Microphase Separation Produces Interfacial Environment within Diblock Biomolecular Condensates

Reviewer #1 (Public Review):

This is an interesting, informative, and well-designed study that combines theoretical and experimental methodologies to tackle the phenomenon of higher-resolution structures/substructures in model biomolecular condensates.

The authors have adequately addressed my previous concerns.

Reviewer #2 (Public Review):

Summary:

Latham A.P. et al. apply simulations and FLIM to analyse several di-block elastin-like polypetides and connect their sequence to the micro-structure of coacervates resulting from their phase-separation.

Strengths:

Understanding the molecular grammar of phase separating proteins and the connection with mesoscale properties of the coacervates is highly relevant. This work provides insights into micro-structures of coacervates resulting from di-block polypetides.

Weaknesses:

The results apply to a very specific architecture (di-block polypetides) with specific sequences.

Author response:

The following is the authors’ response to the previous reviews.

The authors have addressed my comments. As a final minor point, regarding comment 2, these condensates are likely viscoelastic rather than purely viscous. It is prudent to indicate that the data may refer to an apparent viscosity.

We added the following text to the manuscript to highlight the viscoelastic nature of ELP condensates, and the relationship of reported values with the steady state viscosity. “It is worth noting that the reported values, although related, may not quantitatively represent the steady-state viscosity. This discrepancy arises from the slow relaxation timescale inherent in ELP condensates with viscoelastic properties.”