Experimental study of the excited-state properties and photostability of the mycosporine-like amino acid palythine in aqueous solution.
Characterization of the excited states of the mycosporine-like amino acid palythine (lambda(max) = 320 nm) in aqueous solutions was achieved experimentally. The low value for the photodegradation quantum yield, (1.2 +/- 0.2) x 10(-5), confirms that palythine is highly photostable in air saturated-aqueous solutions. Laser flash photolysis of acetone in the presence of palythine allowed for the observation of a transient spectrum which is consistent with the triplet-triplet absorption of palythine. Kinetic treatment of the transient signals yields a lifetime of the triplet state of ca. 9 micros and a triplet energy around 330 kJ mol(-1). The photoacoustic calorimetry results are consistent with non-radiative decay as the major fate of excited palythine. A comparison of the photodegradation quantum yields and photophysical properties of palythine with those previously determined for the other mycosporine-like amino acids, shinorine and porphyra-334, suggests that geometrical isomerization around the C=N bond may contribute to the rapid deactivation of this group of molecules.
Conde
Federico Rubén
FR
Departamento de Química, FCEyN, Universidad Nacional de Mar del Plata, Funes 3350, B7602AYL, Mar del Plata, Argentina.
Churio
María Sandra
MS
Previtali
Carlos Mario
CM
D000596:Amino Acids / Q000737:chemistry* / Q000528:radiation effects*; D002151:Calorimetry; D003511:Cyclohexanols / Q000737:chemistry* / Q000302:isolation & purification / Q000528:radiation effects*; D003512:Cyclohexanones / Q000737:chemistry / Q000528:radiation effects; D005998:Glycine / Q000031:analogs & derivatives* / Q000737:chemistry / Q000302:isolation & purification / Q000528:radiation effects; D007536:Isomerism; D007700:Kinetics; D010782:Photolysis; D011789:Quantum Theory; D000461:Rhodophyta / Q000737:chemistry; D012996:Solutions; D053545:Spirulina / Q000737:chemistry / Q000528:radiation effects; D014867:Water / Q000737:chemistry
D000596:Amino Acids; D003511:Cyclohexanols; D003512:Cyclohexanones; D012996:Solutions; C523105:palythine; C421025:porphyra-334; D014867:Water; D005998:Glycine