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Experimental Investigation of the Interactions of Hyperactive Antifreeze Proteins with Ice Crystals

Abstract Details

2010, Doctor of Philosophy (PhD), Ohio University, Physics and Astronomy (Arts and Sciences).

Antifreeze proteins (AFPs) evolved in cold-adapted organisms and serve to protect them against freezing cold conditions by arresting ice crystal growth and inhibiting ice recrystallization. The freezing point depression by AFPs is defined as thermal hysteresis (TH) and AFPs are classified as hyperactive (hypAFPs) and moderate according to their TH activities. The mechanism of action of AFPs is not well understood. In particular, it is not clear what determines the concentration dependence of TH and whether the binding of AFP to ice is irreversible. Additionally, it is not known why some types of AFP are hyperactive compared to others and it was suggested that hyperactivity might be related to basal plane affinity of hypAFP to ice.

The present study utilizes the techniques of microfluidic devices and fluorescence microscopy to study the interaction of AFPs with ice crystals. With novel temperature controlled microfluidic devices, we showed the accumulation and affinity of hypAFPs on the basal plane of ice. This supports the view that hypAFPs adhere to the basal plane. Additionally, for the first time in literature, small ice crystals of 30-50 µm sizes covered with adsorbed GFP tagged hypAFPs were stabilized in supercooled non-AFP solutions for hours with no observed ice growth in temperature controlled microfluidic devices. Repeated TH experiments of ice crystals incubated in AFP solutions before and after the exchange of liquids in microfluidic devices gave the same TH activity. This finding clarifies our understanding of concentration dependence of TH. Furthermore, we found that hypAFPs protect ice against melting as well as freezing, resulting in superheated ice. Ice crystals were superheated up to 0.5 °C above their equilibrium melting temperatures and remained stable in this superheated state for hours. Measurements of fast melting velocities added additional evidence to the observed superheating of ice in AFP solutions. The experimental results of the current study provide strong evidence that AFPs bind to ice surfaces via irreversible binding. We have demonstrated that the use of microfluidics in combination with fluorescence microscopy is a valuable technique to study the binding mechanisms of AFPs and the concentration dependence of AFP activity.

Ido Braslavsky, Dr (Advisor)
143 p.

Recommended Citations

Citations

  • Celik, Y. (2010). Experimental Investigation of the Interactions of Hyperactive Antifreeze Proteins with Ice Crystals [Doctoral dissertation, Ohio University]. OhioLINK Electronic Theses and Dissertations Center. http://rave.ohiolink.edu/etdc/view?acc_num=ohiou1268166115

    APA Style (7th edition)

  • Celik, Yeliz. Experimental Investigation of the Interactions of Hyperactive Antifreeze Proteins with Ice Crystals. 2010. Ohio University, Doctoral dissertation. OhioLINK Electronic Theses and Dissertations Center, http://rave.ohiolink.edu/etdc/view?acc_num=ohiou1268166115.

    MLA Style (8th edition)

  • Celik, Yeliz. "Experimental Investigation of the Interactions of Hyperactive Antifreeze Proteins with Ice Crystals." Doctoral dissertation, Ohio University, 2010. http://rave.ohiolink.edu/etdc/view?acc_num=ohiou1268166115

    Chicago Manual of Style (17th edition)