How to blow out a molecular lantern: interaction of aequorea victoria green fluorescent protein and its variants with singlet oxygen

Bibliography: p. 147-152Herein, we studied the interaction between Aequorea victoria Green Fluorescent Proetein and some of its mutants with exogenous single oxygen using spectroscopic and electrophoretic techniques. According to our results, exogenous 02 mainly oxidizes the ??-barrel of the proteins, resulting in formation of a covalent protein dimer. Further characterization of the underlying mechanism utilizing monomeric variants, suggested the interface of the natural occurring dimer as the initial area of oxidation, specifically the histidine in position 148 (H148). By mutating this residue to a less reactive side chain, its involvement in the 02 mediated mechanism was corroborated. The reactivity of endogenous 02 towards fluorescent proteins, was also analyzed by direct excitation of the proteins chromophores. Spectroscopy data suggested a variety of complex mechanisms, including generation of 02 and photodecarboxylation, occurring upon irradiation of the protein. Taken together, these results indicate that production of exogenous and/or endogenous 02 during standard imaging techniques influences fluorescent proteins, which could deteriorate the data obtained from the studied system

Quality changes during frozen storage of blue shrimp (Litopenaeus stylirostris) with antioxidant, α-tocopherol, under different conditions

Fresh blue shrimp (Litopenaeus stylirostris) muscle was stored with antioxidants under different conditions: ANTIOX 2%, packed in bilayer film of polyamide-low density polyethylene film (PA-LDPE) with 2% α-tocopherol; ANTIOX 4%, packed in PA-LDPE film with 4% α-tocopherol; and ANTIOX-GLAZED, samples stored glazed with 2% α-tocopherol. Shrimps packed in PA-LDPE without α-tocopherol were used as CONTROL. All samples were stored at –20 °C for 120 days. As compared to the CONTROL, the shrimp stored with the antioxidant showed lower lipid oxidation (0.10-0.14 vs 1.58 mgMA/kg of muscle), lost less firmness and astaxanthin content. ANTIOX 2% and ANTIOX-GLAZED showed the lowest concentrations of formaldehyde (0.081-0.083 μM/g). There were no significant differences in color and sensory properties, but differences in the integrity of the muscle fibers were observed. The treatments with α-tocopherol maintained the shrimp muscle quality during frozen storage. However, no significant differences were found between these treatments