Molecular sensor can spot pyrophosphate anions, say scientists in Australia.  The sensor could be used to monitor biological reactions such as DNA polymerisation, important for looking at how drugs treat diseases like HIV and cancer.

The molecule, known as a receptor, was designed by Katrina Jolliffe and colleagues at the University of Sydney, New South Wales. It is based on a modified cyclic peptide structure and was designed to complement the large size and shape of the pyrophosphate ion. The receptor binds tightly and selectivity to pyrophosphate ions under conditions like those found in the human body.

'Pyrophosphate ions are released upon hydrolysis of ATP in many important biochemical reactions,' explained Jolliffe.  'Therefore, the ability to selectively detect pyrophosphate ions under physiological conditions will provide sensors that could be used to monitor these reactions.'

To make the molecule, Jolliffe modified a cyclic peptide by incorporating oxazole groups into the ring and attaching two pendant arms that coordinate to zinc ions.  These metal centres are involved in binding the pyrophosphate ions.  

The receptor has a fluorescent component loosely attached.  When a pyrophosphate anion is present, it displaces the fluorescent indicator, causing a change in the fluorescence of the solution.

Phil Gale, an expert in anion coordination at the University of Southampton, UK, said only a very small number of pyrophosphate selective receptors that function in water have been found so far. 'Receptors and sensors that can distinguish between the wide variety of biological molecules containing phosphate may find future use in diagnostic applications,' said Gale. 'This receptor marks a significant step towards that goal.'

Alison Stoddart