Histidine oxidation photosensitized by pterin: pH dependent mechanism

Quenching of the Singlet and Triplet Excited States of Pterin by Amino Acids

“…where k O2 q is the quenching rate constant by O 2 . Most of our studies described in references (19)(20)(21) were carried out using a concentration of amino acids around 100 lM. Under these experimental conditions, and according to the k q (singlet or triplet) values determined in this work (Table 1), only the longlived triplet excited state of Ptr was significantly quenched by the amino acids.…”

Photosensitization of peptides and proteins by pterin derivatives

“…More recently, the mechanism involved in the photosensitization of biomolecules by pterins were investigated in a series of studies carried out with free nucleotides [28][29][30] and amino acids [12][13][14]. It was shown that pterins can act as photosensitizers through both type I and type II mechanisms and that the predominant one depends on a combination of many factors, such as quantum yields of Taking into account the studies mentioned in the previous paragraph, a set of competitive mechanisms can be summarized to explain the photooxidation of different biomolecules (S) by pterin derivatives (Pt) (reactions [1][2][3][4][5][6][7][8][9][10][11][12] …”

“…In general, it is accepted that the photosensitization of proteins occurs mainly through the reactions of 1 O 2 with tryptophan (Trp), tyrosine (Tyr), histidine (His), methionine (Met) and cysteine (Cys) side-chains [7]. Nevertheless, in recent reports, it has been demonstrated that pterins photosensitize peptides [8,9], proteins [10,11] and their components [12][13][14] mainly through a type I mechanism.…”

“…Pterins are photochemically reactive in aqueous solutions, and upon UV-A excitation, they can fluoresce, produce reactive oxygen species (ROS) [23][24][25] and, as mentioned above, photosensitize the oxidation of biomolecules [8][9][10][11][12][13][14].…”

Performance and Mechanism of UV/Immobilized Cu-TiO2System to Degradation Histidine

“…Figure 5(a), both doped and undoped systems could degrade histidine effectively, while the degradation through the Cu-TiO 2 adsorption or photodegradation by UV separately was negligible. Moreover, according to the reported research by Castaño et al [30], lixiviation was neglectful compared to the removal effect of histidine. Thus, the reaction product between UV and TiO 2 may be responsible for the degradation performance.…”