Singlet oxygen photosensitisation by GFP mutants: Oxygen accessibility to the chromophore

Aiming at the rational development of genetically-encoded photosensitisers, the production of singlet oxygen has been assessed for a number of class-2 Green Fluorescent Protein (GFP) mutants by means of time-resolved near-infrared luminescence detection. The accessibility of molecular oxygen to the chromophore seems to play a major role in the ability of GFPs to photosensitise singlet oxygen and this can be modulated by introducing specific mutations such as replacement of His148 by a less bulky amino acid. GFPs are also good singlet oxygen quenchers, hence further developments in this area should also seek to eliminate those amino acids with the highest quenching ability, particularly those at the protein surface and in the vicinity of the chromophore

Synthesis, Spectroscopic and Photophysical Characterization and Photosensitizing Activity Toward Prokaryotic and Eukaryotic Cells of Porphyrin-Magainin and \u2013Buforin Conjugates

Cationic antimicrobial peptides (CAMPs) and photodynamic therapy (PDT) are attractive tools to combat infectious diseases and to stem further development of antibiotic resistance. In an attempt to increase the efficiency of bacteria inactivation, we conjugated a PDT photosensitizer, cationic or neutral porphyrin, to a CAMP, buforin or magainin. The neutral and hydrophobic porphyrin, which is not photoactive per se against Gram-negative bacteria, efficiently photoinactivated E. coli after conjugation to either buforin or magainin. Conjugation to magainin resulted in the considerable strengthening of the cationic and hydrophilic porphyrin\u2019s interaction with the bacterial cells as shown by the higher bacteria photoinactivation activity retained after bacterial suspension washings. The porphyrin-peptide conjugates also exhibited strong interaction capability as well as photoactivity toward eukaryotic cells, namely human fibroblasts. These findings suggest therefore that these CAMPs have the potential to carry drugs and other types of cargoes inside mammalian cells similarly to cell-penetrating peptides