title: Experimental study of the excited-state properties and photostability of the mycosporine-like amino acid palythine in aqueous solution.
abstract: 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.
authors.affiliation: Departamento de Química, FCEyN, Universidad Nacional de Mar del Plata, Funes 3350, B7602AYL, Mar del Plata, Argentina.
authors.forename: Federico Rubén
authors.initials: FR
authors.lastname: Conde
authors.forename: María Sandra
authors.initials: MS
authors.lastname: Churio
authors.forename: Carlos Mario
authors.initials: CM
authors.lastname: Previtali
mesh_terms: 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
chemical_list: D000596:Amino Acids; D003511:Cyclohexanols; D003512:Cyclohexanones; D012996:Solutions; C523105:palythine; C421025:porphyra-334; D014867:Water; D005998:Glycine