# Doppler Fluctuation Spectroscopy of Intracellular Dynamics in Living Tissue

## TL;DR

This paper develops a theoretical framework and experimental validation for analyzing intracellular dynamics in living tissue using Doppler fluctuation spectroscopy, revealing a Doppler edge related to active transport regimes.

## Contribution

It introduces a comprehensive theory for light scattering from persistent intracellular transport and validates it with simulations and experimental biodynamic imaging.

## Key findings

- Identification of a Doppler edge in living tissue spectra
- Analytical derivation of autocorrelation functions for different transport regimes
- Experimental detection of Doppler edge in 3D tissue using holography

## Abstract

Intracellular dynamics in living tissue are dominated by active transport driven by bioenergetic processes far from thermal equilibrium. Intracellular constituents typically execute persistent walks. In the limit of long mean-free paths, the persistent walks are ballistic, exhibiting a "Doppler edge" in light scattering fluctuation spectra. At shorter transport lengths, the fluctuations are described by lifetime-broadened Doppler spectra. Dynamic light scattering from transport in the ballistic, diffusive or the cross-over regime is derived analytically, including the derivation of autocorrelation functions through a driven damped harmonic oscillator analog for light scattering from persistent walks. The theory is validated through Monte Carlo simulations. Experimental evidence for the Doppler edge in 3D living tissue is obtained using biodynamic imaging based on low-coherence interferometry and digital holography.

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Source: https://tomesphere.com/paper/1904.05434