title: Asymmetric collapse in biomimetic complex coacervates revealed by local polymer and water dynamics.
abstract: Complex coacervation is a phenomenon characterized by the association of oppositely charged polyelectrolytes into micrometer-scale liquid condensates. This process is the purported first step in the formation of underwater adhesives by sessile marine organisms, as well as the process harnessed for the formation of new synthetic and protein-based contemporary materials. Efforts to understand the physical nature of complex coacervates are important for developing robust adhesives, injectable materials, or novel drug delivery vehicles for biomedical applications; however, their internal fluidity necessitates the use of in situ characterization strategies of their local dynamic properties, capabilities not offered by conventional techniques such as X-ray scattering, microscopy, or bulk rheological measurements. Herein, we employ the novel magnetic resonance technique Overhauser dynamic nuclear polarization enhanced nuclear magnetic resonance (DNP), together with electron paramagnetic resonance (EPR) line shape analysis, to concurrently quantify local molecular and hydration dynamics, with species- and site-specificity. We observe striking differences in the structure and dynamics of the protein-based biomimetic complex coacervates from their synthetic analogues, which is an asymmetric collapse of the polyelectrolyte constituents. From this study we suggest charge heterogeneity within a given polyelectrolyte chain to be an important parameter by which the internal structure of complex coacervates may be tuned. Acquiring molecular-level insight to the internal structure and dynamics of dynamic polymer complexes in water through the in situ characterization of site- and species-specific local polymer and hydration dynamics should be a promising general approach that has not been widely employed for materials characterization.
authors.affiliation: Materials Research Laboratory, Department of Chemistry and Biochemistry, University of California, Santa Barbara, California 93106, United States.
authors.forename: Julia H
authors.initials: JH
authors.lastname: Ortony
authors.forename: Dong Soo
authors.initials: DS
authors.lastname: Hwang
authors.forename: John M
authors.initials: JM
authors.lastname: Franck
authors.forename: J Herbert
authors.initials: JH
authors.lastname: Waite
authors.forename: Songi
authors.initials: S
authors.lastname: Han
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D040761:Biomimetic Materials / Q000737:chemistry*; D004578:Electron Spin Resonance Spectroscopy; D006820:Hyaluronic Acid / Q000737:chemistry*; D006863:Hydrogen-Ion Concentration; D009682:Magnetic Resonance Spectroscopy; D008969:Molecular Sequence Data; D049880:Mytilus edulis / Q000737:chemistry; D011994:Recombinant Proteins / Q000737:chemistry; D012212:Rheology; D013113:Spin Labels; D055672:Static Electricity; D014867:Water / Q000737:chemistry*
chemical_list: D011994:Recombinant Proteins; D013113:Spin Labels; D014867:Water; D006820:Hyaluronic Acid
references.citation: J Am Chem Soc. 2009 Dec 30;131(51):18254-6
references.pmid: 19791740
references.citation: Langmuir. 2008 Sep 16;24(18):10062-72
references.pmid: 18700788
references.citation: Soft Matter. 2010 Jul 21;6(14):3232-3236
references.pmid: 21544267
references.citation: Mar Biotechnol (NY). 2000 Jul;2(4):352-363
references.pmid: 10960125
references.citation: Phys Chem Chem Phys. 2011 May 7;13(17):7732-46
references.pmid: 21423982
references.citation: Appl Microbiol Biotechnol. 2011 Jan;89(1):27-33
references.pmid: 20890598
references.citation: Biomaterials. 2007 Oct;28(28):4039-46
references.pmid: 17574667
references.citation: Biomacromolecules. 2003 Mar-Apr;4(2):293-303
references.pmid: 12625724
references.citation: Biomaterials. 2010 Dec;31(36):9373-81
references.pmid: 20950851
references.citation: Biomaterials. 2007 Aug;28(24):3560-8
references.pmid: 17507090
references.citation: J Am Chem Soc. 2011 Apr 20;133(15):5987-95
references.pmid: 21443207
references.citation: J Chem Phys. 2007 Sep 14;127(10):104508
references.pmid: 17867762
references.citation: Biomaterials. 2010 May;31(13):3715-22
references.pmid: 20144475
references.citation: Macromolecules. 2009 Mar 24;42(6):2168-2176
references.pmid: 20808713
references.citation: Biomaterials. 2010 Feb;31(6):1080-4
references.pmid: 19892396
references.citation: J Am Chem Soc. 2009 Apr 8;131(13):4641-7
references.pmid: 19290661
references.citation: Biochemistry. 2001 Mar 6;40(9):2887-93
references.pmid: 11258900
references.citation: J Cell Physiol Suppl. 1957 May;49(Suppl 1):7-22; discussion, 22-6
references.pmid: 13449108
references.citation: Proc Natl Acad Sci U S A. 2010 Jul 20;107(29):12850-3
references.pmid: 20615994
references.citation: Nat Mater. 2007 May;6(5):327-8
references.pmid: 17471269
references.citation: Biol Bull. 1992 Aug;183(1):123-137
references.pmid: 29304577