Gamma radiolysis and solar photolysis of bilirubin: Similarities and differences

Abstract

Biliverdin is a useful component in various aspects of biochemistry and biosynthesis, but its synthetic preparation is often long-winded. Micro-production (and subsequent isolation) by solar photolysis and gamma radiolysis of bilirubin provides rapid in vitro generation. Both methods are competitive, and this article discusses their merits and limitations for application in biosynthetic research. The investigation assumed a comparative study to evaluate the relative potential of the photolytic and radiolytic phenomena in this respect. The calculated rate of incident energy in the case of solar photolysis was roughly30.4^.10^-2 W, and about 5.70^.10^-4 W during gamma-irradiation (from a ¹³⁷Cs source). In both cases the bilirubin (40 µM) degradation was pronounced in the initial few minutes of exposure, producing respective depletion rates of approximately 6.8 µM/min and 2.4 µM/min. Overall, both applications showed declining bilirubin concentrations close to 90%, after about 30 minutes. However, the corresponding production of biliverdin was higher by about 50% in the photolytic application. To account for heat-up effects in the photolytic application, thermal effects were studied up to 65 °C, and it was found that, as a result of this, a reduction in bilirubin concentration of about 40% was encountered. The species of interest were monitored spectrophotometrically, and the composite results showed that regulated production of biliverdin is possible under certain conditions.