Analysis of the anisotropy decay of trans-parinaric acid in lipid bilayers

Abstract

An analysis is presented of the complex anisotropy behavior of trans-parinaric acid in single component DEPC lipid bilayers. It is shown that a model involving two species with distinct lifetime and motional behavior is required, and is adequate, to explain the observed data. In particular, the observed increase in the anisotropy at long times demonstrates the presence of a species with a long fluorescence lifetime that has a high anisotropy. The time dependence of the anisotropy for these two environments is treated using both a purely mathematical sum of exponentials and a constrained fit based on an approximate solution of the anisotropic diffusion problem. In this latter model the anisotropy is described in terms of the second and fourth rank order parameters, (P2) and (P4), and a single dynamical parameter, D1, the perpendicular diffusion coefficient for this uniaxial probe. The parameters of both models are accurately determined from the fits to the data when two environments coexist and an association is made between lifetime components and distinct rotational sites. The values of the parameters obtained demonstrate the "solid-like" and "fluidlike" nature of these two coexisting environments.

Sphingolipid levels crucially modulate lateral microdomain organization of plasma membrane in living yeast

“…Both anisotropy decays depicted in Fig. 4 exhibit biphasic behavior that is a clear sign of membrane heterogeneity when probe with a phase-sensitive quantum yield partitions between phases with rather different fluidity and/or membrane order [15]. Similar t-PnA anisotropies were observed on mixed-lipid bilayers [15,25,28].…”

“…4 exhibit biphasic behavior that is a clear sign of membrane heterogeneity when probe with a phase‐sensitive quantum yield partitions between phases with rather different fluidity and/or membrane order [15]. Similar t‐PnA anisotropies were observed on mixed‐lipid bilayers [15,25,28]. Importantly, both r ∞,G and r ∞,L , and correlation times ϕ G and ϕ L belonging to the gel (G) and liquid (L) phases, respectively, can be extracted from the data [15,25].…”

“…Anisotropy decays of t‐PnA were fitted by the associative model describing fluorescence depolarization in heterogeneous systems [15]. t‐PnA partitioning between the liquid (L) and gel (G) phases was supposed to exhibit monoexponential anisotropy decay r L ( t ) and r G ( t ), respectively, with distinct correlation times and limiting anisotropies: …”

Insight into the activation mechanism of Bordetella pertussis adenylate cyclase by calmodulin using fluorescence spectroscopy

“…The anisotropy decay pattern at intermediate time will result from a combination of fast and slow decays of the free and bound probe, respectively. This type of behavior was originally observed in membranes [40], proteins [41,42] and nucleic acids [33]. The MEM analysis of the polarized fluorescence decays using the classical 1D model of anisotropy, which associates all lifetimes with all the correlation times, was unable to account for the fast initial decay as shown in Fig.…”

Modulation by Ca2+ and by Membrane Binding of the Dynamics of Domain III of Annexin 2 (p36) and the Annexin 2−p11 Complex (p90): Implications for Their Biochemical Properties

“…To analyze these types of data, methods mainly based on nonlinear least-squares regression have been developed in the literature but involving imposed τ-θ associations (46,(48)(49)(50)(51). On the contrary, MEM allows a non-a priori guess with respect to the τ-θ associations using the twodimensional analysis of the fluorescence-polarized decays (43)(44)(45)52).…”