Fluorescence lifetime distributions of 1,6-diphenyl-1,3,5-hexatriene in phospholipid vesicles

Abstract

The fluorescence emission properties of 1,6-diphenyl-1,3,5-hexatriene ( D P H ) in 1,2-dipalmitoyl-3-sn-phosphatidylcholine and 1,2-dimyristoyl-3-sn-phosphatidylcholine multilamellar vesicles have been measured by using multifrequency phase fluorometry. The fluorescence decay of D P H in the phospholipid vesicles has been analyzed by assuming either that the decay is made up of a discrete sum of exponential components or that the decay is made up of one or more continuous distributions of lifetime components. The fit of the decay curve using exponentials required at least two terms, and the reduced

The transmembrane gradient of the dielectric constant influences the DPH lifetime distribution

“…While earlier experiments provided only indirect evidence for the effect of the dielectric constant on the lifetime distribution of DPH [8], the present results are a first direct proof of the influence of the dielectric constant on the DPH lifetime distribution in the membrane bilayer. The smaller change of the dielectric constant in heavy water resulted in a narrower distribution width (FWHM) and in a higher value at the center of the major component.…”

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With the aim of understanding the origin of the variation of DPH decay parameters on the gradient of the dielectric costant, membrane oxidative damage induced by ionizing radiation has been studied [8]. However, in previous work, changes in the gradient of the dielectric constant were postulated on the basis of the changed membrane properties, like membrane lipids phase state, lipid unsaturation, cholesterol content, etc.

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Fluorescence lifetime distributions of 1,6-diphenyl-1,3,5-hexatriene reveal the effect of cholesterol on the microheterogeneity of erythrocyte membrane

“…The fluorescence was measured through a long-pass filter type RG 370 from Janos Technology (Townshend, VT) which showed negligible luminescence. The experimental data were analyzed assuming either a sum of exponential or a continuous distribution of lifetime values [23]. A program provided by ISS (La Spezia, Italy) was used for the distribution analysis.…”

“…A program provided by ISS (La Spezia, Italy) was used for the distribution analysis. For both the exponential and distribution analysis, the programs minimize the reduced chi-square defined by an equation reported elsewhere [23]. The applicability of distribution analysis in comparison with exponential approach to study lifetime heterogeneity has been already discussed in detail by Alcala et al [35].…”

“…In phospholipid vesicles, we are able to describe the decay using a continuous distribution of lifetime values. The width of the lifetime distribution can be related to the different physical properties of the environment in which the DPH molecules are located, i.e., the membrane microheterogeneity [23].…”