Fluorescent Probes
Other groups use fluorescence techniques and electron spin resonance spectroscopy (ESR) to study phase behavior of lipids. These techniques require the use of a minuscule amount of fluorescent probe or spin label, which was thought not to alter membrane phase behavior. Several groups have begun to question this assumption.
We found that 0.05 mol% of the probe DiIC12 is enough to significantly alter the temperature at which the liquid ordered (lo) and liquid disordered (ld) phases mix in membranes of 1:1 DOPC:DPPC-D62 + 30% cholesterol (Tmix). In fact, 0.5 mol% DiIC12 raised Tmix by an astonishing 6°C. We are now studying the effects of the probes Laurdan and Naphthropyrene on phase transition temperatures.
![DiIC12 concentration dependence of Tmix](imagesJT/tmix.jpg)
Veatch, S.L., Leung, S.S.W., Hancock, B., Thewalt, J. (2007) Fluorescent probes alter miscibility phase boundaries in ternary vesicles. J. Phys. Chem. B. 111:502-504.