Interactions of β-Helical Antifreeze Protein Mutants with Ice

Bar, Maya; Celik, Yeliz; Fass, Deborah; Braslavsky, Ido

doi:10.1021/cg800066g

Cited by 40 publications

(50 citation statements)

References 59 publications

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“…The dependence of the FH activity on the time that was allowed for the adsorption of AFPs on an ice crystal was examined for GFP-TmAFP with a custom-built nanoliter osmometer (32). We found that the FH activity increased with the time of exposure of the ice crystals to an AFP solution.…”

Section: Resultsmentioning

confidence: 99%

Microfluidic experiments reveal that antifreeze proteins bound to ice crystals suffice to prevent their growth

Celik

Drori

Pertaya-Braun

et al. 2013

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

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148

142

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Antifreeze proteins (AFPs) are a subset of ice-binding proteins that control ice crystal growth. They have potential for the cryopreservation of cells, tissues, and organs, as well as for production and storage of food and protection of crops from frost. However, the detailed mechanism of action of AFPs is still unclear. Specifically, there is controversy regarding reversibility of binding of AFPs to crystal surfaces. The experimentally observed dependence of activity of AFPs on their concentration in solution appears to indicate that the binding is reversible. Here, by a series of experiments in temperature-controlled microfluidic devices, where the medium surrounding ice crystals can be exchanged, we show that the binding of hyperactive Tenebrio molitor AFP to ice crystals is practically irreversible and that surface-bound AFPs are sufficient to inhibit ice crystal growth even in solutions depleted of AFPs. These findings rule out theories of AFP activity relying on the presence of unbound protein molecules.thermal hysteresis | ice structuring proteins A ntifreeze proteins (AFPs) are found in a variety of coldadapted organisms, where they serve as inhibitors of ice crystal growth and recrystallization (1, 2). These proteins are a subset of an expanding group of identified proteins, whose salient feature is ice binding (3, 4). AFPs are characterized by their ability to cause a temperature difference (hysteresis) in the melting and freezing of ice and are classified as hyperactive or moderately active according to the magnitude of their freezing hysteresis (FH) activity (5). The FH activity is defined as the difference between the melting temperature of ice crystals and the nonequilibrium freezing temperature at which rapid crystal growth commences. Although the FH activity has been investigated for more than four decades, the actual mechanism of action of AFPs is still not clear. This is partly because the interactions between molecules of AFPs, water, and ice at the ice-water interface are difficult to study experimentally due to the delicate, transitory nature of the ice-water interface.FH activity is thought to be due to an adsorption-inhibition mechanism that states that AFPs bind to ice surfaces and allow ice crystal growth only in surface regions between the bound AFP molecules (6, 7). This patchy growth pattern causes increased local microcurvature of the ice front that leads to larger surface energy, making the transformation of water into ice less energetically favorable and thus reducing the freezing temperature (GibbsThompson effect). It has been argued that the binding of AFPs to ice surfaces must be irreversible, because AFP desorption would result in rapid crystal growth in the areas where the AFP molecules have been desorbed from the ice surface (6,8). This theory has been criticized for assuming that the ice-water interface is sharp, contrary to the experimental evidence that the transitions from an ordered solid phase to a liquid phase at the ice-water interfaces are gradual and occur over seve...

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Section: Resultsmentioning

confidence: 99%

Microfluidic experiments reveal that antifreeze proteins bound to ice crystals suffice to prevent their growth

Celik

Drori

Pertaya-Braun

et al. 2013

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

Self Cite

148

142

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“…Both systems were validated to give comparable results. The nanoliter osmometer experiments were conducted in a cell that has been described previously in detail (14,42,43). The temperature of the custom-designed nanoliter osmometer was controlled through a LabView interface developed by Ido Braslavsky.…”

Section: Methodsmentioning

confidence: 99%

Superheating of ice crystals in antifreeze protein solutions

Celik

Graham

Mok

et al. 2010

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

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126

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It has been argued that for antifreeze proteins (AFPs) to stop ice crystal growth, they must irreversibly bind to the ice surface. Surface-adsorbed AFPs should also prevent ice from melting, but to date this has been demonstrated only in a qualitative manner. Here we present the first quantitative measurements of superheating of ice in AFP solutions. Superheated ice crystals were stable for hours above their equilibrium melting point, and the maximum superheating obtained was 0.44°C. When melting commenced in this superheated regime, rapid melting of the crystals from a point on the surface was observed. This increase in melting temperature was more appreciable for hyperactive AFPs compared to the AFPs with moderate antifreeze activity. For each of the AFP solutions that exhibited superheating, the enhancement of the melting temperature was far smaller than the depression of the freezing temperature. The present findings clearly show that AFPs adsorb to ice surfaces as part of their mechanism of action, and this absorption leads to protection of ice against melting as well as freezing.Gibbs-Thomson effect | ice recrystallization | irreversible binding | melting hysteresis | thermal hysteresis

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“…Bar et al arrive at a similar conclusion based on a systematic study of ice-shaping and TH activity of TmAFP mutants. 125 Drori et al studied whether IBPs must be present in solution to block desorption and ice crystal growth. To this end, unbound TmAFP surrounding the ice crystal was removed, by buffer exchange in the TH gap.…”

Section: B Reversible or Irreversible Ice-binding?mentioning

confidence: 99%

Interaction of ice binding proteins with ice, water and ions

et al. 2016

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Articles you may be interested inExplicit-water theory for the salt-specific effects and Hofmeister series in protein solutions J. Chem. Phys. 144, 215101 (2016) Ice binding proteins (IBPs) are produced by various cold-adapted organisms to protect their body tissues against freeze damage. First discovered in Antarctic fish living in shallow waters, IBPs were later found in insects, microorganisms, and plants. Despite great structural diversity, all IBPs adhere to growing ice crystals, which is essential for their extensive repertoire of biological functions. Some IBPs maintain liquid inclusions within ice or inhibit recrystallization of ice, while other types suppress freezing by blocking further ice growth. In contrast, ice nucleating proteins stimulate ice nucleation just below 0 C. Despite huge commercial interest and major scientific breakthroughs, the precise working mechanism of IBPs has not yet been unraveled. In this review, the authors outline the state-of-the-art in experimental and theoretical IBP research and discuss future scientific challenges. The interaction of IBPs with ice, water and ions is examined, focusing in particular on ice growth inhibition mechanisms.

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Interactions of β-Helical Antifreeze Protein Mutants with Ice

Cited by 40 publications

References 59 publications

Microfluidic experiments reveal that antifreeze proteins bound to ice crystals suffice to prevent their growth

Microfluidic experiments reveal that antifreeze proteins bound to ice crystals suffice to prevent their growth

Superheating of ice crystals in antifreeze protein solutions

Interaction of ice binding proteins with ice, water and ions

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