On the Theory of Grafted Weak Polyacids

Israels, Rafel; Leermakers, F.A.M.; Fleer, G.J.

doi:10.1021/ma00089a028

Cited by 222 publications

(323 citation statements)

References 11 publications

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“…4) show a qualitative agreement with the mean-field theory of weak polyelectrolyte brushes (Supplementary Note 4 and Supplementary Fig. 7) 22,23 , which predicts that the brush should collapse with increasing salt concentration (C), but only as a relatively weak power law (C À 1/3 ). We see a comparatively steeper ionic strength-dependence, which has been previously observed in synthetic polymer systems [24][25][26][27][28][29] and may arise from the local modulation of protein charge-based interactions due to added salt.…”

Section: Resultssupporting

confidence: 79%

Stimuli-sensitive intrinsically disordered protein brushes

et al. 2014

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Grafting polymers onto surfaces at high density to yield polymer brush coatings is a widely employed strategy to reduce biofouling and interfacial friction. These brushes almost universally feature synthetic polymers, which are often heterogeneous and do not readily allow incorporation of chemical functionalities at precise sites along the constituent chains. To complement these synthetic systems, we introduce a biomimetic, recombinant intrinsically disordered protein that can assemble into an environment-sensitive brush. This macromolecule adopts an extended conformation and can be grafted to solid supports to form oriented protein brushes that swell and collapse dramatically with changes in solution pH and ionic strength. We illustrate the value of sequence specificity by using proteases with mutually orthogonal recognition sites to modulate brush height in situ to predictable values. This study demonstrates that stimuli-responsive brushes can be fabricated from proteins and introduces them as a new class of smart biomaterial building blocks.

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Section: Resultssupporting

confidence: 79%

Stimuli-sensitive intrinsically disordered protein brushes

et al. 2014

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“…32 Theoretical calculations have predicted the thickness of grafted weak polyelectrolyte layers to have a maximum as a function of the salt concentration. 33,34 This behavior has been confirmed by experimental findings. 35 Is this non-monotonic behavior also present in grafted hydrogel films of weak polyacid chains?…”

Section: Introductionsupporting

confidence: 74%

Non-monotonic swelling of surface grafted hydrogels induced by pH and/or salt concentration

Longo

Cruz

Szleifer

2014

The Journal of Chemical Physics

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We use a molecular theory to study the thermodynamics of a weak-polyacid hydrogel film that is chemically grafted to a solid surface. We investigate the response of the material to changes in the pH and salt concentration of the buffer solution. Our results show that the pH-triggered swelling of the hydrogel film has a non-monotonic dependence on the acidity of the bath solution. At most salt concentrations, the thickness of the hydrogel film presents a maximum when the pH of the solution is increased from acidic values. The quantitative details of such swelling behavior, which is not observed when the film is physically deposited on the surface, depend on the molecular architecture of the polymer network. This swelling-deswelling transition is the consequence of the complex interplay between the chemical free energy (acid-base equilibrium), the electrostatic repulsions between charged monomers, which are both modulated by the absorption of ions, and the ability of the polymer network to regulate charge and control its volume (molecular organization). In the absence of such competition, for example, for high salt concentrations, the film swells monotonically with increasing pH. A deswelling-swelling transition is similarly predicted as a function of the salt concentration at intermediate pH values. This reentrant behavior, which is due to the coupling between charge regulation and the two opposing effects triggered by salt concentration (screening electrostatic interactions and charging/discharging the acid groups), is similar to that found in end-grafted weak polyelectrolyte layers. Understanding how to control the response of the material to different stimuli, in terms of its molecular structure and local chemical composition, can help the targeted design of applications with extended functionality. We describe the response of the material to an applied pressure and an electric potential. We present profiles that outline the local chemical composition of the hydrogel, which can be useful information when designing applications that pursue or require the absorption of biomolecules or pH-sensitive molecules within different regions of the film.

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“…To calculate the steric ͑repulsive͒ interaction due to brush repulsion we will first evaluate the relation between the brush height and the pH for -caseins in skim milk and will follow the theory of grafted weak polyacids proposed by Israels et al 28 As discussed by De Kruif and Zhulina, 20 -caseins can be described as charged brushes in the ͑''salted brush''͒ regime. In this regime the salt concentration is such that it penetrates the brush and screens the electrostatic interactions between the charged polyacid groups; Ϫ1 ӶH, where H is the brush height.…”

Section: Theoretical Sectionmentioning

confidence: 99%

“…Then the polyacid brush is quasi-neutral; its characteristics are identical to those of neutral brushes. Consequently, in the strong stretching approximation, the brush height then reads 28,29 as…”

Section: Theoretical Sectionmentioning

confidence: 99%

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Stability of casein micelles in milk

Tuinier

Kruif

2002

The Journal of Chemical Physics

227

168

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Casein micelles in milk are proteinaceous colloidal particles and are essential for the production of flocculated and gelled products such as yogurt, cheese, and ice-cream. The colloidal stability of casein micelles is described here by a calculation of the pair potential, containing the essential contributions of brush repulsion, electrostatic repulsion, and van der Waals attraction. The parameters required are taken from the literature. The results are expressed by the second osmotic virial coefficient and are quite consistent with experimental findings. It appears that the stability is mainly attributable to a steric layer of -casein, which can be described as a salted polyelectrolyte brush.

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On the Theory of Grafted Weak Polyacids

Cited by 222 publications

References 11 publications

Stimuli-sensitive intrinsically disordered protein brushes

Stimuli-sensitive intrinsically disordered protein brushes

Non-monotonic swelling of surface grafted hydrogels induced by pH and/or salt concentration

Stability of casein micelles in milk

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