Background: Superoxide dismutases (SOD) are ubiquitous metalloenzymes that catalyze the disproportion of superoxide to peroxide and molecular oxygen through alternate oxidation and reduction of their metal ions. In general, SODs are classified into four forms by their catalytic metals namely; FeSOD, MnSOD, Cu/ZnSOD and NiSOD. In addition, a cambialistic form that uses Fe/Mn in its active site also exists. Cyanobacteria, the oxygen evolving photosynthetic prokaryotes, produce reactive oxygen species that can damage cellular components leading to cell death. Thus, the co-evolution of an antioxidant system was necessary for the survival of photosynthetic organisms with SOD as the initial enzyme evolved to alleviate the toxic effect. Cyanobacteria represent the first oxygenic photoautotrophs and their SOD sequences available in the databases lack clear annotation. Hence, the present study focuses on structure and sequence pattern of subsets of cyanobacterial superoxide dismutases.

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In the cation of the title compound, C12H13N2+·Br−, the dihedral angle between the pyridine and benzene rings is 80.0 (1)°. The anions and cations are connected by inter­molecular N—H⋯Br hydrogen bonds, forming one‐dimensional chains along [100].

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In the title molecule, C22H18N2, all bond lengths and angles are normal. Intermolecular N—H...N hydrogen bonds with an N...N distance of 2.933 (2) Å, link the molecules into chains running along the c axis. The crystal packing is further stabilized by van der Waals forces.