Sequence-dependent self-coacervation in high charge-density polyampholytes. Issue 3 (28th August 2019)

• Record Type: Journal Article
• Authors: Madinya, Jason J.; Chang, Li-Wei; Perry, Sarah L.; Sing, Charles E.
• Is Part Of: Molecular Systems Design and Engineering. Volume 5:Issue 3(2020)
• Page Start: 632
• Page End: 644
• Publication Date: 2019-08-28
• Subjects: Chemistry -- Molecular aspects -- Periodicals; Chemical engineering -- Molecular aspects -- Periodicals; Nanotechnology -- Periodicals; 620.5
• DOI: 10.1039/c9me00074g
• Languages: English
• ISSNs: 2058-9689

Abstract

Abstract : Experiment and theory show how charge monomer sequence can be used to control self-coacervation in blocky polyampholytes. Abstract : Polyampholytes, which contain both positive and negative charges along the backbone, represent a classical model system for certain types of 'intrinsically-disordered proteins' (IDPs). IDPs can possess biological functionality, even in an unfolded state, including the formation of phase-separated regions within a cell; while driven by a number of interactions, electrostatic attractions are thought to be key to forming these structures. This process of electrostatically-driven liquid–liquid phase separation, known as 'complex coacervation', can also be observed in simpler polymer or biopolymer systems. In this paper, we use a series of model polyampholytic polypeptides of increasing blockiness, that undergo 'self-coacervation' due to charge attraction between polycation and polyanion blocks along the same polymer chain. We show that these polypeptides undergo complex coacervation when sequences have at least 8–12 adjacent like-charges, with increasing blockiness leading to a larger two-phase region. We simultaneously develop a theory built on the transfer-matrix formalism developed by the authors, to show how blockiness increases the strength of electrostatic interactions and subsequently promote phase separation. We explore a tradeoff that emerges due to the presence of 'charge-pattern interfaces' where the sequence of polyampholyte charges switches sign, and how these contrast with chain-ends in equivalent homopolyelectrolyte coacervates.