Optimizing end-labeled free-solution electrophoresis by increasing the hydrodynamic friction of the drag-tag

TL;DR

This study uses molecular dynamics simulations to analyze how different hydrodynamic drag-tags affect the efficiency of electrophoretic separation of polyelectrolytes, highlighting the potential of micelles for improved performance.

Contribution

It demonstrates that hydrodynamic size of labels influences drag and shows that designing labels like branched polymers or micelles can enhance ELFSE separation efficiency.

Findings

Linear labels have the highest drag per monomer.

Adding side chains increases hydrodynamic size without lengthening the label.

Transient micelles provide significantly higher hydrodynamic drag.

Abstract

We study the electrophoretic separation of polyelectrolytes of varying lengths by means of end-labeled free-solution electrophoresis (ELFSE). A coarse-grained molecular dynamics simulation model, using full electrostatic interactions and a mesoscopic Lattice Boltzmann fluid to account for hydrodynamic interactions, is used to characterize the drag coefficients of different label types: linear and branched polymeric labels, as well as transiently bound micelles. It is specifically shown that the label's drag coefficient is determined by its hydrodynamic size, and that the drag per label monomer is largest for linear labels. However, the addition of side chains to a linear label offers the possibility to increase the hydrodynamic size, and therefore the label efficiency, without having to increase the linear length of the label, thereby simplifying synthesis. The third class of labels investigated, transiently bound micelles, seems very promising for the usage in ELFSE, as they provide a significant higher hydrodynamic drag than the other label types. The results are compared to theoretical predictions, and we investigate how the efficiency of the ELFSE method can be improved by using smartly designed drag-tags.