Redox absorbance changes of the respiratory chain components of E-Coli following He-Ne laser irradiation

Abstract

Redox absorbance changes of the respiratory chain components of Escherichia coli were measured following He-Ne laser (632.8 nm) irradiation. A dose o 4.3 J/cm super(2) leads to partial oxidation of cytochrome (cyt) b and of cytochrome d, while flavoproteins were found to be slightly reduced. A further dose of 8.6 J/cm super(2) significantly decreased the reduced pyridine nucleotide pool. Inhibitors of flavin photoreactions namely, potassium iodide (KI) and salicylhydroxamic acid (SHAM) were used to check the possibility of involvement of flavins in light absorption. KI did not cause any change in difference absorption spectra of anaerobic minus aerobic cells, however it enhanced laser-induced oxidation of reduced pyridine nucleotides. SHAM inhibited reduction of pyridine nucleotide pool and revealed a second flavoprotein band at 361 nm. Irradiation caused a sharp decrease in absorbance of 361 nm band with concomitant oxidation of cytochrome b and of cytochrome d as well as reduction of flavoproteins. It is suggested that absorption of red light by cyt d followed by its oxidation, may be the primary photoreaction, which initiates some secondary reactions involving flavoproteins.