Conde Federico Rubén, Churio María Sandra, Previtali Carlos Mario
Departamento de Química, FCEyN, Universidad Nacional de Mar del Plata, Funes 3350, B7602AYL, Mar del Plata, Argentina.
Photochem Photobiol Sci. 2007 Jun;6(6):669-74. doi: 10.1039/b618314j. Epub 2007 Mar 20.
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.
通过实验对水溶液中类菌孢素氨基酸紫菜碱（λmax = 320 nm）的激发态进行了表征。光降解量子产率较低，为(1.2 ± 0.2) × 10(-5)，这证实紫菜碱在空气饱和水溶液中具有高度的光稳定性。在紫菜碱存在下对丙酮进行激光闪光光解，可以观察到一个与紫菜碱的三重态-三重态吸收一致的瞬态光谱。对瞬态信号进行动力学处理得出三重态的寿命约为9微秒，三重态能量约为330 kJ mol(-1)。光声量热法结果与非辐射衰变是激发态紫菜碱的主要衰变途径这一情况相符。将紫菜碱的光降解量子产率和光物理性质与之前测定的其他类菌孢素氨基酸（肌醇六磷酸和紫菜-334）的进行比较，表明C=N键周围的几何异构化可能有助于这一类分子的快速失活。
