changes of somewhat lesser magnitude. Association constants for 1 with these analytes ranged from 13.8 M −1 for cAMP to 0.15 M −1 for adenine. We conclude that the changes in fluorescence of 1 in the presence of nucleotides require the presence of a purine base, and are enhanced by ribose and phosphate moieties. The environmentally sensitive fluorescence of 1 suggests that such compounds may be useful as chemosensors for purine nucleotides. |
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