Comment on "Relative Diffusivities of Bound and Unbound Protein Can Control Chemotactic Directionality''

TL;DR

This comment critiques a recent paper claiming a new model for enzyme chemotaxis, demonstrating that it actually reproduces an existing theory and lacks novelty.

Contribution

The authors clarify that the recent model is not new but identical to their previous work, challenging claims of originality.

Findings

The proposed model is mathematically equivalent to previous theory.

The claim of novelty by Mandal and Sen is unsubstantiated.

The critique emphasizes the importance of proper attribution in scientific modeling.

Abstract

This is a comment on a recently published paper in Langmuir: Mandal, N. S.; Sen, A. Relative Diffusivities of Bound and Unbound Protein Can Control Chemotactic Directionality. Langmuir 2021, PMID: 34647749 [arXiv:2103.13469]. In this study, Mandal and Sen claim to propose a new kinetic model to analyze the directional movement of enzyme molecules in response to a gradient of their substrate, with the supposedly new prediction that net movement occurs up the substrate gradient when the diffusivity of the substrate-bound enzyme is lower than that of the unbound enzyme, and movement down the substrate gradient when the diffusivity of the substrate-bound enzyme is higher than that of the unbound enzyme. They develop this theoretical scheme to present an alternative to our previously published theoretical framework [Agudo-Canalejo, J.; Illien, P.; Golestanian, R. Phoresis and enhanced diffusion compete in enzyme chemotaxis. Nano Lett. 2018, 18, 2711-2717; arXiv:2104.02394]. We demonstrate that despite their claim, what they present is exactly the same theory as our work, and therefore, we conclude that their claim of novelty is unsubstantiated.