Adenosine, photoionization

Photoionization of adenosine and guanosine in UV-irradiated ice solutions at 77°K has been detected by ESR measurements.115 The signal was that both of the solvated electron and also of the Py+ ion. 

A further possibility is that the signals arise from hydrated electrons or base radical ions produced by monophotonic ionization of the polymers. However, the quantum yield for photoionization of adenosine is reported to be approximately the same as that of poly(A) and poly(dA) [25], It is unlikely that photoionization of the polymers can account for the signals seen here since there is no detectable signal contribution from the photoionization of single bases [4], The most compelling argument that our pump-probe experiments monitor excited-state absorption by singlet states is the fact that ps and ns decay components have been observed in previous time-resolved emission experiments on adenine multimers [23,26-28]. 

The fluorescence polarization excitation spectrum has been measured for thymine in aqueous solution. " The depolarization at the red edge is attributed to the hidden n, ir transition. Ionization of the lowest excited singlet and triplet states have been determined by the effect of pH on the absorption, fluorescence, and phosphorescence spectra of purines and pyrimidines. " Spectral, polarization, and quantum yield studies of cytidylyl-(3, 5 )-adenosine have also been published. Intermediates in the room-temperature flash photolysis of adenine and some of its derivatives have been identified hydrated electron, radical cations and anions, and neutral radicals resulting from their reactions have been assigned. Photoionization occurs via the triplet state. FMN encapsulated in surfactant-entrapped water pools interacts with polar head groups, entrapped water molecules, and outer apolar solvent. ... 

A photophysical study of the interaction of 2-amino-4,6-dimethylpyrimidine in p-CD has been carried out. Calculations have been carried out in an examination of the isomerism of methyl urocanate. Density functional theory techniques have been used to study the dimerization of thymine units in DNA. The effects of both low intensity irradiation (254 nm) or laser photolysis at 266 nm on adenosine have been reported. The photoionization of various purine and pyrimidine derivatives can be brought about by 266 nm nanosecond laser photolysis. Irradiation of alloxan in the presence of alkenes with allylic hydrogens affords adducts of 5-hydroxy-5-alkenyl barbituric acid. When the alkene is... 

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