... monitored by the reduction of cytochrome c in the presence of NADH at 550 nm [1].Protein determinationProtein content was determined by the Bradford test [20],using bovine serum albumin as standard.PHI ... explain the regulatory effect. In fact, on addition of PHI, the fluorescence of PHR-bound flavin increases. Thisfinding points to a PHI-induced conformational change of PHR, possibly resulting in ... show iron- or sulfur-containing redox-centres in the pure protein. In agreementwith these findings, the emission spectrum of PHI,determined by spectrofluorimetry in the same conditions,exhibited...