pH Wave-Front Propagation in the Urea-Urease Reaction

Wrobel, Magdalena M.; Bánsági, Tamás; Scott, Stephen K.; Taylor, Annette F.; Bounds, Chris; Carranza, Arturo; Pojman, John A.

doi:10.1016/j.bpj.2012.06.020

Cited by 47 publications

(54 citation statements)

References 35 publications

(36 reference statements)

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“…The time to reach pH 7 was thus inversely correlated with the initial pH value after mixing. The trends of the dependence of the induction period on the initial concentrations agree well with those found in our earlier study without ETTMP when the pH value of the stock solution was adjusted with sulfuric or acetic acid 21a. The induction period depends on the nature of the acid, as weak acids can buffer the pH change, thus reducing the reaction rate.…”

supporting

confidence: 88%

“…The final pH value ranged from 8.5 to 9.5; lower values of about 7 are also possible for smaller urea concentrations (Figure 2 c) 21a. The final pH value was determined by the ammonia/ammonium ratio, which depended upon the initial amount of urea and the acid.…”

mentioning

confidence: 96%

“…Unlike diffusive processes alone, in which a chemical becomes progressively more dilute in space, the amplitude of chemical change associated with autocatalytic fronts is constant 21a, 25. In this case it corresponds to the pH change observed in the experiments with well‐stirred mixtures.…”

mentioning

confidence: 99%

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Temporal Control of Gelation and Polymerization Fronts Driven by an Autocatalytic Enzyme Reaction

et al. 2016

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Chemical systems that remain kinetically dormant until activated have numerous applications in materials science. Herein we present a method for the control of gelation that exploits an inbuilt switch: the increase in pH after an induction period in the urease‐catalyzed hydrolysis of urea was used to trigger the base‐catalyzed Michael addition of a water‐soluble trithiol to a polyethylene glycol diacrylate. The time to gelation (minutes to hours) was either preset through the initial concentrations or the reaction was initiated locally by a base, thus resulting in polymerization fronts that converted the mixture from a liquid into a gel (ca. 0.1 mm min−1). The rate of hydrolytic degradation of the hydrogel depended on the initial concentrations, thus resulting in a gel lifetime of hours to months. In this way, temporal programming of gelation was possible under mild conditions by using the output of an autocatalytic enzyme reaction to drive both the polymerization and subsequent degradation of a hydrogel.

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confidence: 88%

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confidence: 96%

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Temporal Control of Gelation and Polymerization Fronts Driven by an Autocatalytic Enzyme Reaction

et al. 2016

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“…The acid produced accelerates the rate of reaction effectively catalyzing its own production. Later analysis suggested that the higher diffusion rate of acid in solution, compared to that of other species, is essential and that oscillations will only be observed for a relatively narrow range of parameters [8][9][10].…”

Section: Introductionmentioning

confidence: 99%

“…If this enzyme is added to a solution of acid and urea, then as ammonia is produced, a rapid switch from acid to base occurs after a controllable period of time [12]. Propagating pH fronts have been obtained in thin layers of solution in the ureaurease reaction and bistability and oscillations were observed in an open flow reactor under certain conditions [10]. However, experimental observations of oscillations under non-buffered conditions with urease are difficult to reproduce.…”

Section: Introductionmentioning

confidence: 99%

Kinetics of the urea–urease clock reaction with urease immobilized in hydrogel beads

Bubanja

Bánsági

Taylor

2017

Reac Kinet Mech Cat

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Feedback driven by enzyme catalyzed reactions occurs widely in biology and has been well characterized in single celled organisms such as yeast. There are still few examples of robust enzyme oscillators in vitro that might be used to study nonlinear dynamical behavior. One of the simplest is the urea-urease reaction that displays autocatalysis driven by the increase in pH accompanying the production of ammonia. A clock reaction was obtained from low to high pH in batch reactor and bistability and oscillations were reported in a continuous flow rector. However, the oscillations were found to be irreproducible and one contributing factor may be the lack of stability of the enzyme in solution at room temperature. Here, we investigated the effect of immobilizing urease in thiol-poly(ethylene glycol) acrylate (PEGDA) hydrogel beads, prepared using emulsion polymerization, on the ureaurease reaction. The resultant mm-sized beads were found to reproduce the pH clock and, under the conditions employed here, the stability of the enzyme was increased from hours to days.

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Photonic Devices Out of Equilibrium: Transient Memory, Signal Propagation, and Sensing

et al. 2017

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Soft photonic materials are important for sensors, displays, or energy management and have become switchable under static equilibrium conditions by integration of responsive polymer features. The next step is to equip such materials with the ability for autonomously dynamic and self-regulating behavior, which would advance their functionality and application possibilities to new levels. Here, this study shows the system integration of a nonlinear, biocatalytic pH-feedback system with a pH-responsive block copolymer photonic gel, and demonstrates autonomous transient memories, remotely controlled signal propagation, and sensing. This study utilizes an enzymatic switch to program the lifetime of the reflective state of a photonic gel, and induces propagation of pH-waves extinguishable by illumination with UV-light. The described combination of nonlinear chemistry and responsive photonic gels opens pathways toward out-of-equilibrium photonic devices with active and autonomous behavior useful for sensing, computation, and communication.

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pH Wave-Front Propagation in the Urea-Urease Reaction

Cited by 47 publications

References 35 publications

Temporal Control of Gelation and Polymerization Fronts Driven by an Autocatalytic Enzyme Reaction

Temporal Control of Gelation and Polymerization Fronts Driven by an Autocatalytic Enzyme Reaction

Kinetics of the urea–urease clock reaction with urease immobilized in hydrogel beads

Photonic Devices Out of Equilibrium: Transient Memory, Signal Propagation, and Sensing

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