Static and dynamic studies of the potential-sensitive membrane probe RH421 in dimyristoylphosphatidylcholine vesicles.
The dynamics of the potential-sensitive styryl dye RH421 in dimyristoylphosphatidylcholine vesicles have been investigated above and below the main phase transition temperature using iodine-laser temperature-jump relaxation spectrophotometry and time-resolved fluorescence lifetime measurements. Equilibrium fluorescence titrations have shown that the affinity of the dye for the membrane is much higher in the liquid-crystalline state than in the gel state. The interaction can be described by either a partition or a binding model and a theory is presented providing a relation between these two approaches. In the liquid-crystalline state bound dye exhibits steady-state fluorescence relaxation processes in the submicrosecond and millisecond time range following a temperature jump. Time-resolved fluorescence measurements show a variation in the fluorescence lifetime across the emission spectrum, suggesting an excited-state process occurring on the subnanosecond time scale. These processes are most likely related to dye and/or lipid reorientation following the temperature jump or excitation pulse. Temperature-dependent changes in the fluorescence excitation spectrum of bound dye suggest that the dye exists in at least two different sites within the membrane.
Zouni
A
A
Fritz-Haber-Institut der Max-Planck-Gesellschaft, Berlin, Germany.
Clarke
R J
RJ
Visser
A J
AJ
Visser
N V
NV
Holzwarth
J F
JF
D002152:Calorimetry, Differential Scanning; D004134:Dimyristoylphosphatidylcholine / Q000737:chemistry*; D005456:Fluorescent Dyes; D007700:Kinetics; D008433:Mathematics; D008567:Membranes, Artificial; D008962:Models, Theoretical; D011726:Pyridinium Compounds; D013343:Styrenes
D005456:Fluorescent Dyes; D008567:Membranes, Artificial; D011726:Pyridinium Compounds; D013343:Styrenes; C070534:RH 421; D004134:Dimyristoylphosphatidylcholine