Nanomechanics of Cation–π Interactions in Aqueous Solution

Lu, Qingye; Oh, Dongyeop X.; Lee, Youngjin; Jho, YongSeok; Hwang, Dong Soo; Zeng, Hongbo

doi:10.1002/ange.201210365

Cited by 102 publications

(91 citation statements)

References 44 publications

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“…Rmfp-1 has an exactly equal amount of cationic and phenolic groups (20 mol%) without any negatively charged residue, which reflects the intrinsic nature of the mussel adhesive. MADQUAT was chosen as the counterpart for the cation-rich polyelectrolyte for complex coacervation as the trimethylammonium group is expected to establish stronger cation-π interactions than the lysine of Rmfp-1 (27). Buffer pH was fixed at ∼3.0 (0.1 M sodium acetate, pK a = 4.8), at which the carboxyl terminus of Rmfp-1 is neutral (it is noted that the mussel adhesive secretes to a marine environment at pH below 3.0) (28).…”

Section: Resultsmentioning

confidence: 99%

“…5A shows the force-distance profile of a MADQUAT-coated mica surface interacting with an Rmfp-1-coated mica surface in 100 mM sodium acetate solution (pH ∼3.0). It is noted that the force curves during moving in and moving out of the two surfaces do not overlap, which was mainly due to the interaction differences between the interacting surfaces during approaching and separation (or so-called adhesion hysteresis as generally observed for adhesive systems) (20,27,39). The approaching force curve shows repulsion, which was mainly due to electrical double-layer repulsion between positively charged surfaces and steric interactions of the opposing polymer chains extended to aqueous solution, in competition with attractive interactions such as van der Waals and cation-π interactions.…”

Section: Physical Properties Of the Like-charged Coacervate Phase Meamentioning

confidence: 98%

“…Recent molecular and surface force measurements have revealed the presence of strong adhesion between the cationic and the aromatic polymers in aqueous solutions, which is believed to be due to cation-π interactions (24)(25)(26)(27), which, over short distances, could be stronger than the electrostatic attraction between oppositely charged polymers in aqueous solutions due to its low desolvation penalty (24,25,27). Cation-π interactions in living organisms play a key role in various cellular activities, including neurotransmissions and ion channels, because they show stronger interaction than hydrogen bonding and electrostatic interaction in wet conditions (24,27). Therefore, it is speculated that the cation-π interaction…”

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confidence: 99%

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Complexation and coacervation of like-charged polyelectrolytes inspired by mussels

Kim

Huang

Lee

et al. 2016

Proc. Natl. Acad. Sci. U.S.A.

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197

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It is well known that polyelectrolyte complexes and coacervates can form on mixing oppositely charged polyelectrolytes in aqueous solutions, due to mainly electrostatic attraction between the oppositely charged polymers. Here, we report the first (to the best of our knowledge) complexation and coacervation of two positively charged polyelectrolytes, which provides a new paradigm for engineering strong, self-healing interactions between polyelectrolytes underwater and a new marine mussel-inspired underwater adhesion mechanism. Unlike the conventional complex coacervate, the like-charged coacervate is aggregated by strong short-range cation-π interactions by overcoming repulsive electrostatic interactions. The resultant phase of the like-charged coacervate comprises a thin and fragile polyelectrolyte framework and round and regular pores, implying a strong electrostatic correlation among the polyelectrolyte frameworks. The like-charged coacervate possesses a very low interfacial tension, which enables this highly positively charged coacervate to be applied to capture, carry, or encapsulate anionic biomolecules and particles with a broad range of applications.polyelectrolyte complexes | complex coacervates | cation-π interaction | like-charged coacervate | surface forces apparatus I t is well known that polyelectrolyte complexes can be formed when oppositely charged polyelectrolytes are mixed in aqueous solutions (1-4). This often leads to fluid-fluid phase separation, the so-called complex coacervation, namely, the appearance of a dense polyelectrolyte-rich liquid phase (coacervate phase) and a more dilute solution phase (aqueous phase, Fig. 1) (3, 4). The formation of polyelectrolyte complexes or coacervate can be impacted by many factors, including structural features of the component polymers (e.g., molecular weight, charge density, functional groups, hydrophilicity and hydrophobicity balance, etc.), mixing ratio and concentration of the oppositely charged polyelectrolytes, and solution and environmental conditions (e.g., pH, ionic strength, temperature, etc.) (3-5).Complex coacervate, which was suggested as "the origin of life" (6), finds application in many engineering and biological systems, such as microencapsulation in food, and in pharmaceutical and cosmetic industries due to the low interfacial energy of the coacervate phase (3,5,(7)(8)(9). Complex coacervate also plays a critical role in the underwater adhesion of many sessile marine organisms such as tubeworms and mussels, which secrete and disperse adhesive proteins to form complex coacervates that facilitate their positioning and spreading over a desired substrate under seawater (10-12).It is believed that polyelectrolyte complexation is driven by mainly electrostatic attraction in long distances between oppositely charged polymer chains in water and by additional molecular recognition driving forces such as chirality, hydrogen bonding, and hydration in short distances, implying that the polyelectrolyte complex is composed of at least one polycation ...

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Section: Resultsmentioning

confidence: 99%

Section: Physical Properties Of the Like-charged Coacervate Phase Meamentioning

confidence: 98%

mentioning

confidence: 99%

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Complexation and coacervation of like-charged polyelectrolytes inspired by mussels

Kim

Huang

Lee

et al. 2016

Proc. Natl. Acad. Sci. U.S.A.

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197

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“…4B): (1) bidentate intercatechol H-bonding is robust in aqueous solution (Ahn et al, 2014); (2) cation-π interactions between Lys and Dopa, Phe, Tyr or Trp, which are surprisingly cohesive in the Mfps (Lu et al, 2013a); (3) Ca 2+ salt bridges between paired pSer residues (i.e. electrostatic interactions), which were first noted in P. californica cement but are reckoned to be more widespread (Zhao et al, 2005;Ashton et al, 2011); and (4) hydrophobic interactions .…”

Section: A B Cohesive Interactions During Deposition (Low Ph)mentioning

confidence: 99%

“…In particular, the H-bonds between Dopa residues are surprisingly robust and can, in the absence of oxidation, maintain noncovalent cohesion across a range of pH (Ahn et al, 2014). With >15 mol% lysine and Dopa in many Mfps, cation-π interactions are well-supported as participants in Mfp-Mfp cohesion (Lu et al, 2013a), but these are unlikely to change significantly between pH 2 and pH 8. As in adhesion, electrostatic interactions are weak at pH 2-3, but their strength probably increases as the increase to pH 8 ionizes more acidic groups without substantially reducing the charged amines ( pK a 10.4).…”

Section: Plaque Cohesion In Seawatermentioning

confidence: 99%

Mussel adhesion – essential footwork

Waite

2017

Journal of Experimental Biology

505

744

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Robust adhesion to wet, salt-encrusted, corroded and slimy surfaces has been an essential adaptation in the life histories of sessile marine organisms for hundreds of millions of years, but it remains a major impasse for technology. Mussel adhesion has served as one of many model systems providing a fundamental understanding of what is required for attachment to wet surfaces. Most polymer engineers have focused on the use of 3,4-dihydroxyphenyl-L-alanine (Dopa), a peculiar but abundant catecholic amino acid in mussel adhesive proteins. The premise of this Review is that although Dopa does have the potential for diverse cohesive and adhesive interactions, these will be difficult to achieve in synthetic homologs without a deeper knowledge of mussel biology; that is, how, at different length and time scales, mussels regulate the reactivity of their adhesive proteins. To deposit adhesive proteins onto target surfaces, the mussel foot creates an insulated reaction chamber with extreme reaction conditions such as low pH, low ionic strength and high reducing poise. These conditions enable adhesive proteins to undergo controlled fluid-fluid phase separation, surface adsorption and spreading, microstructure formation and, finally, solidification.

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Mussel‐Inspired Underwater Adhesives‐from Adhesion Mechanisms to Engineering Applications: A Critical Review

Zhang

Frenkel

et al. 2021

Progress in Adhesion and Adhesives

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Nanomechanics of Cation–π Interactions in Aqueous Solution

Cited by 102 publications

References 44 publications

Complexation and coacervation of like-charged polyelectrolytes inspired by mussels

Complexation and coacervation of like-charged polyelectrolytes inspired by mussels

Mussel adhesion – essential footwork

Mussel‐Inspired Underwater Adhesives‐from Adhesion Mechanisms to Engineering Applications: A Critical Review

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