Researchers at the University of Umeå in Sweden have started to unravel the processes underlying the treatment of jaundice with blue or white light.

When the body breaks down old red blood cells it produces bilirubin, which is insoluble and has to be processed by enzymes which newborn infants, for example, cannot make. Excessive bilirubin levels in the blood cause jaundice, which can lead to brain damage. Phototherapy works by making bilirubin soluble, though the mechanism is still unclear.

In this preliminary work, Burkhard Zietz and collaborators have shown, with time-resolved measurements of bilirubin bound to human serum albumin (the environment in which it is found in the body) that the initial steps on illumination are very fast, taking picoseconds.

These initial steps cannot yet be disentangled, but understanding the dynamics of xanthobilirubic acid, which can dimerise to form bilirubin, may help.

Colin Batchelor