Fluorescence lifetimes of carbocyanine lipid analogs in phospholipid bilayers

Packard, Beverly S.; Wolf, David E.

doi:10.1021/bi00340a033

Cited by 55 publications

(62 citation statements)

References 34 publications

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“…2). From our solution results, model membrane results and literature, 55 we concluded that second lifetime component was more strongly affected by viscosity than the first component. Thus, we focused on the shear-induced changes in the longer exponent, for which values were obtained by tail fitting the portion of the histogram bin where first exponential and IRF are not relevant, i.e.…”

Section: Resultssupporting

confidence: 50%

“…34 The photophysics (e.g. fluorescence lifetime, quantum yield) have been well characterized, 55 and because these dyes share identical chromophores and differ only by their chain lengths, they are useful in definitively assigning their unique photophysical properties to different membrane domains. For most other “raft” associated dyes there is no structurally equivalent counter stain to probe non-raft regions.…”

Section: Introductionmentioning

confidence: 99%

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Endothelial Cell Membrane Sensitivity to Shear Stress is Lipid Domain Dependent

2010

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Blood flow-associated shear stress causes physiological and pathophysiological biochemical processes in endothelial cells that may be initiated by alterations in plasma membrane lipid domains characterized as liquid-ordered (lo), such as rafts or caveolae, or liquid-disordered (ld). To test for domain–dependent shear sensitivity, we used time-correlated single photon counting instrumentation to assess the photophysics and dynamics of the domain-selective lipid analogues DiI-C12 and DiI-C18 in endothelial cells subjected to physiological fluid shear stress. Under static conditions, DiI-C12 fluorescence lifetime was less than DiI-C18 lifetime and the diffusion coefficient of DiI-C12 was greater than the DiI-C18 diffusion coefficient, confirming that DiI-C12 probes ld, a more fluid membrane environment, and DiI-C18 probes the lo phase. Domains probed by DiI-C12 exhibited an early (10 s) and transient decrease of fluorescence lifetime after the onset of shear while domains probed by DiI-C18 exhibited a delayed decrease of fluorescence lifetime that was sustained for the 2 min the cells were subjected to flow. The diffusion coefficient of DiI-C18 increased after shear imposition, while that of DiI-C12 remained constant. Determination of the number of molecules (N) in the control volume suggested that DiI-C12-labeled domains increased in N immediately after step-shear, while N for DiI-C18-stained membrane transiently decreased. These results demonstrate that membrane microdomains are differentially sensitive to fluid shear stress.

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Section: Resultssupporting

confidence: 50%

Section: Introductionmentioning

confidence: 99%

Endothelial Cell Membrane Sensitivity to Shear Stress is Lipid Domain Dependent

2010

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“…In each solvent, fluorescence lifetimes were best fit using biexponential decays [Eq. (12)], consistent with earlier results 41 for DiI. Each value reported in Table 3 42 Using a single exponential to fit the lifetime curve, they obtained a value of 1.12 ns for the decay of DiD in ethanol.…”

Section: Fluorescence Lifetime Measurementssupporting

confidence: 87%

Integrated multimodal microscopy, time-resolved fluorescence, and optical-trap rheometry: toward single molecule mechanobiology

et al. 2007

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Cells respond to forces through coordinated biochemical signaling cascades that originate from changes in single-molecule structure and dynamics and proceed to large-scale changes in cellular morphology and protein expression. To enable experiments that determine the molecular basis of mechanotransduction over these large time and length scales, we construct a confocal molecular dynamics microscope (CMDM). This system integrates total-internal-reflection fluorescence (TIRF), epifluorescence, differential interference contrast (DIC), and 3-D deconvolution imaging modalities with time-correlated single-photon counting (TCSPC) instrumentation and an optical trap. Some of the structures hypothesized to be involved in mechanotransduction are the glycocalyx, plasma membrane, actin cytoskeleton, focal adhesions, and cell-cell junctions. Through analysis of fluorescence fluctuations, single-molecule spectroscopic measurements [e.g., fluorescence correlation spectroscopy (FCS) and time-resolved fluorescence] can be correlated with these subcellular structures in adherent endothelial cells subjected to well-defined forces. We describe the construction of our multimodal microscope in detail and the calibrations necessary to define molecular dynamics in cell and model membranes. Finally, we discuss the potential applications of the system and its implications for the field of mechanotransduction.

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“…65,66 Moreover, Packard and Wolf have shown that fluorescence lifetime of DiI increases with an increase in order of the lipid acyl chains. 19 …”

Section: Resultsmentioning

confidence: 99%

Atomistic simulation of lipid and DiI dynamics in membrane bilayers under tension

Muddana

Gullapalli

Manias

et al. 2011

Phys. Chem. Chem. Phys.

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Membrane tension modulates cellular processes by initiating changes in the dynamics of its molecular constituents. To quantify the precise relationship between tension, structural properties of the membrane, and the dynamics of lipids and a lipophilic reporter dye, we performed atomistic molecular dynamics (MD) simulations of DiI-labeled dipalmitoylphosphatidylcholine (DPPC) lipid bilayers under physiological lateral tensions ranging from −2.6 mN m−1 to 15.9 mN m−1. Simulations showed that the bilayer thickness decreased linearly with tension consistent with volume-incompressibility, and this thinning was facilitated by a significant increase in acyl chain interdigitation at the bilayer midplane and spreading of the acyl chains. Tension caused a significant drop in the bilayer's peak electrostatic potential, which correlated with the strong reordering of water and lipid dipoles. For the low tension regime, the DPPC lateral diffusion coefficient increased with increasing tension in accordance with free-area theory. For larger tensions, free area theory broke down due to tension-induced changes in molecular shape and friction. Simulated DiI rotational and lateral diffusion coefficients were lower than those of DPPC but increased with tension in a manner similar to DPPC. Direct correlation of membrane order and viscosity near the DiI chromophore, which was just under the DPPC headgroup, indicated that measured DiI fluorescence lifetime, which is reported to decrease with decreasing lipid order, is likely to be a good reporter of tension-induced decreases in lipid headgroup viscosity. Together, these results offer new molecular-level insights into membrane tension-related mechanotransduction and into the utility of DiI in characterizing tension-induced changes in lipid packing.

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Fluorescence lifetimes of carbocyanine lipid analogs in phospholipid bilayers

Cited by 55 publications

References 34 publications

Endothelial Cell Membrane Sensitivity to Shear Stress is Lipid Domain Dependent

Endothelial Cell Membrane Sensitivity to Shear Stress is Lipid Domain Dependent

Integrated multimodal microscopy, time-resolved fluorescence, and optical-trap rheometry: toward single molecule mechanobiology

Atomistic simulation of lipid and DiI dynamics in membrane bilayers under tension

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