Long-lifetime lipid rhenium metal-ligand complex for probing membrane dynamics on the microsecond timescale

Abstract

We report the luminescence and spectral properties of a phospholipid analogue containing a long-lifetime luminescent rhenium metal-ligand complex (MLC) covalently linked to the amino group of phosphatidyl ethanolamine. When incorporated into synthetic membranes, this lipid probe displays intensity decay times near 3 microseconds. Importantly, the probe displays highly polarized emission with a maximal fundamental anisotropy of 0.33. This probe is expected to have numerous applications for studies of microsecond diffusion and dynamics of membranes.

Fig. 1.

Absorption and emission spectra of Re-PE in DPPG vesicles at 20°C. Also shown is the excitation anisotropy spectrum of the parent compound [Re(,4,7-Me₂phen)(CO)₃(4-COOHPy)]⁺ in glycerol/methanol at −60°C.

Fig. 2.

Frequency-domain intensity decays of Re-PE incorporated in DPPG vesicles at various temperatures.

Fig. 3.

Frequency-domain anisotropy decays of DPPG vesicles labeled with Re-PE.

Fig. 4.

Reconstructed time-domain anisotropy, decays of DPPG vesicles labeled with Re-PE.

Fig. 5.

Frequency-domain intensity decay of Re(Me₂-phen)(CO)₃ (COOHPy) PF₆ in glycerol.

Fig. 6.

Frequency-domain anisotropy decay of Re(Me₂-phen)(CO)₃ (COOHPy) PF₆ in glycerol.

Scheme I.

Molecular structure of the phospholipid analogue of [Re(4,7-Me₂phen)(CO)₃(4-COOHPy)]⁺(Re-PE).0