Angew. Chem. Int. Edn doi:10.1002/anie.200801516 (2008)

A family of molecular proton sensors that can be programmed to sit at specific distances from the surface of a membrane has been devised by Seiichi Uchiyama and Prasanna de Silva at Queen's University in Belfast, UK, and Kaoru Iwai at Nara Women's University in Japan.

These molecules have position-tuning groups that 'seek out' a local environment that matches their own compatibility with water. They thus distribute themselves at various distances along a radial coordinate of a membranous sphere called a micelle. The local proton concentration determines the intensity of emission from a fluorescent 'reporter' group on the sensor, whereas the asymmetry of local electronic-charge polarity determines the emission wavelength.

All of these details can be mapped. This technique might one day provide clues about how biological surfaces and structures function.