Polymer dynamics, fluorescence correlation spectroscopy, and the limits of optical resolution

TL;DR

This paper critically examines the capabilities and limitations of fluorescence correlation spectroscopy in studying polymer dynamics at nanometer scales, emphasizing its resolution constraints and potential for misleading results.

Contribution

It provides a fundamental analysis of FCS applicability for nanoscale polymer dynamics, highlighting its resolution limits and risks of misinterpretation.

Findings

FCS cannot reliably resolve processes below optical resolution limits.

Improper use of FCS can lead to spurious dynamic measurements.

FCS's effectiveness is constrained by optical resolution in nanoscale studies.

Abstract

In recent years, fluorescence correlation spectroscopy has been increasingly applied for the study of polymer dynamics on the nanometer scale. The core idea is to extract, from a measured autocorrelation curve, an effective mean-square displacement function that contains information about the underlying conformational dynamics. The paper presents a fundamental study of the applicability of fluorescence correlation spectroscopy for the investigation of nanoscale conformational and diffusional dynamics. We find that fluorescence correlation spectroscopy cannot reliably elucidate processes on length scales much smaller than the resolution limit of the optics used and that its improper use can yield spurious results for the observed dynamics.