Wavelength dependence of patman equilibration dynamics in phosphatidylcholine bilayers

Hannabeth Franchino, Evan Stevens, Jennifer Nelson, Thomas A. Bell, John D. Bell*

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review


Assessment of the equilibration kinetics of Patman at the edges of its emission spectra provided additional insights about membrane properties beyond those obtained from end-point fluorescence measurements. Upon introduction of the probe to aqueous suspensions of liposomes, the emission intensity slowly increased about 10-fold (t1/2 = ~ 100 s). The rate of equilibration depended on emission wavelength, and was usually faster at 500 than at 435 nm. However, this trend was reversed for equilibration with lipids at their phase transition temperature. The apparent rotational motion of the dye also differed between the long and short emission wavelengths but did not display the slow equilibration time dependence observed with intensity measurements. These results suggested that slow equilibration reflects relaxation of the immediate membrane microenvironment around the probe rather than slow insertion into the membrane. The data were rationalized with a model that allows two membrane/probe configurations with distinct microenvironments. The analysis suggests that by monitoring the equilibration pattern of Patman, inferences can be made regarding the polarity of two microenvironments occupied by the probe, the distribution of the probe among those microenvironments, and the kinetics with which they relax to equilibrium.
Original languageEnglish
Pages (from-to)877-886
Number of pages10
JournalBiochimica et Biophysica Acta - Biomembranes
Issue number2
Early online date3 Sep 2012
Publication statusPublished - Feb 2013


  • fluorescence anisotropy
  • fluorescence spectroscopy
  • generalized polarization
  • membrane water
  • phase transition
  • solvatochromatic


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