Physical and chemical changes in biological interfaces can be quantified by corresponding changes in the thermodynamic state of the interface. Based on Einsteins approach to thermodynamics, we show that fluorescence spectra of a dye embedded in a lipid membrane is a function of the state of the interface. We derive the coupling between the energy fluctuations of a fluorophore and its environment allowing the thermodynamic susceptibility, in particular, the specific heat of the interface to be estimated from the spectra of the embedded fluorophore. The estimate of the thermodynamic susceptibility is shown to hold not only for quasi-static near-equilibrium measurements, but also for dynamic state changes in lipid vesicles induced by broadband pressure impulses of the order of 1 MPa peak amplitude and 10 microsecond  pulse duration. These experiments also provide crucial insights into how dynamic state changes may affect biological function, for example, during an action potential or during therapeutic use of acoustic impulses in the form of ultrasound or shock waves .
Solvation shell dynamics is a critical determinant of protein and enzyme functions. Here we investigate how the dynamics of the solvation shell changes for molecules embedded in lipid membranes during an acoustic impulse. Solvation sensitive fluorescence probes, Laurdan, embedded in multi-lamellar lipid vesicles in water, were exposed to broadband pressure impulses of the order of 1MPa peak amplitude and 10 \mu s pulse duration. Corresponding changes in emission spectrum of the dye were observed simultaneously across two different wavelengths at sub-microsecond resolution. The experiments show that changes in the emission spectrum and hence the fluctuations of the solvation shell are given by the thermodynamic state change during the process. Therefore, the study suggests that acoustic fields can potentially modulate the kinetics of channels and proteins embedded in lipid membranes by controlling the state dependent fluctuations .
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Physical and chemical changes in biological interfaces can be quantified by corresponding changes in the thermodynamic state of the interface. Based on Einsteins approach to thermodynamics, we show that fluorescence spectra of a dye embedded in a lipid membrane is a function of the state of the interface. We derive the coupling between the energy fluctuations of a fluorophore and its environment allowing the thermodynamic susceptibility, in particular, the specific heat of the interface to be estimated from the spectra of the embedded fluorophore. The estimate of the thermodynamic susceptibility is shown to hold not only for quasi-static near-equilibrium measurements, but also for dynamic state changes in
Solvation shell dynamics is a critical determinant of protein and enzyme functions. Here we investigate how the dynamics of the solvation shell changes for molecules embedded in
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vesicles induced by
membranes during an acoustic impulse. Solvation sensitive fluorescence probes, Laurdan, embedded in multi-lamellar lipid vesicles in water, were exposed to
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1 MPa
1MPa
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microsecond
\mu
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s
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These experiments also provide crucial insights into how dynamic state changes may affect biological function, for example, during an action potential or during therapeutic use of acoustic impulses in the form of ultrasound or shock waves
Corresponding changes in emission spectrum of the dye were observed simultaneously across two different wavelengths at sub-microsecond resolution. The experiments show that changes in the emission spectrum and hence the fluctuations of the solvation shell are given by the thermodynamic state change during the process. Therefore, the study suggests that acoustic fields can potentially modulate the kinetics of channels and proteins embedded in lipid membranes by controlling the state dependent fluctuations