Detecting molecular folding from noise measurements

TL;DR

This paper explores using force variance in single-molecule experiments to detect molecular folding transitions, especially under noisy conditions, and discusses how temperature can improve detection of these events.

Contribution

It introduces a force variance method to identify folding transitions in noisy single-molecule data, applicable to DNA and protein systems, and highlights temperature's role in enhancing detection.

Findings

Force variance reveals folding transitions despite high noise.

Temperature improves detection of folding events at low forces.

Method may extend to identifying intermediate folding states.

Abstract

Detecting conformational transitions in molecular systems is key to understanding biological processes. Here, we investigate the force variance in single-molecule pulling experiments as an indicator of molecular folding transitions. We consider cases where Brownian force fluctuations are large, masking the force rips and jumps characteristic of conformational transitions. We compare unfolding and folding data for DNA hairpin systems of loop sizes 4,8, and 20 and the 110 amino acids protein barnase, finding conditions that facilitate the detection of folding events at low forces where the signal-to-noise ratio is low. In particular, we discuss the role of temperature as a useful parameter to improve the detection of folding transitions in entropically driven processes where folding forces are temperature-independent. The force variance approach might be extended to detect the elusive intermediate states in RNA and protein folding.