• PNAS Chemistry Ad
  • Sign-up for PNAS eTOC Alerts

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

  1. Ido Braslavskya,b,1
  1. aDepartment of Physics and Astronomy, Ohio University, Athens, OH 45701;
  2. bInstitute of Biochemistry, Food Science, and Nutrition, Robert H. Smith Faculty of Agriculture, Food, and Environment, The Hebrew University of Jerusalem, Rehovot 76100, Israel;
  3. cDepartment of Physics, University of California at San Diego, La Jolla, CA 92093; and
  4. dDepartment of Biomedical and Molecular Sciences, Queen’s University, Kingston, ON, Canada K7L 3N6

  1. Edited by David A. Weitz, Harvard University, Cambridge, MA, and approved December 12, 2012 (received for review August 22, 2012)

Abstract

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.

Footnotes

  • ↵1To whom correspondence should be addressed. E-mail: braslavs{at}agri.huji.ac.il.

  • Author contributions: Y.C., N.P.-B., P.L.D., and I.B. designed research; Y.C., R.D., A.A., and I.B. performed research; T.B., M.B.-D., and A.G. contributed new reagents/analytic tools; Y.C., R.D., and I.B. analyzed data; and Y.C., M.B.-D., A.G., P.L.D., and I.B. wrote the paper.

  • The authors declare no conflict of interest.

  • This article is a PNAS Direct Submission.

  • This article contains supporting information online at www.pnas.org/lookup/suppl/doi:10.1073/pnas.1213603110/-/DCSupplemental.

Freely available online through the PNAS open access option.

Online Impact