THE PHOTOCHEMICAL INTERACTION BETWEEN THE TRIPLET STATE OF 8-METHOXYPSORALEN AND THE MELANIN PRECURSORL–3, 4 DIHYDROXYPHENYLALANINE |
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| Authors: | M CRAW M R CHEDEKEL† T G TRUSCOTT § E J LAND† |
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| Institution: | *Department of Chemistry, Paisley College, Paisley PA1 2BE, Scotland, UK;†Division of Environmental Chemistry, Department of Environmental Health Sciences. The Johns Hopkins University School of Hygiene and Public Health, Baltimore, MD 21205, USA;‡Paterson Laboratories, Christie Hospital and Holt Radium Institute. Manchester M20 9BX, England, UK |
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| Abstract: | Abstract— The photochemical interaction between 8-methoxypsoralen (8-MOP) and the melanin precursorL–3,4-dihydroxyphenylalanine(dopaH2) has been studied using laser flash photolysis. Triplet excited 8-MOP was thus found to abstract electrons from dopaH2 ( k ∼ 2 × 109 dm3 mol-1 s-1) to form semireduced 8-MOP and semioxidised dopaH2.The technique of pulse radiolysis was used to establish separately the spectra of (a) the semi-reduced form of 8-MOP at pH 6.5 and (b) the semioxidised forms of dopaH2 at pH 6.5, 5.8, 4.6 and 3.3. The corresponding λmax and extinction coefficients found were: for 8-MOP at pH 6.5, λmax= 350 nm (= 9050 dm3 mol-1 cm-1); for dopa at pH 6.5, λmax= 305 nm (ε= 12000 dm3 mol-1 cm-1) and for dopaH at pH 3.3, λ= 305 nm (ε= 5900 dm3 mol-1 cm-1). |
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