Semidilute Polymer Scaling Controls PEG-induced Protein Phase Separation
- 1New York University Abu Dhabi
Abstract
When does polyethylene glycol (PEG) mass concentration provide a common measure of crowding strength across polymer chain lengths? Here we use bovine serum albumin (BSA) and PEG as a controlled depletion system and measure both coexisting phases to determine binodals, tie lines, and critical points across PEG molecular weights of 4--100 kDa. Phase diagrams for PEG 20, 35, and 100 kDa approximately collapse in mass-concentration coordinates, consistent with semidilute polymer scaling. Generalized free volume theory (GFVT) describes the BSA binodals and tie lines. It also approximately describes binodals for three additional globular proteins in PEG 35K, extending the comparison across proteins spanning 7.2--66.4 kDa. For the binary PEG mixtures tested, GFVT approximates the binodals using an effective polymer size corresponding to the weight-average molecular weight. These results identify a regime in which PEG mass concentration (g/L) provides a transferable measure of depletion-induced crowding.
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BibTeX
@misc{ahmad2026semidilute,
title = {{Semidilute Polymer Scaling Controls PEG-induced Protein Phase Separation}},
author = {M. Ahmad and H. Ouzon-Shubeita and M. Whende and A. Ianiro and A. A. Rebane},
howpublished = {bioRxiv},
year = {2026},
month = oct,
doi = {10.64898/2026.10.25.761614},
url = {https://www.biorxiv.org/content/10.64898/2026.10.25.761614v1},
note = {CC BY-NC},
}
RIS
TY - UNPB
TI - Semidilute Polymer Scaling Controls PEG-induced Protein Phase Separation
AU - M. Ahmad
AU - H. Ouzon-Shubeita
AU - M. Whende
AU - A. Ianiro
AU - A. A. Rebane
PY - 2026
DA - 2026/10/25
PB - bioRxiv
DO - 10.64898/2026.10.25.761614
UR - https://www.biorxiv.org/content/10.64898/2026.10.25.761614v1
AB - When does polyethylene glycol (PEG) mass concentration provide a common measure of crowding strength across polymer chain lengths? Here we use bovine serum albumin (BSA) and PEG as a controlled depletion system and measure both coexisting phases to determine binodals, tie lines, and critical points across PEG molecular weights of 4--100 kDa. Phase diagrams for PEG 20, 35, and 100 kDa approximately collapse in mass-concentration coordinates, consistent with semidilute polymer scaling. Generalized free volume theory (GFVT) describes the BSA binodals and tie lines. It also approximately describes binodals for three additional globular proteins in PEG 35K, extending the comparison across proteins spanning 7.2--66.4 kDa. For the binary PEG mixtures tested, GFVT approximates the binodals using an effective polymer size corresponding to the weight-average molecular weight. These results identify a regime in which PEG mass concentration (g/L) provides a transferable measure of depletion-induced crowding.
ER -