Superheating of ice crystals in antifreeze protein solutions.
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 degrees 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.
Celik
Yeliz
Y
Department of Physics and Astronomy, Ohio University, Athens, OH 45701, USA.
Graham
Laurie A
LA
Mok
Yee-Foong
YF
Bar
Maya
M
Davies
Peter L
PL
Braslavsky
Ido
I
D000327:Adsorption; D000818:Animals; D021301:Antifreeze Proteins / Q000737:chemistry*; D001426:Bacterial Proteins / Q000737:chemistry; D055592:Biophysical Phenomena; D003460:Crystallization; D005615:Freezing; D049452:Green Fluorescent Proteins / Q000737:chemistry; D006358:Hot Temperature; D007053:Ice; D019476:Insect Proteins / Q000737:chemistry; D053544:Marinomonas / Q000737:chemistry; D008856:Microscopy, Fluorescence; D044367:Phase Transition; D011994:Recombinant Proteins / Q000737:chemistry; D012996:Solutions; D013059:Spectrum Analysis, Raman; D013712:Tenebrio / Q000737:chemistry; D013816:Thermodynamics
D021301:Antifreeze Proteins; D001426:Bacterial Proteins; D007053:Ice; D019476:Insect Proteins; D011994:Recombinant Proteins; D012996:Solutions; D049452:Green Fluorescent Proteins