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PHOTOREACTIVITY OF HYDROXYPSORALENS AND THEIR PHOTOBIOLOGICAL EFFECTS IN BACILLUS SUBTILIS *
Author(s) -
Song PillSoon,
Mantulin William W.,
Mcinturff Dyna,
Felkner Ira C.,
Harter Marian L.
Publication year - 1975
Publication title -
photochemistry and photobiology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.818
H-Index - 131
eISSN - 1751-1097
pISSN - 0031-8655
DOI - 10.1111/j.1751-1097.1975.tb06679.x
Subject(s) - intersystem crossing , chemistry , photochemistry , phosphorescence , bacillus subtilis , dissociation (chemistry) , pyrimidine , dna , excited state , delocalized electron , population , psoralen , stereochemistry , fluorescence , organic chemistry , biochemistry , bacteria , singlet state , physics , demography , quantum mechanics , sociology , biology , nuclear physics , genetics
— Although psoralen and many substituted psoralens are potent skin‐photosensitizing agents, hydroxypsoralens are not. A satisfactory molecular interpretation of this structural specificity has been given in terms of dissociation of the hydroxyl group of 5‐ and 8‐hydroxypsoralens in their excited states. The dissociation process in the S 1 state effectively competes with S 1 → T 1 intersystem crossing, thus reducing the photoreactive T 1 population. The T 1 states of the anions are more delocalized than those of neutral psoralens so that they are less reactive toward photocycloaddition with pyrimidine bases of DNA. The lack of significant phosphorescence of hydroxypsoralens in ionizing solvent or in the presence of base at low temperatures (14–77 K.) indicates ineffective S 1 → T 1 and/or effective T 1 → S 0 intersystem crossing. These factors make hydroxypsoralens unreactive, electronically and kinetically, as skin photosensitizers, which are known to react with DNA. In correlation with the hydroxypsoralens' spectroscopic characterization, they are also found to be ineffective or less effective photosensitizers in Bacillus subtilis .